I'm currently using the ADC Pi with various sensors, the setup is easy and it works pretty well.
As a voltage divider is included on the board, I'm not sure I've understood what is the actual input impedance and what voltage is measured by the board.
One of my sensors (http://www.omron.com/ecb/products/sensor/61/d6f-6.html) has an output impedance of 16.7 kOhm, which is quite high, so I read a lower voltage with the board than with a multimeter.
So here are my questions :
1) What is the input impedance of the ADC Pi and what voltage is measured given the onboard voltage divider ?
2) Is it possible to increase this impedance ? (influence of PGA ?)
3) What is the coefficient I must multiply the measured voltage by to get the actual output voltage for the sensor I mentioned before ? (I suppose I will lose in accuracy though)