Difference between thermistor and thermocouple

Thermocouple

The thermocouple is a sensor consisting of two conductors that are different in properties and are welded together. The measurement is due to the formation of a thermal electromotive force (voltage) formed between the conductors. Depending on the cold or hot source, the current on the sensor will change its direction between a positive or negative value. The sensor does not require special settings, you just need to check the readings with the reference device.
Thermistor difference from thermocouple
The measuring range of the sensor varies from -270 to 2500 degrees and depends on the conductors used inside the alloys. For example, a tungsten-rhenium alloy in a thermocouple is able to measure the temperature to 2500 degrees Celsius. The disadvantage of the sensor is a small output signal, which requires the presence of an electronic amplifier and a signal converter. The accuracy of the measurement depends on the size of the device, with an incorrect choice, the temperature error reaches 2.5-4 degrees Celsius.
  • in industry (metal products);
  • in automated control systems (CNC machines).
  • Thermistor

    Thermistor is a semiconductor device operating on the principle of variable resistance. The difference between a thermistor and a thermocouple
As the temperature changes, its internal resistance changes depending on the type of sensor selected. There are two types of this electrical semiconductor:
  • NTC thermistor (resistance decreases with increasing temperature)
  • PTC thermistor (resistance increases with temperature) li>
From the sensor features, its accuracy to the measured temperature can be distinguished. Thermistor error is only 0.05 degrees Celsius. Measuring range: from -50 to +300 degrees on any measured interval.
The difference between a thermistor and a thermocouple
Sensor deficiencies:
  • as the temperature rises, the lifetime is reduced.The manufacturer gives a guarantee of up to 1000 hours;
  • for an accurate reading, calibration with a reference meter is required.

Summing up

The accuracy of temperature readings is certainly higher in thermistor sensors, but thermocouples can boast a large measuring range. The material from which the thermistor is made degrades over time, whereas thermocouples live much longer. Methods for determining the temperature of the sensors differ. For each type, you need your own device or controller that allows you to control the readings. The main selection criterion can be considered the measuring range. If the temperature exceeds the threshold of 300 degrees, a thermocouple should be used. Otherwise, it makes no sense to overpay, you can get by with inexpensive thermal resistances, since the thermocouple is much more expensive.

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