Designing an analog circuit can be a frustrating experience, as noted by Nick Cornford in his Design Idea (DI), “DIY RTD for a DMM.”With a fortnight’s struggle, I completed the design of 4 mA to 20mA, ...

It also cuts the number of RTD array connections (feedthroughs) from 4N to 4 + N. For 28 sensors, the resulting savings are 2N − 2 − N = 26 inputs and 4N − 4 − N = 80 feedthroughs.