inductor tester

[Michael]

All one needs to know about an inductor may be found by applying
voltage and monitoring current.
I have been using this homemade gadget for a while: big ass MOSFET
driven by an appropriate gate driver, 555 timer (with toggle switch to
change ranges and trimpot for fine adjustment), low L shunt and bunch
of caps to keep voltage stable. 3-rd year EE student could do it
(IMHO). OK, one needs to know what s/he is doing as layout does
matter. The problem: every time I drop the jig, I have to fix
something as assembly leaves much to be desired. Well, not exactly,
but it looks ugly.
BOM (including PCB) should be between $5 and $20 (depending ob
quantities), shouldn't it?
Does anybody sell gadget like this?
P.S.: It is taken for granted that a lab has oscilloscope and power
supply.

 

[D from BC]

All one needs to know about an inductor may be found by applying
voltage and monitoring current.
I have been using this homemade gadget for a while: big ass MOSFET
driven by an appropriate gate driver, 555 timer (with toggle switch to
change ranges and trimpot for fine adjustment), low L shunt and bunch
of caps to keep voltage stable. 3-rd year EE student could do it
(IMHO). OK, one needs to know what s/he is doing as layout does
matter. The problem: every time I drop the jig, I have to fix
something as assembly leaves much to be desired. Well, not exactly,
but it looks ugly.
BOM (including PCB) should be between $5 and $20 (depending ob
quantities), shouldn't it?
Does anybody sell gadget like this?
P.S.: It is taken for granted that a lab has oscilloscope and power
supply.

I test inductors with resonant circuits and square wave.
I measure the resonant frequency on the scope.

I can add a bias voltage to get core some core detail too.


D from BC

 

[Tim Williams]

BTDT
http://webpages.charter.net/dawill/tmoranwms/Elec_Inductor.html

When I only want to know the inductance, I resonate it with a cap and the
signal generator via resistor.

Some day I may build a full design, consisting of square wave oscillator,
MOSFET switch and current sense resistor.

If you really wanted to get interesting, you could make a free-running
oscillator which turns on until the derivative of current change (i.e.,
d^2I / dt^2) starts rising (saturation), then turn off for a time period
corresponding to about 5-10 times the total on period (obtained via an
integrator during that cycle).

The rate of rise is sampled (with an analog S&H) and displayed on a meter,
while the saturation point (which jointly determines frequency) is
displayed on another range.

Hey, that's not a bad idea.

Tim