Re: how do clamp meters work?

Hello John,


You could make a crude CT by winding a bunch of turns of fine wire
through a steel washer and also running the current-carrying conductor
through the center. It's not a very good core at 60 Hz, but you will
get a signal that depends on current.


Golly, I've got to try that. That would have to be the cheapest CT there is. Should have kept the rusty washers from out old basketball hoop ;-)


You can also place an air-core coil near a current-carrying conductor
in the proper orientation and induce a small signal into it,
proportional to current.


Maybe there is a pre-calculated setup but if not that would probably require a serious tour through Maxwell's equations. Or just calibrate it if nobody is looking...


Google "Rogowski coil". The idea here is to make an air-core toroidal
coil that encompasses almost all of the flux around a wire. The output
is the time derivative of the current. The good ones, the ones that do
capture most of the flux, can be beautiful.


This is a nice write-up about them:

http://www.coilws.com/Current%20Sense/App1_rogowski.pdf

My very first lesson at my alma mater happened to be at their Rogowski Institute.

--
Regards, Joerg

http://www.analogconsultants.com
.

Relevant Pages

  • Re: how do clamp meters work?
    ... You could make a crude CT by winding a bunch of turns of fine wire ... through a steel washer and also running the current-carrying conductor ... Google "Rogowski coil". ... coil that encompasses almost all of the flux around a wire. ...
    (sci.electronics.design)
  • Re: how do clamp meters work?
    ... through a steel washer and also running the current-carrying conductor ... It's not a very good core at 60 Hz, ... Or just calibrate it if nobody is looking... ...
    (sci.electronics.design)