Clamp Meter

Assuming it is mains wiring.

You can put the clamp meter around one of the wires on the AC current range then switch all the switches in the area. If the wires are connected to a load you should see current/no-current on the meter depending on switch position. Check light bulbs are working if you can't find a load.

You could also use the fluke 322 on it's voltage range with the probe leads. You will need to make contact with the copper inside the wires without getting your hands in contact with the probes. The results will depend on how the switch is wired and how your mains distribution is configured. If you measure between local mains earth and both of the wires you should see a change when you operate the connected switch.

Bob

You can't find the "switched leg" (xxx in the diagram below) with a clamp on meter. The "switched leg" will always have current when the light is on, and never have it when the light is off. The same is true of the hot leg and the neutral leg - if the light is on, there is current in the wire. The clamp meter can be used to determine which wires are the "travellers".

Regarding "switch leg for a three-way switch" :

SW1 SW2 o-------T-------o xxx AC -Hot-o o------+ o-------T-------o | [Light] | AC -Neutral-------------------------+

Above is typical 3-way wiring. The AC could also come in on the right, with slightly different wiring. Or the light could be between the switches. Regardless of how the wiring is run, the two wires marked T are "travellers" and are always accompanied by a third wire when properly installed.

A clamp meter on a traveller will show no current with the light on with one of the switches in the up position, and current in that wire when the same switch is in the down position and the light is on. The same meter clamped on any wire other than a traveller, will always show current when the light is on, regardless of switch position.

This does not apply to your wires - they are not travellers. Proper wiring would have a third wire accompanying the travellers. They could be the switched leg and the neutral or the hot leg and the neutral, but your clamp meter can't tell the difference between hot, switched or neutral leg.

Ed

To get a useful reading with a clamp-on ammeter, you must put it around a single conductor. If you put it around the two-conductor cable normally used in house wiring, you will read zero regardless of the current carried by the wires, as the magnetic fields produced by the supply and return currents will cancel. This will happen with a branch going to a switch, as well as on a simple feed to an outlet.

Re-reading your post I see that you mention a cable to a three-way switch - such a cable would likely have three conductors, where a cable feeding an outlet would only have two (in both cases, plus the bare ground conductor)