Calibration is a comparison of an instrument or control equipment with a reference standard, to ensure accuracy. Usually a report will be made to state condition of the instrument known as calibration certificate.
Obviously there will be a doubt that what kinds of instruments are required to be calibrated. All instruments prone to have a deviation due to age or surrounding conditions are to be calibrated. Some examples are pressure gauge, temperature gauge, flow meter, pressure transmitters, temperature transmitter, weighing meter etc. Calibration shall be performed on specific intervals recommended by the instrument manufacturer.
Selecting reference equipment is an important task in calibration. The selection has to be done ensuring all the test points can have an uncertainty ratio of minimum 4. If it is difficult to calculate the uncertainty at least use reference equipment with a minimum 4 times better accuracy of the equipment under testing with a range too bigger and a better resolution. Select a clean place with good lighting and a controlled stable temperature. Think about the reasons of inaccuracies during testing and try to minimize it.
While preparing the report include maximum realistic reading and information. Different clients may require different formats of report. But the basic contents remain the same.
This is an introduction to calibration. We will go deeper next time.
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