Some explanations for the circuit below:
- This is a CT with 1000 turns secondary. It has high sensitivity down to mA levels so that's why I put an amplifier given that the burden is small (35 ohms).
- The CT has 1000 additional turns for the test winding. So the ratio is 1:1 between secondary and test winding.
- The reference voltage IC is configured to give Vcc/2 = 1.65V which is the DC shift. I'm planning to use a square wave from the micro followed by a high pass filter to feed the test winding. It just need a small current during a quick moment. The switch is to open the winding when no testing. The general purpose of the test winding is, of course, to test the system, so I don't necessarily need to put current in the primary.
My question is: Do I need to connect the test winding to the DC shift like the sense winding? Or do I need to connect it to ground instead?