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Guide for Calibration Laboratories in Calibration of Weights

As a users, we all understand and know that all the standard Weights that we use in our calibration laboratories need to be calibrated by ISO 17025 Accredited Calibration lab.

However, when we are planning to open a new calibration lab or procure a new scope for calibration of test weights, it is always difficult to understand how to go about with it? In such cases, it is always advised to take help of Consultants and other industry experts. We too encourage for the same. But, then we have clients coming to us asking for some basic guide if available towards the same as it becomes difficult for them to approach these high profile experts for small helps.

We are not the experts in this, but we are trying to share whatever we understand in this field and have knowledge about the same. May be it will help you in creating your own internal SOP for your calibration Lab.

Standard Weight in Calibration lab

To keep it brief, we will not go into basic and general requirements which client needs to fulfil to run a Calibration Laboratory.

First and foremost it is important to understand for Calibration of Weights, the Relevant standard need to be followed is OIML R111-1 Standards wherein Weights are classified into different classes such as E1, E2, F1, F2, M1, M2, M3. Onsite Calibration and Mobile Facility for Calibration of weights are not permissible. Weights compulsory need to be calibrated in Permanent Facility against which you receive your NABL Accreditation.

Laboratories need to fulfil Metrological Requirements for Calibration of weights as laid down by NABL alongwith Terms and conditions and other requirements. To know more about this requirements, you can always get in touch with us.

Selection of Reference Weights:

The reference weight shall generally be of a higher class of accuracy than the weight to be calibrated. In the calibration of weights of class E1, the reference weight shall have similar or better metrological characteristics (magnetic properties, surface roughness) than the weights to be calibrated.

Selection of Reference Weights

Note: Standard weights of each class shall have the technical requirements such as shape, construction, material, marking etc as per OIML R111. M1, M2, and M3 class weights are not recommended to be used as a reference for the calibration of weights. However, M1 weights can be used for above 20kg with coarser uncertainty.

Selection of Weighing Balance or Mass Comparator:

One of the most basic question or doubt one has before going for accreditation or scope is that what type of Weighing Balances or Mass Comparator do I need to procure towards the same? Although, you need to appoint a consultant or expert as discussed before for such important decision, but we can surely share some basic knowledge regarding the same.

On the basis of the accuracy class, a mass comparator is to be selected in such a way that its uncertainty component is balanced in proportion to the overall uncertainty of the weighing result. The most important uncertainty component of a mass comparator is calculated from its standard deviation. The specification of the manufacturer can be selected as a first approximation for the value of a standard deviation. It must be taken into account. However, that this indication is decisive for the smallest nominal value. It should therefore not exceed an amount of 30% of the combined standard uncertainty u1 (k=2).


Note: It is not recommended to calibrate a higher accuracy class weight with a lower accuracy class of reference weight and comparator/balance with coarser resolution without the consent of the customer.

Detailed summary of Weighing Balance and Mass Comparator required for Calibration of Weights depending on class of accuracy:

For the reference weights and Comparators used in Calibration of Weights at permanent facility is necessary to Calibrate Comparator/ Balance after 1 year, Weights of E1 and E2 Class every 3 years and Weights of F1 to M1 in every 2 years.

Lastly, it is to be noted that Calibration of weights done by any accredited laboratories is meant for scientific and industrial purpose only.

We have tried to cover all the basic doubts and questions customers have in their mind in this blog. However, information shared by us forms only 30% of the basic requirement and remaining 70% requirements need to be compliance as per NABL requirements and direction provided by external experts.

Based in Mumbai, V CARE IMPEX are one of the top manufacturers of Standard Weights, Test Weights and Weight Box. All our Weights are sold under our Brand Name "VCI PRECI". For any weighing related requirement you can write us on or contact us on +91 9920107524.



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