Calculate current sensing resistor from R=V/I * 1/100.
if you apply 10 volts and the inductor chews 1 ma to get there, then you have
10/.001=10,000 ohms x 1/100 = 100 ohms for R1.
if you need 0.1 ma to get there as f rises, , than R1 becomes 10/.0001 = 100,000 x 1/100 = 1k.
the voltage applied to your inductor should be very large compared to the sense resistor,
we want a voltage source such that V-inductor>>V-sense resistor,
this is why i like to use the ammeter, R-sense will be the value of the shunt inside the meter, which is usually pretty low, somewhere along the lines of 0.01 to 0.1 ohms, so that if we have 10 volts at 1 ma, we have 0.001 A x .1 ohms = 0.0001 volts across the ammeter, so our sense resistor is 1000 times better than if we used the volt meter,
we need to find out what flux level to test at,
to know that, we need the number of turns and on what size and material of core,
since you probably have not hacked into the turns count, we can guess if you tell us what application this xfmr is intended for, such as mic in, line in, or tube output,
then we can calculate how many volts to apply and take it from there.
meanwhile, it turns out they do measure core loss at high frequencies, here is a graph of 50/50 Ni from mag Met,
notice at 100 k that there is a lot of core loss, like 1000 watts per pound, so for a 1/4 pounder with cheese, we have 250 watts core loss,
looking at my dB chart, we see that this means that any mic or line signal will have no chance of exciting the core at 100 k hz,
at 60 hz, loss is 100 milli-watts per pound, so for a double cheezeburger with cheese, we will have about 25 milli-vanelli watts core loss for 50/50 at 10 k-gauss, this seems more reasonable, we could get it way down by dropping the flux, this would lower insertion loss for a moving coil cart, we could get it down to 1 milliwatt/lb. at 0.8 kg, = 0.25 milli-watts for a whopper with cheese,
see that the y axis is plotted on log paper,
and the x axis too,
