Fluke 2042 Cable locator

[John Alexander]

Hi

Sorry that I've only registered to ask a question, but electronics isn't my game.

I'm looking for a way to definitively identify a cable that the 2042T (transmitter) is connected to - the 2042R (receiver) is RF and so there's some ambiguity when breakers are only 13mm centre to centre.

From what I can tell, the transmitter puts a pulsed 125kHz signal onto the live line. The signal is weak (150mV at "level II"), and I'm not sure of the time between pulses.

The transmitters are coded, but let's not even get into identifying the code - just detect the presence of the signal.

I'd appreciate suggestions on how to detect this signal. How do I filter a 230V 50Hz "signal" and how do I detect a 125kHz signal?

Thanks,

John.

[tron9000]

you need a high pass filter to filter the mains out (50Hz) and a scope. Though hooking it up to mains would be a bad idea .

[John Alexander]

I'm using an isolated scope and 100:1 probes, so mains isn't an issue. I'm trying to do away with the scope - it's bulky and tricky to set up, especially on site.

I see that Horowitz and Hill have a few pages on filters - I'll read that and get back to you.

[tron9000]

I'm using an isolated scope and 100:1 probes, so mains isn't an issue. I'm trying to do away with the scope - it's bulky and tricky to set up, especially on site.

I see that Horowitz and Hill have a few pages on filters - I'll read that and get back to you.

that's good. What's the scope? If it's modern it might have an FFT function, which you can use to identify your signal.

[John Alexander]

that's good. What's the scope? If it's modern it might have an FFT function, which you can use to identify your signal.

Scope is a Hantek DSO1152S. I'm trying to get hold of a Multi-Contact Isoprobe III - HP. http://www.conrad-electronic.co.uk/ce/en/product/126120/Probe-Scoop-proof-35-MHz-1001-3540-V-MultiContact-Isoprobe-III-10-HP-set Easier than building my own filter.

Once it's working reliably on the scope, I'll see how to get rid of the scope.

I don't think the FFT would work without a filter - to much of a difference between the 230V "carrier" and the 100mV signal.

[Elf]

I have found with these sorts of "breaker tracer," "wire finder," or "tone and probe" sets that unfortunately there isn't really an easy way to unambiguously find the signal, as it will often get inductively coupled onto other adjacent lines besides also being hard to pinpoint physically.

Hooking the "toner" (transmitter) up across two conductors (e.g. Line and Neutral) in a cable, rather than one conductor and ground, to some extent reduces the spill although it will also reduce the signal you see inductively with the "probe" (receiver). Then you can generally insert the probe right up and between the two wires of the cable, for example where they enter the panel, to get the most direct reading.

I apologize if you are already doing all of the above, and don't mean to discourage you from trying to do other interesting things electrically to try and solve the problem. It just seems to me that given spill/inductive coupling onto other wires, the problem is one of relative measurement anyways, and the inductive probe already contains a working receiver, filter, and signal strength meter. It's just the method of coupling to the inductive probe that might need some work. For example if you want to probe a breaker lug directly, you could do so (carefully) with a mostly insulated piece of wire wrapped around the probe's receiver?