Digital Insulation Tester Meter Megger

[Turpy]

Just received this Megger I purchased on eBay.

I thought it may come in handy now and then for testing various items around the house (love gadgets).
It has three voltage scales, with the highest being 1000v.

The manual (1 page of mostly specs) that came with it says once connected, check the resistance.
Hmmm, but how?
There is a rotary voltage selection switch, with OFF being in the middle, and either side of this it has selections of 1000v, 500v and 250v on both sides.
It's also got a back light switch and PRESS switch for the test.

Can someone please explain how the leads should be connected, what voltages are used for what, which side of OFF should the voltages be used and what sort of resistances are acceptable?

I've emailed the seller for these answers, and his answer was I only sell these things!
Searched the Net without much success.

Have been coming to this forum for years for information, so I hope someone can be of help,

[NCArcher]

Hi Turpy,
The meter you bought is an insulation resistance and earth continuity tester often refered to as a Megger (which is a brand name).
The meter is used to measure the resistance between phases or between active and neutral or between any active conductor and earth. It's also used to test the continuity of the earth conductor.
The three voltage scales are actually the voltage that the meter puts out to test. DO NOT connect the megger to items that contain low voltage electronic components. It will fry them.
To test an extension lead for example, clip one lead to the earth pin and the other to either the active or neutral pin. Select 250V, press the test button and read the resistance off the scale. You should have at least 10M ohm of insulation resistance. Switch the second lead to the other pin and test. Attach the leads to the active and neutral and test.
Then attach the leads to the earth at either end of the ext lead and test. The earth conductor should have less than 1 ohm of resistance. The easiest way to get to the earth pin on the socket end is to plug in a bare plug top(without the cover) so you have access to the backs of the pins.
Pay close attension to where your fingers are when you push the test button because a boot from a megger hurts.
Now that i read back over this it seems about as clear as mud but i hope it helps.

[Ivan in Oz]

Be careful

These High Voltage Insulation Testers

Can and DO Hurt

Can and will KILL!!!

So far I have only been hurt.

I would think that it should also have a "Low Voltage" insulation test Mode

[familyguy]

The reason for the voltage settings up to 1000v is that even though appliances and equipment may be rated for 240v they are required to withstand any voltages surges that may occur, so they are tested at a higher voltage. I don't know the specifics for each type of appliance/equipment, but I do know a local transformer maker that tests the primary secondary insulation at 1000v for all 240v transformers. This is required by law. I've had a boot from these things a couple of times and it is quite unpleasant, but perhaps not as bad a boot from a car spark plug lead.

[Timmo]

It's a good idea to be shown how to use a megger. There are different processes for testing different types of equipment.

There should be a LV ohmmeter function, used for testing motor windings and other devices that have thermistors and other sensitive components.

When testing for earth insulation you test at double the operating voltage. So for a 240v single phase motor you would set it to 500v and for a 415v device you use the 1000v setting for testing earth insulation.

And yes, these things can really hurt. Also don't use them to charge capacitors, if you don't know how to remove one from a circuit, best to pay a professional.

[Sumodog]

Little bit of knowledge is a dangerous thing. Insulation resistance and continuity tester ( commonly known as a "Megger" ) is a tester that is used by electricians to test insulation of the installation. Purpose is to make sure that there is no shorts before connecting the supply.
Integrity of insulation is stressed by applying DC current at 500 V (not double the supply voltage).
Result should be over 1MΩ, unless it is sheathed heating element (they retain moisture) in which case it is reduced to 0.01 MΩ .(AS/NZS 3000.2000.)
I guess it is ok to collect gadgets ( i am guilty of the same crime) but this tool is best left to electrical trade.

[echnidna]

why did you buy a megger as you obviously don't know how or when to use them?

[georgevarghese]

friend,

I can advice u to wait till u learn the usage of megger from the place where u doing apprenticeship. As many people said above, its not fare to fiddle with the instrument unless u dont know how to use it.

good luck

George

[Ivan in Oz]

friend,

I can advice u to wait till u learn the usage of megger from the place where u doing apprenticeship. As many people said above, its not fare to fiddle with the instrument unless u dont know how to use it.

good luck

George

G'Day George,
Might I say "Welcome Aboard"
Good to see someone doing a First Post AND offering help......

Hope you stay and enjoy.

Oh!!
Also I agree with your comments.

Perhaps a $20.oo Digital MultiMeter would suffice

[Turpy]

Thanks heaps to those of you that have posted constructive comments.

Had a play today, and found I had a faulty 15A Extension Cord, so I consider $80 that I paid for it, well worth it.

Very easy to use when you know how.

Cheers

[nev25]

Im with echnidna what did you buy a megger for??

We use it to test the interigty of wireing
And to keep apprentices awake on the job

As Ivan in Oz has said be carefull they can bite (experiance speaking hear)

If you want to learn how to use one you could maybe do a test and tag course at your local Tafe

[thatirwinfella]

i agree with Ivan, unless you know what you're doing with it, a multimeter would have been more appropriate. A poorly or incorrectly used megger can result in damaged appliances, or injury for those with heart problems.

Used properly, it can be handy testing and fault finding device and a wonderful source of enjoyment, when you sneak up behind someone and give them a real shock.

to answer the original question, when it says to test the resistance, it refers to the resistance of the leads. As sparkys frequently connect leads of varying lenght to their meggers, the lead resistance will thus change. By shorting out the two prongs and pushing the test button, the lead resistance will be shown.

On analogue meters there will be an ohms zero adjust dial for you to correct the display. digital meters will either auto adjust, have a zero button, or require you to simply subtract the difference yourself.

typically, the leads are connected as red to the positive terminal on the case, black to the negative. However, in most circumstances it will make no difference to your test results.

The voltage options are used to test the insulation on installations and appliances. Typically twice the working voltage is applied active conductors and measured to earth. As mentioned earlier, beware doing this on electronic circuitry as this will fry many components.

The ohms scale [3ohms on the dial perhaps] is generally used to test the earth resistance of an installation. It's an ohmmeter, plain and simple.

You're very rarely going to have to use it around the house, as any sparky who may do any work for you should have his own. Household stuff has too much internal circuitry for it to be of value... if you're worried about your home appliances, an appliance tester would have been better. Generally they are much easier to use, and less harsh on appliances.

So basically you won't need it and it can get too complicated or dangerous for someone who doesn't know what they're doing to be playing with them.

I'll take it off your hands for twenty bucks...

[georgevarghese]

G'Day George,
Might I say "Welcome Aboard"
Good to see someone doing a First Post AND offering help......

Hope you stay and enjoy.

Oh!!
Also I agree with your comments.

Perhaps a $20.oo Digital MultiMeter would suffice

Thanks man...happy to see u all here. I will try to be an active memeber onwards...

George

[echnidna]

I don't think they use standalone meggers in the test & tag courses run by tafe which are oriented towards people without an electrical background.

[Smurf]

This is a professional testing tool used to test wiring. It must never be connected to any electronic devices or it WILL fry them. Used properly it performs a useful function.

Used incorrectly it's much like handing a loaded firearm to someone who has absolutely no experience with firearms of any kind and doesn't even know how to check if it's loaded. It's just asking for trouble.

Be careful where you put that 1000 volts...