Bob Bruhns wrote:
<>Yes, that will work. But remember, you want equal
voltages across the resistor and the inductor.
Surprisingly, this will not be 50% of the applied
voltage, but it will be about 71% of the applied
voltage. This adds up to about 1.414 times the applied
voltage! You should confirm this by measuring both
voltages directly.
This happens because the impedance of the inductor is
reactive, and the current is equal, so the phases of
the voltages differ by 90 degrees. This phase shift
causes a partial cancellation when the voltages are
added, so 71 + 71 = 100 instead of 142. It's
interesting to observe.
Actually, Bacon, John's entire message was thus... you two agree. and I
present it here, so that others may learn from this experience, as well.
________________
If all you need is a measurement of inductance the easiest thing, is to series up a variable resistor with the choke and apply a low voltage from a filament XFMR (6 - 20 volts. Adjust the resistor so that the voltage measured across the choke is equal to the voltage across the resistor. If for instance, a 10 volt source is used you will measure about 7 volts across the resistor as well as across the choke.
You are probably asking why it is not 5 Volts across each and the answer to
that is because of the phase difference of 45 degrees when XL = R. The sine
of 45 degrees is .707 and .707 X 10 Volts is about 7 volts. But the main thing
is what ever the voltage is, by equalizing the voltage across the resistor and
choke results in the creation of a resistance that is equal to XL of the choke
at 60 CPS.
Measure the resistance of the variable resistor after equalizing the voltage
drops and you have the XL of the choke at 60 cps.
L = XL / 2 * pi * F
L = XL / 6.28 * 60
L = XL / 376.8
Divide the resistance by 376.8 and you have the inductance.
________________________________
Thanks for the response. From all the active posters in here, I admire
and respect the intellect for the electronic abilities and talents
mostly of WA3WDR, K4KYV, WA3VJB, KD5OEI and of course, WA5BXO, and not
necessarily in that order.
--
73 = Best Regards,
-Geoff/W5OMR
