Scoposcopy: Supplement: Arduino’s Method of Inductance Measurement

To complement the earlier video on inductance measurement by resonating tank, I’ll now show a slightly different method used by the Arduino inductance meter.

The Arduino uses a bit of external circuitry to “strike” the inductor-capacitor tank with a brief pulse, then it uses a simple op-amp comparator to detect and display the peaks (really the zero-crossings) of the tank’s ringdown.

This ringing of course is at the resonant frequency. So, even though the inductor isn’t stimulated at anything near its resonance, the Arduino can still use the resonant frequency, detected in the ringdown, to calculate the unknown inductance in the usual manner.

The pancake coil I used here measured 98 microHenry by this method. Using the commercial ProsKit LCR meter it measured 102 microHenry and using the manual FG/Scope/Counter method it was 99.9 microHenry.

So I’m calling this coil 100 +/- 2 microHenry inductance…. accuracy to within 2 percent, which is closer than the normal tolerance on most commercial inductors and capacitors.

The inductance meter schematic and basic program sketch were found here:
along with a good explanation of the operation of the circuit. Thanks, Moser !

My program sketch is just the same as Moser’s except for the LCD readout part and the pin assignment.

My program sketch can be downloaded at:

Another video of mine explaining in more detail this inductance meter is here:

Thanks for watching!

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