Using PASCO sensors - the unofficial guide v1.1, July 2012
PASCO includes a huge range of resources both with it’s sensors and on it’s web site at www.pasco.com. By
necessity the materials on the site must try and cover both the beginning user and the advanced user. As
PASCO is the major supplier of electronic measure to Universities around the world, some times the advice
meets those needs and as a technician or teacher at Primary or Secondary the details we need get buried
amongst that greater detail.
This unofficial guide is intended to assist the Primary or Secondary school user get started more quickly with
PASCO sensors. It avoids, where ever possible, technical jargon and addresses general day to day issues that
we are frequently asked or have come across in our own experience in classrooms and workshops over more
than 20 years. The notes are relatively extensive but try to avoid unnecessary detail. Browse or search through
for the sensor or device specific information you require.
Please note: This guide is provided as general assistance in good faith. In using this guide you acknowledge and
understand that the information on the PASCO web site at all times takes precedence, that specifications and
details may change at any time without notice, that this information may not be complete and is subject to
change and that any results, damage or other issues arising from using this guide are the sole responsibility of
the school and the user.
Underlined text includes hyperlinks to the PASCO web site. Click on a link to open your web browser and go directly to that content on-line (requires
an active internet connection).
General Background
PASCO has two separate “probeware” collections - the original black Science Workshop series of digital and
analogue sensors and the newer PASPort (largely) blue pure digital sensors. The majority of this guide relates to
the PASPort range, however general advice re electrode care and calibration and other notes applies across
both ranges.
ScienceWorkshop Probeware
Science Workshop sensors are basically transducers only - exactly what other manufacturers are still making.
They convert a signal to a voltage that varies within a range of +10 V and -10V. The interface or connection
(such as the Science Workshop 750USB) then contains a D/A (Digital/Analogue) converter that transforms the
signal to one that can be understood.
Analogue sensors have a round multi-pin DIN connector. They can be used with the PASPort system using a
PASPort Analogue Adaptor. However, they won’t be detected automatically - you must choose the sensor
you’ve connected within the software you’re using. As many PASPort sensors have significant user and
performance benefits, please consider carefully before continuing with older sensors. We’d be pleased to
advise.
Digital sensors such as photogates have a 6 mm stereo jack and produce a signal that is only on or off,
blocked or unblocked. Many of these digital sensors, such as photogates, time-of-flight pad, and the like are
recommended for use with PASPort through the Digital Adaptor.
Note: The PASPort Analogue Adaptor can also be used along with an additional adaptor piece to support a
broad range of sensors from other manufacturers that have the same voltage characteristics as PASCO.
Science Workshop sensors are NOT automatically detected. The user must choose the sensor within the
PASCO software. Science Workshop sensors will work with other manufacturer’s systems with appropriate
connectors.
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PASPORT Probeware
PASPORT Probeware is the best choice for most school needs — offering more than 70 sensors to measure
virtually anything plus software support for some additional external USB devices. The PASPORT sensor line is
all-digital, each sensor a computing device of its own complete with digital chip on board. This gives you
plug-and-learn simplicity plus unmatched sensor capabilities. No other manufacturer produces sensors with
these features.
PASPORT also features MultiMeasure Sensors™ — many different sensor measurements in one convenient
sensor box. Makes classroom and equipment management easier, and saves money IF you select carefully
and will use all of the sensor measurements.
With PASPORT, your students can collect data
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Using a standalone option
Directly to a computer
As a remote data logger
Wirelessly to a computer
PASPort sensors are automatically detected by all PASCO software. They will not work with any other
manufacturer’s systems. There are adaptors that will allow selected sensors from other manufacturers to work
with PASPort interfaces/connections.
Working with sensors
What works with what
The PASPort system is based on the concept that all sensors should work with all interfaces/connections/
dataloggers. This is another unique feature of the PASPort system. You do not need to purchase a particular
device in order to use a particular sensor. The general rule is to purchase and use the cheapest and simplest
connection for the particular device and purpose you propose investigating. There are some minor
exceptions to this rule.
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The 2-channel 1 MHz voltage sensor is intended for use with the Xplorer GLX and 850 Universal
Interface. Data capture speeds are limited to 1 Hz with other interfaces.
SPARKVue Lite (free version) for iOS has restricted support. The following sensors are NOT supported:
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PS-2158 PASPORT Analog Adapter
PS-2159 PASPORT Digital Adapter
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PS-2166 Alpha Beta Gamma Radiation Sensor
PS-2165 GLX Voltage Probe
Sensors can not be calibrated with SPARKVue Lite for iOS. Tech Note 1116 has details on how to work around
this restriction.
The full featured “SPARKVue HD” for iPad does not have these restrictions..
The following sensors have sufficiently high power consumption that they may exhibit problems if the
AirLink2 charge drops below 80%-90%:
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PS-2109 Sound Level
PS-2110 CO2 Gas
PS-2120 Rotary Motion
PS-2127 4-Port Type K Temperature Sensor
PS-2128 Visual Accelerometer
PS-2151 Thermocline
PS-2175 GPS
Datasheets
PASPort sensors come factory calibrated and ready to use. Uniquely, they are actual computing devices and
have some programmable memory space on board. In many cases this is not user addressable meaning that
it’s used purely for storing factory settings and communication with the software. Each time a sensor is
connected to an interface, this datasheet handles the parameters for communication with the software.
In a small number of sensors there is additional memory that can store user calibrations, for example Carbon
Dioxide Gas.
From time to time the datasheet may become corrupted if communication between sensor and software is
interrupted. In these cases you may notice:
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the sensor stops operating or is undetected when other sensors are auto detected;
an Xplorer shows the message “Bad DataSheet”;
a digital display in SPARKVue or DataStudio shows the message “NAN”.
A PASPort sensor can be reset with a new factory datasheet using DataStudio:
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Plug the sensor into an interface and then into a computer with DataStudio installed on it. Make
sure DataStudio is not running;
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If you see the small PASPortal window showing the message “I’ve found a new PASPort sensor.
How would you like to use it?”, choose the option to “Ignore Sensor”.
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Hold down the ctrl-sift-D keys all together and start DataStudio. When prompted choose “Create
New Experiment”.
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DataStudio will transfer a new datasheet on to the sensor and the sensor is now ready for use.
If the sensor still fails to be detected or work correctly, repeat the process once more to be sure then return it to Cider House Tech for checking.
Ground Loops
If two or more probes are simultaneously submerged in the same conductive liquid (eg tap water) then a
ground loop or conductive interference can occur between the sensors. This can result in changes in sensor
readings when another sensor is placed within the same solution. Using a USB Link, SPARKLink or other device
without an external power adaptor eliminates this effect as does separate battery powered interfaces.
Avoid using the DO electrode on the water quality sensor at the same time as the other quantities on the water quality sensor in the same solution.
Types of sensors
There are over 70 sensors in the expanding range of PASPort sensors and several other USB based devices that
are detected through the PASCO software. The range as at May 2012 is detailed by curriculum category below.
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Click on any of the sensor names to visit the PASCO web site for full manuals and user instructions. Some sensors are shown more than once where
they apply to two or more categories.
Acceleration
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Acceleration Sensor (2-axis) ( PS-2118 )
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Acceleration Sensor (3-axis) ( PS-2119 )
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Visual Accelerometer ( PS-2128 )
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3-Axis Accelerometer/Altimeter ( PS-2136 )
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GPS Position Sensor ( PS-2175 )
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Photogate and Pulley System ( ME-6838A )
Chemistry
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pH Sensor ( PS-2102 )
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Conductivity Sensor ( PS-2116A )
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Colourimeter Sensor ( PS-2121 )
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High Accuracy Drop Counter ( PS-2117 )
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Oxidation Reduction Potential Probe ( CI-6716 )
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High Precision pH/Temperature with ISE/ORP Amplifier ( PS-2147 )
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Chemistry Sensor ( PS-2170 )
Electricity/Magnetism
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Force
Magnetic Field Sensor ( PS-2112 )
Voltage-Current Sensor ( PS-2115 )
Charge Sensor ( PS-2132 )
Chemistry Sensor ( PS-2170 )
General Science Sensor ( PS-2168 )
Galvanometer ( PS-2160 )
2-Axis Magnetic Field Sensor ( PS-2162 )
High Current Sensor ( PS-2193 )
1 MHz 2-Channel Voltage Sensor ( PS-2190 )
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Gases
Force Sensor ( PS-2104 )
Force Platform ( PS-2141 )
2-Axis Force Platform ( PS-2142 )
High Resolution Force Sensor ( PS-2189 )
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GPS
Dissolved Oxygen Sensor ( PS-2108 )
Carbon Dioxide Gas Sensor ( PS-2110 )
Ethanol Sensor ( PS-2194 )
Oxygen Gas Sensor ( PS-2126A )
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Light
GPS Position Sensor ( PS-2175 )
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Light Sensor ( PS-2106A )
Temperature/Sound Level/Light Sensor ( PS-2140 )
Infrared Light Sensor ( PS-2148 )
Ultraviolet Light Sensor ( PS-2149 )
General Science Sensor ( PS-2168 )
High Sensitivity Light Sensor ( PS-2176 )
Broad Spectrum Light Sensor ( PS-2150 )
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Light Level Sensor ( PS-2177 )
Load Cells and Amplifiers
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Dual Load Cell Amplifier ( PS-2205 )
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Load Cell Amplifier ( PS-2198 )
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100 N Load Cell ( PS-2200 )
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5 N Load Cell ( PS-2201 )
Motion
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pH
Photogate Head ( ME-9498A )
Motion Sensor ( PS-2103A )
Rotary Motion Sensor ( PS-2120 )
GPS Position Sensor ( PS-2175 )
Displacement Sensor ( PS-2204 )
Photogate and Pulley System ( ME-6838A )
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pH Sensor ( PS-2102 )
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High Precision pH/Temperature with ISE/ORP Amplifier ( PS-2147 )
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Chemistry Sensor ( PS-2170 )
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Water Quality Sensor ( PS-2169 )
Physiology
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EKG Sensor ( PS-2111 )
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Respiration Rate Sensor ( PS-2133 )
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Spirometer ( PS-2152 )
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Goniometer Sensor ( PS-2137 )
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Breath Rate Sensor ( PS-2187 )
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Hand Grip Heart Rate Sensor ( PS-2186 )
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Blood Pressure Sensor ( PS-2207 )
Pressure
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Absolute Pressure Sensor ( PS-2107 )
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Barometer/Low Pressure Sensor ( PS-2113A )
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Relative Pressure Sensor ( PS-2114 )
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Absolute Pressure/Temperature Sensor ( PS-2146 )
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Chemistry Sensor ( PS-2170 )
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Quad Pressure Sensor ( PS-2164 )
Radiation
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G-M Tube/Power Supply ( SN-7927A )
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Alpha Beta Gamma Radiation Sensor ( PS-2166 )
Soil Properties
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Flat pH Electrode ( PS-2182 )
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Soil Moisture Sensor ( PS-2163 )
Sound
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Sound Level Sensor ( PS-2109 )
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Temperature/Sound Level/Light Sensor ( PS-2140 )
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General Science Sensor ( PS-2168 )
Spectrometry & Colorimetry
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Colourimeter Sensor ( PS-2121 )
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Water Quality Colourimeter ( PS-2179 )
Temperature
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v1.1, July 2012
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Temperature Sensor ( PS-2125 )
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Temperature Type K Sensor ( PS-2134 )
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Skin/Surface Temperature Probe ( PS-2131 )
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Fast Response Temperature Probe (3 pack) ( PS-2135 )
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Stainless Steel Temperature Probe ( PS-2153 )
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Quad Temperature Sensor ( PS-2143 )
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Thermocline Sensor ( PS-2151 )
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Temperature Array ( PS-2157 )
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Noncontact Temperature Sensor ( PS-2197 )
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Type K 4-Port Temperature Sensor ( PS-2127 )
Timing/Counting
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Time-of-Flight Accessory ( ME-6810 )
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Photogate Head ( ME-9498A )
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Laser Switch ( ME-9259A )
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Freefall Adapter ( ME-9207B )
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Alpha Beta Gamma Radiation Sensor ( PS-2166 )
Water Quality
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pH Sensor ( PS-2102 )
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Dissolved Oxygen Sensor ( PS-2108 )
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Conductivity Sensor ( PS-2116A )
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Turbidity Sensor ( PS-2122 )
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Flow Rate/Temperature Sensor ( PS-2130 )
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Thermocline Sensor ( PS-2151 )
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Water Quality Sensor ( PS-2169 )
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Water Quality Colourimeter ( PS-2179 )
Weather
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Barometer/Low Pressure Sensor ( PS-2113A )
Humidity/Temp/Dew Point Sensor ( PS-2124A )
6-in-1 Weather Sensor ( PS-2154A )
Weather/Anemometer Sensor ( PS-2174 )
Dual Humidity/Temp/Dew Point Sensor ( PS-2156 )
Also available are:
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Spectrometers - manufactured by Ocean Optics, connect via USB and are detected by SPARKVue
1.3.0 or newer. You must update to at least this version to use this feature.
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Digital microscopes and web cams - various manufacturers, connect via USB and are detected by
SPARKVue 1.3.0 or newer as an imaging device.
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Ion Specific Electrodes - a broad range of industry standard electrodes are supported by:
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High Precision pH/Temperature with ISE/ORP Amplifier ( PS-2147 )
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Chemistry Sensor ( PS-2170 )
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Water Quality Sensor ( PS-2169 )
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A growing range of sensor accessories for investigating or demonstrating key concepts eg
diffusion/osmosis chamber.
Care and Maintenance of Sensors
There is something of a misunderstanding that sensors take a lot of care and maintenance. Because of the
PASPort design most in fact need next to no maintenance and, most, no calibration. Some basic care while in
use, cleaning after use if exposed to liquids or chemicals and dry storage is really all they need.
Water proof and water resistance
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v1.1, July 2012
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Most sensors outside of the water quality area are NOT waterproof. No blue sensor box is
waterproof. No interface is waterproof.
All temperature thermistors are waterproof to the point where they connect to the blue sensor
box.
Electrodes are waterproof to the point where they connect to the blue sensor box.
The cuvette holders on colourimeters and the turbidity sensor are waterproof. The main sensor
itself is not.
The bands and grips of the heart rate sensors are waterproof.
Sensors and calibration
The majority of sensors come factory calibrated and usually require no calibration and little or no
maintenance. There may be some exceptional circumstances where you do want to calibrate eg comparing
multiple temperatures within one degree but generally they can be left alone.
Sensors can also be effected by environmental factors, for example a change in temperature effecting the
speed of sound that’s used in the measurement of motion, the composition of specific cuvettes used with a
colourimeter, the amount of atmospheric carbon dioxide. In these cases, PASCO has either a built in
calibration method or a simple “button” method for calibrating. Motion, for example, has a thermistor built
into it that records the current temperature and adjusts the calibration accordingly.
Electrode based sensors will require calibration. These are third party electrodes and will change and age over
time. Industry takes the need for calibration for granted. Good laboratory practice is to always calibrate an
electrode based sensor. However, there are some hints and tricks that can simplify or reduce that process.
Most importantly, in these cases PASCO has designed the software to enable storage of the particular electrode calibration within the
current experiment file. This means that:
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Some electrodes can be calibrated ahead of time and the calibration stored in a file to be used
with that sensor.
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Past calibrations remain with the file so results don’t change when later used with a different or
changed electrode.
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Where electrodes are relatively stable (eg nitrate) or are used irregularly past calibrations can be
retrieved by simply opening a past file used with that electrode.
Other electrodes measurements are effected not only by changes in the electrode but also environmental
factors (eg dissolved oxygen, dissolved carbon dioxide ion selective electrode) and should be calibrated every time
environmental factors change (eg change in air pressure, water composition).
PASCO software and dataloggers have simple calibration methods built in that with a small amount of
practice, allow calibrations to be made generally within a few seconds. The one exception is the free
SPARKVue for iOS. In this one instance, measurements can be taken but not calibrated at the time. A
calibration factor can be applied. Tech Note 1116 has details on how.
Sensor specific hints and tips
A reminder that this guide is provided as general assistance in good faith. In using this guide you
acknowledge and understand that the information on the PASCO web site at all times takes precedence, that
specifications and details may change at any time without notice, that this information may not be complete
and is subject to change and that any results, damage or other issues arising from using this guide are the
sole responsibility of the school and the user. We will endeavour to update the notes as new information or
new releases comes to hand - please check for the latest version.
Please refer to the full list above for additional sensors and links to the PASCO web site for specifications,
manuals and other detail. Where a sensor is not included below, user intervention of any kind is generally not
required.
Acceleration
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Visual Accelerometer ( PS-2128 )
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Standard AA batteries are used with the visual accelerometer when not plugged in to an
interface/connection. Make sure you press and hold the black button on the side for about 2-3
seconds to turn it off. Check carefully that all lights are out to confirm.
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GPS Position Sensor ( PS-2175 )
Like all GPS units, don’t expect the GPS to work inside. A clear view of the sky and hence the GPS
satellites are required. Sample rates are not high enough for amusement park rides - use the 3axis accelerometer with altitude or an iOS device with SPARKVue Lite for these scenarios. GPS
data can be exported as Google Map compatible data and to PASCO’s MyWorld GIS software.
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Photogate and Pulley System ( ME-6838A )
Requires a digital adaptor (PS-2159) for use with PASPort interfaces.
Chemistry
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pH Sensor ( PS-2102 )
The electrode supplied with the PASCO pH sensors is gel-filled - it doesn’t matter if it dries out
and it can actually prolong it’s life if allowed to dry out when stored for extended periods. Small
plastic extensions protect the glass bulb from being scratched but it should be noted that this
also tends to hold some solution around the bulb - gentle stirring either manually or via a
magnetic stirrer is recommended.
A video on calibration of the pH sensor with SPARKVue can be viewed at http://www.youtube.com/watch?v=fUKL8sDiCy4
Cleaning
For most applications, hot water with domestic cleaning detergent can be used for cleaning.
For lime and other hydroxide containing solutions, clean with a 5-10% solution of hydrochloric
acid. For solutions containing organic fouling agents (fats, oils, etc.), clean probe with limonene
or acetone. For algae and bacteria containing solutions, clean probe with a chlorine bleach
containing liquid.
Storage
During term, clean and immerse the pH electrode in the soaker bottle filled with pH 4
buffer solution that contains 1 g of potassium chloride (KCl) per 100 mL of solution.
Alternatively, pH electrode storage solution and standard calibration solutions may also
be obtained from various chemical suppliers.
** Storing the electrode in distilled water will decrease the life of the electrode.
Long-term: Clean and dry the probe. One to two days before you wish to use it again,
restore the probe by soaking it alternately into 0.1 M HCl and 0.1 M NaOH solutions for
two minutes each. Repeat once. Following that, soak in a pH 4.0 buffer solution until
use. If this restoring procedure fails to improve the responsiveness of the electrode, it
should be replaced.
Warranty/ Expected Life
The pH electrode's that PASCO carries are covered by a 1 year manufacturer warranty, not the 5
years of the sensor box itself. The pH sensor should be replaced when it becomes unresponsive
after cleaning and restoration. pH sensor life is around 5 years or more in a typical educational
environment.
Calibration
While PASCO runs an approximate factory calibration prior to shipping, all electrodes age over
time. This means that calibration is required, depending upon the accuracy of result required. We
generally suggest that:
Junior classes requiring comparative results do not need to calibrate.
Senior classes requiring reasonable absolute values should calibrate at least once per semester
and always after restoration. Ideally, this should be every time but time constraints may make this
difficult to fit in.
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Extended investigations, particularly Extended Essays for the IB, should always include calibration.
The calibration for a pH sensor and other electrode based sensors is stored in the file with which
it’s calibrated. This allows easy restoration and transfer of calibration settings without the risk of
accidentally applying a calibration different to that appropriate at the time.
Calibration files can be named with an identifier matching the sensor/electrode pair and placed
in a convenient place on the school network or device for students to open and restore a prior
calibration. Calibration file and sensor/electrode combination go together - save and mark them with appropriate
identification if prior calibrations are to be used.
When calibrating make sure that the pH electrode is not still. A gentle flow of solution across the
electrode is required.
Procedure in DataStudio
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Connect a PASPort interface to the computer via a USB cable or Bluetooth (in the case of
the AirLinks).
Connect a PASPort sensor with a well-maintained pH electrode to the PASPort interface.
Click the Setup button in DataStudio.
In the Experiment Setup window, click the Calibrate Sensors... button.
Enter the first known pH buffer value in the Calibration Point 1 Standard Value text box.
Rinse and dry the pH probe.
Place the pH probe in the corresponding buffer solution, stirring gently.
Stir the pH sensor until the value Present Sensor Measurement value stabilises (about 3
seconds).
Click the Read from Sensor button.
Place the pH sensor in the second pH buffer solution.
Enter the second known pH buffer value in the Calibration Point 2 Standard Value text
box.
Rinse and dry off the pH sensor.
Place the pH Sensor in the second buffer solution.
Stir the pH sensor until the value Present Sensor Measurement value stabilises.
Click the Read from Sensor button.
Click OK. Save the file with an appropriate name if you wish to use the calibration on
later occasions.
Procedure Using the XPlorer GLX
1.
Connect a PASPort sensor with a well-maintained pH electrode to any sensor port of the
Xplorer GLX.
2.
Go to Home/Sensors/Sensors/Calibrate (3).
3.
Enter the first known pH buffer value in the Pt 1 (pH) text box.
4.
Rinse and dry the pH probe.
5.
Place the pH probe in the corresponding buffer solution, stirring gently.
6.
Stir the pH sensor until the pH value displayed at the bottom of the screen stabilises
(about 3 seconds).
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Click the Read Pt 1 button (F3).
8.
Place the pH sensor in the second pH buffer solution, stirring gently.
9.
Press the down arrow until you see Pt 2 (Units).
10. Enter the second known pH buffer value in the Pt 2 (pH) text box.
11. Rinse and dry off the pH sensor.
12. Place the pH Sensor in the second buffer solution.
13. Stir the pH sensor until the pH value displayed at the bottom of the screen stabilises.
14. Click the Read Pt 2 button (F4).
15. Click OK.
16. Save the file with an appropriate name if you wish to use the calibration on later
occasions.
Procedure Using the SPARK SLS or SPARKvue
1.
Connect a well-maintained pH electrode to one of the following PASPort sensor boxes:
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PS-2102 PASPORT pH Sensor
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PS-2147 PASPORT Precision pH/ORP/ISE Amplifier with Temperature
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PS-2169 PASPORT Water Quality Sensor
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PS-2170 PASPORT Chemistry Sensor
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If you are using a SPARK SLS, connect the PASPort sensor box to the SPARK SLS.
If you are using SPARKvue, connect a PASPort sensor to any PASPort interface that is
connected to the computer via a USB cable.
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Press the Home button.
Select pH.
Click Show. (You will see a Graph display.)
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Press the Experiment Tools Button:
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Select CALIBRATE SENSOR.
In the Sensor field, select the sensor that has the pH probe attached.
In the Measurement field select pH.
Calibration Type should remain 2 point (Adjust Slope and Offset).
Click NEXT.
Enter the first known pH buffer value in the Standard Value box in the Calibration Point 1
section.
Rinse and wipe dry the pH probe.
Place the pH probe in the buffer solution corresponding to the value in the Standard
Value box.
Stir the pH sensor in the buffer solution for at least two seconds.
Click the Read From Sensor button.
Place the pH sensor in the second pH buffer solution.
Enter the second known pH buffer value in the Standard Value box in the Calibration
Point 2 section.
Rinse and wipe dry the pH probe.
Place the pH probe in the buffer solution corresponding to the value in the Standard
Value box.
Stir the pH sensor in the buffer solution for at least two seconds.
Click the Read From Sensor button. (The current file is now calibrated.)
Click OK twice to return to the graph display.
Save the file with an appropriate name if you wish to use the calibration on later
occasions.
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Conductivity Sensor ( PS-2116A )
In general, conductivity offers a fast, reliable, nondestructive, inexpensive and durable means of measuring
the ionic content of a sample. Reliability and repeatability are usually excellent. Unlike measurement with ionselective electrodes, such as pH sensors, the response of a conductivity sensor will not drift over time.
The principle drawback of conductivity is that it is not ion-selective, giving a reading proportional to the
combined effect of all ions present. In order to determine the amount of total dissolve solids, you must have
an idea of the ionic composition of the solution being measured. Conductance is the reciprocal of resistance,
and its basic unit is the Siemens [S], formerly called mho. Note that PASCO generally ships a 10x probe as standard with the
conductivity sensor. This means that all readings should be divided by 10 for actual values.
Operating Instructions
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Clean the electrode.
Soak the conductivity electrode in distilled or deionized water for 5 to 10 minutes.
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Dry off the probe.
Immerse the probe in a calibration solution beyond the level of the holes on the electrode.
Tap the probe against the side of the vessel to remove any air bubbles trapped inside.
Monitor the conductivity while stirring the probe in the solution. Continue stirring until the value
stabilizes.
Calibrate the sensor if required (see note below!).
Rinse the conductivity probe with distilled or deionized water between samples.
Wipe dry.
Temperature Effects
Conductivity has a substantial dependence on temperature. Temperature variation causes frequent problems
with conductivity measurements when the solution under testing has a rapid varying temperature. The
change in conductivity is virtually instantaneous.
Cleaning
The single most important requirement of accurate and reproducible results in conductivity measurement is a
clean cell. A dirty cell will contaminate the solution and cause the conductivity to change. Grease, oil,
fingerprints, and other contaminants on the sensing elements can cause erroneous measurements and
sporadic responses.
Cleaning Methods
1.
For most applications, hot water with domestic cleaning detergent can be used for cleaning.
2.
For lime and other hydroxide containing solutions, clean with a 5-10% solution of hydrochloric acid.
3.
For solutions containing organic fouling agents (fats, oils, etc.), clean probe with acetone.
4.
For algae and bacteria containing solutions, clean probe with a bleach containing liquid.
Clean cells by dipping or filling the cell with cleaning solution and agitating for two or three minutes. When a
stronger cleaning solution is required, try concentrated hydrochloric acid mixed into 50% isopropanol. Rinse
the cell several times with distilled or deionized water and remeasure the cell constant before use.
Storage
For short-term storage, leave the cell immersed in deionized water. Any cell that has been stored dry should
be soaked in distilled water for 5 to 10 minutes before use to assure complete wetting of the electrodes. If the
black platinized coating appears to be wearing or flaking off the electrodes or if the cell constant has changed
by 50%, the cell should be replaced or re-platinised.
Calibration
The conductivity sensor should not require calibration to obtain a value that is accurate to within 10%. To
obtain more accurate values, or verify that your conductivity probe is functioning to within specification,
please follow Tech Note 596
•
Colourimeter Sensor ( PS-2121 )
A video on using the colourimeter with SPARKVue can be viewed at http://www.youtube.com/watch?
v=vlJrv8q0q7g&feature=plcp
The PASPORT Colourimeter records 4 wavelengths simultaneously--no need to guess at
wavelength to get a quality measurement. Digital circuitry handles the calculations, calibrations
and adjustments – all you have to do is collect data. It simultaneously reports both absorbance
and transmittance. Calibration is not always required but is recommended at senior levels to
allow for differences between cuvettes. This calibration is stored on the sensor and is performed
via a single button on the sensor itself. Replacement cuvettes are available.
To avoid errors when calibrating, do not use the Colourimeter around bright lights or with turbid solutions. Always close the lid
tightly before taking measurements. For accurate readings, fill the cuvette to the lid with the sample.
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The cuvette holder is waterproof but the unit itself is not.
To calibrate for100% transmittance, insert a cuvette filled with distilled water into the cuvette
holder and tightly close the lid.
Press the green Calibration button on the sensor. The light illuminates to indicate calibration is in
progress.
Wait for the light to turn off and then remove the sample.
To check your calibration, reinsert the cuvette, close the lid, and click the Start button in
DataStudio, the GLX, Xplorer or SPARKVue. All color readings should approximate 100%
transmittance.
•
High Accuracy Drop Counter ( PS-2117 )
The unit can sample up to 40 drops per minute. Additional calibration instructions are included
in Tech Note 473
•
Oxidation Reduction Potential Probe ( CI-6716 )
PREPARATION
1.
Remove the protective soaker bottle and rinse the bottom of the electrode with
deionized water.
2.
Prior to first use or after long-term storage, immerse the electrode in deionised water for
30 minutes.
VALIDATION
1.
2.
3.
4.
5.
6.
Set the probe to read in mV.
Prepare enough pH 7.00 buffered water to completely immerse the membrane of the
electrode.
Add quinhydrone to saturate the buffered water. (Some crystals should be undissolved
after stirring vigorously.)
While stirring, immerse the electrode into the solution.
Measure the potential after the reading stabilizes (30-60 seconds).
The potential should be within +/- 20 mV of the standard values:
1.
Temperature [C]
1.
20
1.
25
1.
30
1.
Standard
Potential [mv]
1.
92
1.
86
1.
79
7.
8.
9.
10.
15.
Remove electrode and rinse thoroughly with distilled water.
Add sufficient crystals of quinhydrone to saturate a solution of 4.01 pH buffer.
While stirring, immerse the electrode into the solution. (The measured voltage should
respond rapidly.)
Measure the potential after the reading stabilises (30-60 seconds).
The potential should be within +/- 20 mV of the standard values:
1.
Temperature [C]
1.
20
1.
25
1.
30
1.
Standard
Potential [mv]
1.
268
1.
263
1.
213
28.
If the difference between the values of the electrode in the two buffers is less
than 177 mV or the potentials are offset from the standard potentials by more than 20 mV, clean
the electrodes.
11. Rinse the electrode with distilled water.
STORAGE
Store in air or distilled water. If stored in air, rinse with distilled water
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MAINTENANCE
Electrodes which are mechanically intact with no broken parts can often be restored to normal
performance by one of the following procedures:
•
General Cleaning: Soak the electrode in 1:10 dilution of household laundry bleach in a
0.1 - 0.5% liquid detergent solution in hot water with vigorous stirring for 15 minutes.
Drain/refill the reference chamber. Soak the electrode in distilled water for at least 10
minutes.
•
Salt Deposits: Dissolve the deposit by immersing the electrode in 0.1 M HCl for five
minutes, followed by immersion in 0.1M NaOH for five minutes, and thorough rinsing
with distilled water.
•
Oil/Grease Films: Wash electrode in a little detergent and hot water. Rinse electrode tip
with distilled water.
•
Clogged Reference Junction: Heat a diluted KCl solution to 60-80oC. Place the reference
portion of the ORP electrode into the heated KCl solution for approximately 10 minutes.
Allow the electrode to cool while immersed in some unheated KCl solution.
•
Protein Deposits: Dissolve the deposit by immersing the electrode in a 1% pepsin
solution with a background of 0.1M HCl for five minutes, followed by thorough rinsing
with distilled water.
After any of these special cleaning procedures, remember to drain/refill the reference chamber, if
refillable. Soak the electrode in storage solution for at least 10 minutes.
If these steps fail to restore normal electrode response, replace the electrode.
Further notes on trouble shooting can be found in Tech Note 1066.
•
High Precision pH/Temperature with ISE/ORP Amplifier ( PS-2147 )
The high precision pH sensor can give pH readings to a resolution of 0.01 with appropriate
calibration. It also supports ISE and ORP probes.
Refer to the notes for PS-2102 (above) on calibration and care of pH sensors.
If pH and temperature are simultaneously submerged in the same conductive liquid (eg tap
water) then a ground loop or conductive interference can occur between the sensors. This can
result in changes in sensor readings when another sensor is placed within the same solution.
Using a USB Link, SPARKLink or other device without an external power adaptor eliminates this
effect.
ISE ELECTRODES
PASCO distributes a range of industry standard Ion Specific Electrodes. These are third party
electrodes and are generally the same as used by other makes of electronic measure, the
electrodes themselves can be inter-changed although not the sensors themselves. Some general
points:
•
Ion selective electrodes are probably the most difficult sensors to use since it requires
additional knowledge on the kind of test being carried out.
•
Some of the electrodes do not age well, particularly dissolved carbon dioxide.
•
Always check and verify that there are no interfering ions in solution. A list of interfering
ions is available for each of the relevant ion specific electrodes.
•
Like the pH probe, calibration details are stored with the experiment file. Ensure that files
are named to match the particular ion specific electrode being calibrated. Follow the
calibration procedure per the pH electrode referring to the following electrode based notes
as required.
•
Constant, but not violent, movement of the electrodes is required for accurate
measurement. A magnetic stirrer can generate heat sufficient to change the solution
temperature so if using one it’s recommended that a sheet of styrofoam or other insulator
is placed between the stirrer and the beaker.
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•
•
•
A range of standards for some of the ion specific electrodes are available through PASCO.
For a list including part numbers for ordering, please refer to Tech Note 422 on the PASCO
web site. Be certain that your standards are uncontaminated. With the High standard 100x
more than the low standard, contamination is pretty easy to do. Rinse thoroughly between
calibration points and blot prior to placing in a standard.
Electrodes can take some time to stabilise. This can vary between particular electrodes. It’s
recommended to calibrate and take readings after the same time. That way, the response
will hit the same point in time. The values may drift further but being consistent with the
time will give consistent calibrations and readings.
PASCO has released the water quality colourimeter and the EZ-Sample test kits as a
considerably easier method of making individual samples than the electrodes. While it does use
consumables, it is recommended considering this alternative if your own skills and knowledge of chemistry tests and
preparation of standards is limited.
CI-6726 Carbon Dioxide Ion Selective Probe
For measurement of dissolved carbon dioxide, this is probably the hardest of all the ion specific
electrodes to maintain. The Water quality colourimeter and EZ-Sample test kit is strongly recommended as an alternative.
•
These electrodes do not age well.
•
Do NOT use a magnetic stirrer. The use of a magnetic stirrer can cause increases in
temperature and inaccurate voltage measurements due to insufficient grounding.
•
Verify that there are no interfering ions in the solution. These include formic acid, acetic
acid, sulphur dioxide and nitrogen dioxide
•
Prior to calibration, soak the electrode for 5 minutes in distilled water then for 5 minutes in
the CO2 standard solution. Full notes on making standards are included in the manual.
•
Check that the tip has been filled with the filling solution and the membrane for holes.
Change filling and/or membrane if problems persist.
•
Hold the probe at around 20o to the vertical to minimise air bubbles that can occur when
holding it vertically.
•
Make sure all standards and solutions are at the same temperature. There is a 2% error for
every 10 C difference in temperature.
•
Refer to the manual for calibration standards and run a 2-point calibration as detailed for
pH.
CI-6727 Calcium Ion Selective Electrode
Calibration standards are available through PASCO. See Tech Note 422 for details.
Store dry for Long Term storage. For short term storage, store in 100ppm calcium standard
(0.030g of CaCl2.H2O per litre of water).
Rinse with distilled water after use. Note that calcium complexes are not detected. Keep the
concentration of SO4 below 50 ppm and of CO4/HCO4 below 280 ppm.
Please also refer to the electrode manual for measurement hints and techniques.
CI-6728 Fluoride Ion Selective Electrode
Calibration standards are available through PASCO. See Tech Note 422 for details.
Please also refer to the electrode manual for measurement hints and techniques.
CI-6732 Chloride Ion Selective Electrode
Calibration standards are available through PASCO. See Tech Note 422 for details.
Please also refer to the electrode manual for measurement hints and techniques.
CI-6733 Potassium Ion Selective Electrode
Calibration standards are available through PASCO. See Tech Note 422 for details.
A slow or sluggish response may indicate surface contamination of the potassium electrode
membrane. Soak the electrode in distilled water for about 5 minutes to clean it and then rinse it
in diluted standard solution.
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There are a wide range of cations that interfere with the potassium electrode if present in high
enough levels. Refer to the manual for a full list and the respective concentrations at which they
may interfere.
Provided that the temperature of a solution has equalised, the electrode can be used between 0
and 40 C and for short times between 40 - 50 C. Room temperature measurements are however
recommended.
Upper limit for detection in pure potassium chloride solutions is 0.1M
For long term storage, store dry with the rubber cap over the tip. For short periods the electrode
can be stored in 1.0 x 10-2M potassium standard.
Please also refer to the electrode manual for further measurement hints and techniques.
CI-6734 Sodium Ion Selective Electrode
Calibration standards are available through PASCO. See Tech Note 422 for details.
Some cations will cause interference in present in high enough levels. The electrode manual has
a full list including the respective concentrations at which they may interfere.
The upper limit of detection in pure sodium solutions is 1 M. This is reduced to 10-1 M in the
presence of other ions. The electrode response is greatly influenced by the pH of the solution at
low levels of sodium ions.
The electrode should be stored in sodium electrode strorage solution, NEVER in air or water. For
long term storage, rinse and dry the sensing glass and cover the glass tip with the protective cap
shipped with the electrode.
If readings appear unstable, soak overnight in the electrode storage solution and allow solutions
to come to room temperature before measurement.
Please also refer to the electrode manual for measurement hints and techniques.
CI-6735 Nitrate Ion Selective Electrode
Calibration standards are available through PASCO. See Tech Note 422 for details. They can also
be prepared as follows:
Ionic Strength Adjuster (ISA) , 2 M (NH4) 2SO4
•
To prepare this solution, half fill a 1 litre volumetric flask with distilled water and add 264
grams of reagent-grade ammonium sulfate, (NH4) 2SO4. Swirl the flask gently to dissolve the
•
•
•
solid. Fill the flask to the mark with distilled water, cap, and upend several times to mix the
contents. ISA is added at the rate of 2 ml of ISA to each 100 ml of standard or sample to
adjust the ionic strength to about 0.12 M.
Reference Filling Solution, 0.l M (NH4) 2SO4 /0.0l M KCl
Nitrate Standard, 0.1 M NaNO3
To prepare this solution, add 8.50 grams of reagent-grade sodium nitrate to a one litre
volumetric flask about half full of distilled water. Swirl the flask gently to dissolve the solid.
Fill to the mark with distilled water, cap, and upend several times to mix the solution.
-1
Nitrate Standard, 1,000 ppm NO 3
To prepare this solution, add 1.37 grams of reagent-grade sodium nitrate to a one litre
volumetric flask about half full with distilled water. Swirl the flask gently to dissolve the
solid. Fill to the mark with distilled water, cap, and upend several times to mix the solution.
•
-1
Nitrate Standard, 100 ppm NO 3
To prepare this solution, add 0.61 grams of reagent-grade sodium nitrate to a one litre
volumetric flask about half full with distilled water. Swirl the flask gently to dissolve the
solid. Fill to the mark with distilled water, cap, and upend several times to mix the solution.
Certain anions can cause interference, malfunction, drift or measurement errors if present in high
enough levels. Refer to the manual for a full list and the relevant concentrations at which they
may cause interference. Interferences such as chloride, bromide, iodide and cyanide can be
removed by precipitation with 0.5 g of silver sulphate added to 100mL of the sample. Nitrite
interference can be removed by adding 0.3 g of sulphamic acid to 100 mL of sample.
The electrode should be stored dry for long term storage, covered with the protective cap
shipped with the electrode. For short term storage, store in 10-2 M nitrate solution.
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Soak in nitrate standard if readings appear unstable and check that the electrode is filled with
reference solution. Allow solutions to come to room temperature and stabilise before
measurement.
Please also refer to the electrode manual for measurement hints and techniques.
CI-6736 Lead Ion Selective Electrode
Calibration standards are available through PASCO. See Tech Note 422 for details.
A surface layer of silver metal cam be formed on the electrode by strongly reducing solutions.
Polish the electrode with a smooth polishing paper, wet with a few drops of distilled water to
restore performance. Rinse after polishing.
The electrode membrane can be “poisoned” by solutions containing copper, mercury or silver.
Ensure that these are not present in any sample to be tested. A wide variety of other
interferences are possible. Please refer to page 10 of the manual for further quite extensive
advice.
For long term storage, dry the sensing pellet and cover the membrane tip with the protective
cap shipped with the electrode. For short periods during the school term, the electrode can be
stored in 1 x 10-2 M lead solution.
Please also refer to the electrode manual for measurement hints and techniques.
•
Chemistry Sensor ( PS-2170 )
The Chemistry sensor combines pH, temperature, voltage and pressure. If pH and temperature
are simultaneously submerged in the same conductive liquid (eg tap water) then a ground loop
or conductive interference can occur between the sensors. This can result in changes in sensor
readings when another sensor is placed within the same solution. Using a USB Link, SPARKLink or
other device without an external power adaptor eliminates this effect.
Please also refer to the notes on calibration and care of pH electrodes (pH Sensor ( PS-2102 )), ORP electrodes and ion specific
electrodes.
Electricity/Magnetism
•
Magnetic Field Sensor ( PS-2112 )
The sensor must be powered up for at least 240 seconds for best resolution.Any measurement of
magnetic field will include any surrounding magnetic fields including that of the Earth. Where
absolute measurements are required the Zero Gauss Chamber (EM-8652) is recommended for
zeroing the sensor. Alternatively, place the sensor away from strong or alternating sources of
magnetic field, orientate it so the magnetic field axis measurements of interest are a minimum
along the measurement axis and press the tare button.
•
2-Axis Magnetic Field Sensor ( PS-2162 )
The sensor must be powered up for at least 240 seconds for best resolution.Any measurement of
magnetic field will include any surrounding magnetic fields including that of the Earth. Where
absolute measurements are required the Zero Gauss Chamber (EM-8652) is recommended for
zeroing the sensor. Alternatively, place the sensor away from strong or alternating sources of
magnetic field, orientate it so the magnetic field axis measurements of interest are a minimum
along the measurement axis and press the tare button.
•
1 MHz 2-Channel Voltage Sensor ( PS-2190 )
Requires an Xplorer GLX or 850 Universal for full 1 MHZ sampling speeds. Sampling with other
PASPort interfaces is restricted to 1 kHz.
Force
•
Force Sensor ( PS-2104 )
The PASCO force sensors employ four strain gauges epoxied to a binocular dual-beam made
from annealed aluminium. The strain gauges are wired to form a full bridge circuit driven by a
constant voltage source. The voltage across the bridge circuit is proportional to the applied force.
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If the beam is over stressed the sensor will fail. Forces over 100 N should be avoided!
•
High Resolution Force Sensor ( PS-2189 )
The PASCO force sensors employ four strain gauges epoxied to a binocular dual-beam made
from annealed aluminium. The strain gauges are wired to form a full bridge circuit driven by a
constant voltage source. The voltage across the bridge circuit is proportional to the applied force.
If the beam is over stressed the sensor will fail. Forces over 100 N should be avoided!
Some of the first release of this sensor had a faulty datasheet. Please contact us to get them
updated.
Gases
•
Dissolved Oxygen Sensor ( PS-2108 )
Much of the difficulty in using the dissolved oxygen sensor comes from over care and maintenance. For
school use this can be considerably simplified. This will give reasonable comparative results. For absolute
results it is recommended that the calibration procedures outlined in the manual be followed.
Before attempting any measurements, allow the dissolved oxygen sensor to warm up by connecting it
to an interface and leaving it for a few minutes. Make sure that the electrode is active by checking that
the computer, airlink or datalogger is turned on.
Never leave the DO electrode stationary in a solution or sample. The electrode uses a small amount of
the dissolved oxygen during operation and left in one place results will drift. Use a magnetic stirrer set
on low, gently stir or otherwise ensure there is a gentle flow of the sample around the electrode.
It’s quite ok, and can be expected, to get results where a % DO is greater than 100%. In areas where
algae are actively producing oxygen, for example, areas of super saturation will occur where the oxygen
hasn’t had time to evenly dissolve through the water. Bubbles coming up against the tip can give similar
high results. Ideally a series of measurements over a period of time in one location should be taken and
the average value used although this isn’t always practical on school trips.
Always measure on site. The amount of dissolved oxygen a sample can hold is effected by temperature,
barometric pressure, water composition and of course by the moving and shaking of the sample itself.
Never ask students to bring samples to school as the results will be far from that of the original sample.
Calibration
•
•
•
•
•
•
DO should always be calibrated on the day and for water of similar composition to what it
is intended to test. In a day where sampling moves from, say, fresh water to salt then
calibrations should be done for both types of water at the time they are to be measured.
For higher level studies measurement in mg/L and correction for temperature and
barometric pressure is recommended. For standard school studies, calibration and
measurement in %DO is quite adequate for good, comparative results and can give results
within 1-2%.
Calibration is done based on a single point. Refer to the step by step instructions on
calibration for your device referred to in the details for the pH sensor.
In the relevant calibration screen choose calibration by % dissolved oxygen - the drop
down defaults to mg/L. Change this by selecting the % option from the drop down menu.
The software will automatically choose a single point calibration method and suggest a
default value of 100% .
Put about 4-5 mm of water of similar composition to the samples to be tested (eg salty for
sea water) in the storage bottle supplied and screw it on to the electrode.
Turn the electrode upside down and make sure the top of the tip is in the air space above
the water.
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•
•
Give the electrode a good shake for about 20 seconds or so. This will super saturate the air
space above the tip with water vapour, making it equivalent to 100% DO at the prevailing
temperature and barometric pressure.
Give the electrode a tap to make sure there is no water resting on the top and then quickly
click or tap “Read from Sensor” in your software or device. Then click OK. As the electrode
will use oxygen from the sample and the water vapour will drop out of suspension it’s
important that the calibration be completed as quickly as possible.
Test your calibration while still holding the electrode upside down by taking a measurement. You
should see the %DO changing and gradually decreasing. If there is no change follow the maintenance
notes below. if the electrode is still unresponsive please contact us to organise a return for further
testing.
Maintenance
Only carry out a change in membrane if the electrode is unresponsive after being connected for several
minutes.
If a sensor is not responding check the electrode as follows:
Unscrew the tip of the electrode about half a turn or so. Check whether the orange O-Ring sealing the
tip is visible. If not, it’s highly likely that it’s missing and the electrode filling solution will have leaked out.
Unscrew the tip the rest of the way and empty any remaining filling solution out of the tip. Hold the tip
up to the light and look down through it to the membrane. Check it for holes and tears.
if the membrane is torn it will need replacing. A black plastic membrane replacement tool shipped with
the electrode along with one of the standard membranes. Push the old membrane out with the tool
and slip the new one into place, using the tool to gently push it back to the top of the tip while taking
care not to tear the new membrane.
Refill the tip with solution using the syringe provided from the bottle provided. Trickle it down the side
of the tip and overfill so once screwed back on you can be sure that there are no bubbles in the tip.
Screw the tip back on, calibrate and test.
Should you have use the standard membrane replacement supplied, please contact us for
replacements. For school use we recommend ordering the low cost replacement tips (PS-2562 - pack of
2) and the corresponding replacement membranes (PS-2561 - pack of 25). They are considerably
cheaper and give adequate results for schools.
After a days use, leave the electrode immersed in clean water over night to flush out any impurities and
store with the electrode storage bottle in place.
If the electrode becomes unresponsive after maintenance, please contact us to organise a return for
further testing.
•
Carbon Dioxide Gas Sensor ( PS-2110 )
View a video on the use of the Carbon Dioxide Gas Sensor at http://www.youtube.com/watch?v=nLKHYkho26M
Calibration of the PS-2110 Carbon Dioxide Gas Sensor is not required for most activities, as the sensor is
factory calibrated. Over time, the sensor’s characteristics may change. To restore the sensor to its factorycalibrated state, perform the calibration in typical outside air conditions (around 400- 450 ppm CO2).
Perform a single point calibration:
•
Go outside and collect a sample of fresh air(400to450ppmCO2).
•
Insert the probe with stopper and sensor assembly into the up right sampling bottle. Be
sure the stopper fits snugly into the neck of the bottle.
•
Bring the sensor/bottle assembly inside and connect it to a PASPORT interface. Observe the
carbon dioxide reading. Wait at least 90 seconds for the reading to stabilise.
•
Press the Calibrate button on the sensor and hold for 3 seconds.
The green light will stay on to indicate calibration has begun.
•
Wait approximately one minute. When the green light flashes
again, calibration is finished.
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•
•
To verify the calibration, observe the sensor’s reading in your software or data logger
screen. The reading should be stable at approximately 400 ppm (±50 ppm).
If the sensor’s reading drifts or seems too high or low, recalibrate.
Use the supplied sampling bottle to collect air samples, such as an atmospheric sample or the CO2 gas
produced from germinating seeds. [Note: Do not try to remove the probe (sensing tube). The probe is not removable.]
•
Ethanol Sensor ( PS-2194 )
Measurement
•
•
•
Ensure that the Teflon membrane is intact and not discolored.
Place the end of the probe just above a solution, or in a gas, containing less than 3% ethanol.
Click the Start button to begin recording data.
The sensor works as when a metal oxide such as alumina is heated to a sufficiently high temperature while
exposed to air, oxygen from the air is absorbed on the surface of the metal oxide, transferring negative charge
to the oxygen and leaving a positively charge surface barrier to electron flow at each grain boundary in the
metal oxide.
Many solvent vapors (such as ethanol) act as reducing agents for this absorbed oxygen, decreasing the charge
barriers and making it easier for electrons to flow past the grain boundaries. The conductivity of the metal
oxide is related to the concentration and chemical composition of the reducing gas
Any of the following solvent vapors will significantly reduce the metal oxide:
Xylene
Toluene
n-Heptane
Benzene
Ethanol
Acetone
Hydrogen
Methyl Mercapatan
Iso-Butane
Formaldehyde
Trimethlamine
Hydrogen Sulfide
Acetic Acid
Propionic Acid
Ammonia
Carbon Monoxide
Methane
Water Vapor
In addition, the sensor should be expected to be sensitive to chemically related solvent vapors.
Usage Notes
The teflon membrane is designed to prevent the sensing element from getting wet. If the sensing element
accidentally gets wet, rinse and dry it quickly. The probe may be degraded or destroyed if the membrane is
ruptured or compromised. Do not immerse the probe. Replace a damaged teflon membrane immediately.
Calibration data is stored in the sensor’s memory until the sensor is calibrated again, even if the sensor is
unplugged from the interface.
Avoid exposure to concentrations in excess of 3% for any of the vapors to which it is sensitive
silicone vapors
corrosive vapors (H2S, SOx, Cl2, HCl,...)
salts
liquid water
high pressures
high-temperatures
high-humidity
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air flow
Calibration (for Ethanol measurements)
Calibration data is retained in memory on the sensor, so regular calibration shouldn’t be needed. If you
suspect calibration is required the following method can be used.
Material
•
1% ethanol in water at the same temperature as the solutions to be measured.
•
Procedure
•
Ensure that the membrane is installed and intact. (If not, refer to the manual for membrane
replacement.)
•
Ensure that the measurement environment has a fairly constant temperature and humidity.
•
Power on the sensor for ~10 minutes before use.
•
Connect the sensor to an interface.
•
Place the probe either in a sealed container above the 1% ethanol solution. Do not
immerse the probe. Avoid getting the probe wet.
•
Wait until the reading stabilises.
•
Press and hold the 1% CAL button on the sensor for at least 4 seconds. (Immediately after a
successful calibration, the sensor’s output reads 1%, and the button is illuminated.)
Storage
The sensor should be stored in a sealed polyethylene bag with clean air at ambient humidity. Do not use silica
gel or store in any bag with a perceptible odor, such as a bag made of PVC, the vapours from which can effect
the sensor.
•
Oxygen Gas Sensor ( PS-2126A )
View a video on the use of the Oxygen Gas Sensor at http://www.youtube.com/watch?v=nLKHYkho26M
The fuel cell probe included with the Oxygen gas sensor is a consumable and will wear out. It was
updated in 2011 to a longer lasting unit (PS-2126A). The most common issue with the sensor is
exhaustion of the fuel in the probe. The probe itself has a two year warranty, distinct from the 5 year
warranty on the sensor itself. In normal school type use the new probe can be expected to last for 5-6
years provided it is stored and used correctly. The older probe can be expected to last up to 3 years
under normal use and when following the storage instructions below. It has a 1 year warranty.
The PASCO oxygen gas sensor has a range of 0-100% compared with competitor’s ranges of less than
27% and as the probe is not contained within the sensor, only the probe needs to be replaced.
If the Oxygen gas sensor reports < 18% oxygen concentration before calibration in ambient outdoor air,
it is a good indication that the probe needs to be replaced. Please follow the steps in the calibration
procedure below to determine whether the probe needs to be replaced prior to ordering to avoid
unnecessary replacement costs.
Calibration
•
•
•
•
•
•
•
•
•
Remove the protective pink tape from oxygen gas sensing probe.
Thread the deflector onto end of the probe.
Attach the probe to the blue PS-2126(A) sensor box.
Connect the sensor to a powered PASPort interface.
Place the sensor in a well-ventilated environment either indoors or outdoors, but away
from sources of CO2 such as motor vehicle exhaust or animal breath.
Monitor the oxygen concentration.
If the concentration stabilises within +/- 0.5 % of a value between 18 - 23% (~ 20 seconds),
press the CAL (20.9%) button on the sensor and hold it for 3 seconds. (The green light will
flash on and off for 4 seconds, indicating that calibration is in progress. After 4 seconds, the
reading should stabilise at 20.9%.)
If the oxygen sensor does not read >18.0% oxygen concentration, please contact us at
Cider House Tech to order to a new probe.
If the oxygen sensor still does not read >18.0% oxygen concentration and the sensor is
within the 5-year warranty, contact Cider House Tech for review.
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v1.1, July 2012
Viability
The probe included with the PS-2126 is expected to last 1-3 years under normal use and is warranted by
the manufacturer for 1 year.
The probe included with the PS-2126A, which is also compatible with the PS-2126, is expected to last
5-6 years under normal use and is warranted by the manufacturer for 2 years. A replacement probe can
be purchased as the PS-6524 Oxygen Sensor Replacement Electrode.
Compatibility
Probes from PS-2126 and PS-2126A Oxygen Gas sensors are interchangeable. There is no need to buy a
new sensor in order to use the newer and longer lasting probe.
Storage
To extend the shelf life of the probe:
•
Store the original probe uncovered in a refrigerator
•
Store the newer probe covered with the protective pink tape and in the refrigerator .
Optimal storage temperature is 5 - 25 C.
GPS
•
GPS Position Sensor ( PS-2175 )
Note that the GPS sensor needs a clear “site” of the sky to get a good signal. Just like the GPS in
your car a fix may take a few minutes under worst case conditions. Sample rates for the GPS
should be left at the default values. Fast values, like those required for amusement parks, are not
possible with a GPS. Use an acceleration sensor instead.
Light
•
Infrared Light Sensor ( PS-2148 )
You do need to point the sensor at the object to be measured!
Motion
•
•
Motion Sensor ( PS-2103A )
While the PASPort sensor has a greater range and shorter dead zone than the industry standard,
there is a short dead zone of 15cm before it will start measuring. Certain objects like golf balls
scatter the signal and are very difficult to measure. Smooth surfaced objects are best.
The sensor includes a thermistor that automatically adjusts for changes in temperature effecting
the speed of sound.
GPS Position Sensor ( PS-2175 )
Note that the GPS sensor needs a clear “site” of the sky to get a good signal. Just like the GPS in
your car a fix may take a few minutes under worst case conditions. Sample rates for the GPS
should be left at the default values
pH
•
pH Sensor ( PS-2102 )
The electrode supplied with the PASCO pH sensors is gel-filled - it doesn’t matter if it dries out
and it can actually prolong it’s life if allowed to dry out when stored for extended periods. Small
plastic extensions protect the glass bulb from being scratched but it should be noted that this
also tends to hold some solution around the bulb - gentle stirring either manually or via a
magnetic stirrer is recommended.
A video on calibration of the pH sensor with SPARKVue can be viewed at http://www.youtube.com/watch?v=fUKL8sDiCy4
Cleaning
For most applications, hot water with domestic cleaning detergent can be used for cleaning.
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v1.1, July 2012
For lime and other hydroxide containing solutions, clean with a 5-10% solution of hydrochloric
acid. For solutions containing organic fouling agents (fats, oils, etc.), clean probe with limonene
or acetone. For algae and bacteria containing solutions, clean probe with a chlorine bleach
containing liquid.
Storage
During term, clean and immerse the pH electrode in the soaker bottle filled with pH 4
buffer solution that contains 1 g of potassium chloride (KCl) per 100 mL of solution.
Alternatively, pH electrode storage solution and standard calibration solutions may also
be obtained from various chemical suppliers.
** Storing the electrode in distilled water will decrease the life of the electrode.
Long-term: Clean and dry the probe. One to two days before you wish to use it again,
restore the probe by soaking it alternately into 0.1 M HCl and 0.1 M NaOH solutions for
two minutes each. Repeat once. Following that, soak in a pH 4.0 buffer solution until
use. If this restoring procedure fails to improve the responsiveness of the electrode, it
should be replaced.
Warranty/ Expected Life
The pH electrode's that PASCO carries are covered by a 1 year manufacturer warranty, not the 5
years of the sensor box itself. The pH sensor should be replaced when it becomes unresponsive
after cleaning and restoration. pH sensor life is around 5 years or more in a typical educational
environment.
Calibration
While PASCO runs an approximate factory calibration prior to shipping, all electrodes age over
time. This means that calibration is required, depending upon the accuracy of result required. We
generally suggest that:
Junior classes requiring comparative results do not need to calibrate.
Senior classes requiring reasonable absolute values should calibrate at least once per semester
and always after restoration. Ideally, this should be every time but time constraints may make this
difficult to fit in.
Extended investigations, particularly Extended Essays for the IB, should always include calibration.
The calibration for a pH sensor and other electrode based sensors is stored in the file with which
it’s calibrated. This allows easy restoration and transfer of calibration settings without the risk of
accidentally applying a calibration different to that appropriate at the time.
Calibration files can be named with an identifier matching the sensor/electrode pair and placed
in a convenient place on the school network or device for students to open and restore a prior
calibration. Calibration file and sensor/electrode combination go together - save and mark them with appropriate
identification if prior calibrations are to be used.
When calibrating make sure that the pH electrode is not still. A gentle flow of solution across the
electrode is required.
Procedure in DataStudio
1.
2.
3.
4.
5.
6.
7.
8.
9.
Connect a PASPort interface to the computer via a USB cable or Bluetooth (in the case of
the AirLinks).
Connect a PASPort sensor with a well-maintained pH electrode to the PASPort interface.
Click the Setup button in DataStudio.
In the Experiment Setup window, click the Calibrate Sensors... button.
Enter the first known pH buffer value in the Calibration Point 1 Standard Value text box.
Rinse and dry the pH probe.
Place the pH probe in the corresponding buffer solution, stirring gently.
Stir the pH sensor until the value Present Sensor Measurement value stabilises (about 3
seconds).
Click the Read from Sensor button.
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10.
11.
12.
13.
14.
15.
16.
Place the pH sensor in the second pH buffer solution.
Enter the second known pH buffer value in the Calibration Point 2 Standard Value text
box.
Rinse and dry off the pH sensor.
Place the pH Sensor in the second buffer solution.
Stir the pH sensor until the value Present Sensor Measurement value stabilises.
Click the Read from Sensor button.
Click OK. Save the file with an appropriate name if you wish to use the calibration on
later occasions.
Procedure Using the XPlorer GLX
1.
Connect a PASPort sensor with a well-maintained pH electrode to any sensor port of the
Xplorer GLX.
2.
Go to Home/Sensors/Sensors/Calibrate (3).
3.
Enter the first known pH buffer value in the Pt 1 (pH) text box.
4.
Rinse and dry the pH probe.
5.
Place the pH probe in the corresponding buffer solution, stirring gently.
6.
Stir the pH sensor until the pH value displayed at the bottom of the screen stabilises
(about 3 seconds).
7.
Click the Read Pt 1 button (F3).
8.
Place the pH sensor in the second pH buffer solution, stirring gently.
9.
Press the down arrow until you see Pt 2 (Units).
10. Enter the second known pH buffer value in the Pt 2 (pH) text box.
11. Rinse and dry off the pH sensor.
12. Place the pH Sensor in the second buffer solution.
13. Stir the pH sensor until the pH value displayed at the bottom of the screen stabilises.
14. Click the Read Pt 2 button (F4).
15. Click OK.
16. Save the file with an appropriate name if you wish to use the calibration on later
occasions.
Procedure Using the SPARK SLS or SPARKvue
1.
2.
3.
Connect a well-maintained pH electrode to one of the following PASPort sensor boxes:
PS-2102 PASPORT pH Sensor
◦
PS-2147 PASPORT Precision pH/ORP/ISE Amplifier with Temperature
◦
PS-2169 PASPORT Water Quality Sensor
◦
PS-2170 PASPORT Chemistry Sensor
◦
If you are using a SPARK SLS, connect the PASPort sensor box to the SPARK SLS.
If you are using SPARKvue, connect a PASPort sensor to any PASPort interface that is
connected to the computer via a USB cable.
4.
5.
6.
Press the Home button.
Select pH.
Click Show. (You will see a Graph display.)
7.
8.
9.
10.
11.
12.
Press the Experiment Tools Button:
.
Select CALIBRATE SENSOR.
In the Sensor field, select the sensor that has the pH probe attached.
In the Measurement field select pH.
Calibration Type should remain 2 point (Adjust Slope and Offset).
Click NEXT.
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13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
•
Enter the first known pH buffer value in the Standard Value box in the Calibration Point 1
section.
Rinse and wipe dry the pH probe.
Place the pH probe in the buffer solution corresponding to the value in the Standard
Value box.
Stir the pH sensor in the buffer solution for at least two seconds.
Click the Read From Sensor button.
Place the pH sensor in the second pH buffer solution.
Enter the second known pH buffer value in the Standard Value box in the Calibration
Point 2 section.
Rinse and wipe dry the pH probe.
Place the pH probe in the buffer solution corresponding to the value in the Standard
Value box.
Stir the pH sensor in the buffer solution for at least two seconds.
Click the Read From Sensor button. (The current file is now calibrated.)
Click OK twice to return to the graph display.
Save the file with an appropriate name if you wish to use the calibration on later
occasions.
High Precision pH/Temperature with ISE/ORP Amplifier ( PS-2147 )
The high precision pH sensor can give pH readings to a resolution of 0.01 with appropriate
calibration. It also supports ISE and ORP probes.
Refer to the notes for PS-2102 (above) on calibration and care of pH sensors and the earlier notes on ORP electrodes and ion
specific electrodes in this document under the previous reference to this sensor and oxidation reduction potential probes.
If pH and temperature are simultaneously submerged in the same conductive liquid (eg tap
water) then a ground loop or conductive interference can occur between the sensors. This can
result in changes in sensor readings when another sensor is placed within the same solution.
Using a USB Link, SPARKLink or other device without an external power adaptor eliminates this
effect.
•
Chemistry Sensor ( PS-2170 )
The Chemistry sensor combines pH, temperature, voltage and pressure. If pH and temperature
are simultaneously submerged in the same conductive liquid (eg tap water) then a ground loop
or conductive interference can occur between the sensors. This can result in changes in sensor
readings when another sensor is placed within the same solution. Using a USB Link, SPARKLink or
other device without an external power adaptor eliminates this effect.
Please also refer to the notes on calibration and care of pH electrodes (pH Sensor ( PS-2102 )), ORP electrodes and ion specific
electrodes.
•
Water Quality Sensor ( PS-2169 )
The water quality sensor combines measurement of dissolved oxygen, pH (with support for ORP
and ISE electrodes), conductivity and temperature on one multi-measure sensor. Please refer to the
specific notes on each individual sensor for tips and notes.
Avoid using the DO electrode on the water quality sensor at the same time as the other quantities on the water quality sensor in
the same solution.
Physiology
•
ECG Sensor ( PS-2111 )
Check that you are viewing "voltage", rather than "heart rate" or "heart rate count".
Check that the sampling rate is set at 200 Hz or greater.
Check that the patches have not expired. (The expiration date should be printed on the package
of the EKG patches.) Fresh patches may be purchased as CI-6620 EKG Patches.
Clean the skin where the patches will be applied and rub it with dry paper towel to remove
natural skin oils that would reduce electrical conductitivity.
Apply adhesive electrode patches to the right wrist, right forearm just below the elbow, and left
forearm just below the elbow.
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Press the patches firmly onto the skin.
Clip the EKG leads to the electrode patches as illustrated on the EKG sensor:
black: right wrist
green: right forearm
red: left forearm.
Arrange the leads so that they hang loosely without straining the patches.
Press the Start button to begin collecting data.
•
Respiration Rate Sensor ( PS-2133 )
The Respiration Rate Sensor provides excellent data before and after exercise. Combining the
Relative Pressure Sensor with a Respiration Belt, this sensor measures the change in pressure that
occurs as the chest cavity expands and contracts during breathing. The Respiration Belt is
wrapped around the chest and the rubber bladder inside the belt is inflated using the attached
squeeze bulb.
You can purchase the respiration rate belt separately if you already have the relative pressure
sensor. You can also use the relative pressure sensor from the respiration rate sensor separately as
needed.
Be careful not to over inflate the belt. High internal pressures make it difficult to measure the
change in pressure resulting from movement of the chest.
•
Spirometer ( PS-2152 )
Sensor ships with two mouth pieces. Additional mouth pieces available in packs of 10 for more
than $7 per mouth piece. Depending on a schools OH &S policies, mouth pieces can be reused
after suitable cleaning or sterilisation. There is a thin membrane inside the tube of the mouth
piece. Once this is broken, the mouth piece must be disposed of.
•
Goniometer Sensor ( PS-2137 )
The Goniometer can be connected to the knee, hip or elbow joints to measure angle changes
during a variety of movements using an angle sensor
The Goniometer Sensor includes one probe for measuring motion of a single joint. To measure a
second joint simultaneously, you will require an additional Goniometer probe and plug it into
the second port of your Goniometer Sensor.
Replacements belts are available for the sensor and come in a pack of two sizes.
The Angle sensor is also available for separate purchase as required.
•
Breath Rate Sensor ( PS-2187 )
The Breath Rate Sensor uses standard disposable dust masks and gives stable output even when
exercising. Breath rate is measured by sensing the pressure changes inside the mask. Tubing from
the sensor connects to the disposable pressure clips which fasten on the side of the mask.
The clips can be sterilised as required and are available for purchase from Cider House Tech.
While we also have the masks available, we recommend purchase of these from your local
hardware store where their economies of scale means that the masks may be considerably
cheaper. It is not recommended that these be reused.
•
Hand Grip Heart Rate Sensor ( PS-2186 )
This sensor replaced the ear clip heart rate sensor and provides more reliable data collection via
extra signal filtering and connection via two hand grips, like those of gym equipment. An
indicator light within the sensor is used to signal when no viable connection is sensed (amber),
when a connection is being established (green) and when a regular pulse is detected (red
flashing). While you can move with the sensor, please do not pull on the hand connection leads or unnecessarily
wave them around or the cable connection may be broken. The Exercise Heart Rate sensor is available for these
more robust activities.
Trouble shooting tips
Within a second or so of gripping the hand grips, the green acquiring light should turn on. If this
is not happening, check the following:
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v1.1, July 2012
•
•
•
There are 4 unbent pins on the cable connecting the hand grips to the blue sensor box.
The cable from the hand grips is fully inserted into the sensor box.
The protective transparent film has been peeled off of all four sides of the stainless-steel
hand grips.
•
You are gripping the electrodes with moderate pressure so that your hands are contacting
all four sides of the electrodes and your hands are not overly dry.
If the green acquiring light is on, but the amber red beats does not pulse please be patient. The
red beats light should begin to flash within 8-20 seconds after the green acquiring light turns on.
If the red light does not turn on after 30 seconds, clean the electrodes and slightly moisten your
hands and try again.
The best data will occur after about 60 seconds of the time of first acquisition so consider
excluding this early data if it suits the investigation. Otherwise a smoothing calculation may be
worth considering.
•
Blood Pressure Sensor ( PS-2207 )
Selection of a BP cuff of the appropriate size is necessary for accurate measurement of BP. The
use of a cuff that is too narrow results in an overestimation of BP, and a cuff that is too wide
underestimates BP. False high pressure readings may result when the cuff is too small. False low
pressure readings can result if the cuff is too large. A cuff with a bladder of an adequate size
capable of going around 80% of the arm is recommended. The following cuffs are available:
PS-2531 Blood Pressure Cuff (small)
PS-2532 Blood Pressure Cuff (standard) included with the sensor
PS-2533 Blood Pressure Cuff (large)
•
Wrap the cuff snugly around upper arm with the mark on the cuff directly placed over the
artery.
•
Measure baseline BP in both upper arms. Where there are significant differences in BP, use
the arm with the higher pressure.
•
The subject should be seated with back and arms supported, feet on floor, and legs
uncrossed, with the upper arm at heart level. Having the arm at a non-standard position
will result in a different result due to hydrostatic pressure.
•
Be sure that the subject stays still and quiet during the measurement.
•
Check that the leak rate is between 2 - 5 mmHg/min
Pressure
•
Chemistry Sensor ( PS-2170 )
The Chemistry sensor combines pH, temperature, voltage and pressure. If pH and temperature
are simultaneously submerged in the same conductive liquid (eg tap water) then a ground loop
or conductive interference can occur between the sensors. This can result in changes in sensor
readings when another sensor is placed within the same solution. Using a USB Link, SPARKLink or
other device without an external power adaptor eliminates this effect.
Please also refer to the notes on calibration and care of pH electrodes (pH Sensor ( PS-2102 )), ORP electrodes and ion specific
electrodes.
Soil Properties
•
Flat pH Electrode ( PS-2182 )
This is an optional electrode compatible with all PASCO pH sensors. It’s used for measuring the
pH of low moisture samples such as soil, cheese and other foods. Clean by rinsing after use.
Calibration can be performed using the same standards as the standard electrode.
•
Soil Moisture Sensor ( PS-2163 )
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The Soil Moisture Probe averages the volumetric water content over the entire length of the
probe, with a zone of influence of about 2 cm around the probe. The zone of influence is with
respect to the flat surface; there is little or no sensitivity at the edges of the probe.
When selecting a site for testing with the probe, it is important to remember that the soil
adjacent to the probe’s surface has the strongest influence on the sensor reading. Therefore, any
air gaps or excessive soil compaction around the probe can significantly affect the readings.
Because the probe has a gap between its prongs, it is also important to consider the size of the
media you are inserting the probe into. It is possible to get sticks, bark, roots, or other material
stuck between the probe prongs, which will adversely affect readings. Finally, be careful when
inserting the probe into dense soil, as the prongs will break if excessive sideways force is used
when pushing them in.
When removing the soil moisture probe from the soil, do not pull it out of the soil by the cable! Doing so
may break internal components and make the probe unusable.
When measuring please choose a soil type that matches the type being tested. This applies the
relevant calibration, stored within the software. You can also create a calibration curve for other
soil types by using several samples of known water concentration where you’re testing a soil that
doesn’t match the standard types available.
Spectrometry & Colorimetry
•
Colourimeter Sensor ( PS-2121 )
The PASPORT Colourimeter records 4 wavelengths simultaneously - blue, green, red and orange.
Digital circuitry handles the calculations, calibrations and adjustments automatically. Generally,
the best colour choice is the colour that gives the most contrast with the test solution eg red
light for a blue solution.
A sensor extension cable is included with the colourimeter for use when plugging directly into a
datalogger is not convenient. 5 cuvettes are included, additional cuvettes can be ordered as part
# PS-2509 in sets of 6. The original Science Workshop cuvettes are different.
Calibration is only required where absolute results are needed to allow for differences in
manufacture of the glass cuvettes or when previous poor calibration is suspected. This is stored
on the sensor for later use via a one button push operation:
To avoid errors when calibrating, do not use the Colourimeter around bright lights or with turbid solutions. Always close the lid
tightly before taking measurements. For accurate readings, fill the cuvette to the lid with sample.
To calibrate for 100% transmittance, insert a cuvette filled with distilled water into the cuvette
holder and tightly close the lid.
Press the green Calibration button on the sensor. The light illuminates to indicate calibration is in
progress.
Wait for the light to turn off and then remove the sample. The calibration for that cuvette is
complete.
•
Water Quality Colourimeter ( PS-2179 )
The PASPORT Water Quality Colourimeter is a variation on the standard colourimeter and is
designed specifically to support chemical analysis of water samples using PASCO's ezSample
Snap Vial water quality test kits. ezSample Snap Vials contain a pre-formulated reagent in a
vacuum sealed ampoule. The tip of the ampoule is scored so students simply place the ampoule
in their sample, snap the tip, and the ampoule fills instantly, mixing with the color-forming
reagent. The Water Quality Colourimeter analyses the solution and reports concentration.
The Water Quality Colourimeter is complete with built-in calibration curves to determine the
concentration of ions in the solution for the ions listed in the specifications. No further calibration
is usually required however a clear ampoule (supplied with each set of tests) can be used to
calibrate with the same single button process as the standard colourimeter should additional
accuracy be required. The calibration is stored on the sensor. Available ezSample snap vials, in
packs of 30, include:
Iron (EZ-2331)
Nitrate (EZ-2333A)
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Ammonia (EZ-2334)
Phosphate (EZ-2337)
Chlorine (EZ-2339)
Total Hardness (EZ-2338)
Alkalinity (EZ-2340)
Carbon Dioxide (EZ-2341)
An extension cable is supplied with the sensor.
Immediately after pressing the green calibration button with a clear calibration ampoule, the
transmittance should be 100.0 and the absorbance should read 0.000. There are two reasons for
this:
•
"0.0" concentration is outside the valid range for any of the tests.
•
The calibrations are based on the assumption that the test dyes are present and fully
developed, which may absorb some light even when the concentration of the ion of
interest is low.
It is also possible to get negative or otherwise erroneous values for the concentration during
measurement. Check the following:
•
The ampoules must be nearly full and free of air bubbles for both calibration and
measurement.
•
The concentration of the ion of interest being measured must be in the range of sensitivity
of the test.
•
The test kits have not expired.
•
The solutions were left to develop for an insufficient amount of time.
•
Sample spilled in the measurement chamber.
•
The colourimeter is functioning properly.
To verify that your system is performing properly, mix or test a standard solution of a
concentration that is in the recommended range of the test run a test measurement.
The range and shelf life of the EzSample tests can be found in Tech Note 1103
Water Quality
•
pH Sensor ( PS-2102 )
The electrode supplied with the PASCO pH sensors is gel-filled - it doesn’t matter if it dries out
and it can actually prolong it’s life if allowed to dry out when stored for extended periods. Small
plastic extensions protect the glass bulb from being scratched but it should be noted that this
also tends to hold some solution around the bulb - gentle stirring either manually or via a
magnetic stirrer is recommended.
A video on calibration of the pH sensor with SPARKVue can be viewed at http://www.youtube.com/watch?v=fUKL8sDiCy4
Cleaning
For most applications, hot water with domestic cleaning detergent can be used for cleaning.
For lime and other hydroxide containing solutions, clean with a 5-10% solution of hydrochloric
acid. For solutions containing organic fouling agents (fats, oils, etc.), clean probe with limonene
or acetone. For algae and bacteria containing solutions, clean probe with a chlorine bleach
containing liquid.
Storage
During term, clean and immerse the pH electrode in the soaker bottle filled with pH 4
buffer solution that contains 1 g of potassium chloride (KCl) per 100 mL of solution.
Alternatively, pH electrode storage solution and standard calibration solutions may also
be obtained from various chemical suppliers.
** Storing the electrode in distilled water will decrease the life of the electrode.
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v1.1, July 2012
Long-term: Clean and dry the probe. One to two days before you wish to use it again,
restore the probe by soaking it alternately into 0.1 M HCl and 0.1 M NaOH solutions for
two minutes each. Repeat once. Following that, soak in a pH 4.0 buffer solution until
use. If this restoring procedure fails to improve the responsiveness of the electrode, it
should be replaced.
Warranty/ Expected Life
The pH electrode's that PASCO carries are covered by a 1 year manufacturer warranty, not the 5
years of the sensor box itself. The pH sensor should be replaced when it becomes unresponsive
after cleaning and restoration. pH sensor life is around 5 years or more in a typical educational
environment.
Calibration
While PASCO runs an approximate factory calibration prior to shipping, all electrodes age over
time. This means that calibration is required, depending upon the accuracy of result required. We
generally suggest that:
Junior classes requiring comparative results do not need to calibrate.
Senior classes requiring reasonable absolute values should calibrate at least once per semester
and always after restoration. Ideally, this should be every time but time constraints may make this
difficult to fit in.
Extended investigations, particularly Extended Essays for the IB, should always include calibration.
The calibration for a pH sensor and other electrode based sensors is stored in the file with which
it’s calibrated. This allows easy restoration and transfer of calibration settings without the risk of
accidentally applying a calibration different to that appropriate at the time.
Calibration files can be named with an identifier matching the sensor/electrode pair and placed
in a convenient place on the school network or device for students to open and restore a prior
calibration. Calibration file and sensor/electrode combination go together - save and mark them with appropriate
identification if prior calibrations are to be used.
When calibrating make sure that the pH electrode is not still. A gentle flow of solution across the
electrode is required.
Procedure in DataStudio
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
Connect a PASPort interface to the computer via a USB cable or Bluetooth (in the case of
the AirLinks).
Connect a PASPort sensor with a well-maintained pH electrode to the PASPort interface.
Click the Setup button in DataStudio.
In the Experiment Setup window, click the Calibrate Sensors... button.
Enter the first known pH buffer value in the Calibration Point 1 Standard Value text box.
Rinse and dry the pH probe.
Place the pH probe in the corresponding buffer solution, stirring gently.
Stir the pH sensor until the value Present Sensor Measurement value stabilises (about 3
seconds).
Click the Read from Sensor button.
Place the pH sensor in the second pH buffer solution.
Enter the second known pH buffer value in the Calibration Point 2 Standard Value text
box.
Rinse and dry off the pH sensor.
Place the pH Sensor in the second buffer solution.
Stir the pH sensor until the value Present Sensor Measurement value stabilises.
Click the Read from Sensor button.
Click OK. Save the file with an appropriate name if you wish to use the calibration on
later occasions.
Procedure Using the XPlorer GLX
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v1.1, July 2012
1.
Connect a PASPort sensor with a well-maintained pH electrode to any sensor port of the
Xplorer GLX.
2.
Go to Home/Sensors/Sensors/Calibrate (3).
3.
Enter the first known pH buffer value in the Pt 1 (pH) text box.
4.
Rinse and dry the pH probe.
5.
Place the pH probe in the corresponding buffer solution, stirring gently.
6.
Stir the pH sensor until the pH value displayed at the bottom of the screen stabilises
(about 3 seconds).
7.
Click the Read Pt 1 button (F3).
8.
Place the pH sensor in the second pH buffer solution, stirring gently.
9.
Press the down arrow until you see Pt 2 (Units).
10. Enter the second known pH buffer value in the Pt 2 (pH) text box.
11. Rinse and dry off the pH sensor.
12. Place the pH Sensor in the second buffer solution.
13. Stir the pH sensor until the pH value displayed at the bottom of the screen stabilises.
14. Click the Read Pt 2 button (F4).
15. Click OK.
16. Save the file with an appropriate name if you wish to use the calibration on later
occasions.
Procedure Using the SPARK SLS or SPARKvue
1.
2.
3.
Connect a well-maintained pH electrode to one of the following PASPort sensor boxes:
PS-2102 PASPORT pH Sensor
◦
PS-2147 PASPORT Precision pH/ORP/ISE Amplifier with Temperature
◦
PS-2169 PASPORT Water Quality Sensor
◦
PS-2170 PASPORT Chemistry Sensor
◦
If you are using a SPARK SLS, connect the PASPort sensor box to the SPARK SLS.
If you are using SPARKvue, connect a PASPort sensor to any PASPort interface that is
connected to the computer via a USB cable.
4.
5.
6.
Press the Home button.
Select pH.
Click Show. (You will see a Graph display.)
7.
8.
9.
10.
11.
12.
13.
Press the Experiment Tools Button:
.
Select CALIBRATE SENSOR.
In the Sensor field, select the sensor that has the pH probe attached.
In the Measurement field select pH.
Calibration Type should remain 2 point (Adjust Slope and Offset).
Click NEXT.
Enter the first known pH buffer value in the Standard Value box in the Calibration Point 1
section.
Rinse and wipe dry the pH probe.
Place the pH probe in the buffer solution corresponding to the value in the Standard
Value box.
Stir the pH sensor in the buffer solution for at least two seconds.
Click the Read From Sensor button.
Place the pH sensor in the second pH buffer solution.
Enter the second known pH buffer value in the Standard Value box in the Calibration
Point 2 section.
Rinse and wipe dry the pH probe.
14.
15.
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17.
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21.
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Place the pH probe in the buffer solution corresponding to the value in the Standard
Value box.
22. Stir the pH sensor in the buffer solution for at least two seconds.
23. Click the Read From Sensor button. (The current file is now calibrated.)
24. Click OK twice to return to the graph display.
25. Save the file with an appropriate name if you wish to use the calibration on later
occasions.
Dissolved Oxygen Sensor ( PS-2108 )
Much of the difficulty in using the dissolved oxygen sensor comes from over care and maintenance. For
school use this can be considerably simplified. This will give reasonable comparative results. For absolute
results it is recommended that the calibration procedures outlined in the manual be followed.
Before attempting any measurements, allow the dissolved oxygen sensor to warm up by connecting it
to an interface and leaving it for a few minutes. Make sure that the electrode is active by checking that
the computer, airlink or datalogger is turned on.
Never leave the DO electrode stationary in a solution or sample. The electrode uses a small amount of
the dissolved oxygen during operation and left in one place results will drift. Use a magnetic stirrer set
on low, gently stir or otherwise ensure there is a gentle flow of the sample around the electrode.
It’s quite ok, and can be expected, to get results where a % DO is greater than 100%. In areas where
algae are actively producing oxygen, for example, areas of super saturation will occur where the oxygen
hasn’t had time to evenly dissolve through the water. Bubbles coming up against the tip can give similar
high results. Ideally a series of measurements over a period of time in one location should be taken and
the average value used although this isn’t always practical on school trips.
Always measure on site. The amount of dissolved oxygen a sample can hold is effected by temperature,
barometric pressure, water composition and of course by the moving and shaking of the sample itself.
Never ask students to bring samples to school as the results will be far from that of the original sample.
Calibration
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DO should always be calibrated on the day and for water of similar composition to what it
is intended to test. In a day where sampling moves from, say, fresh water to salt then
calibrations should be done for both types of water at the time they are to be measured.
For higher level studies measurement in mg/L and correction for temperature and
barometric pressure is recommended. For standard school studies, calibration and
measurement in %DO is quite adequate for good, comparative results and can give results
within 1-2%.
Calibration is done based on a single point. Refer to the step by step instructions on
calibration for your device referred to in the details for the pH sensor.
In the relevant calibration screen choose calibration by % dissolved oxygen - the drop
down defaults to mg/L. Change this by selecting the % option from the drop down menu.
The software will automatically choose a single point calibration method and suggest a
default value of 100% .
Put about 4-5 mm of water of similar composition to the samples to be tested (eg salty for
sea water) in the storage bottle supplied and screw it on to the electrode.
Turn the electrode upside down and make sure the top of the tip is in the air space above
the water.
Give the electrode a good shake for about 20 seconds or so. This will super saturate the air
space above the tip with water vapour, making it equivalent to 100% DO at the prevailing
temperature and barometric pressure.
Give the electrode a tap to make sure there is no water resting on the top and then quickly
click or tap “Read from Sensor” in your software or device. Then click OK. As the electrode
will use oxygen from the sample and the water vapour will drop out of suspension it’s
important that the calibration be completed as quickly as possible.
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Test your calibration while still holding the electrode upside down by taking a measurement. You
should see the %DO changing and gradually decreasing. If there is no change follow the maintenance
notes below. if the electrode is still unresponsive please contact us to organise a return for further
testing.
Maintenance
Only carry out a change in membrane if the electrode is unresponsive after being connected for several
minutes.
If a sensor is not responding check the electrode as follows:
Unscrew the tip of the electrode about half a turn or so. Check whether the orange O-Ring sealing the
tip is visible. If not, it’s highly likely that it’s missing and the electrode filling solution will have leaked out.
Unscrew the tip the rest of the way and empty any remaining filling solution out of the tip. Hold the tip
up to the light and look down through it to the membrane. Check it for holes and tears.
if the membrane is torn it will need replacing. A black plastic membrane replacement tool shipped with
the electrode along with one of the standard membranes. Push the old membrane out with the tool
and slip the new one into place, using the tool to gently push it back to the top of the tip while taking
care not to tear the new membrane.
Refill the tip with solution using the syringe provided from the bottle provided. Trickle it down the side
of the tip and overfill so once screwed back on you can be sure that there are no bubbles in the tip.
Screw the tip back on, calibrate and test.
Should you have use the standard membrane replacement supplied, please contact us for
replacements. For school use we recommend ordering the low cost replacement tips (PS-2562 - pack of
2) and the corresponding replacement membranes (PS-2561 - pack of 25). They are considerably
cheaper and give adequate results for schools.
After a days use, leave the electrode immersed in clean water over night to flush out any impurities and
store with the electrode storage bottle in place.
If the electrode becomes unresponsive after maintenance, please contact us to organise a return for
further testing.
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Conductivity Sensor ( PS-2116A )
In general, conductivity offers a fast, reliable, nondestructive, inexpensive and durable means of
measuring the ionic content of a sample. Reliability and repeatability are usually excellent. Unlike
measurement with ion-selective electrodes, such as pH sensors, the response of a conductivity sensor
will not drift over time.
The principle drawback of conductivity is that it is not ion-selective, giving a reading proportional to the
combined effect of all ions present. In order to determine the amount of total dissolve solids, you must have
an idea of the ionic composition of the solution being measured. Conductance is the reciprocal of resistance,
and its basic unit is the Siemens [S], formerly called mho. Note that PASCO generally ships a 10x probe as standard with the
conductivity sensor. This means that all readings should be divided by 10 for actual values.
Operating Instructions
1.
2.
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4.
5.
6.
7.
8.
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Clean the electrode.
Soak the conductivity electrode in distilled or deionized water for 5 to 10 minutes.
Dry off the probe.
Immerse the probe in a calibration solution beyond the level of the holes on the electrode.
Tap the probe against the side of the vessel to remove any air bubbles trapped inside.
Monitor the conductivity while stirring the probe in the solution. Continue stirring until the value
stabilizes.
Calibrate the sensor if required (see note below!).
Rinse the conductivity probe with distilled or deionized water between samples.
Wipe dry.
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Temperature Effects
Conductivity has a substantial dependence on temperature. Temperature variation causes frequent problems
with conductivity measurements when the solution under testing has a rapid varying temperature. The
change in conductivity is virtually instantaneous.
Cleaning
The single most important requirement of accurate and reproducible results in conductivity measurement is a
clean cell. A dirty cell will contaminate the solution and cause the conductivity to change. Grease, oil,
fingerprints, and other contaminants on the sensing elements can cause erroneous measurements and
sporadic responses.
Cleaning Methods
1.
For most applications, hot water with domestic cleaning detergent can be used for cleaning.
2.
For lime and other hydroxide containing solutions, clean with a 5-10% solution of hydrochloric acid.
3.
For solutions containing organic fouling agents (fats, oils, etc.), clean probe with acetone.
4.
For algae and bacteria containing solutions, clean probe with a bleach containing liquid.
Clean cells by dipping or filling the cell with cleaning solution and agitating for two or three minutes. When a
stronger cleaning solution is required, try concentrated hydrochloric acid mixed into 50% isopropanol. Rinse
the cell several times with distilled or deionized water and remeasure the cell constant before use.
Storage
For short-term storage, leave the cell immersed in deionized water. Any cell that has been stored dry should
be soaked in distilled water for 5 to 10 minutes before use to assure complete wetting of the electrodes. If the
black platinized coating appears to be wearing or flaking off the electrodes or if the cell constant has changed
by 50%, the cell should be replaced or re-platinised.
Calibration
The conductivity sensor should not require calibration to obtain a value that is accurate to within 10%. To
obtain more accurate values, or verify that your conductivity probe is functioning to within specification,
please follow Tech Note 596
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Turbidity Sensor ( PS-2122 )
A video on using the Turbidity sensor with SPARKVue can be viewed at http://www.youtube.com/watch?
v=BAyY0UrJrLI&feature=plcp
The Turbidity Sensor measures light scattered at 90 degrees, the industry standard
(Nephelometric technique). Use of digital signal processing makes measurements extremely
accurate and repeatable. Calibration uses just two cuvettes and takes less than 15 seconds when
required for extra accuracy. An NTU standard, glass cuvettes and a sensor extension cable are
supplied with the unit. Extra cuvettes can be ordered in sets of 6 as part # PS-2509.
The NTU standard has a two year shelf life, after which it should be replaced for best results as
part # PS-2511.
Calibrating
Calibration is stored on the sensor and is gernally only required for extra accuracy when using
different cuvettes or when a poor previous calibration is suspected.
Shake the NTU calibration solution vigorously for 2-3 minutes and then let the solution rest for 5
minutes prior to calibration. This breaks up agglomerated particles. Gently invert the solution a
couple of times and is then ready to be used.
The Turbidity sensor requires a two-point calibration.:
Insert a cuvette filled with distilled water into the cuvette holder.
Close the lid tightly, so that light cannot enter the casing.
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Press the green Calibration button. Release the button. The light should turn on.
When the button light blinks, replace the cuvette with the 100NTU cuvette, close the lid, and
press and release the button.
When calibration is complete, the button light will turn off.
For accurate readings, fill the cuvette to the lid with at least 6 ml of sample and always close the lid tightly before measurements.
Do not use the Turbidity Sensor around bright lights.
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Water Quality Sensor ( PS-2169 )
The water quality sensor combines measurement of dissolved oxygen, pH (with support for ORP
and ISE electrodes), conductivity and temperature on one multi-measure sensor. Please refer to the
specific notes on each individual sensor for tips and notes.
Avoid using the DO electrode on the water quality sensor at the same time as the other quantities on the water quality sensor in
the same solution.
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Water Quality Colourimeter ( PS-2179 )
The PASPORT Water Quality Colourimeter is a variation on the standard colourimeter and is
designed specifically to support chemical analysis of water samples using PASCO's ezSample
Snap Vial water quality test kits. ezSample Snap Vials contain a pre-formulated reagent in a
vacuum sealed ampoule. The tip of the ampoule is scored so students simply place the ampoule
in their sample, snap the tip, and the ampoule fills instantly, mixing with the color-forming
reagent. The Water Quality Colourimeter analyses the solution and reports concentration.
The Water Quality Colourimeter is complete with built-in calibration curves to determine the
concentration of ions in the solution for the ions listed in the specifications. No further calibration
is usually required however a clear ampoule (supplied with each set of tests) can be used to
calibrate with the same single button process as the standard colourimeter should additional
accuracy be required. The calibration is stored on the sensor. Available ezSample snap vials, in
packs of 30, include:
Iron (EZ-2331)
Nitrate (EZ-2333A)
Ammonia (EZ-2334)
Phosphate (EZ-2337)
Chlorine (EZ-2339)
Total Hardness (EZ-2338)
Alkalinity (EZ-2340)
Carbon Dioxide (EZ-2341)
An extension cable is supplied with the sensor.
Immediately after pressing the green calibration button with a clear calibration ampoule, the
transmittance should be 100.0 and the absorbance should read 0.000. There are two reasons for
this:
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"0.0" concentration is outside the valid range for any of the tests.
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The calibrations are based on the assumption that the test dyes are present and fully
developed, which may absorb some light even when the concentration of the ion of
interest is low.
It is also possible to get negative or otherwise erroneous values for the concentration during
measurement. Check the following:
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The ampoules must be nearly full and free of air bubbles for both calibration and
measurement.
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The concentration of the ion of interest being measured must be in the range of sensitivity
of the test.
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The test kits have not expired.
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The solutions were left to develop for an insufficient amount of time.
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Sample spilled in the measurement chamber.
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The colourimeter is functioning properly.
To verify that your system is performing properly, mix or test a standard solution of a
concentration that is in the recommended range of the test run a test measurement.
The range and shelf life of the EzSample tests can be found in Tech Note 1103.
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