Calibration weights are essential for ensuring the accuracy and reliability of scales and balances in a variety of applications, such as laboratories, production and commercial environments. These weights, often referred to as "test weights" or "reference weights", are used specifically for adjusting and calibrating weighing equipment, so that it always delivers reliable and accurate results.
Adjustment versus Calibration
Adjustment means that the internal settings of a scale are changed to ensure it displays the correct values. This is an active intervention that is needed to guarantee consistent measurement results.Calibration, on the other hand, is a checking process in which the accuracy of the scale is assessed. During this process, deviations are documented without the settings of the device being changed. Both processes are crucial for quality management and measurement accuracy.
Accuracy classes according to OIML R111
The OIML R111:2004 standard provides guidelines for the accuracy of test weights. These weights are divided into different classes, ranging from E1 (the highest precision) to M3 (the lowest precision). Here is an overview of the classes:
| Class | Maximum Permissible Error ± (mg) | Application |
|---|---|---|
| E1 | 0.0005 - 0.25 | Ultra-precise analytical balances |
| E2 | 0.001 - 0.75 | High-quality analytical balances |
| F1 | 0.005 - 2.5 | Precision balances |
| F2 | 0.02 - 8 | General precision balances |
| M1 | 0.1 - 50 | Industrial and trade scales |
| M2/M3 | 0.5 - 250 | Less precise industrial applications |
For most scales in industry and trade, an M1 class test weight is usually suitable. These weights offer sufficient accuracy for many applications without the unnecessary cost of higher precision classes.The OIML R111 standard also describes the requirements for material density, geometric shape and other important specifications relevant to the use of test weights.
Choosing the Right Test Weight
Choosing the right test weight is crucial for the accuracy and reliability of the scale. Here are some guidelines:
- Match the Accuracy Class: Choose a weight with a tolerance equal to or better than the readability of the balance.
- Select the Nominal Value: Preferably always use the heaviest weight that can be used on a scale as the calibration weight. This ensures that the scale is calibrated optimally and that accuracy is guaranteed across the full measuring range.
- Check the Tolerance: Make sure the permissible error of the weight matches the precision requirements of the balance.
Example
For a balance with a capacity of 600 g and a readability of 0.001 g, the required test weight is 600 g with a tolerance of ±0.5 mg. A suitable weight would be an F1 class test weight. This weight ensures that the balance measures accurately within the specifications required for precision weighing applications. By using an F1 class weight, the accuracy and reliability of the scale can be guaranteed optimally.
Regular Checking of Calibration Weights
It is important that the calibration weight used for a scale is checked regularly. These checks help to ensure that the weights still meet the required accuracy standards. Moreover, this is often a requirement in quality manuals to ensure consistency and reliability in measurement processes. Regular inspections and recalibrations are essential to meet quality standards and to ensure that measurement results remain accurate.
Protection and Certification
Quality weights require proper care and certification to maintain their accuracy:
- Weight cases: Protective cases in plastic, aluminium or wood help to protect weights from damage.
- Calibration certificates: A calibration certificate guarantees conformity and provides proof of traceability to national measurement standards.
Restoring weights
With intensive use, weights can show minimal deviations over time, so that they no longer fall within the specified standards. Weighing Experts offers a specialised restoration service in our own laboratory, where we correct and adjust weights accurately in accordance with the official OIML R111 standard. For weights that require exceptional precision, we work together with renowned international partners. After the restoration process, the weights are recalibrated and certified, so that they once again fully meet the strict requirements of the international OIML R111 standard.
Conclusion
Calibration weights are indispensable instruments for ensuring the accuracy and reliability of weighing equipment. By choosing high-quality weights and certified calibration services, organisations can meet high measurement and compliance standards. Weighing Experts has all the expertise in-house to help and advise you on calibrating your test weights. Contact us at sales@weegexperts.nl or via our contact form: Calibration and repair