Temperature probes are used to measure fluid temperature in process vessels and piping and ducting systems. The temperature of the probe is assumed to closely approximate the temperature of the process fluid in which the probe is immersed. Deviation between fluid and probe temperatures results from thermal leakage (or stem conduction), where heat is conducted along the probe and out to the environment, thus reducing the probe temperature below the actual fluid temperature. The degree to which this impacts the accuracy of the measured temperature depends on the configuration and characteristics of the probe and inner temperature sensor, as well as the relative magnitudes of heat transfer from fluid to probe and from probe to the environment. These measurement errors affect process control and reaction kinetics.
This article details how process conditions (e.g., process fluid properties and velocity) and probe configuration (e.g., dimensions and materials of construction) influence temperature error. Conditions that result in serious deviations from the actual temperature are highlighted