[Milsurplus] hi volt choke testing questions

[antqradio at juno.com]

Patrick

Check out your copy of "Radiotron Designers Handbook*", 4th Edition,
Pages 250 - 251.  Since a battery or a well designed DC power supply
should have low impedance, just series the resistor (really a pot), the
inductor, the power supply and a DC ammeter to your generator.  Measure
the AC voltage drop on the inductor verses the resistor (wiper on pot) as
before using the common junction to find equal voltage drop at frequency.
 The power supply voltage is then adjusted to provide the correct test
current.  Since this power supply is outside of the measurement loop and
(if I haven't missed something here) it should have no effect on the
measurement.  The resistor (pot) has to pass the same current that the
inductor passes, this may make the measured voltages small (or the pot
big, that is, robust!) but that should be no problem with a good VTVM.  I
guess you could use a DVM but it just doesn't seem right!  I know this
may sound confusing on first (third) read, but the picture on page 250
will clear things up, honest.

*Don't have a copy of Radiotron, 4th Edition?  Shame on you!  Send me
your address, off line, and I will send a copy of the two pages.

Regards from a slightly cooler Arkansas,
Jim

On Sun, 18 Jul 2004 21:51:26 -0500 Patrick Jankowiak
<recycler at swbell.net> writes:
> Anyone have a quick and dirty way to test a power supply choke's 
> inductance while running some current through it?
> 
> I have a weighty 95 ohm one that is 43H with no current. Like to 
> know how much with 200-500mA. It has a gap, so I am pretty sure 
> it's not a swinger, but I doubt it could still be 43H at 300mA.
> 
> I checked the inductance by putting a 5K resistor in series with 
> it and a 20VAC power supply, adjusting the pot till the choke and 
> resistor each had the same voltage across them, and then measured 
> the resistance of the pot, substituted that for the reactive 
> impedance of the choke, and came up with 43H.
> 
> Unfortunately I see no way to pass DC through the choke and also 
> hook up this AC power supply to it. Maybe in series?
> 
> PJ