Another temperature sensitive device, introducing the thermistor. From its name you could guess that its a temperature dependent resistor which varies its resistance as the temperature changes. See Cypress’ application note on using these devices.
A thermistor is a temperature-sensitive resistor in which resistance varies with temperature. There are two types of thermistors: positive temperature coefficient (PTC) thermistors and negative temperature coefficient (NTC) thermistors. This application note describes the more commonly used NTC thermistors, in which resistance decreases with increase in temperature. Based on this principle, temperature is calculated by measuring the resistance.