A clamp-on current probe such as Tektronix sells will work well. If you need
something that will slip over a human arm, Pearson (and others) make
suitable current viewing transformers.
These current viewing transformers are generally built like this:
1) 1 turn primary (the path that the current to be measured takes)
2) 50 turn secondary terminated into 50 ohms
3) 1 amp primary gives 1 volt secondary
While these current probes are built to have only a small response to
E-fields in some cases it can be a problem. In that case a small metal tube
with an open seam can be slipped into the current probe hole. The tube is
connected to the ground at the probe.
The resistor can work but takes some care to get it working right due to
common-mode current.
Dave Cuthbert
Linear Technology
From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Haynes, Tim
(SELEX) (UK Capability Green)
Sent: Thursday, February 08, 2007 9:04 AM
To: rehel...@mmm.com; emc-p...@ieee.org
Subject: RE: Contact Currents
Unfortunately there is no standard that tells you how to measure contact
currents above 1 MHz.
Hmmm...
If I have a small inductor less resistor in series with the RF supply and I
measure the voltage across the resistor and divide by the resistance - maybe
that would do?
I am sure I have measured pulses in EMC tests that use an inductor less 0.1
Ω resistor and the pulses have fast rise-times with many 10's MHz bandwidth
or even more.
I have not measured contact currents in this way but I suspect it will give
a pretty good approximation.
Any other takers?
Tim
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