I. Different Materials

Resistance Temperature Detectors (RTDs) are made of temperature-sensitive metal materials (e.g., Cu50, Pt100, Pt1000), whose resistance values change proportionally with temperature variations.

Thermocouples (TCs) are composed of two dissimilar metal alloys (e.g., platinum-rhodium/platinum, nickel-chromium/nickel-silicon). A potential difference is generated across the two materials when subjected to temperature changes, thus enabling temperature measurement.

II. Different Output Signals

RTDs output resistance signals, while thermocouples output voltage signals.

III. Different Working Principles

The operating principle of RTDs is based on the temperature-dependent resistance characteristic of conductors or semiconductors — the resistance value of a conductor changes as its temperature rises.

The operating principle of thermocouples is based on the Seebeck effect (thermoelectric effect). A thermocouple consists of two conductors of different compositions, with both ends joined to form a closed measuring circuit.

IV. Different Measurement Ranges

RTDs have a relatively narrow measurement range, whereas thermocouples cover an extremely wide temperature measurement range.

V. Different Application Scenarios

Thanks to their high measurement accuracy and excellent stability, RTDs are widely used in low-temperature measurement scenarios.

With superior high-temperature resistance and a broad measurement range, thermocouples are extensively applied in high-temperature measurement scenarios.

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