While both are used to measure temperature, thermocouples are cheaper, faster and stronger compared to resistance thermometer detectors. However, RTDs are more accurate than thermocouples.
The thermocouple and the RTD are types of sensors used to detect temperature and changes in temperature. A thermocouple exposes one side of two different metals to the area where temperature is being checked to produce a voltage. The difference in voltage between the ends of these metals is analyzed to determine the local temperature. An RTD passes electricity through metal exposed to the area and measures its resistance. Local temperature can affect the electrical resistance of metal. However, only metals with known resistances can be used to detect temperatures.