Non contact current meters?

[rcx132]

Something in my workshop is sucking power. I bought one of these meters as it's non contact and can measure current without probing the wire. But turns out that it only works if one wire, eg Live or Neutral is clamped. It won't read anything if a power cord that contains L+N is clamped.

Now I swear that at the data centre where I used to work a guy used to go around with a meter and check how much power servers were drawing by putting some sensor around the 3-core cables that lead to each server. Does such a device exist or was I imagining it?

 

[brightspark]

yes they are available but expensive http://www.epanorama.net/newepa/2013/02/28/current-sensor-for-multi-core-cable/

 

[tlovatt]

I used to have a Megger branded one - quite useful although they are an approximation of the current (claimed to be +- 5% in multi core mode) they are also sensitive to the placement of the wire hence the internal guides to hold the cable central.

 

[hotponyshoes]

Due to the way they work the current flowing down the live side gets cancled out by it flowing back along the nutral so no, they don't work.
Sometimes they will give a reading if something is seriously wrong with the equipment but that would normally trip something out first!

If you are only testing stuff with plugs then you could make a breakout lead - plug wired to a trailing socket with 3 bits of single core cable inbetween . Although if you have to go around unplugging everything you might as well just get someone to watch the meter as you plug stuff back in!

Your local hire center might have a megger type if all your kit is hard-wired?

 

[fizzy]

I take it my method of using sharp needles attached to the probes would be frowned upon these days

When I think of the stuff I used to do when I was younger

 

[brightspark]

I take it my method of using sharp needles attached to the probes would be frowned upon these days

When I think of the stuff I used to do when I was younger

presumably you mean for piercing cable insulation
for testing with leads

 

[fizzy]

presumably you mean for piercing cable insulation
for testing with leads

Yes but I didn't have the proper probes so I literally used needles taped on. Never shocked myself - but was always getting stabbed by the damned things! and they hurt!

 

[frank horton]

hence the name "FIZZY" hahaha.......

 

[Matrixx]

http://www.farnell.com/datasheets/43890.pdf

They do exist.

 

[awemawson]

I have a Rubberflex plug wired to a Rubberflex trailing socket by about 6 inches of 2.5 mm singles cable. To measure current consumption I plug the device under test in via my plug / socket then I can clip round a single core

 

[R-D-R]

I had a similar scenario in the last house. In the end I found I could get the clamp round the wires coming out the mcbs in the consumer unit. once I found the circuit that had draw on it was a case of unplugging devices one by one to find the offender.

 

[500e]

As you have the meter @rcx132 Simple. You could use any old socket but not as safe

I have a Rubberflex plug wired to a Rubberflex trailing socket by about 6 inches of 2.5 mm singles cable. To measure current consumption I plug the device under test in via my plug / socket then I can clip round a single core

 

[carbon]

This is what I have for testing sometimes when access to control boxes is troublesome 2.5mm flex with the live in small loop

 

[brightspark]

This is what I have for testing sometimes when access to control boxes is troublesome 2.5mm flex with the live in small loop


View attachment 170082

same here. sometimes I just turn all the breakers off apart from the circuit where I want to test an appliance that's hard wired in . I just put the clamp over the mains tails if there is a stable load on it. I just take the reading say 10 amps then put the load I want online and take its reading minus the 10 amps

 

[carbon]

Usually I test new machines when I deliver them to the customer as the machines all run very close to 13 amps, and have found the hard way that not all electric supply’s can cope with the loads at startup. So very easy just to plug in and check current load

 

[brightspark]

Usually I test new machines when I deliver them to the customer as the machines all run very close to 13 amps, and have found the hard way that not all electric supply’s can cope with the loads at startup. So very easy just to plug in and check current load

biggest problem will be people having minature circuit breakers fitted and they trip on start up