Thermistor

Definition

A thermistor is a type of resistor whose resistance changes significantly with temperature. It is a temperature-sensitive electronic component commonly used in electrical measuring instruments, temperature control, and temperature compensation circuits.

5 Must Know Facts For Your Next Test

1. Thermistors can be either negative temperature coefficient (NTC) or positive temperature coefficient (PTC), depending on how their resistance changes with temperature.
2. NTC thermistors have a resistance that decreases as temperature increases, while PTC thermistors have a resistance that increases as temperature increases.
3. Thermistors are commonly used in temperature measurement and control applications, such as in thermometers, ovens, and HVAC systems.
4. The sensitivity of a thermistor is determined by its temperature coefficient, with higher coefficients indicating greater resistance changes per degree of temperature change.
5. Thermistors can be used in voltage divider circuits to create temperature-dependent voltage outputs, which are useful for electrical measuring instruments.

Review Questions

• Explain how a thermistor's resistance changes with temperature and how this property is utilized in electrical measuring instruments.
  • A thermistor is a type of resistor whose resistance changes significantly with temperature. Negative temperature coefficient (NTC) thermistors have a resistance that decreases as temperature increases, while positive temperature coefficient (PTC) thermistors have a resistance that increases as temperature increases. This temperature-dependent resistance property is leveraged in electrical measuring instruments, such as thermometers, where the thermistor's resistance change is used to determine and display the measured temperature. The sensitivity of a thermistor, as indicated by its temperature coefficient, determines how much its resistance changes per degree of temperature change, making it a valuable component for accurate temperature measurement and control in various applications.
• Describe how a thermistor can be used in a voltage divider circuit to create a temperature-dependent voltage output, and explain the significance of this application in electrical measuring instruments.
  • Thermistors can be used in voltage divider circuits to create a temperature-dependent voltage output. In a voltage divider, the thermistor's resistance changes with temperature, which in turn alters the ratio of the output voltage to the input voltage. This temperature-dependent voltage output can be used in electrical measuring instruments, such as digital multimeters or temperature controllers, to provide a direct indication of the measured temperature. The voltage divider circuit allows the thermistor's resistance change to be converted into a proportional voltage signal, which can then be processed and displayed by the instrument. This integration of the thermistor's temperature-sensing capabilities with the voltage divider circuit is a crucial aspect of many electrical measuring instruments, enabling accurate and reliable temperature measurement and control.
• Analyze how the temperature coefficient of a thermistor, which determines the rate of resistance change with temperature, impacts its performance and suitability for different applications in electrical measuring instruments.
  • The temperature coefficient of a thermistor is a critical factor that determines the rate of resistance change with temperature, and this directly impacts the thermistor's performance and suitability for different applications in electrical measuring instruments. Thermistors with higher temperature coefficients, either positive or negative, exhibit greater resistance changes per degree of temperature change. This increased sensitivity allows for more precise temperature measurement and control, which is essential in applications such as digital thermometers, temperature controllers, and HVAC systems. Conversely, thermistors with lower temperature coefficients may be better suited for applications where a more gradual resistance change is desired, such as in temperature compensation circuits. The selection of a thermistor with the appropriate temperature coefficient is crucial in ensuring the accuracy, reliability, and overall performance of the electrical measuring instrument in which it is used. Understanding and leveraging the temperature coefficient is a key aspect of effectively incorporating thermistors into the design of various electrical measuring instruments.

Related terms

Resistance: The opposition to the flow of electric current in a circuit, measured in ohms.

Temperature Coefficient: The rate of change of a physical property, such as resistance, in response to a change in temperature.

Voltage Divider: A circuit that produces an output voltage that is a fraction of its input voltage, formed by connecting resistors in series.