Thermistor

Definition

A thermistor is a type of temperature sensor that changes its electrical resistance based on temperature variations. This unique property allows thermistors to be used for precise temperature measurements and control in various applications, including electronics, automotive, and industrial processes. They are categorized into two main types: NTC (Negative Temperature Coefficient) thermistors, which decrease in resistance as temperature increases, and PTC (Positive Temperature Coefficient) thermistors, which increase in resistance with rising temperature.

5 Must Know Facts For Your Next Test

1. Thermistors are widely used in applications such as climate control systems, medical devices, and automotive sensors due to their high sensitivity and accuracy.
2. NTC thermistors are commonly employed for temperature sensing, while PTC thermistors are often used for overcurrent protection and self-regulating heating elements.
3. The resistance of a thermistor can change dramatically with small temperature changes, making them suitable for applications requiring precise temperature measurements.
4. Thermistors are generally more cost-effective than other types of temperature sensors, like RTDs and thermocouples, while still providing good performance.
5. The response time of thermistors can be very fast, allowing them to quickly adapt to changes in temperature, which is critical in dynamic environments.

Review Questions

• How does the resistance change in NTC and PTC thermistors with respect to temperature, and what implications does this have for their applications?
  • In NTC thermistors, the resistance decreases as the temperature increases, making them suitable for accurate temperature sensing in devices like digital thermometers. Conversely, PTC thermistors increase in resistance as the temperature rises, which makes them useful for overcurrent protection in electrical circuits. Understanding how these resistance changes affect their application helps engineers select the right type of thermistor for specific tasks.
• Compare the advantages of using thermistors versus other temperature sensors like RTDs and thermocouples in industrial applications.
  • Thermistors offer several advantages over RTDs and thermocouples in industrial applications. They are generally more sensitive and can detect smaller changes in temperature due to their high resistance change. Additionally, they are more cost-effective, making them accessible for a variety of projects. However, they usually have a more limited operating range compared to RTDs and thermocouples, which may restrict their use in some high-temperature environments.
• Evaluate the importance of calibration for thermistors in ensuring accurate temperature measurements and discuss methods to achieve reliable calibration.
  • Calibration is crucial for thermistors because it ensures that their readings are accurate and reliable. Since their resistance can vary based on manufacturing differences and environmental conditions, regular calibration against known standards is essential. Common methods include using a calibrated reference thermometer or placing the thermistor in a controlled environment where temperature changes are measured precisely. Proper calibration helps maintain the integrity of data collected from thermistors in critical applications.

Related terms

Resistance Temperature Detector (RTD): A temperature sensor that operates on the principle that the electrical resistance of a material changes with temperature, typically made from pure metals.

Thermocouple:

A temperature measurement device made of two different metals joined at one end, producing a voltage that varies with temperature.

Calibration:

The process of adjusting and verifying the accuracy of measurement devices, including thermistors, to ensure reliable readings.