I am looking for some advice or pointers as to whether I need to solve this problem and if so how difficult it is to do so. I have read a post which made an off the cuff remark about needing to using an OP-AMP to be able to use the full range of an ADC is certain circumstances. I think I am in this situation but I have never used an OP-AMP before.
I have a temperature sensor (thermistor I guess) that I am reusing from a pool heating system. I have tested and measured the resistance of the thermistor at 2deg C at around 493k and at 72deg C at 398k. When I hooked it up to my little voltage divider circuit that will feed into a MCP3002 ADC I used a 1M ohm resistor and this gave me 2.21V at 2deg C and 2.36V at 72deg C.
So the issue is that I will only be using a small amount of the ADC range. Using online calculators and reading other posts I see I should drop the fixed resistor to around 450k which I will do but this only increases the voltage range by a small amount.
I can probably get by with this range as I don't need much more than 2 degrees of precision but I thought if it isn't too difficult I might see if I can add to my currently simple circuit (voltage divider and ADC) to increase the used range of the ADC. Clearly I am new at this so please be gentle with your explanations! Thanks!