Inductance and Capacitance Meter Adapter

Posted on Feb 5, 2014

Another project started with three others not finished. What would my Dad say Well one thing he would say is, `Warn people that this project is under construction and has not been proved to work yet`. You have been warned. I had to use a signal generator, resistor, and oscilloscope to measure the value of an inductor for my battery-charger projec

Inductance and Capacitance Meter Adapter
Click here to download the full size of the above Circuit.

t. That was just irritating. So, after looking for a reasonably priced L-C meter and finding none, I started looking at articles for building one. There are many on the net, but I picked a circuit by Iulian Rosu. It looked the best for checking all sizes of inductors with minimum errors due to resistance and core saturation. The capacitance meter was thrown in for convienience and does not pretend to be a circuit in the league with a Gary Novak`s femto farad circuit. It is just a simple capacitance checker. If you look at the schematic below you will see that it is just a re-drawn version of the schematic for Iulian Rosu`s adapter shown in the qsl. net webpage. I added one more position to the range switch to go to 20mH. There is probably a good reason why the increase in range won`t work. I am hoping it is just accuracy. At 20 mH I am just looking for a range confirmation, not an actual measurement. The other change I made to the inductance adapter circuit was to add a 10X gain stage after the detector. I wanted the inductance and capacitance adapters to use the same voltmeter scale and the capacitance adapter did not work so well on the 200mV scale. Oh yes! I also had to change the clock to a 3. 2MHz oscillator with division down to 100kHZ. It was more cost effective (cheaper) to use the 3. 2MHzcrystal and a 4060 IC than to buy a 100kHz crystal. The capacitance circuit is a triggered one-shot that is driven by the crystal...

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