Ted Ozolins wrote: > Well you almost got it right. The clamp is just a basic transformer > being the secondary winding. Since AC current flow changes both in > amplitude and direction, induces a current flow in the secondary > winding, "the clamp". The current is then rectified and the measurement > then is displayed on a meter. I've used high voltage transformers from > old monitors to monitor and trigger alarms signaling excessive current > change. Basically just a home made clamp.
This is getting really OT, but as far as I remember my electricity lectures, what you describe is a current transformer. For it to work somewhat reliably, you have to wind the wire to be measured around a ferrite core, which already has a secondary winding where the current is measured. And yes, it only works for AC currents. The clamps we use (which are admittedly in the higher price range) measure the magnetic field directly using Hall-effect sensors, and also work for DC currents. The nice thing with this measurement principle is that it is independent of the placement of the clamp relative to the wire. It just has to go through the clamp. I couldn't find a nice explanation of the measurement principle, but here's at least something: http://support.fluke.com/find-sales/Download/Asset/1989065_A_w.pdf -- Remy Remove underscore and suffix in reply address for a timely response. -- gentoo-user@gentoo.org mailing list
