Insulation resistance 0.00megger ohm

[NozSpark]

I don't think that the meaning came across very well in SL's post

Insulation resistance meters are good at measuring Mohms, but when it gets into the low kohms range the meter cannot resolve what it is reading and shows 0Mohms,,, Mohms is the scale that they use. You will find that in actual fact that a 0Mohms reading on an insulation resistance meter when measured using a low voltage ohm meter could easily actually be several hundered ohms.

Therefore 0Mohms as measured on an insulation resistance meter will very rarely be a dead short (a dead short being 0ohms as measured on a low voltage ohm meter)

 

[unphased]

Yes Noz, understood. I am the plonker.

 

[NozSpark]

I wouldn't put it like that myself

TBH we try to be factual as we can on this forum, a lot of students come here and they need to understand these subtle differences

So your posts have prompted a decent debate..

Pushey shovey by Sidey though:O

 

[m4tty]

If you ever get 0.00 M ohms on ir then I stick on continuity to read the actual reading which is normally Ohms/kohms Hth

 

[unphased]

Nice one matty.

 

[Sidewinder]

No uphased, you are not the plonker, that's Rodney!

Anyway, you have prompted a debate, and I hope that my essay will help learners understand further.

Noz, you cheeky mare, not pushey shovey, I was just trying to explain!

 

[kme]

If you ever get 0.00 M ohms on ir then I stick on continuity to read the actual reading which is normally Ohms/kohms Hth

S`funny - I was talking to another member of the forum on the `phone yesterday, and we commented on this - it is one of the failings of MFTs (in my opinion), in that there are a range of resistances which you cannot resolve with your meter, on either the low ohms range, or the (insulation) Mohms range.

One of the reasons I carry multimeters - it can be necessary to know EXACTLY how many Kohms you are reading; and the continuity range will read it as out of range at 2Kohms ; yet the insulation range will not give ANY reading below approx 9.484Kohms. That is one heck of a "dead zone" - IF you need to know what the resistance actually is.

Matty - given the above, I do that too, but many times you`ll get a ">2000" display - so you`re no better off.

 

[steptoe]

Oh dearBe Afraid

Be Very Afraid

Plonker - Voila - Our Rodney will be along soon, just dont turn your back :slap

pi55 off

:|

 

[apprentice87]

Hi all,

Only me....

Now, I will attempt to clear up all this "is 0M Ohm the same as 0 Ohm" by putting it all in simple "laymans" terms if you like...

A test meter can only display a result to a certain number of digits; Are we all agreed on that one???

If the meter is set on a M Ohm scale, and you expect it to read 26 ohms, from the meter's point of view, it is the same as you trying to enter 26 trillion [or whatever] into your pocket calculator, you cannot do it, because your calculator does not have a display capable of displaying that many digits.

Look at it like this. Does concorde have a speedo???? I neither know nor care, but say it did; The first graduation on the dial might be 100mph. If the pilot left the handbrake off and the aeroplane rolled 2 miles down a hill at 40mph and knocked down a small town, just because the speedo needle did not move off the stop, this does not mean that the plane did not move...... It was just outside the range of the speedo to detect this movement.

Now back to the is 0M Ohm the same as 0 Ohm????

No, it is CERTAINLY not..

You see, 0M Mhm, means EXACTLY what it says "no millions of Ohms" there may well be 250,000 ohms, but this is still 0M ohms.

Let us all remember learning to count when we were in primary school....

We learnt that there are units, tens of units, hundreds of units and so on, so 304 would be 3 hundred units, no ten units, and 4 units.

If we now ask the question;

"How many thousands of units are there???"

the answer is 0 ... This does NOT mean, that 304 is the same as 0....

john....

 

[SPECIAL LOCATION]

Has thread finally got back to what I originally said in post#2?

:Cheadbang

I sometimes wonder... why bother posting replies anymore! :|

 

[nick1986]

Yeh after meggering It narrowed down what circuit then I found a light fitting outside with water inside it the seal was perished :^O thanks for asking. Cheers

 

[Zeespark]

meggering it?

AndyGuinness

 

[Sidewinder]

Leave it Zee it's not worth it mate!

 

[Zeespark]

OK:good luck: :innocent

AndyGuinness

 

[Steve3948]

meggering it?AndyGuinness

Well I still say "Lets bell it out" and "Lets Megger it out" it's terminology from the old day's I'm afraid.

 

[Zeespark]

Steve, I have no issue with that, I am the same, I just wouldnt want students here scratching their heads thinking what is a megger test is all. I still call an EICR a PIR, so I am in no way immune to this.

AndyGuinness

 

[philbas]

I Hoover it with my Dyson

 

[Andy™]

Steve, I have no issue with that, I am the same, I just wouldnt want students here scratching their heads thinking what is a megger test is all. I still call an EICR a PIR, so I am in no way immune to this. AndyGuinness

there is a smoke detector manufacturer (Aico IIRC?) that has a sticker on the board, which also states 'do no megger circuit' (or something similar)

and a PIR is still a PIR, just the piece of paper its written on is now an EICR

 

[m4tty]

I Hoover with Henry

 

[Zeespark]

It wouldn't surprise Me in the least if that is the case Andy.

AndyGuinness