The measurements of capacitors and coils with small values in the pF and nH range are essential for radio and electronic experiments of the hobbyist. Unfortunately, the more cost-effective commercial meters were not suitable in this range. In 2007, I decided to recreate the famous AADE L/C Meter IIB from Neil Hecht (†).
It uses a test oscillator whose frequency is varied by connecting the unknown inductor or capacitor you‘re measuring. The resulting change in frequency in comparison with a known capacitor is measured by a microcontroller which then calculates the component‘s value and displays it directly on an LCD readout.
Ultimately it took however until 2010 until I developed a updated well-functioning design. The crux of the matter is apart from the oscillator the firmware of the microcontroller. My so-called HBMM (Homebrewers Multimeter) should be able to measure frequencies, inductances, capacitances and additional values of tank circuits. The measurement of L/C now works very well with amazingly high accuracy. The frequency measurement with the uC is, of course, not a really accurate instrument, but sufficient for good estimations.
I have to install still the tank circuit measurement. In the meantime, I also have a suitable commercial LCR meter, the Extech LCR-200.
 Controller |
 Multiplexer |
 LCD |
 Keypad |
 uC PCB |
 Oscillator |
 Relays |
 Oscillator PCB |
 Keypad + LCD |
 Osci + uC |
 HBMM inside |
 HBMM inside |
