Safety and
Product Training
Maggie Stumpfl
Newark element14
2012
Agenda
•
•
•
•
•
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Electrical Measurement Safety
Measurement Basics
DMM’s and Accessories (233 and Clamps)
Process Tools (789)
Oscilloscopes (190-204)
Fluke Website and Support
Electrical Measurement Safety
• Arc Flash
– What is Arc Flash?
– How does Arc Flash happen?
– Has anyone experienced Arc Flash?
• Fluke Safety Video
Electric Shock
• How much current is lethal?
– For a 150 pound human:
• At 10mA muscular paralysis occurs
• At 30mA respiratory paralysis occurs
• Between 75 and 250mA for exposure exceeding 5 seconds the
heart can no longer function. Higher currents stop the heart
faster.
• What voltage is required to generate these currents?
– The resistance under the skin from hand-to-hand is about 1000 Ω
• 30 Volts will cause 30mA to flow
– Your skin protects you up to about 600V where the resistance of
skin ceases to exist
• If the skin is wet or cut resistance drops dramatically
Measurement Categories
• The level and energy of voltage impulses is dependent on the
location. The closer the location is to the power source, the
higher the available fault current, the higher the category.
• IEC 61010 defines four locations or categories:
CAT IV “Origin of installation”
Utility level and any outside cable run
CAT III Distribution wiring, including “mains” bus, feeders
and branch circuits; permanently installed loads
CAT II
Receptacle outlet circuit, plug-in loads
CAT I
Protected electronic circuits
Category Locations
Electrical Measurement Basics
Electrical Measurement Basics
• Instrument Specifications
– Digits: 3 ½, 4 ½, etc.
• Example: 3 1/2: starting from the least significant
digit, 3 “full” digits from 0-9, 1 “half” digit at less than 9.
Ex: 1999
5000 Counts
– Counts: 3200, 4000, 5000, etc.
• 3200 count display reads 0-3199
• 6000 count display reads 0-5999
– 233 and 789 are 3 ½ digit meters
• 233 – 6000 counts
• 789 – 4000 counts
3 ½ Digits
Electrical Measurement Basics
– Resolution
• The smallest change in the measured value that can be
observed
– Resolution is a function of range and counts
» Example: The 233 DMM has a resolution of 0.001V on the
6 Volt range.
Range
Resolution =
6.0V
=
Counts
= 0.001V
6000
• To maximize resolution choose the lowest possible range
Electrical Measurement Basics
• Accuracy
– Closeness with which an instrument reading approaches the true value
– Expressed as a percentage of reading + number of counts
• Reading error
• Range error
– Example:
• Model 233 DMM DC Voltage Accuracy = +/- (0.25% + 2)
• Reading 1.000 Volt on the 6.0 Volt Range Accuracy would be
Accuracy = +/- (0.25% * 1.0V) + (2 * 0.001V)
= +/- (0.0025V) + (0.002V)
= +/- (0.0045V)
True value is between 0.9955V and 1.0045V
Electrical Measurement Basics
• Averaging Meters vs. True RMS Meters
– Imagine this simple circuit:
– The voltage across the resistor will look like this:
• Vavg, the average voltage is 5.0 Volts
– The current through the resistor will look like this:
• Iavg, the average current is 0.5 Amps
– The power dissipated will look like this:
• Pavg, the average power is 5 Watts
– Power = I*V, but Iavg * Vavg = 2.5 Watts ≠ Pavg, Why?
Electrical Measurement Basics
Electrical Measurement Basics
•
Measuring True RMS is important
– Measurement with an averaging meter can yield incorrect results.
•
Averaging meters will report the correct AC value only when measuring a
perfect sine wave
– Any distortion in the sine wave will result in an incorrect reading with an
Averaging Meter
Input Signal
Average
True-rms
Response to
sine wave
Correct
Correct
Response to
square wave
10 % High
Correct
Response to single
phase diode rectifier
40 % low
Correct
Response to 3
phase diode rectifier
5-30 % low
Correct
Electrical Measurement Basics
• What causes non-sinusoidal waveforms?
– Harmonics: multiples of the waveform fundamental frequency
• E.g., a third harmonic of 60Hz is 180Hz
Time Domain
Frequency Domain
– Switching-mode power supplies (PC’s, office equipment)
– Light switch dimmers and electronic ballasts
– Variable Speed Drives
•
Always use a True RMS Meter
Electrical Measurement Basics
• Crest Factor
– What is Crest Factor?
• CF = Peak / RMS Value
• CF for ideal sine wave = 1.414
– Crest factor is an indication of harmonics
• For current or voltage measurements, the higher the CF, the greater the
waveform distortion.
• CF spec is important for accurate measurements. It is only specified for
true-RMS products.
C.F. = 1.43
C.F. = 2.39
C.F. = 4.68
Common Mode Rejection Ratio
• CMRR specifies how well an instrument rejects signals that appear
at both the high and low input terminal
– Specified in dB (20*Log(Applied/Observed))
– Example: The 233 DMM DCV CMMR is 100dB
20*Log(Applied/Observed) = 100dB
Log(Applied/Observed) = 5
Applied/Observed = 105 = 100,000
– So if 100V is applied to both the hi and low terminal of the 233 a
measured value of 100V/100,000 = 1mV could be observed
Normal Mode Rejection Ratio
• NMRR is a measure of how well the instrument can reject noise
between the low and high input terminals
– This is a DC Volts specification only
– DMM’s are typically built to reject 50 and 60 Hz signals while in
DC Mode
– The 233 DMM NMMR specification is 60dB at 50 or 60 Hz
– 60dB equates to a ratio of 1000
• This means the 233 rejects all but 1/1000th of any 60 Hz
noise between the input terminals
DMM’s and Accessories
i2000 flex AC
Current Clamp
233 Remote
Display True
RMS Multimeter
i1010 AC/DC
Current Clamp
233 DMM CAT Rating
• All Fluke CAT Rated Products will be indicated at the input
terminals
• 233 DMM
• CAT III 1000 V
• CAT IV 600V
233 DMM Measurement Functions
Secondary Function
AC/DC 600mV Range
DC Volts
Resistance/Continuity
Hazardous Voltage Indicator
Capacitor/Diode
Temperature
AC Amps/Hz
AC Volts/Hz
DC Amps
Power Off
233 DMM Voltage Measurements
• How does a DMM measure voltage?
– A DMM uses a dual slope integrating Analog to Digital Convertor
(ADC)
– The DMM applies the unknown signal to a capacitor for an exact
amount of time
– The DMM then discharges the capacitor
– The amount of time taken to fully discharge the capacitor is
proportional to the measured voltage
• DMM’s use a Microprocessor with a very accurate clock
Voltage Measurement Considerations
• Input Impedance
– What is the input impedance (resistance) of a voltmeter?
• An ideal voltmeter has infinite input impedance
– Real voltmeters have specified input impedances
• The 233 has an input impedance of 10 MΩ when measuring DC Volts
– Why is this important…measurement error:
12 Volts
10 MΩ
10 MΩ
DMM
What will this DMM read?
Voltage Measurement Considerations
12 Volts
10 MΩ
10 MΩ
DMM
10 MΩ
233 DMM Frequency Measurements
• 5 Hz to 50 kHz for VAC and VDC
• 45 Hz to 5kHz for AC Amps
233 Resistance and Continuity Functions
• How do DMM’s measure Resistance?
– The meter supplies voltage to the circuit (233 Open Circuit Voltage is 2.7 Volts DC)
– Presence of external voltage in circuit being measured causes meaningless
readings and can damage a meter without overload protection
– How it works: Measured V1 across a precision R1 is compared to measured V2
across an unknown Rx
– 233 Resistance Measurement Range is from 0.1 to 40 MΩ
• Continuity Function
– Performs Resistance measurement also produces audible beep when a close
circuit is sensed
233 Capacitance and Diode Functions
233 Temperature Measurement
• Measures temperature using a Type-K Thermocouple
– A Thermocouple is a device consisting of two different metal
alloys that produce a voltage proportional to temperature
– Multiple Type-K probes available
– 233 Temperature range -40 ºC to + 400 ºC
– RANGE button allows switching between Fahrenheit and Celsius
scales
233 Current Measurements
• 233 can measure current directly but the
circuit must be broken and must use proper inputs
• Current Clamps are more commonly used
– Current Clamp Advantage: Do not need to break the circuit
– Current Clamp Disadvantages:
• Less Accurate
• Current must be calculated
• Phase shift (models that produce voltage)
Type of Current Clamps
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Current Transformer
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Hall Effect Sensor
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•
Only functions with AC signals
Acts like the secondary winding of a transformer
Needs no external power
Produces current (scales current: 1mA/A, 10mA/A, etc.) or voltage (scales voltage: 1mV/A,
10mV/A, etc.)
Measures AC or DC by sensing magnetic field
Requires external power
Produces voltage (scales voltage: 1mV/A, 10mV/A, etc.)
Flexible Current Transformer
–
–
–
Only functions on AC signals
Requires external power
Produces voltage (scales voltage: 1mV/A, 10mV/A, etc.)
Other 233 DMM Features
Hazardous Voltage Indicator
Illuminates when voltages exceed
30V or the meter is in a voltage
overload condition
HOLD Button
Allows measured value to
be retained on display
Backlight Button
MIN MAX Button
Captures Minimum, Maximum and
Average and allows switching
between values
RANGE Button
Allows switching between auto and
manual ranging and selecting
ranges
233 Batteries and Fuse
• Batteries
– 2 AA in remote head
– 3 AAA in base
– Two low battery indicators (one for head, one for base)
•
Fuse Replacement
233 Remote Display
• Optical communication when attached to Base
– Conserves battery life
• 2.4 Ghz ISM Band when detached
– 10 meter range
Process Tools (789)
• 789 is a full featured DMM
• Differences from the 233
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–
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No Remote Display
No capacitance measurement
No temperature measurement
AutoHold
• Holds until a new stable reading is available
– Has REL capability
• Allows for measurement of an offset value that
will be subtracted from measured value
4-20 mA Loops
•
•
•
•
4-20 mA Loops are used to
control processes and equipment
Transmitters receive input from
sensors and regulate the current
between 4-20mA
Controllers interpret the 4-20mA
signal and control equipment
and processes
Why 4-20 mA?
– If the controller reads 0 mA
then it recognizes a hardware
failure
– Current will remain constant
even when flowing over very
long distances
24 Volt
Loop
Power
24 Volt
Loop
Power
Testing 4-20 mA Loops
• Using Loop Power the
789 can replace 24 Volt
power supply
24 Volt
Loop
Power
Testing 4-20 mA Loops
• Using Source the 789
can source 4-20 mA
signals to the controller
directly
24 Volt
Loop
Power
Testing 4-20 mA Loops
• Using Simulate the 789
can simulate the
transmitter
24 Volt
Loop
Power
24 Volt
Loop
Power
Testing 4-20 mA Loops
• In addition to being a powerful DMM, the 789 can
– Measure 4-20 mA signals
– Source 4-20 mA signals
– Simulate 4-20 mA signals
– Measure 24 V loop voltage
– Supply 24 V loop voltage
• The 789 performs many functions…
789 Batteries and Fuse
• 4 AA Batteries
• Low Battery Indicator
Fluke 190-204 Oscilloscope
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•
•
•
•
•
4 Isolated Channels
200 Mhz Bandwidth
CAT III 1000 CAT IV 600 Rated
2.5 GS/s sample rate
Connect-and-View™
IP-51 Rated
Oscilloscopes
•
• Electrical Signals are measured
in three domains
110.56 Vac
•
An osciloscope displays a signal amplitude
change over time
Volts
Y axis, Amplitude
(Volts, dB)
A multimeter precisely measures a signals
amplitude
time
•
A spectrum analyzer displays a signal power
level (amplitude) with respect to frequency
dB
X axis, time (Seconds)
Frequency
What is a multimeter?
A Multimeter accurately displays discreet Volts, Ohms and Amp measurements.
Amplitude in Volts
•
•
Time in Seconds
A typical multimeter uses an integrating ADC to convert an unknown voltage
– An integrating capacitor is charged for a precise time span, then discharged.
– The discharge time is proportionate to the unknown signal charging the integrator.
– The longer the integration time, the higher the resolution, therefore more accurate the
measurement becomes. Accuracies as low as 10’s of parts per million (0.001 %) can
be achieved
What is an Oscilloscope?
An Oscilloscope graphically plots signals over time
– The oscilloscope using high speed A to D conversion, samples the unknown input as
fast as possible then graphically plots the unknown samples over time
Amplitude in Volts
•
Time in Seconds
“A picture is worth a thousand words!”
DMM or Oscilloscope?
•
•
A multimeter, presents a single precise measured value
An oscilloscope presents a graphical representation of a signal change over time.
– To obtain precise measurements, the typical DMM converts the unknown input at a
rate of 5 or 10 times per second
– To accurately represent a signal change over time, an oscilloscope can sample the
unknown input up to 2.5 billion times per second (or faster)
Digital Storage Oscilloscope
Lf
Hf
Micro
Processor
Ch A
2.5 GSa/s
A/D
Memory
Optional
Ch Isolation
Input Coupling
•AC or DC
Amplitude
Control
•Attenuation
•Amplification
Channel
Isolation
•Up to 1000
Volt isolation
•Available on
some scopes
A to D
Conversion
•Real time
•Up to 2.5
GSa/s
Triggering
•Edge
•Edge Delay
•Pulse Width
•N-Cycle
System Control
•Sample Storage
•Measure functions
•Graphics processing
•User interface
Input Coupling
• Input coupling determines what is passed on to the signal conditioning
circuit
– AC, Passes AC component only
– DC, Passes both AC and DC components of the signal
Applied Input
Resultant Output
DC Coupling
Gnd Ref
AC & DC Signal Components
Gnd Ref
AC Coupling
Gnd Ref
AC Signal Component, DC is blocked
by capacitor
Display Amplitude Control
• Controls the vertical span of the displayed signal, adjusted in volts per
vertical display division
– mV increases sensitivity
– V decreases sensitivity
Vertical Sensitivity (V/Div)
Amplitude display range
mV
Gnd Ref
Pressing mV increases
vertical sensitivity
Gnd Ref
V
Gnd Ref
Pressing V deceases vertical
sensitivity
Analog to Digital Conversion
• The unknown signal is applied to the analog to digital converter (A/D).
– The A/D process divides the signal into segments at specified time intervals.
– At each time interval the voltage of the signal is determined and stored into
memory
Storage Memory
1
2
3
4
5
6
. . . . . . .
A to D
Conversion
Gnd Ref
Gnd Ref
mS/Div S/Div
Horizontal Time base (s/Div)
Sampling clock interval time
Horizontal resolution
1000
time
Sample Rate
• A digital storage oscilloscope contains a fixed
amount of memory points
– The more memory, the higher the cost and the
longer it takes to fill up over a complete
acquisition cycle
– The fewer memory points the lower the
resolution, the displayed signal time span and
frequency bandwidth
• The sample rate will increase or decrease relative to
the amount of memory and maximum sample rate
• It will automatically adjust the sample rate from its
maximum at the fastest time base setting (nano
seconds/div) to a slower sample rate at the slower
time base settings (example, milli seconds/div)
Memory Depth
Sample Rate & Memory
gS
S
ns
Min
Time base
Digital Oscilloscope Aliasing
• If the acquisition rate is much slower than the frequency of the
measured signal Aliasing can occur
• Aliasing displays incorrect signals
Actual Signal
Signal observed when Aliasing occurs
A/D – Glitch Detection
•
Glitch Detect
– At slow time base settings/ sampling
intervals the A/D can miss glitches
– Over sampling captures min and max
sample points, preventing aliasing and
displaying glitches
Digitized Signal
Actual Signal
Display Pixels
Displayed Max
Sample
Over Sampling Glitch Detect
•The Min & Max samples
displayed in each column
Displayed Min
Sample
Oscilloscope Bandwidth
•
Bandwidth, determines the highest signal frequency the oscilloscope can
accurately reproduce
– The maximum frequency is usually determined by measuring the point at which the
amplitude decreases as frequency increases by no more than -3 db’s (30% change)
– Bandwidth is also dependent on sampling rate
Test Signal
Volume
Frequency 1
Perceived
Volume
Frequency 2
Frequency 3
Triggering
• Triggering, synchronizes the waveform display process every time the
waveform is refreshed or displayed.
Composite image of “UnTriggered” scope
1
4
Acquisition
cycles
3
2
Triggered, resulting in
stable display
T
Triggering Techniques
• Oscilloscopes use several techniques to
trigger on unknown signals
V level
– Edge, a specific voltage level set relative to
either a rising or falling edge.
– Pulse Width, specifies both a specific voltage
level relative to an edge, plus a time interval
between the rise and falling edges (or visa
versa).
– Automatic Connect&View:
• As implied, connect then view, as simple as that!
• Eliminates need to continuously adjust the scope
vertical sensitivity, horizontal time and trigger
settings
time
V level
Trigger
V/Div
Time/Div
Oscilloscope Isolation
Ref A
Ref B
AC to DC Power Adapter,
specially designed to meet
CAT II 1000V/
CAT III 600V Safety rating
•
•
The ScopeMeter input connectors are
insulated to prevent against exposure
to electrical voltages
The input power adapter is isolated
from earth ground, allowing for floating
measurements
Isolated
adapter
DC Out
•
•
A typical bench oscilloscope uses
metal BNC connectors and metal
chassis components, potentially
exposing the user to hazardous
voltages.
To protect against electric shock the
bench oscilloscope is connected
directly to earth ground via wall outlet.
Channel Isolation
CH A
Signal
Input
Common
reference tied to
earth ground
CH A
CH B
Referen
CH A
Referen
ce
Input
Signal
ce Input
Input
CAT II 1000 V/ CAT
III 600V Isolation
•
Bench oscilloscope with exposed metal
BNC connectors and common input
references, for safety reasons are tied to
earth ground
•
Fluke 190 series portable oscilloscope with
insulated BNC input connectors isolated
from earth ground with isolated input
references
CH B
Signal
Input
CH B
Signal
Input
The Fluke ScopeMeter test tools provide
a safe means to measure floating
differential voltages
Using the 190-204 Oscilloscope
• Input Connections
– BNC Connectors are 300V CAT IV
– Fluke 10:1 Probes provide 1000V CAT III
600V CAT IV
Using the 190-204 Oscilloscope
• Resetting the 190-204 to factory settings
Using the 190-204 Oscilloscope
• Hiding Labels and Key Illumination meaning
Using the 190-204 Oscilloscope
• Probe Settings
Using the 190-204 Oscilloscope
• Selecting Input Channels
Using the 190-204 Oscilloscope
• Connect-and-View™
Using the 190-204 Oscilloscope
• Automatic Measurements
Using the 190-204 Oscilloscope
• Average, Persistance, and Glitch Capture
Using the 190-204 Oscilloscope
• Displaying Glitches and suppressing High Frequency Noise
Using the 190-204 Oscilloscope
• Acquisition Rate
Using the 190-204 Oscilloscope
• AC/DC Coupling
Using the 190-204 Oscilloscope
• Bandwidth and Noisy Waveforms
Using the 190-204 Oscilloscope
• Mathematics (FFT)
Using the 190-204 Oscilloscope
• Reference Trace
Using the 190-204 Oscilloscope
• Meter Mode
Using the 190-204 Oscilloscope
• Trend Plot Meter
Using the 190-204 Oscilloscope
• ZOOM Button
Using the 190-204 Oscilloscope
• CURSOR Button
Using the 190-204 Oscilloscope
• Record Waveforms in Deep Memory
Using the 190-204 Oscilloscope
• Scope Record in Single Sweep
Mode
Using the 190-204 Oscilloscope
• REPLAY Button
Using the 190-204 Oscilloscope
• Trigger Level
Using the 190-204 Oscilloscope
• Saving and Recalling
Using the 190-204 Oscilloscope
• FlukeView Scope Software Demonstration
Fluke Support
• Fluke Website and Support
Conclusion
• Questions?