Gonio,

With the inductor input shorted the output should be very close to zero, if it isn't, something is wrong with the circuit. Connect a 100 uH inductor and adjust the trimmer resistor so the meter reads "100". That's it, the output is fairly linear.

The trimmer in mine allows calibration over 0-25 uH and 0-250 uH 0-FSD easily with the given meter. Measure the output and calculate the required series resistor for other meter sensitivities.

Regards,

Alan

How Can i calibrate circuit for 0-100uH and 25uH-200uH

Bert,

It "just worked" for me when I tacked it together on the bit of IC socket. I built it on a solderless breadboard first to confirm it was OK, did three inductor swaps, but otherwise just chucked it together. Try the right Schmitt inverter chip and see if it works then?

I mainly use inductors < 8 uH so a resonance bridge I have tacked together on a fragment of PCB or the resonance meter based on Drew's design is what I generally use for inductor measurement, this meter hardly gets any use except for top-band receivers and ferrite chokes.

I have been using my tone dipper and the tiny C-jig or fixed caps for < 1 uH inductors a lot lately. I was considering building a fixed-tuned tone/regen with a varicap across a really tiny test fixture built around a peg or alligator clip for sub 200 nH inductors. I built the dipper circuit up but haven't got the mechanics of the fixture quite to my liking.

Regards,

Alan

Hi again.

How do you connect it like this?

I can't even make the unit work ,although I tested it with two PCBs I have etched, purposely for this circuit. Any tips?

Before I make this inductance meter, I built a capacitance meter, using 74HC132 (it was just the same, but the Nand gate forced me to connect one more input to the Vcc, forming a Not gate(inverted buffer) like 74HC14.)