RTD

1.  RTD is made up of metals.

2.  Metals have Positive Temperature Coefficient (PTC) of resistance. Hence, the resistance of RTD increases with an increase in temperature and decreases with a decrease in temperature.

3.  The resistance temperature characteristics of RTD's are linear.

4.  It is less sensitive to temperature compared to thermistor.

5.  But, it has-a wide operating temperature range i.e., - 200 to + 650°C.

6.  RTD's are relatively larger in size.

7.  They are costlier.

8.  They have low self resistance

9.  RTD's provide high degree of accuracy and long term stability.

10. They are used in laboratory and industrial applications.

Sensistor

Sensistor is a resistor whose resistance changes with temperature.The resistance increases exponentially with temperature,^[1] that is the temperature coefficient is positive (e.g. 0.7% per degree Celsius).^[2]
Sensistors are used in electronic circuits for compensation of temperature influence or as sensors of temperature for other circuits.^[3]

Sensistors are made by using very heavily doped semiconductors so that their operation is similar to PTC-type thermistors. However, very heavily doped semiconductor behaves more like a metal^[4] and the resistance change is more gradual than it is the case for other PTC thermistors.