Electrical Concepts Distributor Training Program OFF

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1 4½ DIGITS 1 Second LO 10 MX MIN MX Peak MIN MX 400m TRUE RMS MULTIMETER RNGE utohold REL Hz % Concepts Distributor Training Program 87 C/ F m OFF m m COM

2 Concepts olts, mps, Ohms and Continuity oltage (E) Resistance (R) Current (I) olts, mps, Ohms and Continuity oltage [olts] { Electricity is the movement of electrons from one atom to another. pressure necessary to cause this movement is called voltage. This term is named for lessandro olta ( ), an Italian physicist. He was the inventor of the voltaic pile, the first electric battery, and the electrophorus, a device that, once electrically charged by having been rubbed, could transfer the charge to other objects. The unit of electric potential, the volt, is named in his honor. ll electrical circuits must have a source of power, or voltage, to produce work; and one of the most basic tasks of a DMM (digital multimeter) is measuring voltage. oltage may be produced by: Electromagnetism (generators at hydroelectric plants, steam powered or even wind powered). Chemicals (batteries in your car, flashlight or portable radio). Light (photocells). Heat (thermocouples). Pressure (piezoelectricity). Friction (static electricity). oltage is also called electrical potential, because if voltage is present in a conductor, there is a potential (possibility) for current flow. oltage itself does not flow through conductors, but is the pressure that causes current (in amperes) to flow through conductors. typical dc (direct) voltage source is a battery, like the one used in your car. DC voltage is voltage that flows in one direction only. typical ac (alternating) voltage source is created from a generator and reverses its direction of flow at regular intervals. C voltage is used in residential, commercial, industrial lighting and power distribution systems. Your customers understand that a Fluke meter is the perfect tool for their investigation of electronic equipment such as Ts, stereos, CRs and computers, which are plugged into an ac wall outlet and use rectifiers to convert the ac voltage to a dc voltage. nd that is critical to ensure that the proper voltage is supplied to all electrical components in a circuit. dditional loads (new machinery, new outlets, etc.) that have been added to existing circuits may cause excessive voltage drop and energy losses. If there is no voltage present, or if it is too high or too low, the voltage problem should be corrected before investigating further. What you will learn in this module: The history of voltage, amperage and resistance What are the different sources of voltage When to use the continuity function bbreviations for voltage, current and resistance Page Fluke Corporation FCT Concepts

3 HOLD MIN MX RNGE CT CT HOLD HOLD MIN MX MIN MX MIN MX RNGE RNGE voltmeter is used to measure the amount of electrical pressure (voltage) in a circuit. oltage measurements are normally taken to: 1. Establish that there is voltage at a given point. 2. Ensure that the voltage is at the proper level. For instance, if voltage is present on one side of a switch or fuse and not on the other side, the switch or fuse is open and may be defective. The conventional abbreviations and measurement for voltage are as follows: 1. olt is the unit of measurement for the amount of electrical pressure. 2. Electromotive force (EMF) is another way of indicating voltage. 3. is the generally accepted abbreviation for volts. 4. E is the symbol used in calculations for electromotive force. 5. voltmeter is an electrical test instrument used to measure volts. Positive (+) Charge Copper Wire 6.28 Billion Billion Electrons Per Second (1 mpere) Negative (-) Charge Current may be direct or alternating. Direct current (dc) is current that flows in only one direction. lternating current (ac) is current that reverses its direction of flow at regular intervals. The ampere is the electrical unit for the amount of electron flow, just as gallons per minute is the unit that can be used to measure the quantity of water flow. The term ampere was named for a French electrician, ndrè-marie mpére ( ), whose theory became fundamental for 19th century developments in electricity and magnetism. He proved that a magnetic field is generated around a conductor as current passes through it, and that the strength off this field is directly proportional to the amount of current flowing. Different voltage sources produce different amounts of current. Standard,, C and D batteries produce 1.5 volts each, but the physically larger batteries are capable of delivering a greater amount of current. olts, mps, Ohms and Continuity + _ DC m + + Current [mps] [ \ The ampere (amp) is the universal unit of measure for the amount of current flow. Current flows through a circuit when a source of power is connected to a device that uses this power. Current is measured in amperes (), when 6.28 billion billion electrons (the name for this large number of electrons is a coulomb) move past a certain point in one second, this represents one ampere of current. Most DMMs can only measure dc or ac current to 10 amps through the ammeter function. Higher current must be scaled down with a current clamp accessory. Current clamps measure current in a circuit from.01, or less, to 3000 by measuring the strength of the magnetic field around a conductor, and will allow measurements without opening the circuit. This is more convenient and safer, especially for high energy electrical applications. mperage measurements are normally taken to indicate the amount of circuit loading or the condition of a load. Every component (lamp, motor, heating element, etc.) that converts electrical energy into some other form of energy (light, rotating motion, heat, etc.) uses current. When additional loads are added to a circuit, the circuit must deliver more current. The size of conductors, fuses and components determines how much current will flow through the circuit. HOLD RNGE Page Fluke Corporation FCT Concepts

4 RNGE HOLD MINMX The conventional abbreviations and measurement for amperes are summarized as follows: 1. The ampere is the unit of measurement for the amount of current flow. 2. and amps are acceptable abbreviations for amperes. 3. Capital I, for intensity, is used in mathematical calculations to represent amperes. 4. n ammeter (not ampmeter) is an electrical test instrument used to measure amperes. Resistance [Ohms] W Resistance to the flow of current through a conductor is measured in units called ohms, HOLD MIN MX RNGE named after a German physicist, Georg Simon Ohm ( ). He found that resistance limits the flow of current in an electrical circuit: the higher the resistance, the lower the current flow. Likewise, the lower the resistance, the higher the current flow. ll materials have some amount of resistance to current flow. conductor (gold, silver, and copper) is a material that has very little resistance and permits electrons to move through it easily. n insulator (rubber, paper, plastic, etc.) is a material that has a very high resistance and resists the flow of electrons. n ohmmeter is a device that is used to measure the amount of resistance in a component or circuit that is not powered. Resistance measurements are normally taken to indicate the condition of a component or circuit. The conventional abbreviations and measurement for resistance are as follows: 1. The ohm is the unit of measurement for electrical resistance. 2. The symbol for ohms is W (Greek capital letter omega), the last letter of the Greek alphabet. 3. The symbol used in calculations is R, for resistance. 4. n ohmmeter is an electrical test instrument used to measure ohms. Ohm s Law oltage, current, and resistance in any electrical circuit can be calculated by using Ohm s Law, which states that voltage = current x resistance. Thus, if any two values in the formulas are known, the third can be determined. I E E = I x R where: E = olts I = Current in mps R = Resistance in Ohms DMM makes use of the Ohm s Law principle to directly measure and display ohms, amps, or volts. Continuity R Continuity is a quick go/no-go resistance test that distinguishes between open and closed circuits. For example, a wall switch is closed when it is turned to the on position and it is open when it is turned off. n open circuit cannot conduct electricity. closed circuit has continuity. DMM with a continuity beeper allows you to complete many continuity tests easily and quickly. The meter beeps when it detects a closed circuit, so you don t have to look at the meter as you test. The level of resistance required to trigger the beeper varies from model to model of DMM. This test should be done when voltage is NOT present. lways unplug the device or turn off the main circuit breaker before attempting a continuity test. Continuity tests determine: 1. Good or blown fuse. 2. Open or shorted conductors. 3. Operation of switches. 4. Circuit paths (by circuit or conductor tracing). HOLD MINMX RNGE olts, mps, Ohms and Continuity Page 3 Fluke Corporation FCT Concepts

5 Test your knowledge 1. (n) is used to measure the amount of electrical pressure (voltage) in a circuit.. ohmmeter C. voltmeter B. wattmeter D. ammeter 2. The abbreviation for amperes is.. C. amps B. I D. all of the above olts, mps, Ohms and Continuity 3. The Greek symbol to represent ohms is.. F C. µ B. W D Continuity tests determine:. a good or blown fuse. B. open or shorted conductors. C. operation of switches and circuit paths. D. all of the above 1. C 2. D 3. B 4. D Chapter Summary oltage (olts) oltage is the electrical pressure in a circuit. DC voltage flows in one direction and is typically found in batteries. C voltage flows in two directions and is typically generated through electromagnetism. voltmeter is used to measure the amount of electrical pressure (voltage) in a circuit. is the generally accepted abbreviation for volts and E is the symbol used in calculations. Current (mps) Current is the flow of electrons in the circuit. Most DMMs can measure ac or dc current up to 10 amps. Current clamps measure current in a circuit from.01 or less to and amps are the generally accepted abbreviations for amperes, and I is the symbol used in calculations. Resistance (Ohms) Resistance to the flow of current is measured in units called ohms n insulator is a material that has a very high resistance and resists the flow of electrons. The symbol for ohms is W (Greek capital letter omega), and the symbol used in calculations is R, for resistance. Continuity Continuity is a quick go/no-go resistance test that distinguishes between an open and a closed circuit. The meter beeps when it detects a closed circuit. Fluke. Keeping your world up and running. Fluke Corporation PO Box 9090, Everett, W US For more information call: In the U.S.. (800) or Fax (425) In Canada (800)-36-FLUKE or Fax (905) Web access: Fluke Corporation. ll rights reserved. Printed in U.S.. Phase 1, Module 1, Rev 2 Page 4 Fluke Corporation FCT Concepts

6 utohold SETUP db HOLD db ac+dc ac+dc 10 MX 187 FST MN MX MIN MX CNCEL Hz % ms ns m TRUE RMS MULTIMETER 400m REL RNGE COM CT ac+dc ac+dc TEMPERTURE Concepts Diodes, Capacitance, Frequency, Duty cycle Heinrich Hertz, a German physicist born in 1857, experimented with the reflection, refraction, polarization, interference and velocity of electric waves. In recognition of his work, the unit of frequency of a radio wave one cycle per second is named the Hertz. His research soon led to the invention of the wireless telegraph and then the radio, by a young man named Guglielmo Marconi. Frequency [Hertz - Hz] Frequency is defined as the number of times a voltage changes polarity, or states, per second, or the number of cycles that take place per second. The more cycles that take place in one second, the higher the frequency reading. Frequencies are measured in Hertz, which is the number of cycles per second. The electrical grid in the United States is based on a very stable 60-hertz signal, which cycles 60 times per second. Speakers operate at frequencies within the human hearing range. The term frequency spectrum is the range of all possible frequencies. The audio spectrum is the part of the frequency spectrum that humans can hear (20 Hz - 20 khz). The higher the frequency, the higher the tone. s a person ages, the upper limit of their hearing decreases, and so does their sensitivity to a stationary frequency. larms, horns, and bells normally operate at one stationary frequency. Sirens normally operate at a frequency that varies slightly, making it easier to be heard. Frequency measurements can be made on the voltage ( dc, ac, m dc) or current inputs (m / ac or dc). To demonstrate frequency, simply select a meter that hosts frequency as a function. 1. Plug the test leads into the common and the voltage jacks. 2. Configure the meter to measure frequency. 3. Carefully insert the test leads into the nearest wall outlet. 4. The display will read 60 Hz. ariations may be seen if measuring the frequency output of a generator. Frequency measurement applications abound from variable-frequency motor drives to communications equipment and power sources. Many of these measurements once required a dedicated counter, but now can be made with a high-performance DMM. The frequency range of a high-performance DMM should not only cover the high frequency measurements, but also low frequency, down to fractions of a cycle per second, and you should expect high accuracy over this entire range. The Fluke 80 Series and 180 Series meters, for example, are accurate down to ½ cycle per second for effective testing of motor controllers and other equipment, which operate at this level. Duty Cycle + oltage 5 Hz Signal 0 olts - oltage +12 olts 0 olts Time 1 Second 1 Second Duty cycle is the ratio of time a load or circuit is ON to the time a load or circuit is OFF expressed in a percentage. s ON time increases, OFF time decreases. Duty cycle is measured in percentage of ON time: 60% duty cycle is a signal that is on 60% of the time, and off 40% of the time. nother m OFF m F C m m Sine Wave 5 Hz Signal Square Wave Diodes, Capacitance, Frequency, Duty cycle What you will learn in this module: The history of frequency How to demonstrate the frequency function How to demonstrate the duty cycle function How to test a diode Capacitance Page Fluke Corporation FCT Concepts

7 utohold SETUP db HOLD db ac+dc ac+dc 10 MX FST MN MX MIN MX CNCEL Hz % ms m TRUE RMS MULTIMETER 400m REL RNGE COM CT ac+dc ac+dc TEMPERTURE CT 1000 CT CT 1000 CT way to measure duty cycle is dwell, which is measured in degrees instead of percent. Many loads are rapidly cycled on and off by a fast acting electronic switch to accurately control output power at the load. Load operation such as lamp brightness, heating element outputs, and magnetic strength of a coil can be duty cycle controlled olts 50% Duty Cycle 0 olts Time 50% 1 Second 50% Off On Pulse Width Pulse width is a measure of the actual ON time measured in milliseconds. The OFF time doesn t affect signal pulse width at all; the only thing being measured is how long the signal is on (ground controlled). For example, varying the pulse width controls fuel injector on time, which affects the quantity of fuel injected into each cylinder. The output is typically displayed in milliseconds (ms). Diodes, Capacitance, Frequency, Duty cycle + 12 olts 80% Posative D.C. 20% Negative D.C. 0 olts 80% Duty cycled solenoids use a variable duty cycle signal to vary flow or adjust pressure. The longer the solenoid remains open, the more flow and less pressure develops. These solenoids are either feed-controlled or ground-controlled. The Fluke meter allows you to choose which type of signal you are measuring. To demonstrate duty cycle, simply select a meter that has the duty cycle function. 20% Diodes ON diode is a semiconductor device that offers very high opposition to current flow in one direction and very low opposition to current flow in the other direction: in essence, an electronic switch. Diodes are also known as rectifiers because they change ac into pulsating dc and are rated according to their type, voltage, and current capacity. Good Diode Fuel Injection On-Time OFF Good Diode 1. Plug the test leads into the common and the voltage jacks. 2. Configure the meter to measure duty cycle. 3. Carefully insert the test leads into the nearest wall outlet. 4. The display will read 50 percent. Slight variations may be seen as the sine wave varies. 187 HOLD MINMX RNGE OFF 300 m TRUE RMS MULTIMETER m COM + Reverse Bias HOLD MINMX RNGE OFF 300 m TRUE RMS MULTIMETER m COM + Forward Bias Single Beep Pulse Width m OFF m ns F C m m diode has polarity as determined by an anode and a cathode. The anode is the positive lead of a diode and the cathode is the negative lead of a diode. Most diodes allow current to flow only when positive voltage is applied to the anode, and act as an open switch if voltage is removed or reversed. When a diode allows current flow, it is forward-biased. Reverse-bias is the condition of a diode when it does not allow current flow and acts as an insulator. If the current rating of the diode is exceeded and the diode fails, it may short and allow current flow in both directions or it may open and not allow current flow in either direction. Page 2 Fluke Corporation FCT Concepts

8 CT 1000 CT HOLD MINMX RNGE 600 CT 1000 CT MIN MX Bad Diode Bad Diode HOLD MINMX RNGE OFF 300 m TRUE RMS MULTIMETER m COM + Open 177 TRUE RMS MULTIMETER Diodes can be tested using the DMM Diode Test mode or the DMM Resistance mode. The DMM Diode Test mode produces a small voltage between the test leads sufficient to forward bias a diode junction. Normal drop is.5 to.8. dditional tests can be performed with the resistance mode on the DMM. The diode is forward-bias when the positive (red) lead is on the anode and the negative (black) test lead is on the cathode. The forward-biased resistance of a good diode should range from 1000 W to 10 MW and will read OL when reverse-biased. Hz OFF Hz 300 m 10 m COM + and Shorted Capacitance Capacitance is the ability to store energy in the form of an electrical charge. Some DMMs offer the convenience of a capacitance measurement function, which allows you to identify an unknown or unlabeled capacitor and to detect open or shorted capacitors. High-performance DMMs with capacitance functions can typically measure capacitors directly and display their value. HOLD RNGE + _ + Diodes, Capacitance, Frequency, Duty cycle Page 3 Fluke Corporation FCT Concepts

9 Test your knowledge 1. is the number of cycles that take place per second, measured in Hertz.. Duty Cycle C. Pulse Width B. oltage D. Frequency 2. When measuring duty cycle, if on-time increases, off time.. stays the same C. increases B. decreases D. none of the above Diodes, Capacitance, Frequency, Duty cycle 3. Pulse width is a measure of the actual on-time in.. degrees B. milliseconds or microseconds C. percentage D. volts 4. The is the positive lead of a diode.. anode B. cathode C. conductor D. insulator 1. D 2. B 3. B 4. Chapter Summary Frequency Frequency is the number of cycles that take place per second. The term frequency spectrum is the range of all possible frequencies. The audio spectrum is the part of the frequency spectrum that humans can hear (20 Hz to 20 khz). Duty Cycle Duty cycle is the ratio of time a load or circuit is ON to the time a load or circuit is OFF expressed in a percentage. Many loads are rapidly cycled on and off by a fast-acting electronic switch to accurately control output power at the load. Pulse Width The pulse width is a measure of the actual on-time measured in milliseconds. In automotive applications, fuel injector on-time is measured in milliseconds. Diode diode is a semiconductor device that offers very high opposition to current flow in one direction and very low opposition to current flow in the other direction. The anode is the positive lead of a diode and the cathode is the negative lead of a diode. good forward-biased silicone diode displays a.5 to.8 voltage drop. good forward-biased germanium diode displays a.2 to.3 voltage drop. Capacitance Capacitance is the ability to store energy in the form of an electrical charge. This function will measure the capacitor directly and display its value. Fluke. Keeping your world up and running. Fluke Corporation PO Box 9090, Everett, W US For more information call: In the U.S.. (800) or Fax (425) In Canada (800)-36-FLUKE or Fax (905) Web access: Fluke Corporation. ll rights reserved. Printed in U.S.. Phase 1, Module 2, Rev 2 Page 4 Fluke Corporation FCT Concepts

10 Concepts C oltage and Current Measurements C Measurements There are 3 different ways to measure the level of an ac voltage or current: 1. Using a basic average responding meter or clamp meter. 2. Using an advanced True-rms meter or clamp meter. 3. Using an oscilloscope to see the changing peaks and valleys of an ac wave. 0 olts RMS is the abbreviation for the Root-Mean- Square formula that calculates the effective or dc heating value of an ac wave. True RMS voltage detection is most commonly required to measure complex amplitude and time varying signals, such as machine or engine vibration monitoring and complex C power line load monitoring. Most meters display the RMS value or current that is representative of the measurement of an ac wave, not an actual picture of the ac voltage or current wave that is captured when using an oscilloscope. waveform is a representation of how alternating current (C) varies with time. The most familiar C waveform is the sine wave, which derives its name from the fact that the current or voltage varies with the sine of the elapsed time. The sine wave is unique in that it represents energy entirely concentrated at a single frequency. Household utility current has a sine waveform with a frequency of 60 Hz in most countries including the United States, although in some countries it is 50 Hz. There are two types of ac voltage and current waveforms. Sine Wave Positive Peak Negative Peak RMS or effective value (.707 x peak) Positive half a mirror image of the negative half (symmetrical) Non-Sine Wave Peaks and valleys may be pointed or flat Transition between peaks and valleys may be sharp Positive and negative halves may be different The ac value displayed on a meter or clamp meter depends on two things: If you are measuring a sine wave or nonsine wave If your meter or clamp is average responding or True-rms verage Responding vs. RMS n easy way to remember rms vs. average responding is to think about a cup of shortening. If you scoop a cup of shortening out of a container, it may have air in it, but will measure a full cup, a measurement similar to an average responding meter s. If you heat the cup of shortening, the air pockets will disappear with a resulting value up to 30% less, a measurement similar to a True-rms meter s. verage Responding RMS C oltage and Current Measurements What you will learn in this module: RMS voltage and current values Sine and non-sine wave signals True-rms versus average responding Harmonics Problems caused by harmonics Gently curved peak and valley Smooth transition between the peak and valley Page Fluke Corporation FCT Concepts

11 True RMS Meter verage Responding Meter Correct Reading Correct Reading Sine Wave Square Wave Correct Reading 10% High What s all the noise about harmonics? mystery is occurring in today s office buildings and manufacturing plants: Transformers supplying seemingly average loads are overheating. Neutral conductors in balanced circuits are overheating from excessive loads. Circuit breakers are tripping for no apparent reason. Yet the standard troubleshooting procedures show everything to be normal. So what s the problem? In one word harmonics. s we connect more electronic devices to our power systems, the quality of the power becomes more important. Quality can be defined many ways. Stable voltages and undistorted waveforms are two characteristics which are very desirable in power systems. Grounding affects voltage stability, and more importantly, is critical to personal safety. Harmonics are a mathematical model we use to analyze distorted waveforms Harmonics verage Correct Reading Correct Reading True-rms Harmonics are a mathematical model of the real world. Harmonics are simply a technique to analyze the current drawn by computers, 1 Phase Rectifier 40% Low 3 Phase Rectifier 5-30% Low electronic ballasts, variable frequency drives and other equipment which have modern transformer-less power supplies. Ohm s Law states that when a voltage is applied across a resistance, current will flow, such as when you turn on a light or your computer. This is how all electrical equipment operates. In the United States, the voltage we apply across our equipment is a sinewave which operates at 60 Hertz (cycles per second) and is supplied by the power utility. Once this voltage is applied to a device, Ohm s Law kicks in. oltage is not the only electrical component that operates at 60 Hertz, so does the current. When a voltage sinewave is applied to a linear load, the current wave follows the voltage and ends up being another sinewave. Systems which exhibit this behavior are called linear systems. Incandescent lamps, heaters and, to a great extent, motors are linear systems. Harmonics are ac voltages or currents with frequencies that are multiples of the basic frequency. For example, the 3 rd harmonic is 3 times 60 Hz = 180 Hz. Some of our modern equipment, however does not fit in a linear system. Computers, variable frequency drives, electronic ballasts and uninterruptable power supply systems are non-linear systems. In these systems, the resistance is not a constant and in fact, varies during each sinewave. This occurs because the resistance of the device is not a constant. The resistance in fact, changes during each sinewave which can make your line voltage and current non-sinusoidal. verage responding meters and clamps may read incorrectly on circuits connected to these harmonicgenerating loads. djustable speed motor drives Lighting ballasts Laser printers Photocopiers Computers Control systems C oltage and Current Measurements Page 2 Fluke Corporation FCT Concepts

12 Harmonic currents and voltages cause problems in almost every component of an electrical distribution system. Only a Truerms meter will read correctly and help solve power problems when harmonics are present. These harmonic currents create heat. This heat over a period of time, will raise the temperature of the neutral conductor. This rise in temperature can overheat the surrounding conductors and cause insulation failure. These currents also will overheat the transformer sources which supply the power system. This is the most obvious symptom of harmonics problems; overheating neutral conductors and transformers. So how do you know if there are harmonic problems present that require further investigation? Simply look for these conditions. Circuit breaker trips Overheated neutrals and conduit Overheating motors and transformers Induction motors running backwards ibrating panels Computer rebooting In search of harmonics Here s a simple way to determine the extent of harmonic distortion caused by single-phase non-linear load input circuits: Make two separate current measurements: Using an average responding current clamp or meter with a clamp-on. Using a True-rms current clamp meter, such as the Fluke 335, 336 or 337 or a True-rms meter with a clamp-on, e.g. Fluke 87 and i400. Divide the results of the first measurement by the second measurement. This gives you the verage Responding vs. RMS /R ratio. ratio of 1.0 would indicate little or no harmonic distortion. ratio of 0.50 would indicate substantial harmonic distortion The /R ratio method is not a substitute for a harmonic analyzer, but it is a simple practical way to determine whether there s a problem in single-phase branch circuits. Once you know harmonics are present, you can use a Fluke Model 434, 435, 345, 125 or Model 43B to determine the extent of the problem. C oltage and Current Measurements Note: The /R ratio method is useful for single-phase branch circuit currents only and should not be used on three phase loads. Page 3 Fluke Corporation FCT Concepts

13 Test your knowledge 1. (n) is a tool that can display a picture of a sine wave.. true-rms meter B. oscilloscope C. average responding meter D. none of the above 2. In electrical terms, the ac rms value is equivalent to the heating value of a particular waveform - voltage or current.. dc C. peak B. average D. minimum C oltage and Current Measurements 3. n easy way to remember rms vs. average responding is to think about a.. cup of shortening B. vacation in Bermuda C. complex mathematical equation D. clock 4. can generate harmonics.. Personal computers B. Electronic ballasts C. djustable speed motor drives D. ll of the above 1. B D Chapter Summary Sine vs. Non-Sine Waveforms RMS stands for Root-Mean-Square, a mathematical formula that calculates the effective value (or heating) value of any ac wave shape Sine waves are symmetrical and have rounded peaks and valleys True-rms and verage Responding Meters There are two basic categories of meters and clamps: average responding and True-rms Both types will produce similar measurement results when measuring sine waves Only a True-rms meter should be used on non-sinusoidal measurements Harmonics Harmonics are ac voltages or currents with frequencies that are multiples of the basic frequency Examples include signals from variable speed motor controls, solid state controls, certain types of fluorescent lighting, electronic and medical test equipment, and electronic office machines Harmonics can cause problems in power distribution system Fluke. Keeping your world up and running. Fluke Corporation PO Box 9090, Everett, W US For more information call: In the U.S.. (800) or Fax (425) In Canada (800)-36-FLUKE or Fax (905) Web access: Fluke Corporation. ll rights reserved. Printed in U.S.. Phase 1, Module 3, Rev 2 Page 4 Fluke Corporation FCT Concepts

14 Concepts Measurement Safety Don t overlook safety your life may depend on it. Where safety is a concern, choosing a multimeter is like purchasing a vehicle with an air bag, anti-lock brakes and special restraints for your children. You don't want to skimp and save where safety is concerned, lives are riding on it. But what's the issue with multimeters? s long as you choose a multimeter with a high-enough voltage rating, aren't you safe? oltage is voltage, isn't it? Not exactly! Engineers who analyze multimeter safety often discover that failed instruments were subjected to a much higher voltage than the user thought was being measured. There are the occasional accidents when the meter, rated for low voltage, considered to be 1000 or less, was used to measure medium voltage, such as 4160 where there is no protection because it s used above the rated voltage. Unintentional situations will present themselves, such as a momentary high-voltage spike, or transient, hitting the multimeter input without warning, you need to be protected. New safety standards To protect the end user and their equipment against transients, safety must be built into the test equipment. The task of defining specifications for test equipment was recently addressed by the IEC (International Electrotechnical Commission), an organization that develops international safety standards for electrical test equipment. For a number of years, the industry standard was IEC 348, which was recently replaced by IEC While well-designed IEC 348 meters have been used for years by technicians and electricians, the fact is that meters designed to the new IEC standard offer a significantly higher level of safety. Overvoltage categories The most important single concept to understand about the standards is Overvoltage Installation Categories I through I, often abbreviated as CT I, CT II, CT III, etc. higher CT number refers to an electrical environment with higher power available and higher-energy transients. Thus, a multimeter designed to a CT III standard is able to withstand a higher-energy transient than one designed to CT II standards. Within each category, a higher voltage rating identifies a higher transient overvoltage rating: e.g., a CT III-1000 meter has superior protection compared to a CT III-600 rated meter. The real misunderstanding occurs if someone selects a CT II-1000 rated meter thinking that it is superior to a CT III-600 meter. Here are some quick ways to apply the concept of categories to ensure that your customer gets the correct meter for their application: The general rule-of-thumb is that the closer you are to the power source, the higher the category number, and the greater the potential danger from transients. The greater the available short-circuit current is at a particular point, the higher the CT number. Multiple categories There s one scenario that sometimes confuses people trying to apply categories to real-world applications. In a single piece of equipment, there is often more than one category. For example, in office equipment, from the 120/240 side of the power supply back to the receptacle is CT II. The electronic circuitry, on the other hand, is CT I. In building control systems, such as lighting control panels, or industrial control equipment, such as programmable controllers, it is common to find electronic circuits (CT I) and power circuits (CT III) existing in close proximity. Measurement Safety What you will learn in this module: What is a voltage spike or transient? New safety standards IEC categories What are independent testing organizations? What safety features to look for in a DMM Page Fluke Corporation FCT Concepts

15 What do you do in these situations? s in all real-world situations, use common sense. In this case, that means using the meter with the higher category rating. In fact, it s not realistic to expect people to be going through the category-defining process all the time. What is realistic, and highly recommended, is to select a multimeter rated to the highest category in which it could possibly be used. In other words, err on the side of safety. Independent testing is the key to safety compliance Look for a symbol and listing number of an independent testing lab such as UL, CS, TU or other recognized testing organization. These symbols can only be used if the product successfully completed testing to the agency s standard, which is based on national/international standards. Beware of wording such as Designed to meet specification... Designer s plans are never a substitute for an actual independent test. oltage spikes, or transients an unavoidable hazard s distribution systems and loads become more complex, the possibilities of transient overvoltages, sudden temporary changes in voltage or current, increase. Motors, capacitors and power conversion equipment such as variable speed drives can be a prime generator of these transients, along with lightning strikes on outdoor transmission lines. If you re taking measurements on electrical systems, these transients are invisible and largely unavoidable hazards. They occur regularly on low voltage power circuits, and can reach peak values in the many thousands of volts. In these cases, the user depends on the safety margin already built into the meter for protection. The voltage scale and rating alone will not tell you how well that meter was designed to survive high transient impulses. Transient protection The real issue for multimeter circuit protection is not just the maximum steady state voltage range, but a combination of both steady state and transient overvoltage capability. Transient protection is vital. When transients ride on high-energy circuits, they tend to be more dangerous because these circuits can deliver large currents. If a transient causes an arc-over, the high current can sustain the arc, producing a plasma breakdown or explosion, which occurs when the surrounding air becomes ionized and conductive. Remember the old Frankenstein movies with the arc of voltage climbing some rods? Well, the result is an arc blast, a disastrous event that causes more electrical injuries every year than the better-known hazard of electric shock. Use the right high-energy fuses Transients aren t the only source of possible short circuits and arc blast hazards. One of the most common misuses of handheld multimeters can cause a similar chain of events. If the test leads are left in the amp terminals and then accidentally connected across a voltage source, the low input impedance becomes a short circuit! It doesn t matter if the selector dial is turned to volts; the leads are still physically connected to a low-impedance circuit.* That s why the amp terminals must be protected by fuses. Those fuses are the only thing protecting the meter and the end user from harm. *Some multimeters, such as the Fluke 80 and 280 Series, have an Input lert, which gives a warning beep if the meter is in this configuration. Use only a multimeter with amp inputs protected by high-energy fuses. Never replace a blown fuse with the wrong fuse. Use only the high-energy fuses specified by the manufacturer. These fuses are rated at a voltage and with a short circuit interrupting capacity designed for your safety. Measurement Safety Page 2 Fluke Corporation FCT Concepts

16 Look for these safety features in a DMM and it s leads: Proper CT rating for the testing environment Fused current inputs. Use of highenergy fuses (600 or more) High-voltage protection in resistance mode (500 or more) Protection against voltage transients (6 k or more) Independent safety organization approval/ listing (e.g., UL or CS) Meters and test leads with double insulation Meters with recessed input jacks and test leads with shrouded input connectors Safety-designed test leads with finger guards, a non-slip surface and shrouded terminals Meter and test leads made of highquality, durable, non-conductive materials The bottom line Safety is everyone s responsibility. But, ultimately, it s in the hands of the end user. No tool by itself can guarantee safety. It s the combination of the right tools and safe work practices that provides maximum protection. If your customer is faced with the task of replacing their multimeter, ask them one simple question before recommending a meter: What is the worst-case scenario of your job and what category does your use or applications fit? Once known, choose a meter rated for the highest category your customer could be working in. Then, look for a multimeter with a voltage rating for that category matching their needs. While you re at it, don t forget the test leads. IEC applies to test leads, too: they should be certified to a category and voltage as high or higher than the meter. When it comes to your customer s personal protection, don t let test leads be the weak link. Measurement Safety Page 3 Fluke Corporation FCT Concepts

17 Test your knowledge 1. (n) is a sudden change in voltage or current.. surge B. arc C. transient D. rating 2. One of the newest safety specifications developed by the IEC is.. IEC C. IEC 348 B. IEC D. IEC Measurement Safety 3. If a customer is purchasing a meter to measure the lighting system in a large building, they should look for a meter with a rating.. CT I B. CT II C. CT III D. CT I 4. High energy fuses protect the input to the meter.. voltage B. resistance C. current D. None of the above 1. C 2. D 3. C 4. C Chapter Summary Transient Sudden temporary changes in voltage or current Motors, capacitors and power conversion equipment such as variable speed drives can be prime generators of transients IEC (International Electrotechnical Commission) n organization that develops international safety standards for electrical test equipment General rule of thumb the closer you are to the power source, the higher the category number Overvoltage Installation Categories I through I CT I Electronic (Copy machines, computers and other electronic equipment, etc.) CT II Single-phase receptacle connected loads (ppliance, portable tools, and other household and similar loads, etc.) CT III Three-phase distribution, including single-phase commercial lighting (Lighting systems in larger buildings, equipment in fixed locations, main electrical feeds in industrial plants, etc.) CT I Three-phase at utility connection, any outdoors conductors (Overhead line to detached buildings, run between meter and panel, underground line to pump well, etc.) Fluke. Keeping your world up and running. Fluke Corporation PO Box 9090, Everett, W US For more information call: In the U.S.. (800) or Fax (425) In Canada (800)-36-FLUKE or Fax (905) Web access: Fluke Corporation. ll rights reserved. Printed in U.S.. Phase 1, Module 9, Rev 2 Page 4 Fluke Corporation FCT Concepts

18 Fluke. Keeping your world up and running. Fluke Corporation PO Box 9090, Everett, W US Fluke Europe B.. PO Box 1186, 5602 BD Eindhoven, The Netherlands For more information call: In the U.S.. (800) or Fax (425) In Europe/M-East/frica +31 (0) or Fax +31 (0) In Canada (800)-36-FLUKE or Fax (905) From other countries +1 (425) or Fax +1 (425) Web access: Fluke Corporation. Specifications subject to change without notice. Printed in U.S. 1/2009 FCT Distributor Training Program C-EN-N Rev