I am using the Waveshare High-Precision AD/DA Board with my Pi to read an analogue 0-5v signal.

I am using a 5V reference voltage, but I can't seem to read full scale.

  • Applying 0V reads out -344 bits (~0V)
  • Applying 3.3V reads out 5559000 bits (~3.3V)
  • Applying 5V reads out 6698000 bits (~4V)

Can anybody advise on how I can read full scale? I'm using PiPyADC.


  • What does reads out x bits mean? You haven't given enough information to provide an answer. – joan Mar 18 at 11:34
  • Sorry, PiPyADC is a python script and reads the bits out (which are generated by the ADC) and converts to a voltage reading. It seems to max out at approximately 6698000 bits, which is equal to a voltage of 4V. My issue is it's meant to go up to 5V but I don't seem to be achieving this span – Tom Mar 18 at 11:53
  • So your resolution is ~0.6 microvolt per bit? Is this value documented somewhere? How precisely do you measure the voltage that you apply? – Dmitry Grigoryev Mar 18 at 12:58

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