All kind of instruments, equipments and machines are subjected to normal wear and tear. Even how careful you are in using your instruments and equipment it will eventually degrade over a period of time. That is why calibration is a must to keep the accuracy and precision of any measuring instruments. With the improved accuracy the product quality can also be ensured.
We have known the reasons why we need to have our testing instruments calibrated. But what is calibration anyway? Calibration is the process that is used to compare a particular measuring instrument with a known measurement or standard to determine if the values indicated by your measuring instruments adhere within the set standard. Normally, the accuracy of the set standard should be about ten times than the accuracy of the measuring device that is being tested. But most of the standard organization around the world accepts the 3:1 accuracy ratio.
Typically, there are 3 main objectives why instruments are being tested. First is the traceability. That is to ensure that the reading from a measuring instrument is consistent with other measurement, specifically with the standard measurement. Second is accuracy. Calibration is done to ensure the accuracy of the instrument reading, and; Third, is reliability. The calibration process is made to make sure that the measuring instrument that you are using can be trusted.
Sometimes, calibration process also includes the repair of the measuring instrument while being calibrated. At the end of calibration, a certificate provided by the calibration expert will show the result of the calibration listing the range of force value generated by the standard machine against the range of values generated by the instrument that is being calibrated. The report would show the output values of the instrument before and after the calibration process.
Furthermore, it is important that correct equipments are used and proper procedure is followed during the conduct of calibration. The calibration service should performed by authorized personnel working in suitable experimental environment. Calibration is often done in calibration laboratory. Most countries in the world have a system of accreditation for calibration laboratories. Accreditation from an official accreditation body is a sort of recognition to a calibration laboratory, acknowledging its competence to calibrate measure or test an instrument. Accreditation signifies quality calibration service.
How often the instrument should be calibrated?
There is no set standard on how often an instrument should be calibrated. The calibration should be carried out depending on what type of instrument it is, and how often it is used. One should look at the required uncertainty of each instrument. An accredited calibration certificate is valid for one year. However, there are cases that the instrument reproducibility is better than the uncertainty required than the interval between calibrations, and then you might need calibration in five years or so. There are also cases, that instrument’s reproducibility approaches the uncertainty needed, the calibration interval is shorter than one year. Maybe calibration must be done in monthly or weekly basis depending on the subsequent result.