Using a different ADC reference seems to mess the calculations about truerms HOT 1 CLOSED

Dear Paul,

Thank you for making use of my TrueRMS code.
I searched out that the Arduino nano is ATmega328 based and supplied from 5V. By selecting the internal reference, the reference voltage is set to 1.1V. See: https://www.arduino.cc/reference/en/language/functions/analog-io/analogreference/
This means that the DC-bias at the ADC input should be designed to be: 1.1/2 = 0.55V and the AC voltage amplitude to the ADC input should be limited to max 0.55V. In principle, nothing has to change from the library when selecting a different ADC reference voltage. The mid range code value of the ADC remains the same (512). 'VoltRange' should be the peak-to-peak voltage that corresponds to the 0..1.1V ADC input voltage range. I hope this will explain your problem with the readout.

Best regards,
Martin

from truerms.