I'm using a 10 bit ADC on my PIC microcontroller. For some reason I have to do a dummy read and give a delay of about 200 us before I do my actual ADC reads. I get inaccurate readings if I switch from reading a high voltage (near the bus) to a low voltage (near the ground) without doing a dummy read and then a delay before doing the actual read. Is this normal?

 

I suggest you post your ADC code and the PIC MCU info.

Tim S.

 

You need a settling time before reading from different ADC channels.
Its in the PIC spec.