Inductance Meter Adapter Circuit, Turns Your Digital Voltmeter to Inductance Meter

Measuring inductance is important in making your hand-made inductors, especially when you do-it-yourself (DIY) your coil winding. An inductance meter adapter circuit would be helpful since you can measure inductance using your general purpose digital voltmeter (DVM). This circuit cost much cheaper compared to already made inductance meter instrument. Here is the scehamtic diagram of the circuit:

The circuit is very simple, containing only one voltage regulator chip and one NAND gates chip. This inductance meter adapter provide two measurement range, low range for measuring 3uH to 500uH  inductor values, and high range for 100uH to 5mH. Calibrating this inductance meter is easy. First you need to calibrate the zero offset. Connect your DVM to the output of this circuit, and select 200mV range for the DVM. Short the inductor measurement probe and adjust the sero calibration to give zero volt reading on your DVM.  To calibrate the low range, pick a known inductor around 400uH. Select 2V range for your DVM. Measure the inductor and adjust the low-cal pot to give 1mV per uH inductance. For example if you use a 390uH then you should adjust the low calibration pot to give 390mV reading on your DVM. To calibrate the high range, switch the range of the adapter circuit to high, and use it to measure a known inductor with values around 5 mH. Calibrate the high-cal pot to give 100mV reading per 1 mH inductance. [Source: Marc Spiwak]