Standard for Calibration of Temperature Indicator

What procedure are you using now?

Or, is this another "I'm supposed to calibrate this thing, but I don't know how, so please give me the answer" question?

I'd suggest a search of calibration procedures on the internet as a start. Maybe even read the instructions that came with the instrument you are attempting to calibrate.

Good luck.

This is not equipment I deal with, but I think you disconnect the thermocouple and apply a mV DC source to the indicator. The voltage you apply will depend on the type (J,K etc.). Refer to thermocouple tables. The other way would be to dip the TC in some standard temperature baths such as freezing point of mercury, triple point of water, melting point of gallium, boiling point of water, etc. The first way would be the simplest and would require only one standard. As was said, you should consult the calibration manual for the equipment.

Some industries define the calibration intervals and accuracies for furnaces, like USA aerospace industry supports NADCAP and AMS2750D.

Other industries are government regulated, for instance the US FDA specifies the temperature accuracy standards for some food cooking processes. I still see mercury in glass thermometers on retorts.

Plants that aren't industry or government regulated have temperature accuracy specs defined by the plant's quality and/or engineering group.

Regulated temperature sources like oil baths, dry blocks or ice baths are used to achieve and hold the temperatures.

Calibrations can be done to an individual sensor or an entire loop or by comparison to a calibrated sensor.

If you're looking for standards to rattle on about, here's a paragraph from ISA-MC96.1-1982, Temperature Measurement Thermocouples

"Recommendations and suggestions are given below for simple and ordinarily adequate
procedures for checking installed thermocouples. These are not intended to be completely selfsufficient, however, and usually it will be advantageous to consult more detailed treatments as well.

"Temperature Measurement," Part 3 of the Performance Test Codes Supplement on Instruments and Apparatus, PTC 19.3, published by the American Society of Mechanical Engineers, gives thorough coverage to the use and calibration of thermocouples.

Calibrating procedures for new thermocouple materials are given in NBS Special Publication 300, Volume II, "Precision Measurement and Calibration-Temperature." This describes various testing methods and the precautions which must be observed in order to attain various degrees of accuracy. In particular, it describes in detail the methods developed and used at the National Bureau of Standards.

Further information is available in E-220-72, "Calibration of Thermocouples by Comparison Techniques," published by the American Society for Testing and Materials."

In particular, it describes in detail the methods developed and used at the National Bureau of Standards

NBS has been called NIST since 1988.