Learn how thermistors work and their various types. Discover their principle of operation, applications, and importance in different fields.
Introduction
A thermistor is a type of resistor that is sensitive to changes in temperature. The name “thermistor” comes from “thermal resistor.” These devices are commonly used to measure temperature, control the temperature of a device, or compensate for temperature changes in electronic circuits. In this article, we will explore how thermistors work and their various types.
Principle of Operation
Thermistors work based on the principle that the resistance of a material changes with temperature. The resistance of a thermistor decreases as the temperature increases and vice versa. This property is known as the temperature coefficient of resistance (TCR). TCR is defined as the rate at which the resistance of a material changes with temperature.
Thermistors are made of ceramic or polymer materials that have a high TCR. When the temperature of a thermistor changes, the number of free electrons in the material also changes. This alters the flow of current through the thermistor, which results in a change in its resistance.
There are two types of thermistors: positive temperature coefficient (PTC) and negative temperature coefficient (NTC). PTC thermistors have a positive TCR, which means that their resistance increases as the temperature increases. On the other hand, NTC thermistors have a negative TCR, which means that their resistance decreases as the temperature increases.
Applications
Thermistors have a wide range of applications in different fields. They are commonly used in electronic circuits to measure and control temperature. For example, they can be used in temperature sensors, thermostats, and temperature controllers.
Thermistors can also be used in medical applications such as temperature probes and fever detectors. They are also used in automotive applications, such as measuring the temperature of engine coolant, transmission fluid, and intake air.
In addition to these applications, thermistors are used in various industrial processes. They can be used to measure temperature in industrial ovens, kilns, and furnaces. They are also used in the food industry to measure the temperature of food during processing and storage.
Conclusion
Thermistors are an essential component in many electronic circuits, medical devices, and industrial processes. They are a cost-effective and reliable way to measure and control temperature. Understanding how thermistors work and their different types is crucial in selecting the appropriate thermistor for a particular application.
Types of Thermistors
As mentioned earlier, there are two types of thermistors: positive temperature coefficient (PTC) and negative temperature coefficient (NTC). However, these two types can be further classified based on their materials, properties, and applications.
PTC Thermistors
PTC thermistors are made of materials such as barium titanate, lead titanate, and lead zirconate titanate. They have a positive TCR, which means that their resistance increases as the temperature increases. PTC thermistors are commonly used in overcurrent protection, temperature compensation, and self-resetting fuses. They can also be used as temperature sensors in medical and automotive applications.
NTC Thermistors
NTC thermistors are made of materials such as semiconductors, oxides, and polymers. They have a negative TCR, which means that their resistance decreases as the temperature increases. NTC thermistors are commonly used in temperature sensors, thermostats, and temperature controllers. They can also be used in motor protection, automotive, and medical applications.
Interchangeability
Interchangeability is an important characteristic of thermistors. Interchangeability refers to the ability of different thermistors to provide the same response when exposed to the same temperature change. Interchangeability is critical in applications where multiple thermistors are used, such as in automotive and industrial applications.
Thermistors can be calibrated to improve their interchangeability. Calibration involves measuring the resistance of a thermistor at various temperatures and creating a calibration table. The calibration table can then be used to convert the resistance of a thermistor into a temperature reading.
Conclusion
Thermistors are a critical component in temperature measurement and control systems. Their ability to provide a reliable and accurate temperature measurement makes them suitable for use in a wide range of applications. Understanding the different types of thermistors and their properties is essential in selecting the appropriate thermistor for a particular application. Whether you are designing an electronic circuit, a medical device, or an industrial process, thermistors can provide a cost-effective and reliable solution for temperature measurement and control.
