In scientific labs, instruments are calibrated to help maintain their performance and accuracy. Hence, it’s a process that is an integral part of any instrument. The manufacturer has to keep in mind the calibration factor and design the product accordingly. This article gives a basic understanding of the level of importance calibration holds to the manufacturer of the device.
Calibration and its Relevance to Manufacturing
Calibration is the process of finding the relationship between two unknown readings. Broadly speaking, it is a process of comparison. The readings may be shown by an instrument such as a voltmeter. Every value that is attained as the result of an observation is standardised with the units given by the System of Units (SI).
An instrument might exhibit incorrect values if it has received an electric shock or vibration, or when it has been exposed to hostile conditions. Sudden changes in the weather might also put it out of calibration.
As mentioned above, calibration helps determine the quality of measurement. The quality, in turn, affects customer usage. This is where the process of calibration comes into major significance for the manufacturer. If the reading from an instrument does not exhibit consistency with other measurements, the device is branded to not work. There comes a drop in its sales and eventually the manufacturer runs at a loss.
An important terminology when we speak of calibration is tolerance. Tolerance is the permissible deviation from a specified value. Every instrument has a calibration tolerance indicated with it. The asset requires to be adjusted if the output value exceeds the specified tolerance value. This denomination is stated by the manufacturer on a data sheet. A data sheet contains up to four tolerance levels. Tolerance 1 is the narrowest and tolerance 4 being the broadest.
Another term is accuracy ratio. It expresses the relationship between the accuracy of the test standard and accuracy of the instrument under test. Manufacturers recommend an accuracy ratio of 4:1 for any asset.
All calibrations are done in accordance with an internationally recognised standard. Measurements prove to be a lot more useful when they relate to similar measurements. These can be made at different locations or time. A dynamic factor such as this helps keep the process of manufacturing in control. This is called traceability.
Calibration Laboratories and Certificates
Anybody who wishes to correlate their measurements with SI units may send their readings to a calibration laboratory. A calibration lab primarily provides calibration standards. It covers all types of calibration such as volumetric, weight, temperature, etc. It also offers verification and calibration services for laboratory equipment.
Acute care is taken when it comes to the environmental conditions of the lab. Even a slight relocation may either result in an improvement of the measurement or it may make the instrument go out of calibration. When using high-precision devices, a raise in performance can be seen if they are kept in regulated temperatures. For example, these can be an air bath or an oil bath where a temperature of ±10 mK is maintained.
These results are presented as a calibration certificate. This certificate may contain information like the owner’s identity, the credibility and authorisation of the lab, measurements made using the instrument and likewise. The ISO Guide 25 lists the requirements of a calibration certificate.