Homebrewers Multimeter HBMM 2010

Description

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.

Schematics


HBMM01.jpg
Controller
HBMM02.jpg
Multiplexer
HBMM03.jpg
LCD
HBMM04.jpg
Keypad
HBMM05.jpg
uC PCB
HBMM06.jpg
Oscillator
HBMM07.jpg
Relays
HBMM08.jpg
Oscillator PCB
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Pictures


HBMM09.jpg
Keypad + LCD
HBMM10.jpg
Osci + uC
HBMM11.jpg
HBMM inside
HBMM12.jpg
HBMM inside

References

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