Rockwell Automation

Newark Safety and Product Training

Maggie Stumpfl

2012

Agenda

• 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, feedersand 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

– 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

5000 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 6.0VResolution = = = 0.001V Counts 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• Pavg ≠ Iavg * Vavg because power is proportional to the average of the current

squared or the average of the voltage squared

• Instantaneous Power = I2R = V2/R

• So Pavg = Avg(I2) * R = Avg(V2) R

• If we take the average of the square in the previous example we get:

VRMS = = 7.071 Volts - and –

IRMS = = .7071 Amps

Pavg = IRMS * VRMS = 7.071 Volts * 0.7071 Amps = 5 Watts

• We need RMS values to get the correct measurements

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

True-rms

Correct

Correct

Correct

Correct

Average

Correct

10 % High

40 % low

5-30 % low

Input Signal

Response to sine wave

Response to square wave

Response to single phase diode rectifier

Response to 3 phase diode rectifier

Electrical Measurement Basics• What causes non-sinusoidal waveforms?

– Harmonics: multiples of the waveform fundamental frequency• E.g., a third harmonic of 60Hz is 180Hz

– Switching-mode power supplies (PC’s, office equipment)– Light switch dimmers and electronic ballasts– Variable Speed Drives

• Always use a True RMS Meter

Time Domain Frequency Domain

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) = 5Applied/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

233 Remote Display True

RMS Multimeter

i2000 flex AC Current Clamp

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

AC Volts/Hz

DC Volts

Secondary Function

AC/DC 600mV Range

Resistance/Continuity

Power Off

Hazardous Voltage Indicator

Capacitor/Diode

Temperature

AC Amps/Hz

DC Amps

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:

10 MΩ DMM

10 MΩ

12 Volts What will this DMM read?

Voltage Measurement Considerations• Input Impedance Continued

• If the DMM is “ideal” then it will read6 Volts. This is a simple voltagedivider

• If it’s a 233 DMM with 10 MΩ input impedance then the top 10 MΩ resistor and the 10 MΩ input impedance of the meter are in parallel. Two 10 MΩ in parallel create a 5 MΩ resistance. The measured voltage becomes:

Vmeasured =

• Be aware of your meter’s input impedance relative to what you’re measuring• Some Fluke DMM’s have a Low Z mode

– Used to overcome “Ghost” voltages

10 MΩ DMM

10 MΩ

12 Volts 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• Capacitance

– Discharge capacitors before measuring– The 233 charges the capacitor with a known current for a known

period of time, measures the voltage and calculates the capacitance.

– 233 Capacitance measurements from 1 nF to 9999 μF• Diodes

– 233 forces a current through the diode– Good silicon diodes will have a forward bias volgare drop of 0.5-

0.7 Volts– Shorted diode will generate an audible beep– Reverse bias diodes will read “OL”

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• Current Transformer

– 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.)

• Hall Effect Sensor– 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 FeaturesHazardous Voltage Indicator

Illuminates when voltages exceed 30V or the meter is in a voltage

overload condition

Backlight Button

RANGE ButtonAllows switching between auto and

manual ranging and selecting ranges

MIN MAX ButtonCaptures Minimum, Maximum and

Average and allows switching between values

HOLD ButtonAllows measured value to

be retained on display

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

– 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 thatwill 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 currentbetween 4-20mA

• Controllers interpret the 4-20mAsignal and control equipmentand processes

• Why 4-20 mA?– If the controller reads 0 mA

then it recognizes a hardwarefailure

– Current will remain constanteven when flowing over verylong 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 controllerdirectly

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• 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

X axis, time (Seconds)

Y a

xis,

Am

pli

tud

e (V

olt

s, d

B)

Z axi

s, F

requen

cy (H

ertz

)

110.56 Vac

Vo

lts

time

• A multimeter precisely measures a signals amplitude

• An osciloscope displays a signal amplitude change over time

• A spectrum analyzer displays a signal power level (amplitude) with respect to frequency

dB

Frequency

What is a multimeter?• A Multimeter accurately displays discreet Volts, Ohms and Amp measurements.

• 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

Time in Seconds

Am

plitu

de in

Vol

ts

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

“A picture is worth a thousand words!”

Am

plitu

de in

Vol

tsTime in Seconds

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

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

System Control•Sample Storage•Measure functions•Graphics processing•User interface

Ch A2.5 GSa/s

A/D

Lf

Hf

Optional Ch Isolation

Micro Processor

Memory

Triggering•Edge•Edge Delay•Pulse Width•N-Cycle

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

Gnd Ref

Applied Input Resultant Output

DC Coupling

AC Coupling

AC & DC Signal Components

AC Signal Component, DC is blocked by capacitor

Gnd Ref

Gnd Ref

Display Amplitude Control• Controls the vertical span of the displayed signal, adjusted in volts per

vertical display division– mV increases sensitivity– V decreases sensitivity

mV

V

Gnd Ref

Gnd Ref

Gnd Ref

Vertical Sensitivity (V/Div)Amplitude display range

Pressing mV increases vertical sensitivity

Pressing V deceases vertical sensitivity

Analog to Digital Conversion

1 2 3 4 5 6 . . . . . . . 1000

Horizontal Time base (s/Div)Sampling clock interval timeHorizontal resolution

mS/Div

• 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

S/Div

A to D Conversion

Storage Memory

Gnd RefGnd Ref

Sample Rate & Memory• 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)

Mem

ory

Dep

th

time

Cost

Sam

ple

Rat

e

Time base ns Min

S

gS

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

Over Sampling Glitch Detect•The Min & Max samples displayed in each column

Displayed Max Sample

Displayed Min Sample

Display Pixels

Oscilloscope Bandwidth

Frequency 1 Frequency 2 Frequency 3

• 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

Perceived Volume

Triggering• Triggering, synchronizes the waveform display process every time the

waveform is refreshed or displayed.

1

2

3

4

Composite image of “Un-Triggered” scope

T

Triggered, resulting in stable display

Acquisition cycles

Triggering Techniques• Oscilloscopes use several techniques to

trigger on unknown signals– 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

V level

V level

time

V/Div

Time/Div

Trigger

Oscilloscope Isolation• 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

• 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.

Isolated adapter DC Out

AC to DC Power Adapter, specially designed to meet CAT II 1000V/ CAT III 600V Safety rating

Ref A Ref B

Channel 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 A Signal Input

CH B Signal Input

CH A Reference Input

CH B Reference Input

CAT II 1000 V/ CAT III 600V Isolation

Common reference tied to earth ground

CH A 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?