How can I add a negative voltage with a positive voltage?

Question

I am trying to measure the output voltage of a full H-bridge. I will post an image of the circuit that I am going to use. The design of the H-bridge is a bit more complex in reality but it is only necessary to know the voltage measurement circuit in the output:

(R1 = R2 = 2M, sorry)

I use a symmetrical power supply on OP1 since the output will be +1 when Vab = 24V and -1 when Vab = -24V. I want to shift the output voltage of OP1 to get an always positive signal (since I will be using a uC that has as Vanalog = 3.3V and GNDA = 0V) so I thought of adding the output voltage of OP1 with 1.65V.

Should I use a symmetrical power supply for OP2 or can I use a simple power supply for this opamp?

If anyone has an opinion about my circuit or thinks that there is a more efficient and elegant way to do it (I think that there is) they would help me if they write it in the comments.

Answer 1

One good OpAmp alone will do this. There are calibrated instumentation amplifiers available, that include all 5 resistors with small tolerances for typical gain values.

R3 parallel to R4 must be equal to R5.

^{simulate this circuit – Schematic created using CircuitLab}