I've connected an SCT013 Split Core Transformer to the differential 2_3 inputs on an ADS1115 ADC+PGA which connects to an Arduino Uno Genuino via I2C.
I followed this exactly: YouTube Tutorial
In attempting to measure power usage of my 3D printer, space heater, PC PSU and washer machine, everything works as expected, however, when connected to the old Kenmore 87376100 dryer in this house I'm renting a room in, the setup detects current draw when the machine is off. The current draw readings vary wildly.
Only when I remove the power cord from the SCT013 do the readings drop to zero.
The SCT013 I'm using is the 20A model with built in burden resistor that translates the 20A induced to 1V DC.
My guess is that I don't fully understand AC circuits and there's probably either interference in the mains lines from other connected devices or the dryers wiring has something to do with this. I say this because connecting the SCT013 to the washer machine (connected to the same 2 gang outlet box) produces extremely normal and predictable results: power spikes when the main tumbler is in motion agitating the clothes, and drops in power consumption between cycles when water is only draining or filling.
I attempted to use an SCT013 with 100A rating with multiple different burden resistors but found the 20A model more straight forward since the dryer's information plate says 120VOLTS 60Hz 6 AMPS.
I've also attempted the entire circuit with my own custom code and an ESP32 Devkit, exact same results.
I have a spare ADS1115 brand new in the packaging, but based on being able to correctly measure current draw from every device I've tried except the dryer, I'm thinking the ADC isn't the issue.
Just to be clear, I understand my scaling factor is incorrect regarding the output (0.2-0.3A)
The values range from 0.1-0.8 regardless of if the machine is running or not.
my Ender 3 Pro reads about 0.065-0.07 with both the bed and hotend preheating, zero when off
my 120v 60Hz 1500w space heater generates readings of 0.247-0.260 when on max and zero when off
again, measuring the dryer's power cord produces readings of 0.1-0.8 both on and off
I'm sure I can fix the math to get these numbers correct, but the effort doesn't seem justified when I can't get the dryer to read 0.000 when off.
Please let me know what additional information you'd like!