Thermocouples have two dissimilar metal wires joined at the hot junction. As temperature changes, a millivolt signal is read at the cold junction. The most common types of temperature thermocouples are type j thermocouples and type k thermocouples. Advantages of thermocouple sensors include: low cost, small size, wider temperature ranges and faster response than RTDs. The disadvantages of using temperature thermocouples include: they are less linear and accurate than RTDs, a matching extension wire is needed, and thermocouples are sensitive to electrical noise.
Resistance Temperature Detectors (RTDs) have a linear increase in resistance as temperature rises. RTDs come in 2-,3- or 4-wire versions. A 2-wire RTD signal is affected by the distance to the controller. 3-wire or 4-wire RTDs can compensate for line losses.
Thermocouple Sensors: Type J, Type K, Type T
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For more thermocouple products, also see the Temperature Sensors & Transmitters section:
Ideal temperature thermocouple for the plastics processing industry.
Ideal temperature thermocouple for nozzles, extruder barrels, die heads, molds and other surface temperature sensing applications.
Suitable as indoor ambient air temperature sensors.