Inductance Measurement Frequency and Resistance Adjustment Newbie Tips
I read a good eBook on AC circuits and now have a better idea of what is going on in the Rose Hullman inducance measurement. I also know the constraints of my poorman's function generator: (1) maximum frequency is 450kHz, (2) output current limit is TTL (25mA).
So I think I need to adjust two parameters to get the required condition of absolute reactance and resistance equal.
I also guess the following: when the required condition is met, two things must happen at the same time (1) phase shift 45 degrees, (2) Vr = 0.707 Vs.
It is a bit difficult to measure the phase shift, because the two waves are too "flat", therefore difficult to locate the peak or bottom. On the other hand, wave amplitude is relatively easy to measure.
My measurement procedure is summarised below.
(1) By trial and error, select a frequency range, turn frequency trim pot to about middle, try a couple of discrete resistors to get a resistor value where Vr is roughly 0.7 of Vs.
(2) Then fine tune frequency to get Vr/Vs ~= 0.7.
It took me less than 10 minutes to get the result, as shown below.
Big penzu picture