Two way switch continmuity check

[Casterbridge]

Have connected earth to line by CU to underatke some continuity testing and for testing line switching. I am pretty much taking resistance readings whenever I go along the circuits to see if everything makes sense ... I have arrived at a two way switch, and just wanted to check something - I am pretty sure it is right, but you experts will know ...

At both switches I am taking COM1 and Earth readings under different switching scenarios ... Both switches on, both swiches off, 1st off, second on, and 1st on and second off.

When both are either on or off, I get a COM2/Earth reading only.

When one is on and one is off, I get a COM1/Earth AND a COM2/Earth reading.

I think I get two readings when one is off and the other is on because I get continuity directly through the lamp on one leg and also via the second switch to the lamp the other way ... is that right ????

 

[EFLImpudence]

You should be testing at the light and operating the switches.

 

[Casterbridge]

You should be testing at the light and operating the switches.

Yes I am - I test at the light for L - Earth, then at the light for S/L - Earth which also checks switching is on line, ..., but I was testing everything I could so did the test at the switches also ... it was only because I got these readings that it got me thinking ... so is it right?

 

[flameport]

I think I get two readings when one is off and the other is on because I get continuity directly through the lamp on one leg

Lamps must be removed before testing. Otherwise, results are meaningless.

 

[EFLImpudence]

Look at the bottom diagram and you can see where the continuity would be.

Of course, L1 and L2 could be either terminal and one of your switches may be wired the opposite way round compared to the other, although it does not matter operationally.

 

[Casterbridge]

I think I get two readings when one is off and the other is on because I get continuity directly through the lamp on one leg

Lamps must be removed before testing. Otherwise, results are meaningless.

... Yes, when I say lamp, I am eat the ceiling rose - no lampos are in.

 

[Casterbridge]

I think I get two readings when one is off and the other is on because I get continuity directly through the lamp on one leg and also via the second switch to the lamp the other way ... is that right ????

.. so I am right?

 

[PrenticeBoyofDerry]

I am puzzled by what you are trying to prove, if the lights are looped in at ceiling rose test at the ceiling rose, testing between loop live and CPC, will confirmed continuity of supply, testing between switch live and CPC, will confirm that your switching arrangements are in order, then the highest reading would dictate the documented r1+r2.

As you are only thinking you are getting continuity at the points of switching, really does not help.
The most important thing is if you are getting alternate open and closed circuits after each switching operation at the light, the values are you getting, then with the Ze added and the device type with correction factor applied, will the circuit disconnect in time.

 

[Casterbridge]

Ok thanks - I get your point.