Electronic – Measuring difference of potential between two inputs


I know potential is always about difference so you can't just measure a potential but it's difference with some other potential.

Let's say I have a GND and two inputs each one 0-5v and I have a ADC measuring 0-1V being 0.0 v == GND. I can't change the reference.

I want to amplify small differences between the inputs and measure the difference with the maximum resolution. Is there an easy way to subtract V1 – V2 and supply the result to the ADC?

Best Answer

I think what you are looking for is an op-amp set up as a subtractor:

enter image description here


The above is the simplest form of a differential op-amp, however, it is best to use instrumentation amplifier (wikipedia) setup as mentioned in the comments. It is basically the same concept, but with the use of two extra op-amps (that works as buffers) you can prevent the input signals to be interferred by the load, giving you a much more acurate reading.

Here is the instrumentation amplifier setup:

enter image description here

Do a little reading on the link above, it is fascinating how they work.