Applications involving heating invariably require temperature measurement instrumentation. Temperature instruments typically consist of a thermowell, a sensor and a transmitter to convert the sensor data to an industry-standard signal such as 4 to 20 mA or fieldbus digital communications. Temperature sensors come in many shapes and sizes, but for industrial use, two technologies cover the majority of applications: thermocouples (TCs) and resistance temperature detectors (RTDs).
It is not difficult to find resources discussing the differences between the two technologies. But, for purposes of this article, which is part one of a two-part series, we will focus on some of the more nuts-and-bolts aspects of the selection process. In addition, this article will describe ways to improve temperature-measurement performance regardless of the selected sensor technology.