measuring cable capacitance...
- Thread starter Ken C
- Start date
chrisallan
Go on - bodge it!
YOU CAN USE A MULTIMETER with capacitance-measurement capability to measure the length of wire or cable to an open circuit. The capacitance of a pair of wires (or a wire to a shield) is directly proportional to the length of the wire. If you know the capacitance per foot of wire, then you can calculate how far it is to the open circuit. To determine the capacitance per foot, take a trip to the hardware store, use a known length of wire, and measure the capacitance with the multimeter. You must zero the multimeter's capacitance function before making any measurements. To zero the meter, select the capacitance function and separate the leads. Then, make the measurement and simply divide the total capacitance of the wire or cable by the total length to determine the capacitance per foot. Once you have this figure, and you're sure that the suspect wire or cable carries no power or signals, you can measure the capacitance, C. The wire length in feet to the open circuit is C divided by the capacitance per foot.
Andrew L Weekes
Reverse Engineer
As suggested a meter with capacitance range can do this.
There may be several measurements that are relevant in a cable - there will be a core-screen capacitance in a screened cable, and a core-core capacitance too, particularly if not individually screened.
Andy.
There may be several measurements that are relevant in a cable - there will be a core-screen capacitance in a screened cable, and a core-core capacitance too, particularly if not individually screened.
Andy.
thanks guys. i'm a bit thick here. my multimeter has 2 slots labelled Cx for measuring capacitance, but i will have difficulty sticking some wire from a cable in there. seems its made for measuring capacitance of capacitors only, and nothing else. i had assumed that i could just use the leads that came with the meter, and measure the C at one end, say between L and N, at one end, with the other end open -- but right now i cant see how to do it.
enjoy
ken
enjoy
ken
Andrew L Weekes
Reverse Engineer
Ken,
Solder a couple of component leg offcuts onto your cable you want to test (e.g. 1 to the screen, the other to the centre core).
Poke these into the slots and read the answer.
Should work if you select a low range (pF).
Andy.
Solder a couple of component leg offcuts onto your cable you want to test (e.g. 1 to the screen, the other to the centre core).
Poke these into the slots and read the answer.
Should work if you select a low range (pF).
Andy.