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Meggar Insulation tester

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electricano

New Member
anyone ever used meggar insulation tester?i wonder what is it used for?can anyone explain to me?why do we need to use it?
 

andrew2022

New Member
to test insulation on wires.

e.g. when a house is re-wired your susposed to carry out various tests before connecting it to the supply. 1 test is the insulation. u must also use double the normal voltage (thats why u have 250v, 500v and 1000v)
nd yes, i have used one before, many times
 

Nigel Goodwin

Super Moderator
Most Helpful Member
It's also used for testing "work experience lads" :lol:

I've got another one next week :twisted:

I would like to point out that I use a WW2 exWD megger for this, one with a handle you wind - the modern battery powered ones give a much greater kick!.

Their actual use is for measuring insulation, it's basically a high resistance ohmmeter - but instead of putting 1.5V across the circuit it puts 500V. It doesn't get much use these days at work (in fact it never really did), we mainly use a PAT Tester.
 

Exo

Active Member
electricano said:
anyone ever used meggar insulation tester?i wonder what is it used for?can anyone explain to me?why do we need to use it?
It's also used to test the isolation of electrical engines between frame and coils
 

Phasor

Member
. u must also use double the normal voltage (thats why u have 250v, 500v and 1000v)
They do come in higher voltages, for testing transformers and high voltage cables - The one I have been using recently does 2.5kV and 5kV. Also we use an 80kV test set, and if we need more than that, we have a truck with a 250kV transformer on the back :twisted:
 
megger

Megger- Insulation resistance tester.

Used to test insulation.......good the insulation is.

get a multy core cable test between red and black wire with an Ohm meter, if insulation is goog (no damaged insulation betweenwires) you should read some meg ohms ( 40MOhm) on the meter.

But if you apply high voltage ( domestic 240V), There would be short or leak if insulation cannot stand for high voltages .

To test the insulation we apply high voltage ( Megger usualy 500V for domestic insulation) to test the insulation resistence.

Under this voltage the resistance should read 1MOhms on the scale.
Then we know It has good insulation meterial and can stand for high voltages (240V for domestic )
 

panic mode

Well-Known Member
It's used to test ANY insulation, not just wires.
That's one of the tools electrical safety inspector brings to check
each of our machines before we ship them to customers. Same
goes for individual components (power supplies, motors, cable assemblies etc.) that do not have approval logos (cUL, CSA).
As machine builder, we get inspectors come every three-four days
and megger is used quite often.
 

spuffock

Member
The Megger is current limited, it will give about 8 milliamps into a short circuit. If you have a good contact with the skin, it is just possible to show no obvious reaction to it. One of the younger electricians tried the old "Hold these wires,mate" routine on me. I washed my hands first, and held the croc clips tightly with wet hands while he wound the handle like fury. Afterwards, I walked away from him thinking "wait for it!"
Sure enough, "AAAGH F***!!!" He HAD to try it himself. :twisted:
 

Nigel Goodwin

Super Moderator
Most Helpful Member
spuffock said:
The Megger is current limited, it will give about 8 milliamps into a short circuit. If you have a good contact with the skin, it is just possible to show no obvious reaction to it. One of the younger electricians tried the old "Hold these wires,mate" routine on me. I washed my hands first, and held the croc clips tightly with wet hands while he wound the handle like fury. Afterwards, I walked away from him thinking "wait for it!"
I always tell the work experience lads to hold the leads as tight as they can - but they never believe you 8)

Although the last lad we had (called Nick) did, and as a result he didn't get a shock.
 

Klaus

New Member
grrr_arrghh said:
why does holding it tighter reduce the shock?
Think 'short circuit', how many volts are across a short? zilch, the resistance is too low.
The megger is current limited so the output voltage can only build up across some appreciable resistance. With a dead short you have the maximum current flowing, with the minimum voltage required to push it along. :shock:
Klaus
 

Nigel Goodwin

Super Moderator
Most Helpful Member
grrr_arrghh said:
why does holding it tighter reduce the shock?
It's a high impedance source, so the lower the resistance on the output the lower the voltage - by holding the leads as tight as you can, particularly if you have damp or sweating hands, it pulls the voltage too low to feel.

'spuffock' suggested 8mA, I would have thought it was less than that, I'll measure it next time it's out. A 10 megaohm digital meter pulls the voltage output down to about 350V from 500V.
 

Phasor

Member
Nigel Goodwin said:
A 10 megaohm digital meter pulls the voltage output down to about 350V from 500V.
That's pretty poor performance - Aussie requirements are that the output voltage is 500V +/- 10% when loaded with 1 megohm (ie, 450-550V). What model are you using?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Phasor said:
Nigel Goodwin said:
A 10 megaohm digital meter pulls the voltage output down to about 350V from 500V.
That's pretty poor performance - Aussie requirements are that the output voltage is 500V +/- 10% when loaded with 1 megohm (ie, 450-550V). What model are you using?
It's a Record 5G/203, I presume it probably dates from the 2nd World War, it's got War Department marks on it - and it's in a nicely sewn leather case.
 
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