Solution:

Actually, we use look-up table and some simple formula to complete the conversion, the following is for your information: 1. Look-up table We use look-up table to convert impedance (we output current about 200 uA to RTD and get voltage from it, then calculate impedance according to voltage and current) to temperature first. In fact, we don't build look-up table completely because of space available. The way we adopt is shown as below: 0 degree => xxx#1 (by look-up table) 0-10 degree => calculate from xxx#1 and xxx#2 (by interpolation) 10 degree => xxx#2 10-20 degree => calculate from xxx#2 and xxx#3 20 degree => xxx#3 ................. and so on 2. Output linearization Transfer temperature to voltage or current (which depends on your output range) with linearization.