cap meter box

David Moran’s Capacitor Meter Project

Hi guys, I just received an email from David Moran and he sent me his capacitor meter project with pictures and a little presentation. Here are the details and schematic.

Here is the schematic of my capacitor meter I built and have used quite a bit. It will measure from zero to 0.1uf with 300pf at mid range. It is an oscillator that makes noise fed into a bridge circuit that will null out the noise when balanced. Once built, you must clip in known value capacitors and hand calibrate the dial.

I built my unit into a cheap push on battery light the output can go to a small audio amp, audio input of a computer, or try a piezo speaker. The noise is rather annoying, so you may want to use a scope to view it if you must test many capacitors.

Capacitor meter schematic

capacitor meter schematic

And here is a picture with the finished project:
cap meter box

Thank you David, you’ve done a great job!


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  • Pentaconto

    Well, but… Please any data of the coil wath use this circuit ???? (L-CORE_SOFT in the schematics)

    • David Moran

      I am just learning to use TinyCAD and had trouble finding the right coil from the menus. I used a small 1 k ohm center tapped transistor transformer with 8 ohm output (not used) I use the meter to test capacitors I have made or variable ones from old radios.

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