I have set up my raspberry pi to read from the MAX1204. To know if I'm reading the proper value, I use a multimeter at the input channel of the ADC, and compare it to what I read through my program. This works great. However, when I disconnect my multimeter, I don't read the same value. If I was reading 1.264 - 1.268 (correct measurement), I now read 1.248- 1.252.
I assume it's due to the internal capacitance of the multimeter, or some other reason. How can I set up a capactiance or a way to read the correct readings without constantly needing to have the multimeter plugged in? I tried using a 0.01uF, 0.1uF and no luck.
Block Diagram (to try and replicate schematic):
Edit: it would seem that when changing my multimeter to the 2V option va the 20V, thé close it 1.276 but the ADC is still reading 1.25. Which means I have a 25 mV difference between voltage and readings.