Arduino DUE adding DC offset from waveform generator


I am attempting to measure voltage in the range 0-3.3V from a waveform generator (wfg) (connected to an isolator) using an analog pin. I have a diode and 10K resistor connected in series (to produce a half wave rectified wave). I am printing the measured voltage to the serial monitor. I am monitoring the input wave with an oscilloscope.

I have observed two problems;

  1. When the ouput from the wfg is connected to the arduino, there is a DC offset, raising the 0V level which affects my threshold values when i attempt to measure zero crossing. Is there a way i can prevent this?

  2. The above effect does not occur when, before i proceed with any other code in the main loop, i read the analog pin and print its value to the serial monitor. I have not managed to find any information about this online. Are there any possible reasons for this?


Solved; need another resistor attached to ground.