Computer Software Module
UCCS Physics Labs
Table of Contents
Computer Startup
LabPro Interface
Logger Pro Program
Calibrating Sensors
Pressure Sensor
Getting Help
2
3
3
9
10
11
FYI
FYI
Astronauts are not allowed to eat beans before they go into space because passing wind in a spacesuit
damages them.
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Computer startup
This section will be an instruction manual for the lab computers and the software
we will be using this semester. If you have a good knowledge of computers and
windows then you only need to follow the steps. For those of you who are
unfamiliar or dislike computers read the full explanation for each of the steps.
• Turn on the power
To start the computer you first need to turn on the power. Computers
seem to have an endless variety of power switch locations, so this may not be
trivial to do for the first time. The computer may already be on first try move the
mouse and see it the computer wakes up. If this does not work the computer will
have to be powered up. To power up the computer push the larger of the two gray
oval buttons located in about the middle of the front panel of the computer. Some
lights will turn on and the computer will begin to go through its start-up
procedure.
• Starting Windows 2000®
The computer should load the windows program automatically on boot-up.
If it fails to do to load Windows tell your instructor right away. You will need to
use your UFP account name and password. Be sure to log-off before you leave!
You can save any data files to your UFP account and access them later from any
other machine on or off campus (with a network connection to the campus). See
the IT department to setup your account or further information on the computer
network.
• Connecting the LabPro
Connect the power cord to the LabPro (lower left corner of the box). The
LabPro will make a series of beeps when it is powered up. The USB cable is
connected to the port on the middle of the right side of the box and to either port
on the back of the computer. Sensors connect to either the slots on the left
marked “Ch 1” to “Ch 4” or on the right side to the “Dig/Sonic” ports. Each
sensors has it’s own kind of plug if it does not work on one bank of inputs try the
other.
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How does the LabPro box work?
We live in an analog world, meaning that most of the
measurements we make are in the base 10 numbering system,
e.g.: 2.35 miles, -1038 kg, 0.0034 sec, etc. Computers are only
capable of understanding ON or OFF, or 1’s and 0’s. This is a
base 2 numbering system. The computer fools us into thinking
it knows more because it can display analog numbers. It does
this by combining large amounts of 1’s and 0’s, e.g.: 12 as seen
by the computer takes 4 digits: 1, 1, 0, 0. The problem
becomes, how do we get our measurements into the computer?
The answer is something called an Analog-to-Digital converter
(A/D for short). The LabPro box contains four of these A/D’s,
one for each input channel. An A/D does exactly what its
name implies, it can convert an incoming analog signal into its digital equivalent. This
digital number can then be transferred to the computer. The A/D in the LabPro boxes are
capable of converting up to 70,000 readings per second and is 12 bits wide. The higher
the number of “bits” the more accurately it can convert an analog number into a digital
number.
The Logger Pro program
•
Open the Logger Pro program
•
Open the icon on the desktop that is called “Logger Pro 3.x”.
•
To open a program you need to double-click on the program icon. A
double-click is a rapid succession of two left button mouse clicks over
the program group or program icon.
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•
Opening screen
•
The first screen you will see is default experiment window. It will contain a
data table and a graph window. If you already have sensors connected when
you start up the program the lab pro can detect them and might automatically
set up the window accordingly. Neat!
Menus: These are drop-down lists
of all the features in the program.
Data Table:
Data is
displayed in
a tabular
form.
Tool Bar: Contains buttons
of the most commonly used
functions in the program.
Plotter/Graph: Where
data is displayed in a
graphical format.
Clicking on the
numbers at the
ends of the axis
can change the
limits of the axis.
Figure 1 – Logger Pro opening screen.
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•
If you see the following screen it means the lab pro has not been setup
properly.
Or a window similar
indicating that the lab
pro is not connected.
•
Make sure the USB cable is firmly attached at both ends.
•
Make sure the interface has power.
•
If you still do not get a connection ask instructor for help.
The Menus
File menu
This menu is basic to most windows
programs. It contains the tools
needed to open, close, create and
save files. It also contains printing
commands and the exit
command.
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Experiment menu
This menu contains the tools needed to
setup and adjust the Lab Pro and
whatever sensors are connected.
The Toolbar
This is where you find the most used commands.
This is the most important button in the program!
This button starts the data collection process. Data collection will
only stop if the preset time limit is reached or the start button is hit
again (which will turn into a “stop” when running).
These tools are used to scale the graph. From left to right:
Auto scaling, Zoom in and Zoom out.
Zoom in: If you want to get a closer look a part of a graph,
drag-out a box around the area and click on this button.
Zoom out: Clicking on this button will zoom out your view
of the graph.
Auto scale: This button will adjust the graph so that all the
data will be shown.
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This button will bring up the sensor dialog box. From this
window you can select which sensor is connected to each of the
ports. The lab pro is capable of automatically detecting a sensor
when it is plugged in. Calibration of each of the connected
sensors can be also be performed from this screen.
I will write individual programs for each lab.
This toolbar will allow you to navigate through
the program pages.
Data Collection
Clicking on this button will bring up the controls for
the timing and data collection.
Use this dialog box to
set/adjust the total
collection time. Set the
data collection to stop
after the time expires or
repeat on a continuous
loop. Sampling rate and
collection triggering are
other options.
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Software explanation
We will be using the Logger Pro software. Everything should be ready to go if you
open the file listed in the lab procedure. Here is a little extra on the workings of the
Logger Pro software for those of you who like to now these things.
Note: This is for your information only. If you opened the
correct file everything should already be setup for you.
This button (located in the toolbar) will bring up
the sensor control window (shown below).
List of analog
sensors available for
channels 1-4.
A photogate sensor
should be shown in
DIG/SONIC 1.
List of digital
sensors available for
DIG/SONIC 1-2.
Status of photogate. Place your hand
in gate and the status will change to
“blocked”.
This indicator is also available on the
toolbar.
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How do you Calibrate Logger Pro?
The only sensor we will use this semester that will need any calibration, is the
pressure sensor. Therefore, my discussion on calibration will concentrate on how to
calibrate this sensor.
If you think back on how the Lab Pro box works, all sensors send signals back to the Lab
Pro that are only related to the real-world values, like Pascals.
Example: The raw data sent back from the force sensor is a voltage in the range
of –5 volts to +5 volts. What a calibration does is convert this raw voltage data into
something meaningful, like Pascals. The relationship between the raw data (voltage) and
needed data (Pascals) happens to be linear. Therefore, if we can find the equation of this
Useful data (Pascals)
relationship we can convert any raw data into useful data.
Calibration point
#2
#1
To calibrate the pressure sensor, we need to
find this calibration line. We need a minimum
of two points to define any line. The two
easiest pressures to get are atmospheric
pressure (the pressure of the air around us) and
Raw data (voltage)
zero pressure (we pump all the air out).
Now that you know how a calibration works you can perform one if needed.
However, this will take up too much of your time to do by hand. The Logger Pro
software has a calibration package, use it to calibrate the pressure sensor.
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Calibrating the Pressure Sensor
Follow these steps to calibrate the Pressure sensor:
Choose ‘Experiment>>Calibrate…’ from the menu bar.
Click on the Pressure icon. Click the
button.
Use the syringe with the Pressure Sensor to produce a pressure very near
zero. The sensor has a 3-way valve at the end of a plastic tube leading
from the sensor box. With the syringe connected to position 3, align the
blue valve control to position 1 (see the diagram below).
2
1
3
Push the plunger on the syringe all the way in and move the blue stem
control to position 2, thus closing both the syringe and Pressure Sensor to
atmosphere. To produce the near-zero pressure, pull the plunger out to the
20-cc position. If everything is sealed, the voltage reading should be very
near zero. If not, repeat this step.
Type 0 in the Value 1 edit box.
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When the displayed voltage reading for Input 1 stabilizes very near zero,
click
Keep
.
Open the Pressure Sensor to atmosphere by moving the blue valve control
to position 3.
Enter the current atmospheric pressure in kPa (get this value from your
instructor) in the Value 2 edit box.
When the displayed voltage reading for Input 1 stabilizes, click
then click
Keep
,
.
Getting Help On-line
You can always talk to your instructor for help!
If you need help and your lab instructor is busy you can get help using the
computer. You can use the help program located under the Help menu. Hitting the “F1”
key will also bring up the help program.
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