Understanding Calibration - The Process Explained

The word calibration is associated with the concepts of accuracy of standard or measuring instrument where measurement error and uncertainty are dealt with.

Calibration is a process where you can compare measuring instrument with a measurement standard to facilitate the relation between the values indicated by the instrument and those of the standard.

A measurement device that is unknown is compared against the better standard by calibration. Calibration is often considered as the process of adjusting the output/indication on a measurement instrument to arrive at the value of the applied standard, within a specified accuracy. For example you can correct and adjust the indication of errors in thermometer using calibration constants. So, it will have true temperature in Celsius at specific points on the scale. It can be applied in computing also where you can calibrate an interactive white board pen or other input method to establish relationship between the physical pen position and the position of the cursor on the screen.

In order to provide confidence in the accuracy of calibration results, there has to be demonstrable traceability. That means the results achieved through calibrating measurement standard used has be traceable back to standards (held at a national measurement institute) through an unbroken chain of comparisons where each link has declared a kind of measurement uncertainties. Trained and authorized personnel have to use appropriate equipment and procedures in the calibration process. Traceability was greatly emphasized. Organizations, documents, measurements and techniques within a large and diverse measurement community fall into the concept of traceability. For this reason it becomes important to be systematic to interact with each other or with our clients.

The topics of measurement traceability, quality assurance programs etc, are normally linked to the topics of measurement uncertainty by modern metrological notions. The employment of calibrated standards or instruments is an essential component of uncertainty budget. A reference value, i.e. an International System (IS) unit, which can be transferred by the calibration process to the instrument/artifact under calibration process that creates the unbroken chain of comparisons required for traceability.

Whether they are simple devices or high-tech systems nobody can be sure. Since calibration is the only process that determines the measurement capabilities of the instruments, they normally have to be calibrated.