Importance of Equipment Calibration
Have you calibrated yours?
What is calibration?
Directly from the dictionary, it means “the process of checking a measuring instrument to see if it is accurate”, as stated in the Cambridge dictionary. However, according to the International vocabulary of metrology – Basic and general concepts and associated terms (VIM): 3rd Edition published in 2008 by the International Organization for Standardization, the full definition of the term “calibration” is a set of operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties and, in a second step, uses this information to establish a relation for obtaining a measurement result from an indication (JCGM, 2008). Those with engineering background often understand this term as “an activity where the instrument being tested is compared to a known reference value, or a higher reference standard” (SST, 2020).
How important is calibration?
No matter how high-quality the instrument is, it will drift over time and lose the ability to provide high accuracy measurements. Hence, it is extremely important to have your instruments calibrated at suitable intervals.
Every time you calibrate your instrument, it lowers the measurement uncertainty hence improve the measuring instrument’s accuracy. This ensures that all the measurements taken with the instrument are accurate and reliable. In addition to this, calibration supports the standard requirements where instrumental precision is needed for demonstration of compliance to relevant sources/references. The common ones would be ISO 9001, 14001, 18001, or ISO/TS 16949 etc (SST, 2020).
Traceability is the concept of setting up a valid calibration of a measuring standard or instrument by comparing step-by-step with better standards that can be up to an accepted national/international standard (Arora, 2006).
Most commonly, traceability can be done by comparing two or three measurements of the same parameter to check the reliability and reproducibility of that measurement. To allow comparison, a measurement must always be traceable to the acceptable standard, and this is applicable even for a single measurement. The reason is that a measuring instrument’s reading should be highly accurate in terms of physical unit of measurement, which in turn, should be traceable to its ultimate fundamental unit via calibration.
The diagram below shows an example of a traceability chain. Here, Unit X had its measuring instruments’ calibration done at Lab 2, which had its standard calibrated from Lab 1. Lab 2’s standards is traceable to the NML through Lab 1. Therefore, we can also conclude that Unit X has traceability to NML.
Of course, this is just a simple example to help you visualize the traceability chain; there can be chains of various length in the real world. Although there is no restriction on the number of steps in a traceability chain, uncertainty in the measurement due to error in measurement process becomes the limiting factor.
Where/when do you need calibration?
The measuring process is crucial in the fields of science, industry, and commerce. It is also greatly applied in our everyday life (Arora, 2006). For example:
- Health care: body temperature measurements using thermometer, blood pressure measurements etc
- Checking the time of day with a clock/watch
- Marking the length of cloth for tailoring
- Power consumption billing from an energy meter
Although these activities seem very normal and minor, calibration for them should not be neglected because the accuracy and reliability will be doubtful if they are not calibrated. Calibration ensures that a measuring instrument provides values that are accurate and reliable quantitatively. Therefore, it is essential to always carry out calibration when required in any measurement process.
Arora, S., 2006. Role of measurement and calibration in the manufacture of products for the global market: A guide for small and medium sized enterprises, Vienna: United Nations Industrial Development Organization (UNIDO).
JCGM, J. C. f. G. i. M., 2008. International vocabulary of metrology – Basic and general concepts and associated terms (VIM). 3rd edition ed. s.l.:International Organization for Standardization.
SST, S., 2020. What is Calibration?. [Online]
Available at: https://www.sst.com.my/updates/what-is-calibration/
[Accessed 10 September 2020].
Written by Khei Yinn Seow
Posted on September 24, 2020