What is calibration and what is its importance? Calibration is vitally important wherever measurements are important, it enables users and businesses to have confidence in the results that they monitor, record and subsequently control.
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Calibration is defined as an association between measurements – one of a scale or accuracy made or set with one piece of equipment and another measurement made in as similar a way as possible with a second piece of equipment. The piece of equipment or device with the known or assigned accuracy is called the standard. Standards vary from country to country depending upon the type of industry; whilst manufacturers designate their measurement criterion and recommend the frequency and level of calibration, depending upon industry requirements, how often the device is used and the specific application.
Some companies will offer a pre-calibration test where they test equipment first, to determine whether it is suitable for calibration, whilst others will submit all equipment for calibration whether or not it is working properly.
In general use, calibration is often regarded as including the process of adjusting the output or indication on a measurement instrument to agree with value of the applied standard, within a specified accuracy however this is actually two processes: calibration and adjustment. It is important therefore to understand exactly what service you require. It is also important to understand what is being calibrated and how the calibration is being performed. As an example, consider a digital thermometer that uses an external temperature probe. Many companies are surprised to learn that their calibration is performed using a simulated temperature value that is applied to the thermometer only. Here, a test instrument is attached to the digital thermometer and a voltage equivalent to a specific temperature is applied to the digital thermometer. The result is then recorded and the thermometer considered to be calibrated.
Many users require, and probably expect, a more rigorous calibration to be performed that reflects real world usage. Here, the preferred method is to test both the digital thermometer and the temperature probe together (in other words a ‘system test’) and to use a real heat source. The value displayed by the system being tested is then compared against the standard (the system with a known or assigned accuracy from the first paragraph!).
Why is Calibration So Important?
Calibration defines the accuracy and quality of measurements recorded using a piece of equipment. Over time there is a tendency for results and accuracy to ‘drift’ particularly when using particular technologies or measuring particular parameters such as temperature and humidity. To be confident in the results being measured there is an ongoing need to service and maintain the calibration of equipment throughout its lifetime for reliable, accurate and repeatable measurements.
The goal of calibration is to minimise any measurement uncertainty by ensuring the accuracy of test equipment. Calibration quantifies and controls errors or uncertainties within measurement processes to an acceptable level.
So if you know that a particular food product needs to be kept above 68°C and the instrument system you are using displays a figure of 68.8°C then provided the system is calibrated to be accurate within 0.5°C at 68°C you can be confident the food is safe, if the system has an accuracy of 1°C though then you cannot be certain that the food’s temperature has been correctly controlled. Food is, of course, only one example of why it is essential to have a confirmed calibrated level of accuracy. Manufacturing processes that require specific controlled curing temperatures are another in fact the list goes on.
In summary, calibration is vitally important wherever measurements are important, it enables users and businesses to have confidence in the results that they monitor record and subsequently control.