RTD and thermocouple temperature sensors need to be in close proximity to the point of measurement. In most cases, however, they are not rugged enough to be inserted directly into the gas or liquid of interest. As a result, these sensors must be protected by thermowells or installed against a pipe or vessel to take a surface-temperature measurement.
Thermowells have been successfully used for decades in many applications, but they have certain drawbacks — mainly related to their intrusive nature. Inserting a thermowell into a pipe or vessel can pose significant installation challenges. Once installed, the thermowell is exposed to potential damage, and it can interfere with the flow of the medium under measurement.