Temperature sensors are found all around us, from the cars we drive to the industrial plants building the consumer goods we use every day. The two most popular devices that engineers use are thermistors and thermocouples for temperature sensing. Both devices are great options for sensing and controlling temperature, but they should not be used interchangeably. When making this decision, you should make choices based on the application's exact specifications.
Thermistors are thermally sensitive resistors because they perform small and incremental resistance changes (correlated to temperature variations).
Thermocouples – these sensors reflect proportional changes in temperature. They do this through varying voltages created between two dissimilar metals that have been electrically bonded together.
There are three main things to consider when choosing between thermistors and thermocouples. These include:
Temperature Ranges – both NTC thermistors and thermocouples can operate within a wide range of temperatures, making them ideal for varying applications. An NTC thermistor should be used between -50 to 250 °C, whereas a thermocouple should be used between -200 °C to 1750 °C.
Accuracy of Sensor – A thermocouple, when compared to an NTC thermistor, has lower accuracy. Thermocouples need to convert millivolts to temperature to create accurate compensation and control. NTC thermistors are a highly accurate temperature sensor, even through incremental changes (within the specified operating range).
Application – Both sensing devices are used in a wide range of applications. It is most common to find NTC thermistors in health and safety equipment. They are used in thermometers and fire detectors. They are used in these applications because they are accurate and stable. A thermocouple is more often found in industrial settings because they are durable and inexpensive to produce.
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