I need some advice on protecting the micro controller when measuring an AC power line (300VAC max). I do not have much experience in this matter.
My circuit is supplied with a fly-back switcher because of high power requirements. The supply to the micro controller is isolated.
I now want to measure the voltage, phase and freq at the input of the fly-back switcher (directly on the AC power line). I'm using a resistor and 2 clamping diodes to protect the I/O pin.
Is this enough protection? But the circuit is not isolated anymore, except on the switcher side.
How do I go about isolating the measuring part without using a transformer. Can I use an opto-coupler?
Or is it unnecessary to isolate the measuring part while the supply is isolated?
The circuit must conform to standards for commercial use (SABS - South African Bureau of Standards).
Please any good information will help.
Regards