You ask for diagram, that what you get!!
If you look (maybe with magnifies glass) you can see NTC or PTC (Negative Temperature Coefficient resistor, Thermistor) or (Positive temperature coefficient resistor).
All the answers you can find on the net if you look all need bit of work (just looking on the net). Nothing is for free.
if it contains an internal ADC you just need a temperature sensing ic like lm35d
and if your controller doen't have any ADC you need to have an ADC ic like ADC0804
communicate between them and you will get the temperature.
yes, but when you use a constant current, you need to know the NTC/PTC curve values ... for example, you need to know the 25degree tempuratur ohmsk value, typical 1000ohms.
so if use 1mA constant current you will get 1V over the NTC/PTC, wiht 25degrees.
but use as sau_sol says, a IC to measure temp, and use a chip wiht internal ADC, for example a MicroChip PIC16F874 !!
but you still need two find out what you want to use NTC or PTC ...
LM35d is a simple transistor type IC for measuring temperature having 3 pins
1. supply
2. output voltage
3. gnd
it give an increase in 10mV for 1 degree Centigrade rise in temperature
so if your controller have an internal ADC as in PIC and AVR controllers you can use them
or you can use an external ADC ic
the problem is for first time you need to calibrate your lm35d
i.e. you have to check the room temperature and feed in the controller for further calculations
making this value as a reference for the temperature