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Internal Calibration Vs External Calibration

Internal Calibration Vs External Calibration

Scientifically weight is a very broad concept apart from just being a unit of measurement. Some define weight as scalar quantity while others define it as a vector quantity. Despite different theories about weight and weight measurement, operational weighing instruments have been in practice for ages now even before some of these theories existed.

Almost all industries incorporate weighing balances or scales to some degree in their day to day operations. Today, industrial scales are available with different degree of accuracy, weighing capacity, sizes etc. Nevertheless, we find weighing instruments all around us in our everyday life.

Whether in an industrial setting or at your regular grocery shop, weighing scales are repeatedly subjected to loading and unloading. This can cause a weighing scale to lose its accuracy after a brief period of time. Thus they need to be calibrated on a regular basis to maintain its precision and accuracy. Additionally, certain industrial settings demand regular weighing scale calibration as their regulatory procedure.

For the purpose, you can determine whether your weighing instrument accuracy by the way of metrologically traceable calibration.

First Let’s Understand What Calibration Is,

Calibration can be defined as a process of ensuring the accuracy of the weighing instrument by adjusting the instrument against the standard weight.This process ensures that produced results are well within the accepted range. A weighing instrument must undergo maintenance regularly in order to improve quality, longevity and consistency of the output results. Hence calibration becomes a need for each industry.

Industries can perform internal calibration or external calibration, whichever is most suitable according to their operational needs. Today, many third party calibration laboratories are also making their services available to industries. Nevertheless, industries need to have approvals to external certified calibration mass for calibration of weighing instruments for industry standards such as ISO 9000.

How Will You Choose Between Internal Calibration and External Calibration?

Let’s understand the difference between internal calibration and external calibration.
  • Internal Calibration:

Internal calibration setting allows weighing instrument to calibrate itself without needing any human intervention.  Weighing instruments with internal calibration facility are often equipped with built-in calibration weights and are operated with the help of a motor. Such advanced weighing scales are provided with special menus to carry out the process. Once the process is over the instrument’s calibration accuracy can be measured with the help of various other technologies.

Furthermore, many advanced weighing balances or scales come with a manual as well as automatic internal calibration functions. With the manual type of function, an operator is required to prompt the calibration process, whereas an automatic calibration process is carried out at preset intervals.   

But such advanced instruments are expensive and may add extra cost to the company’s overall budget. On the other hand, by investing in the technology businesses can save costs associated with recalibration at the vendor side. Additionally, in house calibration saves turnaround time for the calibration process. Thus many industries opt for setting up their own calibration laboratories, which may also reduce their overall costs when they need to calibrate large inventory of scales.

As internal calibration requires minimum human intervention and is able to achieve greater accuracy, this function is especially preferred by precision laboratories.


  • External calibration:

In external calibration, the weighing instrument is calibrated externally with the help of a set of approved calibration weights. One of the pre-requisite is that the approved standard calibration weights must be maintained in their optimum condition. These known weights are used to calibrate and verify instruments calibration. The calibration process is much faster and easier to understand. If the weighing instrument shows the exact weight as that of the standard-setting piece then it is considered as an indicator that instrument is calibrated.

However, as the process is done manually, the chances of human error increase. Also, conditions of standard weights and instrument feeling of the user affect the outcome of the calibration process.

As external calibrations are performed outside of the organizational facility, it increases the chances of larger downtime. Thus many laboratories and calibration service providers also perform calibration on-site.

How to Determine Which Type of Calibration is Suitable for Your Business?

Choosing between any of these calibration systems depends largely on many factors. If you have a limited budget and you prefer routine calibration then external calibration can be the best option for your business. However, the process requires time and resources. In order to achieve accurate calibration, businesses need to take proper care of standard weight as well as weighing balance. Additionally, facilities need to maintain optimum conditions to sustain the desired calibration. Today, large size weighing scales such as platform scales; caravan scales etc are equipped with electronic calibration that improves overall calibration process.

On the other hand,the internal calibration process is automatic and reduces overall downtime for equipment. Also, you will not be required to maintain external standard weights etc.

Thus businesses must select between the two calibration systems by considering all the pros and cons.