Larry Benko wrote:
Roy,

It is amazing how a simple concept such as impedance can be made obscure
but most current probes are spec'd this way by the manufacturers and
test procedures for DO-160E (FAA aircraft testing) call out probes the
same way. By saying that a current probe has a transfer impedance of
0dB-ohm means 0dB relative to 1 ohm, but R = V/I so 0dB-ohm means that
for 1A of current thru the primary of the probe produces 1V across a 50
ohm load. Similarly a -20db-ohm transfer means that 1A produces .1V
across a 50 ohm load. For most of us, this means a 1 turn primary and a
50 turn secondary which yields a theoretical primary impedance or 0.02
ohms. One of the probes I have says the primary impedance is less than
.1 ohm.

Larry Benko, W0QE

Thanks for the explanation. My concern is with the insertion impedance,
which at 0.02 or even 0.1 ohm, is certainly adequately low for this
device -- as long as it's properly terminated.

Roy Lewallen, W7EL