ACS712 problem when sensing an inductive load

I’m sending the Vout of an ACS712 20A to an ADC pin on Arduino Uno. According to it’s datasheet, the Output sensitivity is 66mV/A. So what I do is multiply by 5/1024, then -2.5V and then divide by 66mV/A or 0.066V/A
When it’s a resistive load, I get the same Amp value as my Tester does, but when it’s an inductive load, I don’t get a quality measure. I mean, with an AC motor, my tester prints 0.3A and my ACS712 ‘‘senses’’ 1.2A. What could it be? Do I have to make a special filter? I think what my ACS712 senses is some harmonics produced by the motor’s inductive load.

I can think of three possible issues (or a combination thereof):

  • Electrical noise on the ADC input line. Check with an oscilloscope.
  • The sensor senses peak rather than RMS.
  • You’re not actually supplying only 0.3A.