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27th November 2011 23:55

Alan Yates wrote...


Almost any N-channel JFET will do. For these low frequencies devices used typical at audio will work fine. You should be able to find one of BF245, J310, MPF102. If you still can't find some I can send you some.



25th November 2011 05:35

Richard wrote...

Hi Alan,

I can't seem to find an easy source(cheap) for 2n5454 jfet's. What would be a good alternative? I am a bit of a noob that's why I'm asking. Going to build this circuit and use a pic as a frequency counter and do the calc's in that.

Regards and thanks


24th February 2010 13:41

Alan Yates wrote...


You mean the circuit layout is inadequate for tiny inductance measurements, or there is no circuit diagram supplied?

The layout isn't too critical, as you can null-out the test fixture strays. Most of all it has to be stable so it doesn't drift during measurements. I have a small piece of PCB with banana plugs attached that fits onto the unit and holds IC socket pins for small inductors. To calibrate (null) the unit I short the adapter with a wide, thick shunt wire, measure the base frequency and cal frequency, then replace the short with the inductor to me measured. It can resolve the inductance of the shunt depending on how far you push it into the sockets so you have to be a little careful if making relative measurements.

The circuit is in EMRFD book. Not sure about the copyright, which is why I did not reproduce it. If you like I can ask W7ZOI about putting up the diagram.



24th February 2010 03:55

Paul Debono wrote...

I just cannot see a proper circuit for the nanohenry tester ??