24-08-2012, 04:04 PM
(24-08-2012, 03:12 PM)Skywave Wrote: If it isn't then that source resistance needs be allowed for in the resulting arithmetic - which is the point I was trying to make in my last two posts.
Yes, absolutely. Alan said he ensured the output of the generator at the output terminals was constant, hence eliminating generator Zout from this, but it's a point worth making for the sake of anyone thinking of trying this technique...
I tend to use the technique in reverse, given that I trust that the output impedance of my favourite generator (Wavetek 162) is precisely 50 ohms, so having first measured the e.m.f., it's pretty simple to determine the Zin of the DUT.
I also have a couple of power amplifiers - which I really must build into a proper box sometime - and these have a Zout that is essentially zero. Very handy for this sort of thing. I use those for measuring loudspeaker drive units, a procedure that also uses a known source impedance for certain tests.
Cheers,
Mark
