Resistance Temperature Detectors (RTD) and Thermocouple are the most common sensor types used to measure temperatures. These are preferred over the others for measurements because they avoid the tedious process of conversion, and get the measurements with ease. The main difference between RTD and thermocouple is their operating principle and manufacture.

RTD vs Thermocouple

RTD Thermocouple
RTD is more suited to measure lower ranges of temperature. The measuring range of an RTD lies between -200°C to 500 °C. A thermocouple can measure a larger range of temperature. The measuring range lies between −180 °C to 2,320 °C
RTD exhibits a very good stability with low amounts of shifts Thermocouples have poor stability with results less repeatable over time.
RTD is more accurate than a thermocouple Thermocouples have poor accuracy
RTD is very sensitive and can register small changes in temperature. Thermocouples have poor sensitivity which means that a small change in temperature is not recognised by it.
RTD has a good response time The thermocouple has a faster response time than an RTD
The output presented by an RTD is linear The output of a thermocouple is non-linear
RTDs are more expensive than a thermocouple A thermocouple is cheaper than an RTD