Ring continuity test results. Help please.

[Bennewman]

I'm rather new to testing and interpreting results. Did a test two weeks ago on a new ring installed then with continuity results L-L 0.37, N-N 0.36, E-E 0.60 and L- E 0.25. All good. Tested it today and got results L-L 0.17, N-N 0.17, E-E 0.39, L-E 0.05. Not good. I'm testing it again tomorrow and I think I know where I went wrong. I didn't null the leads, either two weeks ago or today. (notice today's results are all approx. .2 ohm less than two weeks ago). My confusion is that I'm assuming the results I got two weeks ago are correct and today's are wrong...but, how could I have taken OFF .2 ohms by not nulling the leads today??? Or two put it better, how can nulling the leads add .2 ohm??

 

[markc123]

If you don't null your test leads you'll also be testing the resistance of the test leads...this could literally be any figure. You either null or deduct the sum of the leads.

 

[Hobsoni]

You couldn't have nulled the leads 2 weeks ago.

 

[telectrix]

you probably didn't null the leads the first time. that would account for the higher reading. i can't see where the L-E reading comes in when you're testing e-e on a ring.

 

[Bennewman]

Yes but the original figs calculate correctly. the new one's don't. I can't have an E- E reading more than double the L-L. should be approx. 1.67 right? Also, I can't have an L-E at sockets after cross connecting at 0.05 if the E-E is 0.39 and the L-L is 0.17. That's why I'm assuming the original figs are right and the new one's are wrong. But how can I add resistance by not nulling. It's not possible, right?

 

[Hobsoni]

you probably didn't null the leads the first time. that would account for the higher reading. i can't see where the L-E reading comes in when you're testing e-e on a ring.

R1+R2 one would imagine.