Thermistor is a special type of resistor whose resistance is dependent on temperature I.e its resistance varies or changes in response to temperature. The resistance of a thermistor decreases with increasing temperature. This is due to the properties of the semiconductor material that the thermistor is made with. It derived it name from the term “thermally sensitive resistor”. They are made up of ceramics and metal oxides. Thermistor was first discovered by Michael Faraday in 1833.
Thermistor is divided into two types they include:
1. Negative Temperature Coefficient (NTC) Thermistor– This type of thermistor, resistance decreases with temperature to protect inrush over voltage conditions and it is installed in parallel in a circuit.
2 .Positive Temperature Coefficient (PTC)– This type of thermistor, the resistance increases with temperature to protect against over current conditions and it is installed in series in a circuit.
Uses And Applications Of Thermistors
- They are used for voltage regulation, volume control, time delays, and circuit protection.
- They are used in circuit (surge) protector to prevent over current from damaging an electrical or electronic device plugged in.
- They are used in digital thermometers to accurately measure someone’s temperature. They are inexpensive, reliable and respond quickly,that is why they are used in digital thermometers.
- They are used in Microwave to determine and regulate the internal temperature (prevent overheating which could lead to fire)
- They are used in recharging of rechargeable batteries to prevent the charger from getting too hot.
- They can be used in the making of fire alarm.
- They are used in automotive (cars, trucks and buses) to determine the temperature of oil and coolants. Unlike its usage in microwave, they do not prevent or regulate the vehicle from overheating rather it serves as a signal to know when the car is overheated. They connected to indicators on the dashboard of the automotive.
- Thermistors are can also be used to regulate temperatures for safe and cost effective operations in the handling and processing of food item.