Thermistors

Definition

Thermistors are temperature-sensitive resistors that exhibit a significant change in resistance with varying temperatures. They are typically made of ceramic materials and are used in various applications, including temperature sensing and circuit protection. These components can be classified 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 electronic circuits for precise temperature measurement due to their high sensitivity to temperature changes.
2. NTC thermistors are commonly found in applications like temperature sensors, while PTC thermistors are often used for overcurrent protection in circuits.
3. The resistance of a thermistor can change dramatically within a small temperature range, making them ideal for applications where quick response is essential.
4. Thermistors can be more accurate than traditional temperature sensors such as thermocouples or RTDs (Resistance Temperature Detectors) due to their steeper resistance-temperature curve.
5. The self-heating effect can occur when using thermistors, leading to inaccurate readings if the device generates heat while measuring temperature.

Review Questions

• How do NTC and PTC thermistors differ in their response to changes in temperature?
  • NTC thermistors decrease in resistance as temperature increases, making them useful for applications requiring a drop in resistance with higher temperatures. In contrast, PTC thermistors increase in resistance when temperature rises, which can be beneficial for protecting circuits from overcurrent situations. Understanding these differences allows engineers to choose the appropriate thermistor type based on specific application requirements.
• Discuss the role of thermistors in electronic circuits and how their properties make them suitable for temperature measurement.
  • Thermistors play a critical role in electronic circuits by providing precise temperature measurements and protection against overcurrent conditions. Their high sensitivity to temperature changes allows for quick and accurate readings, making them ideal for applications such as HVAC systems and consumer electronics. The steep change in resistance with temperature makes them more responsive than traditional sensors, which is essential for maintaining optimal operation in various devices.
• Evaluate the advantages and limitations of using thermistors compared to other types of temperature sensors in practical applications.
  • Thermistors offer several advantages over other temperature sensors like thermocouples and RTDs, including higher sensitivity, faster response times, and lower cost. However, they also have limitations, such as a limited temperature range and susceptibility to self-heating effects that can lead to inaccurate readings. In practical applications, engineers must weigh these pros and cons to determine whether a thermistor or another type of sensor best meets the specific needs of their project.

Related terms

Resistor:

A component that resists the flow of electric current, resulting in a drop in voltage across it.

Conductivity:

A measure of a material's ability to conduct electric current, which is affected by temperature for both conductors and insulators.

Temperature Coefficient: A numerical value that indicates how much a material's resistance changes with temperature.