What are the major differences between a thermocouple and an RTD?
The most notable difference between a thermocouple and an RTD is the principle of operation and manufacturing. A thermocouple is made of two dissimilar metals joined so that a potential difference generated between the points of contact is a measure of the temperature. An RTD, operates on the principle that electrical resistance of certain metals changes in a predictable way depending on the rise or fall in temperature. The two measurement tools each have their own advantages and disadvantages. Advantages of the thermocouple include a wide range from -300°F to 2300°F, fast response time (under a second in some cases), low initial cost and durability. Overall, thermocouples are able to withstand rugged applications. Disadvantages for thermocouples are their wide accuracy range, especially at elevated temperatures, difficult to recalibrate (seeing as though they are dependant upon the environment) and, finally, installation can be expensive if long lengths of thermocouple wire are needed
