I've used your ADCPi boards (ADC PI Plus) for a few projects (raspberry pi 2 & 3) and and I like them. However, in two of my recent uses I've been getting the error:
'TimeoutError: read_raw: channel xx conversion timed out' (where xx is any of the channels)
The error can be thrown after running for a few seconds or after a few hours. It also happens when I run your 'demo_readvoltage.py' code.