Explain the working principle and application of different temperature sensors with neat sketches.

Introduction to Temperature Sensors

Temperature sensors are devices that measure temperature and convert the measured value into a readable output. They are widely used in various applications including industrial, medical, HVAC, and consumer electronics.

Types of Temperature Sensors

1. Thermocouples

   • Working Principle: Thermocouples work on the principle of the Seebeck effect, where a voltage is produced at the junction of two different metals when there is a temperature difference.
   • Applications: Used in high-temperature environments (e.g., furnaces, gas turbines, and engines).

   

2. Resistance Temperature Detectors (RTDs)

   • Working Principle: RTDs operate on the principle that the resistance of certain metals changes with temperature. The most common materials are platinum, nickel, and copper.
   • Applications: Used in industrial processes, heating systems, and laboratory settings where accurate measurement is crucial.

   

3. Thermistors

   • Working Principle: Thermistors are temperature-sensitive resistors, typically made from ceramic materials. Their resistance decreases with an increase in temperature (negative temperature coefficient - NTC) or increases with an increase in temperature (positive temperature coefficient - PTC).
   • Applications: Commonly used in temperature measurement, automotive applications, and household appliances.

   

4. Infrared Sensors

   • Working Principle: Infrared sensors detect temperature by measuring the infrared radiation emitted by an object. This method allows non-contact temperature measurement.
   • Applications: Widely used in medical applications (such as forehead thermometers), industrial monitoring, and thermal cameras.

   

5. Bimetallic Temperature Sensors

   • Working Principle: These sensors consist of two different metals bonded together. As temperature changes, the metals expand at different rates, causing the bimetallic strip to bend and activate a mechanical switch.
   • Applications: Commonly used in thermostats and mechanical temperature indicators.

   

Summary

Temperature sensors play a crucial role in various sectors, providing essential data for monitoring and controlling temperature in processes and environments. Each type of sensor is suited for specific applications based on its operating principles and characteristics.