Dry Well Calibrator:
A temperature calibrator that uses a precision oven to source precise temperature. This style of calibrator is often used for the verification of temperature sensors.
Excitation Current:
A constant current applied to an RTD probe to determine actual resistance for temperature measurement. Typical values are 2 mA or less to minimize self-heating of the probe.
IPTS-68:
International Practical Temperature Scale of 1968. A temperature standard adopted in 1968 that uses intrinsic standards to define the measurement of temperature.
ITS-90
International Temperature Scale of 1990. A temperature standard adopted in 1990 that uses intrinsic standards to define the measurement of temperature. This standard modifies the intrinsic standards of IPTS-68 with additional intrinsic references.
Lead Resistance Compensation:
A compensation method used with 3 and 4 wire RTDs and resistance measurement. This method negates the error associated with lead resistance when making an RTD measurement.
Reference Temperature:
The temperature at which a thermocouple temperature measurement is referenced. For Fluke Calibration tools, this is the temperature where the thermocouple mini-plug is connected to the calibrator.
Rφ:
The resistance value of an RTD probe at 0 °C. Example PT100-385, Rφ = 100 Ω.
RTD:
Resistance Temperature Device, a temperature measurement sensor that has predictable changes in resistance with a change in temperature. The most common RTD is the platinum PT100-385.
Seebeck Effect:
Thermoelectric effect in which the voltage potential increases with temperature (thermocouples) in a junction of dissimilar metals.
Triple Point of Water:
This temperature reference point is the intrinsic standard at which water is liquid, ice and gas. This reference point defines 0.01 °C.