Amprobe MEGATEST-5000 User Manual

MEGATEST 5000

5000 V MEGOHMMETER

Model#: AMB-5 KVD

Owner’s Manual

1. ACCIDENT PREVENTION AND SAFETY MEASURES.................................................................................................... 2

1.1 D

1.2 A

URING USE ....................................................................................................................................................................... 2

FTER USE.......................................................................................................................................................................... 3

2 OVERVIEW............................................................................................................................................................................... 4

2.1 P

2.2 M

2.3 W

2.4 P

URPOSE OF THE DEVICE ..................................................................................................................................................... 5

EASURING PRINCIPLE ....................................................................................................................................................... 5

HAT IS INSULATION RESISTANCE ...................................................................................................................................... 5

OSSIBLE FIELDS OF APPLICATION ....................................................................................................................................... 5

2.4.1 Other possible fields of employment....................................................................................................................... 6

2.5 USE OF THE GUARD ............................................................................................................................................................. 6

2.6 N

OTES ON INSULATION MEASUREMENTS.............................................................................................................................. 7

3 PREPARING THE INSTRUMENT FOR USE....................................................................................................................... 8

3.1 I

3.2 P

3.3 S

NITIAL CHECKS .................................................................................................................................................................. 8

OWER SUPPLY FOR THE INSTRUMENT ................................................................................................................................. 8

TORAGE ............................................................................................................................................................................ 8

4 WORKING INSTRUCTIONS.................................................................................................................................................. 9

4.1 D

4.2 D

4.3 K

4.4 S

ESCRIPTION OF THE INSTRUMENT ...................................................................................................................................... 9

ISPLAY ........................................................................................................................................................................... 10

EYBOARD ....................................................................................................................................................................... 11

UMMARY OF THE MEASURING MODES .............................................................................................................................. 12

4.4.1 Factory-set configurations.................................................................................................................................... 13

4.4.2 Previously memorised configurations................................................................................................................... 14

4.4.3 Extemporaneous instrument configuration........................................................................................................... 14

4.5 I

NSTRUMENT CONFIGURATION AND MEASUREMENT PERFORMANCE ................................................................................... 15

4.5.1 Measurement preparation selection...................................................................................................................... 15

4.5.2 MAN Mode............................................................................................................................................................ 15

4.5.3 AUTO Mode.......................................................................................................................................................... 15

4.5.4 TIMER Mode ........................................................................................................................................................ 16

4.5.5 PROGR Mode ....................................................................................................................................................... 16

4.5.6 Measurement of polarization index....................................................................................................................... 17

4.6 E

XAMPLES OF INSULATION MEASUREMENT........................................................................................................................ 19

4.6.1 Measuring the insulation of the windings of an electrical machine...................................................................... 19

4.6.2 Measuring on a power plant................................................................................................................................. 20

4.6.3 Checking the efficiency of an insulator................................................................................................................. 20

4.6.4 Estimating the insulating strength ........................................................................................................................ 21

4.7 S

4.8 R

AVING THE MEASUREMENTS WHICH WERE PERFORMED .................................................................................................... 22

ECALLING MEMORISED MEASUREMENTS.......................................................................................................................... 22

4.9 PRINTING OUT MEMORISED MEASUREMENTS ................................................................................................... 22

4.10 DELETING MEMORISED MEMORIES..................................................................................................................................... 23

4.11 R

4.12 E

4.13 U

ESTORING THE INITIAL CONFIGURATION .......................................................................................................................... 23

RROR CODE DESCRIPTION ................................................................................................................................................ 23

SE OF THE SERIAL PORT................................................................................................................................................... 24

4.13.1 Reading and downloading the results of the measurements on a computer.......................................................... 24

5 MAINTENANCE..................................................................................................................................................................... 25

5.1 R

5.2 C

EPLACING THE BATTERIES............................................................................................................................................... 25

LEANING THE INSTRUMENT ............................................................................................................................................. 25

6 TECHNICAL SPECIFICATIONS......................................................................................................................................... 26

6.1 TECHNICAL FEATURES ...................................................................................................................................................... 26

6.1.1 Measuring the insulation. ..................................................................................................................................... 26

6.1.2 Current which can be delivered............................................................................................................................ 26

6.1.3 Voltage measurement............................................................................................................................................ 26

6.1.4 Safety .................................................................................................................................................................... 26

6.2 G

ENERAL FEATURES ......................................................................................................................................................... 27

6.2.1 Electric features.................................................................................................................................................... 27

6.2.2 Safety .................................................................................................................................................................... 27

6.2.3 Mechanical features.............................................................................................................................................. 27

6.2.4 Power supply ........................................................................................................................................................ 27

6.2.5 Display.................................................................................................................................................................. 27

6.3 A

MBIENT CONDITIONS ...................................................................................................................................................... 27

6.3.1 Ambient conditions of use ..................................................................................................................................... 27

6.3.2 EMC...................................................................................................................................................................... 27

6.4 S

6.5 R

TANDARD EQUIPMENT ..................................................................................................................................................... 28

EPLACEMENT PARTS ....................................................................................................................................................... 28

7 WARRANTY CONDITIONS ................................................................................................................................................. 29

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1. Accident prevention and safety measures

Please read and understand these instructions BEFORE using the AMB-5KV-D.
This instrument can generate dangerously high voltages.
Only specialised personnel, well trained about electricity and its effects must use it.

When testing, the following is important:

• DO NOT TAKE MEASUREMENTS IN AN EXPLOSIVE ATMOSPHERE. i.e. GAS,
FUELS OR DUST.

• Do not take measurements in wet environments

• Do not touch exposed metal parts; i.e. alligator clips, ends of test leads, circuits, etc.,

while taking measurements

• Prevent any accidental contact of yourself or others with the measuring voltage.

• Make sure the test voltage does not damage any component unable to withstand it.

The following symbols have been used in this manual:

o

p

t

Warning: comply with the instructions in the manual. Any improper use could
damage the instrument, the equipment being tested or cause personnel
injury.

Danger High Voltage.

Instrument with double insulation.

1.1 During use

Following are two general guidelines for setting up the tests. These must be integrated
from time to time with a detailed analysis depending on the actual circumstances.

While measuring on equipment:

- Seal off the testing area and do not allow other people to approach it. If
necessary, put up a sign.

- Have enough room available, plus properly insulated tables or supports.

- Take note of which parts could be live should there be defective insulation.

- Keep the area and the measuring cables clean from dust, oil or other foreign

matter.

- On a routine basis, check for any abrasion or breakage on the measuring
cables.

- Never exceed the maximum testing voltage for which the tested device was built
and/or rated.

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When measuring insulation:

- Cut power off from the installation before preparing for the tests.

- Seal off the testing area and do not allow other people to approach it throughout

the duration of the tests.

- Seal off the installation being tested, disconnecting those branches of it which
are not involved in the test.

- When measuring a section, make sure the test leads are at least 1 “ (25 mm)
apart in order to avoid discharges or unwanted coupling.

- Isolate areas not involved, so unwanted voltages do not reach them.

- Take note of which parts could be live should there be defective insulation.

- Never exceed the maximum insulation voltage the installation was built for.

- Disconnect from the installation any equipment (transformers, bells, intercom

systems, antenna systems, pumps, timers, lights…) which might be damaged by
the measuring or might make it less reliable.

Danger due to capacitance. Measuring over a very large installation or on
condensers can lead to a dangerous accumulation of power. Always wait for

p

the voltage to go back to zero before disconnecting the instrument.

WARNING

1.2 After use

• Once measuring has been completed, press the OFF key to turn the instrument off.

• If you expect not to use the instrument for a long period of time, take the batteries out.

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2 Overview

Thank you for purchasing one of our instruments, we are a leading company in the field of
electrical measuring equipment.
Amprobe has been in the marketplace for over 50 years, and intends to satisfy our
customers’ requirements by providing increasingly reliable and innovative products.

The AMB-5KV-D “MEGATEST 5000” is for demanding and professional customers who
are looking for increasingly accurate INSULATION measurements.
It provides flexible measuring, easy programming and accuracy. It can measure up to
5000V while keeping control of every factor involved (insulation resistance, voltage and
measuring time).

This instrument has been made according to the strictest rules on safety, using top quality
material and technical methods.
No effort has been spared to create a product that can adapt to changing standards and
regulations in the field of insulation measurement. That is why this instrument will be in the
forefront for years to come.

This manual contains all the information needed to use the instrument correctly. It also
points out the dangers due to its improper use, specifying the precautions to be taken in
order to ensure the safety of the user, the instrument and the equipment being tested.

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2.1 Purpose of the device

This instrument can be used to measure the insulation of installations, equipment,
insulating material and so on.
Testing must be performed with no other voltage present, and after having disconnected
the parts not being measured or which are unable to withstand the testing voltage.
This instrument is also able to measure the voltage present before the test, to display it
and to inhibit starting up of the measurement in case the tested element should be live.
The pre-set measures are, in most cases, sufficient for using the instrument without any
additional programming, employing the settings that were prepared at the factory.

2.2 Measuring principle

The instrument applies the requested voltage to the object being tested (material or
equipment or installation), measures the circulating current and calculates the relevant
insulation resistance.
While measuring, the instrument simultaneously detects and displays the resistance,
making it possible to calculate its variation through time.
In certain situations (e.g. very large electrical installations or measures on condensers),
there can be a stray capacity parallel to the resistance to be measured. This stray capacity
is due to the presence of conductors running next to each other, and can sometimes be
quite high. In such a case, the value of the resistance displayed can start out from a very
low value and reach - in no short time - the real value of the insulation resistance.
In this case, therefore, the measurement is deemed to have been completed only when
the displayed resistance value stabilises at less than a certain tolerance (normally 10%).

2.3 What is insulation resistance

We are used to thinking of insulation as a total inhibition of the passage of electrical
current. This approximation is valid in most cases.
However, when we have to measure an insulation resistance, this approximation no longer
holds true: we can imagine an inhibition that is not total, but simply very great.
Insulation is known to depend on the physical features of the material involved and on its
dimension, and from an electrical point of view appears as a resistance, of course of a
very high value. The higher the resistance the better the insulation.
Every kind of material has its maximum permissible voltage, depending on its thickness.
When this value is exceeded, the insulation may be perforated (discharge). This voltage
value is called insulating strength, and its value is always related to the thickness of the
material. When measuring insulation, one must never exceed the maximum permissible
voltage (insulating strength x thickness of the material) since it can lead to deterioration of
the material (perforation).

2.4 Possible fields of application

This instrument is most frequently used to make sure the insulation of electrical
installations or equipment complies with the relevant regulations.
Measurements taken in the "PROGR" mode make it possible to increase the voltage
slowly. This way the efficiency of an insulator can be checked out, the insulation
resistance should stay more or less the same even when the voltage is increased. Should
the resistance diminish as the voltage is increased, this will mean that the insulator is not a
good quality one. Continuing the test might lead to an electric discharge and the
perforation of the material.

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When the meter is in its "TIMER" mode, set a duration of 10’ to determine the efficiency of
an insulator at a certain voltage. During the test, insulation resistance may diminish,
remain steady or increase. Diminishing resistance means insulation is not good. On the
contrary, the more the resistance increases the better the insulation.
This instrument can also be used in a laboratory, and without regard for legal regulations,
in order to establish the efficiency of electronic equipment, installations or boards. This
kind of use, however, requires further technical skills so as not to damage the device being
tested.

2.4.1 Other possible fields of employment

In the field of automobiles, this instrument can be used to check the efficiency of the
battery ignition, spark plug cables or spark plugs without having to dismantle parts in
difficult locations.

Sparking promptness measurement in heating plants: a spark is generated in order to start
combustion in gas and Diesel fuel systems. As time passes, the spark generator - just like
the spark plug in a car - loses its efficiency and spark generation becomes increasingly
difficult.
A diagnosis can be performed by measuring the insulation of the electrode that launches
the spark. If insulation is poor, then it will be necessary to replace the electrode. If the
insulation is good, then it will be necessary to check the generator creating it.

Measuring insulation efficiency for manufacturers of transformers or electric motors.
The quality of the insulation can be monitored in order to take countermeasures in case of
deterioration, before the quality goes below the acceptable level.

2.5 Use of the guard

In certain cases, surface currents may falsify the measurement.
Application of a voltage to an insulator that you want to measure can create two different
currents: one flowing inside the specimen, the other moving across its surface. They are
parallel. If you want to measure only the resistance due to the current flowing inside the
specimen (which is the meaningful resistance), you will have to use another wire to absorb
the surface current (see figure).

(+) (-)

GUARD

Measurement current
Surface leak current

Since the voltage between the GUARD and (-) is very low, only those currents indicated
above will circulate.

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2.6 Notes on insulation measurements

Measurement of such a high resistance as insulation resistance is very critical, since the
currents involved are minute, even lower than those circulating inside our nervous system.
When performing measurements, in order to avoid making mistakes take the following
precautions:

• Keep the measuring cables suspended in the air, or at most resting on one point only.

• The area surrounding the measuring equipment and the equipment being tested must

be free of any object.

• Nobody must circulate near the cables or the resistance being measured.

• The operator must not move and, especially, must not move his/her arms.

These precautions are especially important when measuring resistances higher than
50GΩ.

Such precautions are required because any kind of movement leads to capacity variations
that introduce themselves parallel to the resistance being measured. Each capacity
variation implies a variation of the electrical charge; if the capacities are very small, then
the relevant currents will interfere with the equally small ones circulating in the test
specimen.
We advise you always to use the Guard terminal.

Even the presence of air currents can affect the results of the measurement.

The diagram below shows the stray resistance due to air conduction and the stray
capacitance, Sc, present between the operator and the measuring circuit.

RESISTANCE

BEING MEASURED

Sc

INSTRUMENT

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3 Preparing the instrument for use

3.1 Initial checks

Before being shipped, the instrument is checked from an electrical and a mechanical point
of view.
Every precaution has been taken so the instrument can be delivered without damage.

However the user is advised to look the instrument over quickly in order to check for any
damage during shipment. In case of any fault, contact the forwarding agent at once.

We also suggest making sure that the package contains every part listed under heading

6.4. In case of any discrepancy, contact the dealer.

Should it be necessary to return the instrument, please follow the instructions under the
heading 7.

3.2 Power supply for the instrument

The instrument is fed by 4 each, 1.5 volt, “D” size alkaline batteries (not included)

Endurance with new batteries is as follows:

250 measurements V = 5000 V Rx = 5 MΩ (minimum) t = 1 min.
450 measurements V = 500 V Rx = 500 kΩ (minimum) t = 1 min.

Before measuring, make sure that the "low battery” indicator is not lit (chap. 4.2, symbol

4).
When the "low battery” indicator is lit, measurements can still be performed, but with very
low resistance, it might not be possible to reach the rated voltage, and the measurement
would not be valid.

3.3 Storage

If the instrument has been kept in a cold environment and the measurement must be
performed in a warm place, the sharp change in temperature would make humidity
condense and this would falsify the measurement.
In this case, 15 min. must be allowed for the instrument to stabilise its temperature and
allow the condensation to evaporate.

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