Just finished designing an LC meter.
Its a simple oscillator that puts either capacitor or inductor with the component being measured.
I found I had to adjust slightly the sums to make the pc display output the exact correct value. But I expected that was down to component tolerances.
Got the first one working fine.
So I built a second one and that measured capacitors fine but the inductor measurement was out by a factor of two, so way out.
I removed the capacitor and inductor off the pcb and they measured fine.
I was then starting to suspect my oscillator circuit.
Then luckily spotted a solder bridge on the LC switch.
Removed it and the meter was then very close to the other one.
I was pleased to find a resolution to problem that explained exactly the results I was getting. The short put the pcb inductor in parallel with the one under measurement and so read as twice as much inductance.
So the laws of physics stand.
F=1/(2 pi sqrt(LC))
Its a simple oscillator that puts either capacitor or inductor with the component being measured.
I found I had to adjust slightly the sums to make the pc display output the exact correct value. But I expected that was down to component tolerances.
Got the first one working fine.
So I built a second one and that measured capacitors fine but the inductor measurement was out by a factor of two, so way out.
I removed the capacitor and inductor off the pcb and they measured fine.
I was then starting to suspect my oscillator circuit.
Then luckily spotted a solder bridge on the LC switch.
Removed it and the meter was then very close to the other one.
I was pleased to find a resolution to problem that explained exactly the results I was getting. The short put the pcb inductor in parallel with the one under measurement and so read as twice as much inductance.
So the laws of physics stand.
F=1/(2 pi sqrt(LC))
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