Nulling Test leads

[Andy434]

Hi all
i just sent my fluke tester off for calibration, and came back as a fault so needs sending off for fixing, now sods law i have my NICEIC assessment Thursday, so had to purchase the testers within my local wholesalers (as will take 10 days to get to get old ones back)
so i got the Di-LOG DL9118 MFT, seems ok but, having an issue with nulling the leads for live loop testing??
i can only find the option to null leads on continuity test
am i meant to calculate the lead resistance or dose it do it automatically

does anyone know?

thank you in advance, as i this i have warn google and tube out trying to answer this question

 

[multimick]

why would you want to null leads for live testing ?

 

[static zap]

I downloaded manual Page 17 is looking hopeful.
(but yet to find test current for resistance test)
-- I best leave advice to someone who has one ..!!!... --

 

[Dustydazzler]

I have Never null the leads for live testing , infact it never even crossed my mind...

 

[buzzlightyear]

so i got the Di-LOG DL9118 MFT, seems ok but, having an issue with nulling the leads for live loop testing??
i can only find the option to null leads on continuity test

only on r1and r2 you null them . on the megger it starts screaming and even me .

 

[Andy434]

Hi Multimick, am i wrong in thinking that any additional resistance of my leads will effect the result of the ZS live test?
with the fluke tester always nulled the leads for both live and dead testing
however yesterday when i unpacked the tester i tested a very simple installation of a 2 way garage DB that feed 2 x DSO wired in 4mm T+E that was about 6inches away from the DB (via surface 20mm conduit)
at the DB i measured 0.75ohms , i then changed the leads to the plug lead and at the socket i got 0.66ohms
unless the metal clad sockets was picking up an earth from the wall ( which i guess could be possible, but guess the db fixed to the same wall would also pick the same )
so i put the results down to the leads giving different amount of resistance

am i wrong?

 

[multimick]

nothing to wory about in my opinion and if you explain this to your assesor he wil be impressed, any discrepancy of around 0.05 is due to leads ,meters probes ,slight oxidisation on copper etc etc . assesors are only human and your enthusiasum will show through , no need to null leads for live tests ,also remember live tests will vary constantly also rember it's Zdb at the consumer unit not Zs
[automerge]1581462017[/automerge]

 

[buzzlightyear]

however yesterday when i unpacked the tester i tested a very simple installation of a 2 way garage DB that feed 2 x DSO wired in 4mm T+E that was about 6inches away from the DB

I bet you thought it was xmas time again tearing in to the carboard box ,idlest
it did not come in a fiffys banana box like the fluke .lol.

 

[static zap]

any discrepancy of around 0.05 is due to leads ,

Zeroing things that are unstable gets you to this mathematical quandry

 

[Highresdis]

Hi Multimick, am i wrong in thinking that any additional resistance of my leads will effect the result of the ZS live test?
with the fluke tester always nulled the leads for both live and dead testing
however yesterday when i unpacked the tester i tested a very simple installation of a 2 way garage DB that feed 2 x DSO wired in 4mm T+E that was about 6inches away from the DB (via surface 20mm conduit)
at the DB i measured 0.75ohms , i then changed the leads to the plug lead and at the socket i got 0.66ohms
unless the metal clad sockets was picking up an earth from the wall ( which i guess could be possible, but guess the db fixed to the same wall would also pick the same )
so i put the results down to the leads giving different amount of resistance

am i wrong?

If you're wrong, I am too. On my Fluke, I null my leads on EFLI setting with all probes touching the earth bar, and this takes about 0.11 ohms from the Ze result. The plug attachment needs nulling separately with the supplied thingy, if you still have it.
This gives the Zero symbol on the screen, separately to the Zerod continuity symbol.

 

[Risteard]

As above, Fluke has this where you null leads for loop testing.

Megger does not.

However the newer Meggers (e.g. 1700 series) have an option in the settings to adust lead resistance. I think the default's something like 0.07 Ohms for a standard lead set, but this may need to be altered for fused leads etc.)

 

[NDG Elecs]

As above, Fluke has this where you null leads for loop testing.

Megger does not.

However the newer Meggers (e.g. 1700 series) have an option in the settings to adust lead resistance. I think the default's something like 0.07 Ohms for a standard lead set, but this may need to be altered for fused leads etc.)

Sorry this is not related to live loop testing but your post made me think about the 1700 series..

I hate the 1700s for the way they do not display negative values. The 1552 and. It's ilk were much better in that way and you could easily and confidently do simple maths to get end to end values etc without endless button pressing.. also those blo0die silicone leads... gggggrrrrrrrr!!

 

[radiohead]

I've never used a meter where nulling the leads on a loop test was possible.

 

[Mike Johnson]

It's on about the sixth illustration: https://dam-assets.fluke.com/s3fs-public/166x____qreng0000.pdf