Thermistor

Definition

A thermistor is a type of temperature sensor that exhibits a change in electrical resistance in response to changes in temperature. These sensors are made from ceramic materials that exhibit either a positive temperature coefficient (PTC) or a negative temperature coefficient (NTC), which means their resistance increases or decreases, respectively, with temperature. Thermistors are widely used in various applications for precise temperature measurements and control, making them essential in data acquisition systems.

5 Must Know Facts For Your Next Test

1. Thermistors are highly sensitive and provide accurate temperature readings, making them suitable for applications requiring precision.
2. NTC thermistors are commonly used for temperature measurement and are favored for their sensitivity at lower temperatures.
3. PTC thermistors are often used as resettable fuses because their resistance increases significantly at a certain temperature, limiting current flow.
4. Thermistors can be used in a variety of settings including HVAC systems, automotive applications, and medical devices for monitoring body temperature.
5. The resistance-temperature characteristics of thermistors can be described using the Steinhart-Hart equation, which provides a mathematical relationship between resistance and temperature.

Review Questions

• How do the characteristics of NTC and PTC thermistors differ in terms of their application in temperature measurement?
  • NTC thermistors decrease in resistance as temperature increases, making them ideal for accurate temperature measurements across a range of values. They are commonly used in applications like climate control and electronic devices where precise monitoring is essential. In contrast, PTC thermistors increase resistance with rising temperatures, making them suitable for overcurrent protection in circuits as they limit current flow when excessive heat occurs.
• Discuss how thermistors integrate into data acquisition systems and the advantages they offer over other types of temperature sensors.
  • Thermistors are integrated into data acquisition systems due to their high sensitivity and accuracy, allowing them to capture precise temperature data. Unlike other sensors like thermocouples or RTDs, thermistors can respond quickly to temperature changes, which is crucial for real-time monitoring. Their small size also makes them easier to install in compact spaces, enhancing the overall performance of monitoring systems in various applications.
• Evaluate the importance of understanding the resistance-temperature relationship of thermistors when designing a monitoring system.
  • Understanding the resistance-temperature relationship is crucial when designing monitoring systems using thermistors because it directly affects the accuracy and reliability of temperature readings. The Steinhart-Hart equation helps in defining this relationship mathematically, allowing engineers to calibrate systems for precise measurements. This knowledge enables the selection of appropriate thermistor types for specific applications, ensuring optimal performance and accuracy in critical environments like medical devices and environmental monitoring systems.

Related terms

Temperature Coefficient: The rate at which a material's electrical resistance changes with temperature, which can be positive or negative.

Data Acquisition System: A system that collects, measures, and analyzes data from various sensors to monitor and control processes.

RTD (Resistance Temperature Detector): A type of temperature sensor that uses the predictable change in electrical resistance of certain materials with temperature to measure temperature.