Instrumentation amplifier - schematic review

Question

I'm trying to make an instrumentation amplifier to measure a sine wave signal of 0 - 1Vpp (max) 50Hz that comes from a non-invasive current sensor (30A SCT-013-030). It gives 1Vpp at 30A current.

This is the circuit I made. The output goes to an MCU.

According to this note, my circuit with the selected values should have GAIN = 3.

I would like to know if this circuit is okay for that kind of application.

Also, I found on the internet that in AC-coupled signals require a common-mode voltage applied to both inputs of the circuit. And that voltage should be the less of the maximum value of the signal which in my case would be 0.5V Do I need that voltage in my case?
What does it do exactly?

Link to the schematics

Answer 1

AC coupling would make your current reading frequency related. The transformer has to have somehow a reference potential, i.e not floating. If you have a single supply, then it should be biased to Vref/2.

^{simulate this circuit – Schematic created using CircuitLab}

As said, best way is to have DC coupled signal with anti-alias filter. You will have a DC offset, that you can eliminate it with high sampling and HF pass digital filter (for example > 20 Hz pass). In such way you have all harmonics with true amplitude, no need to re calibrate for 50/60Hz.