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## Safety and Product Training

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**Safety and Product Training**Maggie Stumpfl Newark element14 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, feeders and branch circuits; permanently installed loads • CAT II Receptacle outlet circuit, plug-in loads • CAT I Protected electronic circuits**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 beAccuracy = +/- (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**• 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 Correct 40 % low 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 • Switching-mode power supplies (PC’s, office equipment) • Light switch dimmers and electronic ballasts • Variable Speed Drives • Always use a True RMS Meter Frequency Domain Time 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) = 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**Resistance/Continuity Secondary Function Hazardous Voltage Indicator Capacitor/Diode AC/DC 600mV Range Temperature DC Volts 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: What will this DMM read? 12 Volts DMM 10 MΩ 10 MΩ**Voltage Measurement Considerations**12 Volts DMM 10 MΩ 10 MΩ 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 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 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 ButtonAllows 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 • 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 fromsensors 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 789can source 4-20 mA signals to the controllerdirectly 24 Volt Loop Power**Testing 4-20 mA Loops**• Using Simulate the 789can 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**Z axis, Frequency (Hertz)**Y axis, Amplitude (Volts, dB) Volts time X axis, time (Seconds) Oscilloscopes • 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 • Electrical Signals are measured in three domains 110.56 Vac dB Frequency**Amplitude in Volts**Time in Seconds 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**Amplitude in Volts**Time in Seconds 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!”**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)**Micro**Processor Lf Ch A 2.5 GSa/s A/D Hf Memory Optional Ch Isolation 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 • 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 AC Coupling Gnd Ref 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 Gnd Ref mV Pressing mV increases vertical sensitivity Gnd Ref V Gnd Ref Pressing V deceases vertical sensitivity**Gnd Ref**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 . . . . . . . 1000 A to D Conversion Gnd Ref mS/Div S/Div Horizontal Time base (s/Div) Sampling clock interval time Horizontal resolution**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) Cost Memory Depth time gS Sample Rate 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