The purpose of this information is to give guidelines in estimating the speed of response you might expect from a thermocouple or an RTD.
In defining any transient condition such as a temperature change, it is important that a standard measuring point be established to provide a basis of comparison.
In temperature transducers, the time constant is defined as the time required, in seconds, for the temperature sensor to respond through 63.2% of the total temperature change.
Speed of Response
The factors affecting the response rate of a temperature probe in a fluid are:
a) The mass of the probe surrounding the active temperature sensitive point
b) The thermoconductivity of materials used in manufacturing the transducer
c) The mass and conductivity of the measured fluid
d) The velocity of the fluid over the probe