Bob,

Here's a variation of Jack's suggestion. Use two power supplies, one for 
AC excitation the other for DC excitation. Isolate the DC supply from 
the inductor under test with an inductor you know doesn't saturate. The 
exact value of this isolation inductance is not important. Similarly, 
isolate the AC supply from the inductance under test with a large 
capacitor (one whose impedance is way smaller than the inductor's 
impedance). Finally, place a small valued resistor in series with the 
inductance under test.

With this configuration, you can use an oscilloscope to measure the 
phase shift between the AC excitation voltage and (say) the inductor's 
voltage and back calculate the inductance. The accuracy of this 
configuration is limited to how accurately you can measure the 
resistor's value and how accurately you can measure the phase shift.

If the phase shift is phi degrees, then the inductance is:

     L = R/(2piF)*tan(phi)

You could also look at the relative amplitudes (e.g. the voltage across 
the resistor relative to the voltage across the inductor and the 
resistor), but I believe this is less accurate.

Scott
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist