For a test bed, we want to measure temperatures with NTC sensors (~10kOhm at RT) for the range 10°C to 70°C. Our test machine accepts auxiliary signal through CAN-bus, so we used a Raspberry with a "CAN-hat" to prototype the temperature measurement (three-point probing) and configure the test machine.
We now want to scale it up to 80 (phase 1) then 320 (phase 2) channels. We already have all the necessary NTC sensors (recovered from previous projects). So far we have 2 solutions which are not satisfying:
An all inclusive solution by a provider for a hefty price
Acquiring eight 10-channel Ohm meters + eight RS-232 to CAN. That's about $100 to $150 per channel. That would slash the price in 2 compared to solution 1.
In both cases, that's more than the cost of the RPi + the CAN-hat per channel. I would expect that scaling up a prototype would mean reducing the price per unit.
Is there any less resource-intensive solution(s) we are missing? Ideally measurement with 3 or 4-point method would be wished.
Thank you. edit: accuracy around 1K, resolution around 0.1K.