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Calibration is the act of checking and adjusting a particular type of devices. The devices which make use of this procedure are the measuring instruments.

At this point there are several notions which need to be explained in order to fully understand this process.

In the physical sciences, measurement is the activity of obtaining and comparing physical characteristics of real-world objects and events.

All the aforementioned issues highlight the need of a certain act of checking and adjusting to a certain standards that is commonly known as calibration.

Calibration ensures that a measuring instrument displays an accurate and reliable value of the quantity being measured. How does it do that? By making use of a set of operations that establish, under specified conditions, a comparison with a higher standard that can be traced to a national or international standard or an acceptable alternative.

To have a valid measuring instrument, we need to apply to it a formal test method by using a reference standard to create its calibrated parameters. The standard original sample is “cleaned” up of any “impurities” in order to make it flawless. This is how the value of the applied standard is reached. The measurement instrument being calibrated must agree with the previously mentioned value, within a specified accuracy.

The main features which are taken into account when calibrating a certain device are: precision, accuracy and reproducibility. The precision or resolution of a measuring device is simply to what fraction of a degree it is possible to make a reading. However, this precision does not mean the reading is true.

Measuring devices which are calibrated to known fixed points (e.g. a thermometer is calibrated to 0 and 100C) will be accurate (i.e. will give a true reading) at that point. For many purposes reproducibility is important. That is, does the same thermometer give the same reading for the same temperature.

From the above examples, it is clear that for measurement data to be reliable, the amount of variation in measurement must be known. Thereafter, attempts should be made to improve the measurement system so that the variation is minimized, by means of calibration.