I am using an ACS712ELCTR-30A-T breakout board to measure the current on a 230V AC appliance. I have connected the hot wire of the AC connection to the two measurement terminals of the breakout board. The breakout board looks like this:
I have added a 5V DC source to VCC and ground and am using a voltmeter to measure the output. I started with the appliance turned off and it more or less correctly showed 2.53V on the OUT pin. This might seem strange as it is not properly centered at 2.5V, however I am using a voltage converter from 12V to 5V that is set up by hand and it supplying 5.06V is very likely. I then turned the appliance to its maximum power. I am not really sure what its consumption is, but based on the components used it should be between 0.5 and 1A. I would expect some kind of change in the voltage of OUT against ground. However it still shows 2.53V. The 30A version of that chip has a resolution of 66mV per ampere, therefore it should jump to at least 2.56V (2.53 + 0.5 * 0.066) on the voltmeter. The voltmeter (0.01V resolution) not changing its value means the current of the appliance would be less than
1 / 6.6 = 0.15A which is impossible.
An obvious issue would be that this chip cannot measure AC current, however the datasheet indicates the opposite.
The Allegro™ ACS712 provides economical and precise solutions for AC or DC current sensing