insulation resistance test

[still learning.]

hi again, I havedone a test in my garage it has it's own cu with two cb's one for lights one for sockets. I have one double socket. I did the test on the socket, I took the line, neutral, earth wires out and did the test and got a reading 1000m and the ohm's sign ( I take it this is 1 megga ohm ) but shouldn't I get a reading of at least 2 megga ohm, I even tested a length of brand new cable and got the same result. My test lead has a flat bit where it got squashed in the case, I thought that could that be reason for my low reading's. but continuity is fine?

cheers

 

[ezzzekiel]

reading will depend on condition of insulation, however new cable should be way higher - suspect the squashed lead is causing the reading plug a diff lead in and retest

 

[andekoch]

1000m and ohm symbol is 1000 megga ohm ie very high 1000 megga being 1 billion so the meter is saying 1 billion ohms. check your meter manual and you will proabaly find this is how your meter reports an off scale reading.

 

[robd]

You want the same result as if you hold your testers out in front of you and test accross nothing at all, fresh air, i.e. no contact between any of the conductors, for example you might get a reading >200 mega ohms (greater than 200 million ohms). That should do you nicely! In some instances loads on the circuit will give you a low reading or a dead short, for example transformers, smoke detectors etc.

 

[still learning.]

I have done the test like that and got the same 1000m and the ohm's symbol. I have a metrel 3002 and it has a tick or cross at the end of each test and I get a tick with this reading to say it has passed. it does the other tests ok like continuity and this is why I am unsure if it is my leads or not.

 

[robd]

got a reading 1000m and the ohm's sign ( I take it this is 1 megga ohm ) but shouldn't I get a reading of at least 2 megga ohm,

You are getting at least 2 megga ohms, megga being million, you're getting 1000 megga ohms.

I have done the test like that and got the same 1000m and the ohm's symbol. I have a metrel 3002 and it has a tick or cross at the end of each test and I get a tick with this reading to say it has passed. .

If you're getting 1000megga ohms AND a tick to say it is passed, I can't see the problem, it's testing out exactly as it should pal.

 

[still learning.]

ok thanks, so if there was a problem it would have shown 1m and the ohm sign (1 megga ohm) but mines ok cos i'm getting 1000megga ohm. is that right

 

[robd]

Yeah 1 is your minimum value but anything under 2 requires further investigation, think that's how the saying goes

 

[J@mes]

yes, that is fine. why not take a picture of the display and we may be able to help better?

But by the sound of it, you are getting 1000M Ohms.

 

[still learning.]

mine then is saying >1m ohm so anything with that reading would need investigating because it's under 2?

 

[J@mes]

deleted

 

[still learning.]

tried uploading a photo but it won't let me it say's te file is too big and i don't know how to make it smaller.
thanks for all you help.

 

[robd]

depends if it's 1 mega ohm or 1000 mega ohm which you put in your first post...I suspect you're getting your wires crossed, if it is 1000 mega ohms you're 1000 times greater than the minimum value which, I think is safe to say is more than sufficient!

Now I'm off to the pub Have a good one

 

[SimpleSimon]

If you are testing with the probes out in front of you nothing attached and press the button it'll read >1000 this symbol > means 'greater than' so greater than a 1000 megohms. This is the best reading.
A bad reading will read 1.0 megohms.
Remember insulation is a high resistance reading.
Continuity is a low resistance reading. Your going to see figures of 0.x because they are smaller readings.

 

[telectrix]

tried uploading a photo but it won't let me it say's te file is too big and i don't know how to make it smaller.
thanks for all you help.

try reducing the resolution on your camera before taking the photo. you need to set it at something like 640 x 480. no use trying to upload a 10megapixel image.

 

[still learning.]

Thanks, this is what I am getting

 

[telectrix]

there you are then. >1000Meg. ticks the box. good reading.

 

[still learning.]

It was just that in the books it say's that 1 megga ohm is acceptable but anything under 2 megga ohms needs investigation and because I was getting greater than 1 and not 2, I wasn't sure. thanks for clearing that up.

 

[Sintra]

You are getting greater than 1000 not 1.