Reasking this question with a proper schematic:
I am doing a ratiometric measurement of a Thermistor. The thermistor is located over 5 metres away from the ADC and all other components. This is going to be a resistance of the cables of upwards of several Ohms.
The opamp driving the ADC will be doing a Kelvin 4-point measurement.
The Thermistor is supplied by a 2.5V Voltage source, which will be the reference for the ADC.
However, where should I connect the reference pin of the ADC - on the PCB, or 5 metres away right on the thermistor voltage divider?
If I do it on the PCB, the voltage the ADC sees as the reference will be different to the actual voltage 5 metres away will it not? Will this defeat the point of a ratiometric measurement?
Then if I do it 5 metres away, there will be a lot of inductance in this wire, so I will need a larger buffer capacitor next to the Vref pin to ensure the voltage doesnt have large spikes during each conversion