As explained by All About Circuits in their article Introduction to Temperature Sensors: Thermistors, Thermocouples, RTDs, and Thermometer ICs, temperature sensors are integral to various technologies, from computers and cars to home appliances and air conditioners. The five most common types of temperature sensors include thermistors, thermocouples, resistance temperature detectors (RTDs), and both analog and digital thermometer integrated circuits (ICs).

Thermistor Basics: NTC vs. PTC Thermistors

Thermistors, or thermal resistors, detect temperature changes through resistance variations. There are two types:

  • PTC (Positive Temperature Coefficient): Resistance increases with temperature.
  • NTC (Negative Temperature Coefficient): Resistance decreases as temperature rises, making NTC thermistors the most commonly used type.

The resistance-temperature relationship in thermistors is non-linear and is described mathematically using the NTC thermistor resistance equation.

Linearizing Thermistor Behavior

Given their non-linear nature, thermistors often require linearization for accurate measurements. Two common linearization techniques are:

  1. Resistive Mode Linearization:
    In this method, a normal resistor is placed in parallel with the thermistor. When the resistor’s value matches the thermistor’s resistance at room temperature (25°C), the linearization is symmetrical around room temperature.
  2. Voltage Mode Linearization:
    Here, the thermistor is placed in series with a resistor, forming a voltage divider connected to a stable reference voltage. This configuration produces a more linear output voltage over a temperature range.

Applications of Temperature Sensors

Temperature sensors are widely used in everyday devices and industrial equipment:

  • Home and Appliances: Thermostats, refrigerators, and kitchen appliances.
  • Automotive: Monitoring engine oil and coolant temperatures.
  • Electronics: Preventing overheating in computers and smart devices.

Choosing the right temperature sensor involves understanding the media being measured, the accuracy required, and environmental conditions such as temperature range and humidity.

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Article with all rights reserved, courtesy of allaboutcircuits.com.