What Calibration Weights Do I Need?

Once you’ve purchased a weighing scale or balance, it’s important to ensure that you continue to look after it to make sure it gives accurate weighing results with every use, and a key way of doing this is through calibration.

We understand that it can be confusing when purchasing calibration weights for the first time – different calibration weights are suitable for different scales and balances, so it’s crucial that you choose the correct set for your application.

In this blog, we’ve made a simple guide to buying the right calibration weights, including an easy to read calibration weight class chart that gives simple overview of which weight classes should be used where.

Why is calibration important?

Calibration is important for all scales and balances, whether you are a regular or less frequent user. How often you should calibrate your weighing instrument depends entirely on your intended application and the type – analytical balances that are carrying out highly precise and important tasks may want to calibrate before every use, whilst a larger platform scale carrying out irregular industrial weighing could afford to be calibrated once a week for example.  

Scales and balances are affected by a number of different factors such as humidity, heat and position, so regular calibration can ensure that your instrument keeps giving accurate weighing results. Calibration makes sure that these outside interferences do not skew your weighing data, and that your weighing remains accurate.

Types of calibration weight classes

Before we go any further, it’s important to note that the full spectrum of test weights is M3, M2, M1, F2, F1, E2, E1 and E0, where M3 is the least accurate and E0 is the most. The weights listed below are representative of the classes currently available on the Inscale website.

M1 Class Test Weights – M1 Class Weights are the most widely used weights and are used to calibrate scales where exact precision is not required. All Class III approved weighing scales use these calibration weights.

F1 Class Test Weights – Another common weight class, F1 Class Calibration Weights are used for standard precision balances and scales, usually in laboratory, quality control or testing environments. These weights offer a higher degree of accuracy but are more affordable than both E1 and E2 Classes.

E2 Class Test Weights – Some of the most precise test weights available, E2 Class Test Weights would be used on balances with extremely fine resolutions, such as analytical balances or micro balances. They are most commonly found in test and calibration houses in the pharmaceutical and chemical industry.

E1 Class Test Weights – E1 Class Test Weights are the highest possible accuracy class available on Inscale, and are used in similar circumstances to E2 Test Weights above.

What weight class do I Need?

To help with choosing the correct calibration weight for your scale or balance, we’ve created a simple suggested calibration weight class chart.

What is OIML?

OIML stands for the International Organisation of Legal Metrology and is the international standards body that sets the standard tolerances of calibration weights, weighing scales and balance. It was created in 1955 to provide a global legal standard in metrology, and any country that are member of OIML use the OIML Recommendations to create National Standards of Metrology. In short, GOV.UK describes the role of OIML as:

“Its main objective is to achieve international harmonisation for legal metrology, providing an important basis for measurement credibility, eliminating technical barriers to trade in measuring instruments and promoting international trade by confidence in measurement capability.”

In the UK, the Office for Product Safety and Standards (OPSS) co-ordinates input into international forums such as OIML, to ensure that regulatory standards are met internationally in accordance to UK manufacturers, legislators and enforcers. 

Still unsure about what calibration weight class is right for you? Speak to a member of our team on 01908 972660 or Get In Touch with us and we will be happy to point you in the right direction.

To see our full range of test weights, please click here.