What is Calibration and Why is it Important?

What is Calibration?

Imagine a watch with seconds pointer that takes longer than a second to tick; it means the watch will not show the correct time and defeat its purpose altogether. In such a scenario, the watch would need to undergo a correction in its instrument setting. Simply putting it, once the seconds pointer is repaired or corrected the watch starts showing correct time. Applying the same concept to an industrial instrument and its subsequent repair is known as calibrating the instrument. Therefore, Calibration is the setting or correcting of a measuring device or base level, usually by adjusting it to match or conform to a dependably known and unvarying measure. The calibration process generally involves using the instrument to test samples of one or more known values called ‘calibrators’; just like any equipment that may be used to repair a watch.

Why is Calibration important?

Instrument Calibration is a necessary and important part of any instrument system & process instrumentation and one of the most essential primary processes that ensures instrument accuracy. A process plant is made up of many instruments like transmitters and controllers that can cause drift and lead to inaccurate readings; for the control and safety of other instruments, instrument calibration becomes of foremost importance.

How is Calibration Done?

To understand calibration process, we need to first understand that most instruments do not work in isolation. They work together in a cluster, also known as “loop” in industry parlance. So calibration essentially means calibrating instruments in a loop. Because of complicated interconnection, loops frequently undergo drift which requires their calibration.

If you want to calibrate instruments in a loop there are two ways of going about it – you can either calibrate each of the instruments individually (known as individual calibration) or you can calibrate the loop as a whole (known as loop calibration).

Individual calibration is one of the earliest known methodologies. This essentially means removing the instruments from their loop and individually calibrating them, although one of the best known methods, this is time consuming and can lead to errors in connections.

Loop calibration is, therefore, a more reliable method. A loop calibration is a set of instruments that are grouped and calibrated together. The input and output of the whole group determines the pass or fail status of the calibration. This means, if there is an error in one it will lead to a domino effect of errors on all other instruments that are part of the loop. Loop calibrator thus requires a special kind of calibrator, known as loop calibrator, that is equipped to handle and effectively calibrate instruments in loop. Loop calibrators, can again, be portable (i.e. handheld) or stationary. Portable calibrators are more popular, obviously because they are more convenient to use.

Individual calibration is also not very effective in measuring long time drifts, whereas a device that can handle loop calibration will generally enable measuring long time drifts which is less time consuming and ensures higher accuracy.