What is a Thermistor? How Do They Work?

What is a thermistor

Ultimate Guide to Thermistors

Thermistors may not be a household term, but they play a crucial role in our everyday lives. So exactly what is a thermistor?

These tiny devices have a big impact on everything from temperature monitoring in electronic gadgets to regulating temperature in your car’s engine.

At Process Parameters Ltd, a leading UK-based sensor manufacturer and temperature sensor supplier, we understand the vital role thermistors play.

In this blog, we unravel the mystery of thermistors, exploring what they are and how they work.

What is a Thermistor?

A thermistor, short for “thermal resistor,” is a type of temperature-sensitive resistor that exhibits a significant change in resistance with temperature.

Unlike regular resistors, which have a constant resistance, thermistors are designed to have resistance values that vary dramatically as the temperature changes.

Thermistors are tiny but powerful electronic components that play a crucial role in a wide range of industries, from automotive to healthcare, and from aerospace to consumer electronics.

These miniature temperature-sensitive devices are the unsung heroes behind the precise temperature monitoring and control systems that underpin many of our everyday devices and complex industrial processes.

At Process Parameters, we supply data loggers with thermistor probes. View some of our thermistor data logger products here, or contact us if you’re not sure which device is best for your application.

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Data logger with thermistor probe
A data logger with a thermistor probe

Types of Thermistors

There are two main types of thermistors: Negative Temperature Coefficient (NTC) and Positive Temperature Coefficient (PTC) thermistors.

NTC Thermistors

These thermistors exhibit a decrease in resistance as temperature increases. The resistance-temperature relationship for NTC thermistors is highly nonlinear.

PTC Thermistors

PTC thermistors, on the other hand, display an increase in resistance as temperature rises. Their resistance-temperature curve is also nonlinear but in the opposite direction.

Key Characteristics and Properties

Thermistors are known for their unique properties:

  • High sensitivity to temperature changes
  • Fast response time
  • Wide temperature measurement range
  • Compact and cost-effective

Historical Background

The history of thermistors dates back to the early 19th century when scientists began to notice the relationship between electrical resistance and temperature. Over time, technological advancements have led to the development of precise and reliable thermistors for various applications.

How Do Thermistors Work?

At the heart of a thermistor’s operation is its resistance-temperature relationship. As temperature changes, the electrical resistance of a thermistor changes accordingly. This property forms the basis for its temperature-sensing capabilities.

NTC Thermistors

Negative Temperature Coefficient (NTC) thermistors exhibit a sharp decrease in resistance as temperature rises. This means that their resistance decreases as the surrounding temperature increases. The resistance vs. temperature curve for NTC thermistors is highly nonlinear, making them ideal for precise temperature measurements.

NTC thermistors find applications in:

  • Temperature sensors in electronic devices
  • Temperature compensation in circuits
  • Thermal protection in power supplies

PTC Thermistors

Positive Temperature Coefficient (PTC) thermistors, on the other hand, experience an increase in resistance as temperature increases. This nonlinear resistance-temperature curve makes PTC thermistors suitable for applications such as overcurrent protection and temperature regulation.

Common uses of PTC thermistors include:

  • Overcurrent protection in electrical circuits
  • Temperature regulation in heating elements
  • Motor protection in appliances

Factors Influencing Thermistor Performance

Several factors can influence the performance of thermistors, including environmental conditions, self-heating effects, and ageing. Understanding these factors is essential for ensuring the accurate operation of thermistors in various applications.

Applications of Thermistors

Thermistors have found their way into a wide range of applications across different industries. Some notable examples include:

  • Temperature monitoring in consumer electronics
  • Engine temperature regulation in automobiles
  • Medical devices for patient temperature monitoring
  • Industrial processes and HVAC systems

The advantages of using thermistors in these applications include their precision, reliability, and cost-effectiveness.

What is the Difference Between an RTD and a Thermistor?

This table summarises the key differences between Resistance Temperature Detectors (RTDs) and thermistors in terms of their resistance vs. temperature relationship, temperature range, accuracy, stability, response time, and cost.


Resistance Temperature Detector (RTD)


Resistance vs. Temperature

Nearly linear relationship

Highly non-linear

Temperature Range

-200°C to 600°C (or higher)

-50°C to 150°C (NTC)

-50°C to 250°C (PTC)

Accuracy and Stability

High accuracy and stability

High accuracy (within specified range)

Response Time

Slower response time

Faster response time


Generally more expensive


The choice between an RTD and a thermistor depends on the specific requirements of your application.

RTDs are favoured for their high accuracy and stability, especially in a wider temperature range, while thermistors are known for their cost-effectiveness and fast response time in moderate-temperature applications.

Choosing the Right Thermistor

Selecting the right thermistor for your application requires careful consideration of factors such as temperature range, accuracy requirements, and response time.

Consulting with experts and considering the specific needs of your project can help you make an informed choice.

At Process Parameters Ltd, we take pride in being a trusted temperature sensor supplier, providing a wealth of experience and industry-leading products to find you the right set-up for your application.

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What is a Thermistor: Conclusion

In conclusion, thermistors are remarkable devices with a vital role in various technologies. Understanding what thermistors are and how they work can help you appreciate their significance in modern electronics and beyond.

Whether you’re a technology enthusiast or an engineer, thermistors are a fascinating aspect of our connected world.

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For more in-depth information about thermistors and related topics, explore the following resources:

Feel free to reach out if you have any questions or need further assistance with thermistors or related topics.

Thermistor FAQs

What is the definition of a thermistor?

A thermistor is a temperature-sensitive element that exhibits a change in electrical resistance with variations in temperature.

What is the difference between RTD and thermistor?

Thermistors and RTDs differ in the material they are made of: thermistors are made of mixed metal oxides, and RTDs are made of pure metal such as nickel or platinum.

Guide to Temperature Measurement with Thermistors