How does a thermistor's resistance change with temperature?
1 Answer
A thermistor is a type of temperature sensor that exhibits a significant change in resistance with variations in temperature. The two most common types of thermistors are Negative Temperature Coefficient (NTC) and Positive Temperature Coefficient (PTC) thermistors. The behavior of each type is different:
NTC Thermistors:
As the name suggests, NTC thermistors have a negative temperature coefficient, meaning their resistance decreases as the temperature increases. In other words, the resistance of an NTC thermistor decreases as it gets hotter and increases as it gets colder. The resistance-temperature relationship in NTC thermistors can often be approximated by the Steinhart-Hart equation or the Beta equation, depending on the specific thermistor's characteristics.
PTC Thermistors:
On the other hand, PTC thermistors have a positive temperature coefficient, which means their resistance increases as the temperature rises. When the temperature drops, the resistance decreases. PTC thermistors are less common than NTC thermistors but are used in certain applications where their unique behavior is advantageous.
Both NTC and PTC thermistors are made of semiconductor materials, and their resistance-temperature relationship is mainly due to the behavior of charge carriers (electrons and holes) in the semiconductor lattice. As the temperature changes, the number of charge carriers and their mobility vary, influencing the overall resistance of the thermistor.
It's worth noting that the resistance-temperature relationship of a thermistor is not linear but follows a specific curve. Manufacturers usually provide a resistance-temperature curve in the thermistor's datasheet, which helps in accurately measuring and interpreting temperature based on the resistance value of the thermistor. This non-linear response allows for precise temperature measurements in certain temperature ranges, making thermistors useful in various applications, such as temperature monitoring, compensation, and control systems.
NTC Thermistors:
As the name suggests, NTC thermistors have a negative temperature coefficient, meaning their resistance decreases as the temperature increases. In other words, the resistance of an NTC thermistor decreases as it gets hotter and increases as it gets colder. The resistance-temperature relationship in NTC thermistors can often be approximated by the Steinhart-Hart equation or the Beta equation, depending on the specific thermistor's characteristics.
PTC Thermistors:
On the other hand, PTC thermistors have a positive temperature coefficient, which means their resistance increases as the temperature rises. When the temperature drops, the resistance decreases. PTC thermistors are less common than NTC thermistors but are used in certain applications where their unique behavior is advantageous.
Both NTC and PTC thermistors are made of semiconductor materials, and their resistance-temperature relationship is mainly due to the behavior of charge carriers (electrons and holes) in the semiconductor lattice. As the temperature changes, the number of charge carriers and their mobility vary, influencing the overall resistance of the thermistor.
It's worth noting that the resistance-temperature relationship of a thermistor is not linear but follows a specific curve. Manufacturers usually provide a resistance-temperature curve in the thermistor's datasheet, which helps in accurately measuring and interpreting temperature based on the resistance value of the thermistor. This non-linear response allows for precise temperature measurements in certain temperature ranges, making thermistors useful in various applications, such as temperature monitoring, compensation, and control systems.