The contents here are to help in understanding the concept of calibration and the guidelines
that are associated with it. The intent is also to share the most appropriate activities that
ensure the quality of measurement; to the reader it can help as a framework to navigate
their own calibration activity. Coincidentally calibration has been a field with which I began
my career. Of course technology and guidelines have changed drastically since I first started.
Although it is an essential action it does not get deserved recognition.
The information is based on the internal calibration SOP Osworld follows for its Stability
chambers and Incubator calibration. The method is based on legislation and regulations that
govern calibration needs and we have also ensured that it meets customer expectation.
What is calibration?
How many users or non-technical people understand what calibration is? Unfortunately
it’s one of the least talked about activity during equipment purchase or maintenance.
Many times it is carried out as a routine periodic practise, just another procedural
Even while selecting a vendor for calibration activity it is generally with a perception that
anybody can do it.
It does not matter if the measurement result is correct since nobody will realize as the
evidence of calibration performed validity which is the sticker on the equipment is good
enough to satisfy management or auditors.
Often the user, engulfed with a heavy daily workload of testing and documentation fails to
provide the person who performs calibration with proper oversight. There will be no
supervision, no counter check as the calibration work is considered the least among primary
On the other hand if this fact is understood by laboratory staff that if calibration of
measuring instruments is done improperly the indicated and recorded values will be false.
Which means the samples will not be exposed to the pre-set conditions and all the
painstaking effort of testing will be in vain.
This wrongdoing is equivalent to a person who fills gas in his car-who pays for certain
quantity of fuel but ends up getting less.
I wish to describe in layman’s terms the need of calibration, how it is meant to be carried
out and what is meant by reference standard and the importance of authentic traceability.
Calibration is a method whereby a measuring device is verified, adjusted to be accurate and
to indicate real value which is precise with a deviation only up to a point within permitted
Calibration is a process by which measures or measuring devices are compared to a
standard to produce a consistent result at all times and in all places.
At the 1984 Olympic games in Los Angeles, Carl Lewis won the 100 metres in 9.99 seconds
creating a new world record. Thereafter, at the 1986 Good Will games in Moscow, the
Canadian Ben Johnson broke Lewis’s record by clocking 9.95 seconds to complete a distance
of 100 meters.
There are two measures involved in this race which determine the winner. One is distance
(100 meters) and the other is time. Both these measures have to be accurate to compare
two results. Keeping in mind that the difference between the times of both players was just
0.05 seconds speaks of the level of accuracy involved. Moreover, the same record was
further broken by a few athletes twenty and thirty years later. This indicates that the
measurement had to be accurate overs decades and if there were even the slightest error
the Olympic Games record performances would be unreliable, inconsistent and conflicting.
What is a standard measure?
Any device that is the originally measured device or its measuring capability in terms of
accuracy is compared with a standard device by an authorised regulatory body.
Which organization administers calibration activity world over?
The text highlighted below is sourced from a reliable calibration accreditation site and
reproduced in totality to avoid misplacement of facts.
Traditionally, metrology was organized by the users of specific areas. The measurements related to
trade and safety have been under legal metrology and regulated by the local legislation. The purpose
of legal metrology has been to ensure correct measurement results in trade to protect customers.
Scientific metrology has been developed freely in research institutes when doing physical research in
order to develop more accurate measurement methods and equipment. Besides these two ‘paths’
there has always been metrology cooperation inside different organizations. As an example the
World Meteorological Organization (WMO) has developed and standardized the measurement
equipment and techniques related to meteorological observations. The basis of modern metrology is
set in Convention of the Metre, which is a diplomatic treaty which gives authority to the General
Conference on Weights and Measures (CGPM), the International Committee for Weights and
Measures (CIPM) and the International Bureau of Weights and Measures (BIPM) to act in matters of
world metrology, particularly concerning the demand for measurement standards of ever increasing
accuracy, range, diversity, and the need to demonstrate equivalence between national measurement
standards. The backbone of metrology is the International System of Units (SI). Metrology organizations are built to maintain and improve the International System of Units (SI) and provide accurate measurement and calibration services. The International System of Units (SI) is maintained by BIPM (International Bureau of Weights and Measures) in France. The task of the BIPM is to ensure worldwide uniformity of measurements and their traceability to the International System of Units (SI). National laboratories represent the top metrology level. They are responsible for maintaining and developing traceability and for providing the highest accuracy calibrations. Accredited and other calibration services are then providing the traceability to the users
The above information details a chain of traceability which is a predominant area of
calibration. This traceability ensures a uniform measure across the world.
Osworld’s internal calibration plan
The two important aspects in our protocol are Traceability and Measurement Uncertainty.
With reference to the previous example, visualize the race between Lewis and Johnson was
measured against different standards. Or for that matter Olympics in an Asian country
deviated with result to an Olympic result of a European country. If Asia and Europe were
governed by two different bodies each having its own measurement traceability that is
different from each other.
It is imperative to maintain an effective traceability chain. Osworld ensures that the primary
standard calibration devices are calibrated against master devices which are calibrated in an
accredited laboratory. The working standards that we use for validation and onsite mapping
cycles are all calibrated using primary standards.
It is unrealistic to calibrate measuring devices to a 100% accuracy level. Depending on full
range there could be some possibility of error. The error is also called the uncertainty
parameter of the device. The uncertainty is a pre-defined value which is considered as
acceptable criteria if the deviations found during calibrations is within the prescribed value.
At all times note the uncertainty values mentioned on primary standard calibration
document and it is also imperative to record the uncertainty value found while calibrating a
device. The uncertainty value should be within the specified tolerance limit to certify that
the unit under calibration is okay and fit for use.
There are different techniques, hence follow the instructions that govern the calibration
procedure for the particular device. You can have your own SOP for calibration but make
sure it is documented and followed thoroughly for obtaining consistent result.
After the calibration is completed a sticker mentioning important information pertaining to
the calibration, such as date of calibration, next due date and name of person performing
calibration should be fixed on the device.