piclist 2007\03\20\140851a >
Thread: [PIC] Clamp-Ammeter
face picon face BY : Alan B. Pearce email (remove spam text)

>> Umm, I think you have a problem with mixed units.

>I am talking about measuring the magnetic field produced by current
>in a conductor.A voltage will be induced in the terminals of a winding
>wounded around the toroid when the magnetic flux is changing in time.
>I will process this induced voltage to the project requirements.That
>is it.No need to deal with the current coming out of the secondary coil.

Umm, wrong. The magnetic field induces a current in the coil, and the
voltage you get out of that will depend on what resistor you put across the

This resistor will have a temperature co-efficient that will almost
certainly not meet the accuracy spec you are being asked for.

The various current probes we have around here all suffer from some form of
temperature drift, and the best ones talk in terms of accuracy of about 2%,
which is 10^2 worse than you are asking for.

Then as Vasile points out, you will not get a consistent magnetic field in a
clamp on system. The only way to do that is to thread a wire through a
permanently closed toroid. The changing air gap will cost you 1-2%, again a
couple of orders of magnitude worse than you are wanting.

<08df01c76b17$da1bbfe0$1979f682@space.rl.ac.uk> 7bit

See also: www.piclist.com/techref/microchip/devices.htm?key=pic
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