3 Fluke testers, different results?

[doogle]

testing an installation(that we have just finished) where the client want to choose a few circuits and check it against the test sheets, Now the circuits are 3- 240mm single core cables in parrallel (24 in total in a data centre) I have tested r1+r2 with 3 different fluke multi function testers that have been callibrated and i get different readings every time,as in 1 tester will give me 2 or 3 different readings on the same circuit , the next 2 or 3 completely different readings and so on,changed batteries, swaped leads, but nothing seems constant, doing my head in,one told me a 6m run had more resistance(0.05 no way) than a 70m run(0.01), only thing i can think of is Edmunsons can't callibrate properly and are ripping us of, think readings should all be about 0.00 -0.01 but getting -0.03 to 0.18( different every time)

 

[lewlec]

hi
ye, same problem with my 1653 from new. never the same reading twice..... wont get another one!

regards
gary

 

[Silly Sausage]

You're trying to measure quite low values at the limit of the range/resolution of the instruments so any errors from probe contact etc. will appear to be amplified.

+/- 0.2 ohms I wouldn't really lose any sleep over.

 

[Marvo]

Can you give the model numbers of the 3 testers you've used?

 

[doogle]

Thanks for that, Fluke does seem a bit random compared to the meggers we used to use, is there a meter that can measure resistance in micro ohms?

 

[doogle]

forget that, just googled it, thanks again

 

[doogle]

Will do Marvo, but tomorrow

 

[needasparks]

Most people get there meters checked but never their leads, I get through loads of leads as they get abused all the time.

 

[MarkieSparkie]

As Archy hinted you are expecting precision beyond the capability of your Fluke MFTs. If you wish to measure such values with greater precision you require a special type of micro-ohmeter called a Ductor. Probably best to hire one if you do not have a regular requirement as they are expensive pieces of kit.

 

[doogle]

the Fluke meters were 1632's

 

[Engineer54]

As Archy hinted you are expecting precision beyond the capability of your Fluke MFTs. If you wish to measure such values with greater precision you require a special type of micro-ohmeter called a Ductor. Probably best to hire one if you do not have a regular requirement as they are expensive pieces of kit.

You also need to know how to use a Ductor tester too, ...ie, test kit settings and testing position of current and potential spikes.... You'll also have to substantially bridge the cables at one end under test, as you don't use wander leads with this kit!! lol!!

 

[Dean Williams]

ive tested for over 6 years with various meters and never come across a high Ze on a TNC-S. Now i've got this fluke 1652C ive found two seperate installations with the tnc-s Ze over 0.68!!!. is it the meter or just a coincidence???

 

[needasparks]

ive tested for over 6 years with various meters and never come across a high Ze on a TNC-S. Now i've got this fluke 1652C ive found two seperate installations with the tnc-s Ze over 0.68!!!. is it the meter or just a coincidence???

How are you nulling the leads ?