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ELECTRICAL TEST EQUIPMENT

(ETE 1-4)

Learner Guide

TABLE OF CONTENTS

OBJECTIVES PAGE 1 INSTRUCTIONS PAGE 2 PROGRAMME NO. ETE-1 OBJECTIVE PAGE 3 RESOURCE NOTES PAGE 4 PRACTICAL EXERCISE NO. 1 PAGE 8 NOTES PAGE 11 PROGRAMME NO. ETE-2 OBJECTIVE PAGE 12 RESOURCE NOTES PAGE 13 PRACTICAL EXERCISE NO. 2 PAGE 16 PRACTICAL USAGE EXERCISES PAGE 19 PROGRAMME NO. ETE-3 OBJECTIVE PAGE 20 RESOURCE NOTES PAGE 21 PRACTICAL EXERCISE NO. 3 PAGE 27 PRACTICAL USAGE EXERCISES PAGE 30 PROGRAMME NO. ETE-4 OBJECTIVE PAGE 31 RESOURCE NOTES PAGE 32 PRACTICAL EXERCISE NO. 4 PAGE 35 PRACTICAL EXERCISE NO. 5 PAGE 37 CONCLUSION PAGE 38

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OBJECTIVES OF THIS SERIES What will you be able to do? (When you have completed this series). ETE-1 Identify and describe the purpose of:

o Probe Testers. o Voltmeters. o Ammeters. o Ohmmeters. o Multi-meters. o Mega-Ohmmeters. o Earth leakage Testers. o Safety and care in the use of electrical test equipment.

ETE-2 Use and read both analogue and digital multi-meters. ETE-3 Use and read mega ohmmeters. ETE-4 Use and read probe testers and earth leakage testers.


INSTRUCTIONS FOR SELF STUDY The general learning procedure for effective Learner Controlled Instruction is:

o To read through the "resource notes". o To follow any instruction given at the foot of each page in this Learner workbook. o Watch the relevant video programme. o Practice the task as demonstrated in your normal training environment. o Have your Course Controller assess your competency (NB. This is usually done by way

of a CRITERION test, devised by your training department, or by the governing authorities training board for your particular trade.)

NOTE: You may view the videos as many times as you feel necessary in order that you fully understand or "see" how a particular job is done.


PROGRAMME NO. ETE-1 AN OVERVIEW OF ELECTRICAL TEST EQUIPMENT

OBJECTIVE At the end of this programme you will be able to identify by name and describe the purpose of electrical testing equipment pertinent to the electrical trades (excluding high voltage transmission). WHAT RESOURCES WILL YOU NEED?

o This workbook. o The video programme No. ETE-1. o Variety of electrical test instruments including multi-meters, mega-ohm meters, probe

testers, earth leakage tester. HOW WELL MUST YOU PERFORM? Evidence that you have learned the subject matter to the required standard is obtained by:

o Achieving a YES response to all criteria set out on a criterion mark sheet. o Your Instructor or Course Controller.

READ RESOURCE NOTES BEFORE WATCHING THE VIDEO.


RESOURCE NOTES ETE-1 "AN OVERVIEW"

WHAT IS ELECTRICAL TEST EQUIPMENT?

o Electricity is usually an "invisible force". However, as we all know, one can "feel" it - usually as a result of carelessness when working on "live" equipment.

o Electricity is used most effectively to do "work", e.g. to operate motors, lighting, heating and numerous other applications.

o Electricity can exist in both AC. and D.C. form and range from light to heavy current. o Test equipment is necessary for one or more of the following reasons:

1. To establish the existence of an electric flow. 2. To establish the form of the electrical force i.e. be it AC or DC. 3. To measure its value in terms of voltage (Potential Difference) or Amperage (Current Flow). 4. To assess resistance to flow in ohms. 5. To establish safe conditions for the use of electrical apparatus.

o An electrical test instrument therefore is a device which establishes the existence and value of electrical force or electrical operation.

TYPES OF TEST EQUIPMENT Perhaps the simplest of all test equipment is the good old "test lamp", usually a homemade device consisting of a bulb (globe) holder and two connector leads. This is however dangerous, especially if used on AC. circuits, but is considered "safe enough" for low voltage D.C. work (e.g. on your car). A test light can only do one thing ... it can tell you that a circuit is "live" ... but how do you establish what the "value" of the electrical effect is? A more effective instrument is a volt-meter. Voltmeters, when connected to a circuit will be activated by the electrical source and also provide a "reading" of the available voltage (Potential difference). Nowadays, voltmeters are usually installed as permanent meters on electrical distribution units etc. Voltmeters may be obtained as AC. instruments or D.C. instruments. On electrical installations the need to check the current draw, or AMPERAGE, is usually important. To do this an AMMETER would be connected into the circuit. Ammeters are also rated as either A.C. or D.C.


TYPICAL CONNECTION FOR AMMETER (A) AND VOLTMETER (B) ON A.C. LINE

NOTE: The connecting of voltmeters and ammeters differs. Voltmeters are always connected in "parallel". Ammeters are always connected in "series".

TYPICAL CONNECTION FOR AMMETER (A) AND VOLTMETER (V) ON COMMON EARTH D.C.

LINE Another important electrical test instrument is the "ohmmeter" used to measure electrical resistance. It is important to remember that ohmmeters are not connected to live circuits! Ohmmeters are normally battery operated and are used to measure the resistances of such components as heating elements, electronic components such as resistors and for heavier applications such as motor windings. Nowadays nearly all portable instruments are combined into a single piece of equipment, usually referred to as a MULTI-METER. MULTI-METERS Nearly all multi-meters of modern design have the built-in ability to measure amperage, volts and ohms. They also posses the ability to measure both A.C. and D.C. supplies. Many too are capable of providing such functions as milli-amp, diode checks and other useful capabilities. A common feature of all multi-meters is that they have a "function switch" which must be set to a specific position in order to measure various electrical values.


As mankind moves further into the "high tech" era we are now able to obtain multi-meters which are electronic and provide liquid crystal displays (L.C.D.) for reading. This takes the guess work out of reading complicated needle type displays. A meter with a L.C.D. display panel is known as a DIGITAL type meter. Needle type meters are referred to as ANALOGUE meters. MEGA-OHM METERS In certain applications it is necessary to establish very high resistance values for example in electric motor stator windings for purposes of testing the insulations. A regular ohmmeter is not able to provide values over a few thousand ohms (K Ω). On the other hand, a mega-ohm meter can provide readings in the Mega (1 million) range. All mega-ohm meters have built in D.C. generators, to create a voltage surge that is sent through a conductor on test. Various voltages may be necessary and for this reason it may be necessary to have two or three mega-ohm meters in your shop. The average meter is capable of creating from around 50V up to 500V. Two types of mega-ohm meters are generally used today namely "motorised" or "electronic". This indicates how the D.C. voltage is generated. In the case of a "motorised" meter the voltage is created by manually turning a crank handle. Electronic instruments simply require the push of a button to activate a battery circuit which in turn creates the necessary volt surge. Most mega-ohm meters also have, in similar style to multi-meters, a "function switch" which provides a low ohms scale reading. This convenient function allows the instrument to be used as a continuity tester or to measure resistances of small value down to approximately one ohm. NOTE: The term "megger" is often used by electricians to describe any Mega-Ohmmeter. Megger is a "brand name" of a popular tester, manufactured by the James G Biddle Company in Plymouth, Pennsylvania U.S.A. OTHER TEST EQUIPMENT The modern day electrician will find himself performing many diagnostic chores. One instrument that every electrician will inevitably make use of is the next test instrument described, namely the "Probe Tester" also called a "Line Tester".


The probe tester is used to test the voltage at plug socket points and in other situations including 3 phase Distribution Boards. An instrument that is complementary to the probe tester is the "Earth Leakage Tester". This device is essential for ensuring the "safety" of domestic and other circuits which are protected with an earth leakage unit. The Earth Leakage Tester is used for checking:

o Correct operation of the Earth Leakage unit. o Correct polarity of wiring in the wall socket. o The condition of the earth in the wall socket.

SAFETY AND CARE WITH TEST EQUIPMENT

o In many instances you will use test instruments on live circuits. Under such conditions keep in mind that electricity can kill! All the rules regarding safety with electricity still apply when you're testing.

o If you are not sure about the use, or connection of an instrument then do one of two things:

1. Read the instructions. 2. Consult your Supervisor / Instructor.

o To avoid serious damage to ohmmeters (including mega-ohmmeters) make sure that there is NO CURRENT FLOWING.

o Discharge capacitors before making a meter connection (ask your Course Controller for details if you have not been shown how this is done).

o Do not "bridge" an instrument across a switch as this could energise the circuit. o Wherever possible or necessary, isolate circuits at the distribution point. Don't rely

solely upon a line switch as the polarity could be wrong and the neutral live! o Don't use spark generating meters (i.e. mega meters) in explosive environments. o Protect instruments from moisture, dirt, oil, corrosive vapours, excessive heat,

excessive cold, vibration and high inductive electrical/magnetic fields. o Test and replace meter batteries frequently. Don't store an instrument that has a

battery (e.g. ohmmeter) for long periods with the battery installed. Preferably take the battery out to prevent leakage or corrosion.

o Consult the operators guide I manual for details on battery and fuse replacement on instruments so equipped (usually electronic multi-meters).

o Store equipment in protective case and in a clean, dry storage area.


PRACTICAL EXERCISE NO. 1 INSTRUCTIONS 1. Watch the video ETE-1. 2. Answer the questions on test below. NB: The video may be viewed more than once, should you require.



PRACTICAL EXERCISE NO. 1

Answer the following questions.

1. What is an electrical test instrument? ________________________________________________________ ________________________________________________________ 2. What 3 basic functions does a multi-meter have? i) __________________________________________________ ii) __________________________________________________ iii) __________________________________________________ 3. What is important, concerning the meter connection, when using: i) Voltmeter. ______________________________________ ii) Ammeter. ______________________________________ iii) Ohmmeter. ______________________________________ 4. What instrument would be used to test a wall socket? ________________________________________________________ 5. What 3 functions has an Earth Leakage Tester? i) __________________________________________________ ii) __________________________________________________ iii) __________________________________________________ 6. What instrument is used to test the "insulation" of electrical equipment or installations? ________________________________________________________ 7. When working on "live" equipment it is essential that you do what? ________________________________________________________ ________________________________________________________ 8. If you are unfamiliar with an instrument what should you do? ________________________________________________________ ________________________________________________________ 9. What instrument must you not use in an explosive environment? ________________________________________________________

YES

NO


10. List 7 conditions that you should avoid when using and storing test instruments. i) ________________________________________________________ ii) ________________________________________________________ iii) ________________________________________________________ iv) ________________________________________________________ v) ________________________________________________________ vi) ________________________________________________________ vii) ________________________________________________________

CHECK YOUR ANSWERS WITH YOUR COURSE CONTROLLER.

YES

NO


NOTES:


PROGRAMME NO. ETE-2 USING AND READING MULTI-METERS

OBJECTIVE At the end of this programme you will be able to use and read analogue and digital multi-meters in typical situations. WHAT RESOURCES WILL YOU NEED?

o This workbook. o Video programme No. ETE-2. o Assorted multi-meters. o Electrical apparatus / appliances.

HOW WELL MUST YOU PERFORM?

o Achieve a YES response to all criteria as set out in Criterion Test. o In accordance with ruling electrical regulations.

PLEASE READ RESOURCE NOTES THAT FOLLOW BEFORE WATCHING VIDEO.


RESOURCE NOTES ETE-2 "MULTI-METERS"

WHAT IS A MULTI-METER? As the name implies it is a meter having more than one function virtually all multi-meters today are capable of providing the following functions:

o Measuring both A.C. and D.C. Volts. o Measuring both A.C. and D.C. Amps. o Measuring Ohms (Ω) up to several kilo-ohms.

One of the earliest types of multi-meters was called an AVO-meter. The letter A, V and 0 representing Amps, Volts and Ohms. These rather bulky meters are best suited for technicians working on bench functions - but are perhaps the most accurate instruments for high precision measuring. Many multi-meters are designed to be portable and light weight. Perhaps the most popular instrument is the "Fluke" which is accurate, robust and easy to operate and read. There are 2 classifications of instrument types namely: 1. ANALOGUE. 2. DIGITAL. ANALOGUE METERS An analogue type meter features a moving pointer which swings across a demarked display face. The pointer is usually very thin and care must be taken to ensure that, when taking a reading, one observes the pointer from directly overhead. A small mirror surface is normally set into the display face in order that the operator can line up the pointer image thus ensuring an accurate reading. Two test leads are provided with each multi-meter. The test leads are connected into the meters sockets. A black lead is normally employed to act as the "common" or negative lead. TIPS IN USING AND READING ANALOGUE METERS 1. Meter should always be used in a flat-level position (failure to do so will result in inaccurate readings). 2. Meters pointer should be, at rest, directly in line with the left hand zero on Volt / Amp meter scale. (Fine pointer adjustment can be made by very carefully turning the adjusting screw which is situated at the bottom centre of the display face). 3. The Function switch should be set to the desired position before connecting the test leads to the work being checked. 4. NEVER connect the test leads to a potentially live circuit or appliance when the function switch is set to the Ohms (Ω) position. 5. Hold test probes by the insulated portion only especially when working on live circuits / appliances.


6. When "reading" the meter observe the pointer from directly overhead. if you can see the pointers reflection in the mirror than you are not reading accurately. The pointer and its reflection must be "co-incident". One of the biggest problem areas, when reading an analogue meter, especially for inexperienced operators, is that the wrong interpretation of reading is noted. To obtain the correct reading you must observe the following points: 1. Always select the correct "function" on the function switch. 2. Note which analogue 'scale" matches the selected function. For example, if you have selected AC. volts on the function switch then "read" the pointer on the AC. volts scale. 3. Note also whether the function switch has been set to an "expanded scale range". For example, you meter may have X 1, X 10 or even X 100 on its D.C. volts selection. If you have the function switch on X 1 then you simply "read" the pointer I scale as you see it. However, if the function switch is set to X 10 then you have to multiply the pointer / scale reading by 10 to obtain the actual value. 4. When using the meter as an "ohmmeter", select the function switch to any of the "ohms (Ω)" settings. Connect the two free ends (probes) of the test leads. The pointer should swing across the scale, to the right, and come to rest on zero (0) ohms. If it does not, then adjust the pointer position by slowly turning the "ohm adjusting wheel" until the pointer is exactly on zero. NB: If you cannot achieve a "zero" reading by adjustment than check: a) That the test leads are in good order or, b) That the meters battery is not discharged / flat. 5. If when measuring a resistance the pointer moves only slightly then change the function switch position to a higher range. For example; in the "Ω" position the pointer moves very slightly. Re-set the function switch to "10K Ω" position and RE- CALIBRATE" the pointer to zero. Re-assess the measured work piece and remember to multiply to reading by 10. GENERAL NOTES ON ANALOGUE TYPE MULTIMETERS 1. Wherever and whenever possible, store a multi meter in its protective case. 2. Keep meters in a dry area such as in a cupboard. 3. Remove meter battery if you don't intend using the instrument for a long time (e.g. when you go on holiday!). 4. When replacing a battery make sure you do not reverse the polarity. Always fit + to + ,and - to -. 5. Don't wind or wrap the test leads around you meter. Coil them neatly and store in the case when not in use. 6. Treat your meter with care. Avoid bumping or dropping as this will render the instrument useless. 7. Connect voltmeters and ammeters correctly. Voltmeters across the load (i.e. parallel), Ammeters in series. 8. Switch the function switch to the OFF position when you have finished working. 9. Read the meter operating instructions carefully before making any connections.


DIGITAL METERS "Digital" type meters provide either a "liquid crystal display" (L.C.D.) or a "light emitting display (L.E.D.). An advantage of any digital meter is the reduced chance of misinterpreting a reading. The "Fluke" type meter is typical of most digital types and is the type demonstrated in the video presentation. NB: If your meter is of different make, you should familiarise yourself by READING the operators manual / instructions that are supplied.

TIPS WHEN USING / READING DIGITAL MULTI-METERS 1. Perform a "battery" check as per the manufacturers instruction. 2. Connect test leads to the meter sockets, usually a COM (or common) socket is shown - this is for the black lead. 3. Connect the coloured (usually red) lead to the socket relevant to the test you wish to perform. 4. Select the "function" you wish to perform (e.g. D.C. volts) by turning the rotary selector / function switch to the desired position. 5. Connect test leads to the test piece (i.e. the item you are testing) remembering to observe the basic rules of: a) Voltmeters in parallel. b) Ammeters in series. c) Ohmmeter to a "dead" circuit. 6. Observe I note the reading displayed on meters display panel. GENERAL NOTES Observe the same instructions as provided for analogue meters when using or storing your digital meter.


PRACTICAL EXERCISE NO. 2 INSTRUCTIONS 1. Watch video ETE-2. 2. Answer questions on the test below. 3. Practice using your multi-meter in your workplace.



PRACTICAL EXERCISE NO. 2 PROGRAMME ETE-2

Tick the correct answer.

1. An Analogue meter is used in: a) The upright position. b) A flat and level position. c) A hand-held position. 2. The function selection of the multi-meter should be: a) Set to desired position before making test connection. b) Set to desired position after making test connection. c) Set to the off position at all times. 3. The test leads may be connected to a potentially live circuit / appliance only if: a) The meter is set to Ohms position. b) The meter is set to "off" position. c) The meter is set to volts or amps position. 4. An accurate analogue meter reading is obtained when: a) You can see the pointer reflection in the scale mirror. b) The meter pointer is set to zero. c) The pointer is coincident with its reflection. 5. If you are unable to "zero" the ohmmeter pointer then you should: a) Reverse the test leads and battery. b) Check the test leads and battery. c) Select an expanded scale range. 6. When you are faced with a new or "strange" multi-meter you should: a) Read the operating instructions carefully. b) Try the meter out on a 9V battery. c) Dismantle the meter to see how it works. 7. When storing your meter you should: a) Wrap the test leads around it. b) Coil the test leads and fit into case. c) Keep test leads connected to avoid loss.

YES

NO


CHECK YOUR RESPONSES BY: a) Reading the resource notes. b) Watching the video. c) Asking your Instructor.


PRACTICAL USAGE EXERCISES The following suggested exercises will assist you in obtaining experience in the use and reading of your multi-meter. If facilities exist try using both analogue and digital meters on the same work so as to see how they compare in use.

EXERCISE RESULTS

Exercise (1) Establish the available voltage of 1,5 volts battery cell.

__________________ V. (Analogue) __________________ V. (Digital)

Exercise (2) Measure the current flow in a D.C. (low voltage) circuit. NB: Ask your Course Controller for the test apparatus.

__________________ (Analogue) __________________ (Digital)

Exercise (3) Measure the voltage present on an A.C. circuit. NB: Ask your Course Controller / Instructor for the necessary appliance / installation.

__________________ (Analogue) __________________ (Digital)

Exercise (4) Establish the value of assorted ceramic resistors.

R1 ____________________________

R2 ____________________________

R3 ____________________________

R4 ____________________________

NB: Observe all safety rules when working on live circuits. Test A.C. circuits only in the presence of your Instructor.


PROGRAMME ETE-3 USING AND READING MEGA-OHMMETERS

OBJECTIVE At the end of this programme you will be able to use and read a typical mega-ohmmeter in situations that require its application. WHAT RESOURCES WILL YOU NEED?

o This workbook. o Video programme No. ETE-3. o Assorted mega-ohmmeters. o Electrical appliances of installations as prescribed by your Instructor or Course

Controller. HOW WELL MUST YOU PERFORM?

o Achieve a YES response to all criteria as set out on a Criterion Test. o In accordance with ruling electrical regulations.

PLEASE READ RESOURCE NOTES OVER PAGE BEFORE WATCHING THE VIDEO!


RESOURCE NOTES ETE-3 "MEGA-OHMMETERS"

WHAT IS A MEGA-OHMMETER? In its simplest form it is an ohmmeter that is capable of assessing resistances of extremely high values (mega = 1 million). WHERE IS SUCH AN INSTRUMENT REQUIRED? It is required to check any electrical installation or apparatus where insulation is important. In fact another name for a mega-ohmmeter is simply a "Resistance Tester". In industry we need a mega-ohmmeter to check the "electrical integrity" of motors, generators, switch gear and supply circuits in accordance with ruling safety regulations. WHY IS INSULATION SO IMPORTANT? Every piece of electrical apparatus or appliance has two basic components, namely: 1. A Conductor. 2. An Insulation. The conductor allows the free passage of electron movement (i.e. electrical flow). The insulation prevents electron flow. Thus an electric cable consists of a conductive core surrounded by a layer of insulation. The heavier the current the thicker the insulation.

SECTION THROUGH A TYPICAL CABLE.

When the insulation material (such as rubber, P.V.C. or ceramic) is damaged, polluted or aged, current can escape causing either a "short" or a "grounded circuit". A mega-ohmmeter can "sense" any potential leakage when a high voltage D.C. surge is passed through a circuit. Insulation therefore can be described as the means to contain the flow of electricity thus preventing "shorts and grounds" which could prove fatal to persons coming into contact with electrical apparatus.


TYPES OF MEGA-OHMMETERS There are basically two types of such meters namely:

o Motorised, and o Electronic.

MOTORISED A more descriptive name would be "hand driven" because such a type has to be "cranked" by the operator. This action rotates an inbuilt generator or "magneto" which in turn creates a high tension surge of voltage out of the meters test leads. ELECTRONIC In such a type the high tension surge is created via a battery and an electronic circuit. Operation of such a type is by the simple pushing of a button. NB: You will often hear electricians refer to such meters a "Megger testers" or just megger. This term is actually a trade name of an actual "make" of mega-ohmmeter. Both motorised and electronic meters are normally equipped to act as ordinary ohmmeters, used primarily when you need to establish circuit "continuity", or measure values of relatively low resistance. As with multi-meters it is important that you "read" the correct scale and select the correct function when you use a mega-ohmmeter.


TYPICAL MEGA-OHMMETER APPLICATIONS Insulation to earth (i.e. checking whether a circuit is potentially grounded -this could kill you on high voltage equipment). EXAMPLE NO.1: TESTING A 380 VOLT A.C. INDUCTION MOTOR (SIX PIN CONNECTION)

1. When all source of power has been totally isolated:

o Remove terminal box cover. o Remove terminal nuts. o Remove wiring. o Remove any bridge pieces.

2. Establish continuity (using ohmmeter) between termination lugs (e.g. A1 - A2).Make a rough sketch of these positions. 3. Connect one mega-ohmmeter test lead to earth on motor frame. 4. Connect other lead to A1 and take a reading. 5. Take a reading A1, B1, C1, B2, C2, A2. 6. Compare all readings. CONCLUSIONS EXAMPLE NO.1 1. All readings should show above 1.00 M Ω. 2. Difference between highest and lowest reading must not exceed 10%. If a reading shows below 1.00 M Ω the motor insulation is faulty and requires further examination or drying out.


Note: For a 380 V motor a mega-ohmmeter with a rating above 750 volts is required. On motorised mega-ohmmeters the handle should be turned rapidly, approximately 180 - 240 r.p.m. EXAMPLE NO.2: DOMESTIC INSULATION (BEFORE CONNECTION TO MAINS) 1. Ensure that main input supply is disconnected from supplier. 2. Main switch at Distribution Board is off. 3. All bulbs (globes) removed from sockets. 4. All wall sockets switched to ON position (i.e. closed). 5. Connect test lead to earth block. 6. Connect other test lead to Neutral side of main switch. 7. Select the 500 volt range (or use megger rated at 500 volts). 8. Crank handle (or press button) and take a reading. 9. Next, connect test lead to Live side of main switch. 10. Take a reading. 11. Finally, take a reading between Live and Neutral on main switch. CONCLUSIONS EXAMPLE NO.2 Theoretically the test should yield an infinity reading (∞). Any reading below 1 M Ω would not be considered safe and thus the installation would not pass electrical inspection in terms of standard codes of practice. READING THE ANALOGUE SCALE You will notice that the M Ω scale is not linear, i.e. the divisions between values are not equally spaced. The closer we get to infinity the more "cramped" are the divisions. Illustrated below is a typical "face" of a mega-ohmmeter.

It is considered that a low M Ω reading, around 1.00 M Ω or less on an insulation test or earth test, would present an unsafe condition.


Reasons for unsafe conditions include: o Water or dampness in circuits. o Physical damage to insulation. o Incorrectly wired circuits.

SAFETY PROCEDURES WHEN USING MEGA-OHMMETERS 1. Insulation and continuity test must always be made on "dead" circuits. 2. Where applicable capacitors in circuits should be discharged both before and after a mega-ohm test. 3. Never use an insulation tester in explosive environments -a spark generated by the meter could set off an explosion. 4. Ensure that test probe insulation is in perfect condition (see notes on test leads). 5. Do not contact metal portion of probes during the test - a painful shock will result, or worse. 6. Do not work with damp equipment or damp leads as this too will result in electric shock. 7 Keep test instruments clean and dry. TEST LEADS The condition of test leads is extremely important ... if the leads are faulty this may lead to incorrect readings. A possible unsafe condition may be passed as safe because of faulty test leads. It is good and safe practice to check the test leads in the following way.

o Connect test leads to the instrument. o Select the "ohms" scale on selector switch. o Crank handle or press button. o Observe pointer movement. o Conclusion: The pointer should move across scale to the zero mark. If it does not,

then the leads are faulty or the internal meter fuse has blown. CARING FOR YOUR METER A good quality mega-meter is extremely costly. Careless handling and incorrect usage could damage a meter beyond repair. Practice the following tips and your meter should last for your lifetime.

o Check the battery and replace if it is "low". o Remove the battery if you intend storing the meter for long periods (e.g. in excess of

one month). o Periodically inspect the test leads and probes for any damage to the insulation or

probes. o Coil up the leads neatly when storing - don't wrap them around the meter. o Store your meter in its protective case. o Don't connect the instrument to a "live" electrical circuit. o Don't use mega-testers on electronic circuits (this could damage the apparatus on

test). o Discharge any capacitors in a test circuit before connecting the meter.


Important: Long cables may build up a capacitive charge even when isolated. If you're not aware of this ask your Course Controller how this occurs.

o Keep your fingers away from the metal probes during a mega-test. You will receive a shock which, although not fatal, may cause you to jump and lose your balance.

o Select a meter that can produce at least 2 x the rated voltage of the apparatus on test. (E.g. for a 220 volt circuit use a 500 volt meter).

o Last, but not least, READ the operators manual especially if the meter you have differs to that which will be demonstrated in the video programme.


PRACTICAL EXERCISE NO. 3 INSTRUCTIONS 1. Watch video ETE-3. 2. Answer questions on the test below. 3. Practice using your insulation tester in your workplace under the guidance of your Supervisor, or Instructor.




Tick the correct answer.

1. Another name for a mega ohmmeter is: a) An Ammeter. b) A high range meter. c) An insulation tester. 2. A popular name for such a meter is: a) A "Fluke". b) A "Megger". c) A "Megaphone". 3. The ohmmeter Ω selection on a mega-ohmmeter is normally used as: a) A continuity tester. b) A high volts tester. c) A calibration device. 4. A typical application for mega-ohmmeter is: a) Testing electronic capacitors. b) Testing insulation to earth. c) Testing line voltage. 5. When using a "motorised" meter the handle is turned at: a) Approximately 180 - 240 r.p.m. b) Approximately 50 - 100 r.p.m. c) Approximately 1500 - 2000 r.p.m. 6. When using any type of mega-ohmmeter you must be sure that the circuit / appliance on test is: a) Switched off at the wall socket. b) Isolated from source. c) Positively charged. 7. If the pointer does not move when performing a M Ω test you should: a) Replace the batteries. b) Test the leads. c) Overhaul the meter.

YES

NO


8. When storing the meter for long periods you should: a) Ensure that the battery is fully charged. b) Ensure that the leads are not connected. c) Ensure that the battery is removed. 9. When selecting a meter to test an appliance or installation ensure that its output voltage is: a) At least twice that of the appliance / installation. b) At least half that of the appliance / installation. c) At least 1000 volts. 10. When using new or strange meter, for the first time you should first: a) Experiment on various work pieces. b) Ask your Instructor how it works. c) Read the instruments operators manual. CHECK YOUR RESPONSES BY: a) Reading the resource notes. b) Watching the video. c) Asking your Instructor.

YES

NO


PRACTICAL USAGE EXERCISES The suggested exercises will assist you in obtaining experience in using and reading mega-ohmmeters. NOTE WELL: DO NOT PERFORM ANY TEST ON LIVE OR RUNNING EQUIPMENT! If you are not sure about how to discharge capacitors or cable runs ask your instructor before you test such apparatus. EXERCISE 1: DOMESTIC APPLIANCE Use your tester to check: a) Insulation to earth, and b) Insulation between windings on a typical appliance such as a fridge motor, vacuum cleaner, or similar unit. EXERCISE 2: INDUSTRIAL APPLIANCE Use your tester to check: a) Insulation to earth on a 6 point 3 phase induction motor. EXERCISE 3: CIRCUIT INSTALLATION Use your tester, in the presence of your Instructor to test the earth insulation on a 220 volt house or office circuit.


PROGRAMME NO. ETE-4 USING AND READING LIVE LINE TESTERS

AND EARTH LEAKAGE TESTERS

OBJECTIVE At the end of this programme you will be able to use and read both a live line tester (probe) and an earth leakage tester, in typical situations. WHAT RESOURCES WILL YOU NEED?

o This workbook. o Video programme No. ETE-4. o Electrical appliances or installations as prescribed by your Course Controller or

Instructor. HOW WELL MUST YOU PERFORM?

o Achieve a YES response to all Criteria on tests. o In accordance with ruling local regulations.


RESOURCE NOTES ETE-4 LIVE LINE TESTERS & EARTH LEAKAGE TESTERS

Both a "live line tester" and an "earth leakage tester" are commonly utilised in both factory, office and domestic situations. The primary need for such instruments is to establish safety factors. LIVE LINE TESTERS This instrument, also known as a probe tester, or "Duspol", is to the electrician the same as a stethoscope is to a doctor. As its name suggests the instrument is used to "probe" into potentially "live" electrical circuits and establish: a) If a voltage is present. b) If polarity is correct. c) On modern testers - what the voltage value is.

TYPICAL LIVE LINE TESTER.

USAGE OF LIVE LINE TESTER 1. TESTING VOLTAGE AT WALL SOCKET

o Using an insulated probe, open the socket guards / protectors (i.e. via the earth socket) ... and switch on.

o Insert neon leg of tester into the live socket. o Observe the neon light. If it glows than a voltage is present ... if not, then: o Insert neon leg into neutral socket. If it glows then socket wiring is incorrectly

wired (i.e. polarity is wrong). o Insert other leg of instrument into opposite socket. o Press (or squeeze) the actuating button (or ring) and observe the voltmeter. o Spring loaded "flag" will settle in sight glass. o Take reading on the A.C. volts scale. o NB: Instrument may vibrate in your hand, but only if it is on an A.C. supply.


SAFETY TIP Never assume a socket is dead if the tester itself has not first been checked. Use the tester in a socket that you know works (e.g. one that is being used by a fellow worker). If the tester works on a (known) live socket then you may safely assume that a socket that tests dead is in fact dead. 2. TESTING VOLTAGES ON 3 PHASE SYSTEM

a) Testing between live phases (Red, White, Blue) readings should yield reading of 380 volts.

b) Testing between a live phase and neutral will yield a 220 volt reading. NOTE: DO NOT attempt to test a live board unless you have received the necessary training or you are in the presence of your supervisor. 3. SAFETY TIPS FOR LIVE LINE TESTER

o Use an insulated probe (i.e. plastic or wood) to open wall socket guards. o Only hold the tester by its insulated handles, never touch the bare probes

during use. o Keep the probe points away from your body.


o Carry the tester in your hands ... don't hang it around your neck.

NOW WATCH THE VIDEO! THEN ... COMPLETE EXERCISE ON FOLLOWING PAGE.





1. What 3 conditions does a live line tester check? i) __________________________________________________ ii) __________________________________________________ iii) __________________________________________________ 2. If the "neon lamp" glows when the probe is inserted into the neutral socket, what does this tell you? ________________________________________________________ ________________________________________________________ 3. How is the "tester" tested? ________________________________________________________ ________________________________________________________ 4. If the tester "vibrates" on a test, what does this tell you? ________________________________________________________ ________________________________________________________ 5. List 4 safety tips for using live line testers. i) __________________________________________________ ii) __________________________________________________ iii) __________________________________________________ iv) __________________________________________________

CHECK YOUR ANSWERS BY READING NOTES OR IN THE VIDEO.

YES

NO


EARTH LEAKAGE TESTER The primary purpose of an earth leakage tester (E.L.T.) is to check the value, in milli-amps, at which an earth leakage unit trips. A TYPICAL E.L.T. IS ILLUSTRATED BELOW.

USING THE EARTH LEAKAGE TESTER

o Ensure that the control knob is turned fully anti-clockwise before plugging the 3 pin plug into a socket.

o Ensure that the pointer rests on the "zero" position. o Switch the socket on. o The red indicator lamp should come on. If both red and amber lamps come on then

the switch wiring polarity is reversed (i.e. Live and Neutral connections are crossed). NB: This situation must be corrected before continuing with tests.

o Under normal conditions: Press and hold in the activating button. Slowly rotate the control knob clockwise. Observe the pointer / scale reading at the time that the earth leakage trips.

NOTE: The trip should occur somewhere between 15 and 30 milli-amps. (According to the "SAB.S. Code of Practice for Wiring of Premises" - regulation No. 4.5.4a).

o If, during the test, the amber lamp comes on and the pointer does not move then the earth is faulty. This condition should be corrected immediately by a competent electrician.

CARE OF EQUIPMENT

o Keep instruments clean and dry. o Check condition of leads, probes and plugs to ensure that they are in no way

damaged.

NOW WATCH THE VIDEO THEN COMPLETE THE EXERCISE ON FOLLOWING PAGE.



PRACTICAL EXERCISE NO. 5 (E.L.T.) PROGRAMME ETE-4


1. Before connecting the tester ... what should you first ensure? ________________________________________________________ ________________________________________________________ 2. Which colour indicator will come on, under normal conditions, when the tester is plugged in? ________________________________________________________ ________________________________________________________ 3. What fault exists if both red and amber lamps come on when the tester is connected? ________________________________________________________ ________________________________________________________ 4. What milli-amps reading is "normal" for the tripping on an earth leakage unit? ________________________________________________________ ________________________________________________________ 5. What happens, on the meter, if a faulty earth exists? ________________________________________________________ ________________________________________________________

YES

NO


CONCLUSIONS You have now completed the electrical test equipment module. Please note that other instruments are available and new models appear on the market continuously. Before using any new instrument we strongly recommend that you read the operating instruction manual before using. IMPORTANT Knowledge of the use of any testing devise does not automatically entitle you to perform a test. When working on or around live electrical apparatus or installations you must always obey all safety regulations, and have the necessary permits / authorisation to do so.

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