Megger CM500 User Manual

User Guide

CM500 Multi-Function Installation Tester

Safety Warnings 3

Initial Setup 4

General Description 6

Features, Controls and Connections 8

Operation 10

Backlight 10

Auto shut-off 10

Switched probe

SP2 10

Checking Earth Potential 10

Voltage and Frequency Measurement 10

Polarity Indication 11

Determining Phase Sequence 12

Continuity Testing and Low Resistance measurement 12

Test Lead Resistance Nulling 12

Low Resistance Continuity measurement 13

Continuity Bleeper 13

Low input resistance voltmeter 13 5Ω Threshold 13

Insulation Testing and High Resistance measurement 14

Loop Impedance Measurement 15

Bonded Metalwork Testing 16

Prospective Short Circuit Current (PSCC) 17

PFC measurement accuracy 17

Earth Loop Resistance measurement at 15 mA 17

RCD Testing 18

No Trip Tests 20

Trip Tests 20

Auto Sequence RCD Test 22

Earth Resistance Measurement 24

Earth Electrode Resistance Measurement 24

Condition and Warning Indication 26

Test Results, Storage, Deletion and Retrieval 27

Serial Cable Connections 30

Specification 31

Accessories 35

Publications 36

Basic and Service Error calculation 37

Repair and Warranty 39

Symbols used on the instrument

Caution: Refer to accompanying notes

Equipment protected throughout by Double or reinforced Insulation (Class

II)

Equipment complies with current EU Directives

Complies with IEC / EN 61557

Contents

SAFETY WARNINGS

Q Safety Warnings and Precautions must be read and understood before the instrument is used. They must be observed

during use.

Q The circuit under test must be switched off, de-energised and isolated before test connections are made when carrying

out insulation and continuity tests.

Q Continuity of protective conductors and earthed equipotential bonding of new or modified installations must be verified

before carrying out an earth fault loop impedance test, or RCD test.

Q Circuit connections and exposed metalwork of an installation or equipment under test must not be touched.

Q Do not move the rotary selector switch position while a test is in progress.

Q The LCD ‘neon’ voltage indicators cannot reveal a Neutral - Earth reversal.

Q After insulation tests, capacitive circuits must be allowed to discharge before disconnecting test leads.

Q The instrument should not be used if any part of it is damaged.

Q Test leads, probes and crocodile clips must be in good order, clean and with no broken or cracked insulation.

Q U.K. Safety Authorities recommend the use of fused test leads when measuring voltage on high energy systems.

Q Replacement fuses must be of the correct type and rating.

NOTE

THE INSTRUMENT MUST ONLY BE USED BY SUITABLY TRAINED AND COMPETENT PERSONS

Read this page before using the CM500.

Your

CM500 has been set up as shown on the label on the

front of this User Guide:-

The

first line gives the setting, which modifies the way the

instrument behaves.

The second line gives the printer report language. This may be Language 1, which is English, or Language 2 which is the language noted on the third line of the label.

Instrument Setup

The instrument setup mode allows you to change the setting, the printer speed and the printer report language.

To display the current setup modes:-

1. Press and hold the

backlight key, then turn the rotary

selector switch from the from ‘OFF’ position to the ‘RCL’ position. The code (printer speed) is displayed.

2. Release the

backlight key.

3. Toggle the

I key to scroll through and display the current

setup modes. as follows:-

To change the Printer speed

1. Toggle the I key to scroll through and display the

code.

2. Press the

SAVE key. The current speed setting is

displayed.

3. Toggle the

RCL keys until the required speed setting is

displayed.

4. To save the new setting, press the

SAVE key. The bleeper

sounds and is displayed. To abort the new setting, press the

EXIT key. is displayed.

To select the Printer language

1. Toggle the I key to scroll through and display the

code.

Initial Setup

2. Press the SAVE key. The current printer report language is displayed as 1 (English) or 2 (as given on the type label on the previous page).

Note:- Language 2 can be changed using the CM500 Setup Disk supplied.

3. Toggle the

I key until the required language setting is

displayed.

4. To save the new setting, press the

SAVE key. The bleeper

sounds and is displayed. To abort the new setting, press the

EXIT key. is displayed.

To select the Setting

1. Toggle the I key to scroll through and display the code.

2. Press the

SAVE key. The current setting is displayed as A

(Continental Europe) or b (U.K.).

3. Toggle the I key until the required setting is displayed.

4. To save the new setting, press the

SAVE key. The bleeper

sounds and is displayed. To abort the new setting, press the

EXIT key. is displayed.

CM500 Setup Disk

The program on the disk enables the second printer language to be changed into any of the separate languages. The program may be run directly from disk. Connect the PC to the instrument via a serial lead.

for DOS type: a:\cm500set and press: Return.

for Windows™ 3.1 or 3.11:

1. From the Program Manager options, select: File

2. From the options given, select: Run.

3. Type:

a:\cm500set and press: Return.

For Windows™ 95:

1. Select the Start menu.

2. Select the

Run option.

3. Type:

a:\cm500set and press: Return.

Follow the instructions given by the program.

The MEGGER CM500 Multi-function Installation Tester is a compact instrument designed to perform all of the functions required by the electrical contractor to fully test domestic, commercial and industrial wiring. Specially designed to comply with U.K., European and other International wiring regulations and standards, the

CM500 may be used on all single and three phase systems with rated voltages up to 300 Volts a.c. rms to earth/ground.

Measured values are indicated on a large backlit analogue/digital LCD and may also be stored in internal memory for later recall to the display, direct printing via a standard serial printer, or downloaded to a PC for storage, analysis and report generation.

The

CM500 is supplied as standard in a protective test and carry case, and with the necessary mains plug lead and 2-wire lead set required to commence testing. Optional accessories include the SP2, a 2-wire lead set with test switch built into one of the probes providing remote operation, and a 5 metre 2-wire lead set for increased accessibility.

Key Features

•

No Trip loop Impedance test

• Storage of test results in memory

• Direct serial printer driver output

• RS-232 Output for PC storage

• Recall stored results to the display

• RCD Ramp test function

• Analogue arc and digital display.

• Selectable backlight

• Optional switchable probe (SP2)

Test Capability

• Insulation

Test voltages of 250V, 500V and 1000V.

• Continuity testing

Fast bleeper Test lead resistance nulling Automatic polarity reversal (

Setting A)

• Loop Testing

Operates regardless of mains polarity (Setting A) Two wires only needed for testing Automatic test start on voltage detection Direct indication of short circuit current. Phase - phase, phase - neutral & phase - earth tests Simple earth electrode test

• RCD Tests

Tests selective (delayed) general and d.c. sensitive RCDs. Two wires only needed for testing Contact voltage and loop resistance displayed. Selectable test current for programmable devices

• Supply voltage and frequency measurement

• Phase sequence indication

• Mains outlet polarity indication

Application

The CM500 may be be connected live to earth or between live conductors of systems that have a rated voltage of 300V a.c. rms to earth and an installation (overvoltage) Category

III or lower.

This means that the

CM500 may be connected to any fixed wiring of a building installation, but not to primary supply circuits such as overhead cables. To maintain user safety and ensure accurate measurements, only use the test leads supplied or

General Description

recommended for use with this instrument. The

CM500 is fuse protected to 440V 10kA. The maximum current which could flow through this fuse in the case of a fault is limited to 10 kA by the impedance of the test leads. There is a fuse accessible in the battery compartment which protects the Insulation and Continuity range. If warning of a ruptured fuse is given during a test, and if the warning symbol is present when attempting to carry out an insulation test with the test leads shorted together, this fuse must be replaced by another fuse of the same type and rating i.e. 500 mA (F) 500 V H.B.C. 10 kA.

Fuse Replacement

To replace the fuse, disconnect the test leads, switch the instrument Off and with a screwdriver, loosen the captive screw holding the battery compartment cover in place. Remove the cover. Depress the fuseholder slightly, and turn a quarter turn anti-clockwise to release. Remove the holder and replace the fuse with one of the correct size and rating. Relocate the fuse holder, depress and turn a quarter turn clockwise. Replace and re-secure the cover.

Battery Replacement

When the low battery symbol appears, the cells are nearly exhausted and should be replaced as soon as possible. When the battery is exhausted, the instrument will not perform tests and the cells must be replaced. Use Alkaline cells IEC LR6 (AA) or 1,5 V nickel cadmium cells only.

To install or replace the cells,

disconnect the test leads, switch

the instrument Off and loosen the captive screw holding the battery compartment cover in place. Remove the cover, lift out and disconnect the battery holder to access the cells. Ensure that the replacement cells are fitted with the correct polarity, in

accordance with the symbols on the battery holder moulding.

Carefully re-connect the battery holder to the plug, replace the battery holder in the compartment, and re-secure the cover. Remove the cells if the instrument is not going to be used for any extended period of time. Stored results are retained when the battery is disconnected.

Test Leads

All test leads form part of the measuring circuit of the instrument and must not be modified or changed in any way, or be used with any other electrical instrument or appliance. The power cord supplied with the

CM500 is a test lead that forms part of the measuring circuit of the instrument. The overall length of this lead must not be altered. If the power cord plug is not suitable for your type of socket outlets, do not use an adaptor. You may change the plug once only by cutting the cord as close to the plug as possible and fitting a suitable plug.

The colour code of the cord is:

Earth (Ground) Yellow/Green Neutral Blue Phase (Line) Brown

Note:

A plug severed from the power cord must be destroyed, as

a plug with bare conductors is hazardous in a live socket outlet.

Incorrect battery cell polarity can cause electrolyte leakage, resulting in damage to the instrument.

Features, Controls and Connections

Press I and TYPE key to:

• Select test parameters

• Enter test result identification

Auto Shut-off Operates after 5 minutes of inactivity by the instrument

(30 seconds in Bleeper mode)

Turn Rotary Selector Switch to:

• Select test position

• Select Download (RCL)

• Select ‘OFF’

Press TYPE key to:

• Select test voltage (MΩ)

• Select type of RCD

• Delete data (in combination with

I key)

Insulation test positions

Continuity test position

VAR test selection

Push TEST

button to:

• Initiate the selected test

• Repeat selected test

Touch finger to Earth Test Pad to:

• Check potential between the Earth connection and your finger

Press key to:

• Display other test results

Press and hold key to:

• Save test results

RCD test selection

Backlight key

Continuity Bleeper position

Lead resistance null position

Recall / Download position

‘OFF’ position

150mA 40ms test selection

Loop test selection

Fuse

Ruptured

Low Battery

voltage indication

3 Phase

sequence

RCD Test

Selection

RCD Type Selection

Lead resistance

null ‘On’

Over / Under

Range

Excessive

Noise

Single Phase

Polarity indication

Plug polarity

Thermal

Trip operated

Touch button -

Earth >100 V.

CM500 Display

CM500 Connections

Backlight

The display backlight gives a clear display of measurements in poor lighting conditions. The backlight will briefly operate when the

CM500 is switched on. To switch the backlight on, press the

key. Press the key again to switch the backlight off. To conserve battery power, the backlight will automatically switch off after a period of 15 seconds (if the battery voltage is low, this period is automatically reduced).

Auto Shut - Off

To extend battery life and reduce unnecessary drainage, the CM500 uses advanced battery management techniques, switching functions off when they are not required. For example, if an external voltage of 25 V or less is applied, no value is displayed unless the backlight is switched on. After a period of inactivity by the instrument, the

CM500 will switch itself off, preceded by a series of bleeps. To switch the instrument back on, press any key.

Switched Probe SP2

This is an accessory which can be used anywhere that the 2-wire lead set is specified in this User Guide. The press button probe duplicates the function of the

TEST key on the instrument,

allowing quick and easy testing.

Checking Earth Potential

To quickly distinguish live and earth, this feature provides display indication if a voltage greater than 100 V exists between the earth connection and your finger.

1. In any switch position except

OFF, RCL and (Ω) ,

connect the earth connection (black for the 2-wire lead set, green for the 3-wire lead set) to earth.

2. Touch a finger to the metal pad on the front panel. This is safe and will not endanger you.

3. If a voltage greater than 100 V exists between the finger (normally at earth potential) and the earth wire, the warning symbol is displayed.

Voltage and Frequency Measurement

The CM500 will display the supply voltage and frequency in all switch positions except

(Ω) , RCL and OFF. The DISPLAY

key will alternate between voltage and frequency.

Power plug connection

1. Insert the power cord plug into an installation socket.

2. Supply voltage and polarity are displayed.

3. Press

DISPLAY to alternate between supply voltage and

frequency.

2-wire lead set connection

If an installation socket is not available, use the 2-wire lead set.

1. Connect the red and black leads to the two conductors to be tested.

2. Voltage between the leads and polarity are displayed.

Note:- Though displayed, when using the 2-wire test set, ‘neon’

Operation

The SP2 probe test key circuit is hazardous live during a test. It is safe in normal use.

Continuity of the

SP2 probe non replaceable fuse must be

confirmed (by testing in the Bleeper range) before making any

measurement.

indication is invalid and should be ignored.

3. Press

DISPLAY to alternate between supply voltage

and frequency.

3-wire lead set connection

If an installation socket is not available and it is necessary to connect to all three conductors, use the 3-wire lead set.

1. On a single phase system connect the red lead to phase, the black to neutral and the green to earth.

2. Supply voltage and polarity are displayed.

3. Press

DISPLAY to alternate between supply voltage and

frequency.

Note: For connection to a three phase system, see ‘Determining Phase Sequence’.

When connected, the instrument will display the supply voltage indicated in the following table:

Polarity Indication

If connected to a single phase power supply by a plug or by the 3-wire lead set, three LCD ‘neons‘ marked

L-PE, N-PE and L-N

respectively will indicate supply polarity. If a voltage is detected between their respective two wires, the ‘neon’(s) will activate. A ‘neon’ will usually flash if one connection is open circuit.

Note:- The presence of a voltage between phase and earth does not prove earth continuity, as the earth could have a high resistance and a voltage would still be measured. To test earth continuity refer to the sections on loop resistance or RCD testing.

Setting A is set, the CM500 will automatically switch Line and

Neutral as appropriate, when in any of

LOOP, Re (earth) or RCD

test functions. This enables a test to be performed without inverting the plug connections. The live terminal of the wall

socket is identified by the addition of a separate symbol adjacent to the ’neons’. The Phase / Neutral reversal and symbol display does not occur in Setting A Insulation and Continuity ranges, and does not occur in Setting b.

Setting A - LOOP, Re (earth) and RCD

Mode

RCD Tests (all Currents)

Loop Resistance

Continuity

Insulation

Download to PC

Off

Switch Position

Voltage Display

L-PE

L-N

L-PE

L-N L-N L-N

L-N

N-PE

No Display

Off

RCL

(MΩ

) L-N

(MΩ) N-PE

(MΩ

) L-PE

(Loop) L-PE/Re

(Ω) R (Ω)

(Ω)

(Loop) L-L/L-N

(RCD) positions

Normal Supply

L-PE N-PE

L-N

L-N Reversed

Neutral Live

Neutral

Open Circuit

Earth

Open Circuit

Operation (Contd.)

Setting A - MΩ and Ω, and Setting b

Determining Phase Sequence

When connected to all conductors of a three phase system, the CM500 automatically displays the sequence of phase rotation.

Connect the

CM500 as follows:Line 1 Red phase Red lead Line 2 Yellow phase Green lead Line 3 Blue phase Black lead

If connected as above, the symbol is displayed when the

sequence is 1:2:3, or Red-Yellow-Blue. The symbol is displayed when the sequence is 1:3:2, or Red-Blue-Yellow. If one of the lines is faulty, neither of the symbols is displayed and the normal ‘neon’ polarity indication is shown.

To measure the phase to phase voltages, the following switch positions are used:-

Switch position Voltage Shown

(MΩ) L-PE Red and Green Leads V

1-2

(MΩ) L-N Red and Black leads V

1-3

(MΩ) N-PE Black and Green leads V

2-3

Continuity Testing, Low Resistance and kΩ Measurement

The CM500 will measure low resistance from 0.01Ω to 99.9Ω and will automatically change range to kΩ up to 99.9 kΩ using the 2-wire lead set. Up to 10 Ω of test lead resistance may be subtracted using the test lead resistance nulling range. Measurement is displayed on the large digital display, and the analogue scale from 0 Ω to 20 Ω, or 0 to 20 kΩ.

Setting A, automatic polarity reversal is carried out with the

CM500 measuring resistance with both positive and negative current flow. Normally the average of the two results will be displayed.

Test Lead Resistance Nulling

The CM500 measures total resistance between its terminals, including the resistance of the test leads. The value of the test leads can be automatically nulled.

1. Firmly short the ends of the test leads together.

2. Select (Ω) lead resistance null position.

3. Press the

TEST key. The test leads are checked.

0.00 Ω is displayed to confirm that a new lead value has been stored.

CM500 will automatically display any voltage over 25 V

between the two test leads, and inhibit testing if >5 V.

Normal Supply

L-PE N-PE

L-N

Normal Supply

Neutral Live

Neutral

Open Circuit

Earth

Open Circuit

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Megger CM500 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual