Negative Voltage @ ADC

[AbhijitR]

Hello!

Recently trying to make one voltmeter which should display negative voltage i.e. -17.5V to 0V, tried to search the forum with more or less subject but nothing popped up, after googling got some idea about using op-amp and off set the voltage etc.

Was curious to know if someone has got something to add on this topic, if tried earlier, it will save some time in building the hardware and use same for coding.

Thank you.

Abhi

[kersing]

If you only need negative voltages and the meter can be powered by battery you could just use the circuits negative voltage as ground for the meter and the circuit ground as meter positive voltage. This won’t work if you power your meter from a power supply that supplies a ground equal to circuit ground.

[AbhijitR]

Hi! Kersing

Many thanks for the input, i will try that to check the results, the meter is not powered with battery but a separate SMPS.

Thank you again.

Abhi

[kersing]

Make sure the smps is one of the 'isolated' types so it does not share a ground with the circuit you are measuring. If it does share a ground you risk releasing magic smoke...