With this simple temperature to voltage converter circuit we can do a precise measurement of the temperature in a room. A NTC resistor or a thermistor is used as a sensor that has a strong temperature dependence.
If the NTC temperature rises then the output voltage rises with 0.5 V per 10C.
Conversion factor depends on the type of thermistor resistance used. If you want to read the temperature directly on an universal measurement device then the value of R9 must be choosed so that the desired sensitivity is achieved (R8 must be equal with R9).
The power supply voltage level is not critical; D1 zener voltage can be between 4.7 V and 8.2 V. The current consumption is about 12 mA.