ACS712 AC Current sensor not sensing anything

[easylab4kids]

Sorry I created some confusion.
This is the proper snapshot when the sensor is powered on. Weird is the signal moves from top to bottom. Not smooth at one (milli-) voltage level. I dont know why.. perhaps I am a bit inexperienced on using/reading 'scopes? I'm a Python support by profession.

but no DC offset, but positive and negative output swing. That is strange, since there is no negative supply on the board.

The reason for that is, my 'scope was in "rolling"-mode and the snapshot is the moment I pressed the ON/OFF switch.

Did you power the sensor while testing?

Yes, I did using the Fnirsi lab power supply.

BTW thanks for the quick responses, I'm investigating, but not making much progress on measuring AC low-power .

[Roberthh]

The oscilloscope picture you show are strange.
- Do you use a proper oscilloscope test probe, in this case a 1:1 probe
- Are the ground clips attached?
- Which power source do you use for the fnirsi power supply. As far as I understand, that thingy has no own mains supply and requires to be powered from another source - which by the way is NOT good, because it adds a more reasons to fail.

I have attached a current sensing transformer like the one in the ZMCT103C to a LED load and a resistor load an captured the output signal with the oscilloscope. You can see that the LED takes a current only for a short time during the input wave. That could show up in your pictures as well.

LED Load, average AC current 30mA

LED_30mA.png (42.21 KiB) Viewed 2577 times

Resistor load, Average AC current 30mA

Resistor_30mA.png (42.32 KiB) Viewed 2577 times