Temperature calibrators come in a wide variety, and what one person refers to as a temperature calibrator, another person may call a temperature indicator or temperature simulator. In a purely metrological sense, a temperature calibrator must be able to verify that a temperature sensor is reading the actual temperature, within some tolerance, in the environment in which it is applied. To do this, it must be compared to a standard that is exposed to that same temperature. Reading the temperature from a thermocouple, resistance temperature device (RTD) or a thermistor, and then simulating that output through a transmitter to an indicator to confirm that it is reading correctly is not a calibration. A temperature calibrator must consist of a stable temperature source capable of reaching the desired range of temperatures, a probe traceable to SI units, and an accurate way to read the temperature output from the standard and the device being tested to compare the readings. Anything other than this cannot be considered a true temperature calibrator. Therefore, a temperature calibrator is a set of instruments combined to perform the calibration.
A combination of instruments to create a range of stable temperatures, read those temperatures using a standard probe, and compare that reading to a temperature probe being tested, can be considered a temperature calibrator. Varying degrees of accuracy can be achieved by the combination of these components. Some baths and wells may have temperature sensors in them but readings from these internal sensors should only be used as a reference temperature. However, this internal sensor might be accurate enough for the purpose of the temperature calibration if its accuracy is at least 4 times more accurate than the temperature sensor being tested. Otherwise, a standard probe and an accurate way to read the output from the probe should be used.
WIKA calibration baths and dry blocks can produce a range of stable temperatures, and WIKA precision thermometers (formerly branded ASL) can accurately measure the temperature from a standard probe and a test probe immersed in a dry block or bath to perform a temperature calibration. A combination of a dry block or bath, a standard probe and an accurate way to read both the standard probe and the probe being tested (DUT - Device Under Test), make a suitable temperature calibrator.
With these instruments, temperature calibration is possible in ranges from -200 … +1,300 °C (control range -55 … +1,100 °C).