Do I need to Null Test Instrument.

[seftonbarn]

Probably a noddy question but here goes. When testing earth fault loop impedance do you first have to null the test instrument. If the answer is yes are there any practical tips when nulling the types of test leads that incorporate a 3 pin plug for testing socket outlets?

 

[telectrix]

depends on which make of tester you have. with megger, you don't null for EFLI testing. i believe that with the flukes you do.

 

[tony mc]

Try connecting a piece of metal between the line and earth pin of the plug & then null the leads.

You can buy a tool for this but a coin will do the trick!
fluke null | eBay

 

[Silly Sausage]

You need to Zero the leads on a Fluke.
It stores it memory, even after turning it off, so you only need to do it once.
Do it 1st thing in the day for peace of mind.

 

[seftonbarn]

Try connecting a piece of metal between the line and earth pin of the plug & then null the leads.

You can buy a tool for this but a coin will do the trick!
fluke null | eBay

Funny enough, I thought of using a coin but daren't suggest it through fear of abuse.

 

[MarkieSparkie]

It's important to short all three leads (L,N,E) of either test lead set on a Fluke 165x series MFT, leaving say the N open circuit may cause it to introduce an error term due to the lead acting as an antenna impressing RF voltage on to the very sensitive high impedance input of the tester.
Also, although the Fluke 165x series MFT does store the current value of lead null in non-volatile memory, every time the lead set is changed (BS 1363 set to 3 lead set or vice versa) the tester MUST be re-nulled, as the MFT can't store both test lead sets null value or distinguish which is which and apply the correct null.

 

[ackbarthestar]

I adapted an old 13A BS1363 panel socket which I used to null out my Fluke 1653 instrument.

 

[brman]

I used to use an old socket but found it could give unreliable contact. I now use a 50 pence piece. Jams nicely between the plug pins! Just don't spend the 50p by mistake.... :lol: