AD590 conditioning: advice needed

The schematic doesn't show any bias supply for the AD590; the version I used was two-terminal and acted as a current limiter (source), i.e. (+) terminal to +12V and (-) terminal to sense resistor (other side of sense resistor to ground). Like most ICs, it needs power (current from a voltage supply) to operate!

For safety in a remote location, you can ensure current limiting by biasing it through a second resistor, in case of a short of your wiring against ground.

Frank:

Personally I would encourage you to look at the more modern digitally interfaced temp sensors. There are dozens of choices available these days and they connect right up to your microcontroller with just one or two digital bus pins. Messing around with an analog sensor, a scaling circuit, and an A/D converter hardly make sense anymore from a cost standpoint except in only the most stringent applications. Consider for example TI's TMP100 which offers temp readings to 10-bits accuracy (half degree) on an I2C interface.

- mkaras

I'm sorry, but this will not work, your simulation uses a wrong model, and the concept with a single positive supply wanting to create a negative voltage for -20°C is impossible. Put the temperature transducer from +9V to R1, which can be 10k. Buffer it x1 and the output will be 10mV/K. Better to take an AD596, which has already a voltage output. Then you can think how to subtract 2.73V and scale it up to your needs.