The difference between thermistor and thermocouple

Thermocouple


Thermocouple is a sensor consisting of two conductors that are different in properties and are welded together. Measurement occurs due to the formation of thermal electromotive force (voltage) formed between the conductors. Depending on the cold or hot source, the current at the sensor will change its direction between the positive or negative value. The sensor does not require special settings, you just need to check the readings with the reference device.
The difference between thermistor and 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 capable of measuring temperatures up to 2500 degrees Celsius.
The disadvantage of the sensor can be attributed to 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 the wrong choice of temperature error reaches 2.5-4 degrees Celsius.
The difference between thermistor and thermocouple

Thermocouple is widely used in the following industries:
  • in scientific research and medicine;
  • in industry (production of metal products);
  • in automated control systems (CNC machine tools).

Thermistor


The thermistor is a semiconductor device operating on the principle of variable resistance.
The difference between thermistor and thermocouple

When the temperature changes, its internal resistance changes depending on the type of sensor selected. There are two varieties of this electrical semiconductor:
  • NTC thermistor (resistance decreases with increasing temperature);
  • PTC thermistor (resistance increases with temperature).

Of the features of the sensor, you can select its accuracy to the measured temperature. The error of the thermistor is only 0.05 degrees Celsius.
Measurement range: from -50 to +300 degrees on any measured interval.
The difference between thermistor and thermocouple

Sensor flaws:
  • with a rise in temperature, the service life is shortened. The manufacturer guarantees up to 1000 hours of operation;
  • accurate readings require calibration with a reference meter.

Summarizing


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 temperatures at the sensors differ. For each type, you need your own device or controller that allows you to monitor the readings.
The main selection criterion can be considered the measurement range. If the temperature exceeds the threshold of 300 degrees, a thermocouple should be used. Otherwise, it makes no sense to overpay, you can do with inexpensive thermal resistances, since the thermocouple is much more expensive.

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