The following characteristics of the thermistor show the relationship between temperature and resistance as shown in the following figure.
For control it is necessary to convert resistance into voltage, here is the basic circuit for converting resistance into voltage.
Thermistor with a positive coefficient (PTC, Positive Thermal Coefcient) Graph of the characteristics of the PTC thermistor:
In operation, the PTC thermistor takes advantage of changes in resistivity with temperature, and generally the resistance value increases with temperature exponentially.
The resistance area is nearly linear.
For the temperature compensation technique using a bridge amplifier circuit, it is better to use this type of resistance sensor because the bridge circuit can be adjusted to its equilibrium point.
The output voltage value is:
Or another formula that can be used to determine the output voltage:
until
