Accuracy of Industrial Weighing Scales

Industrial weighing scale accuracy

The article was updated on 18-12-2019.

Inaccurate weight measurements could lead to a faulty end result. The scale’s precision and resolution both contribute to the scale’s accuracy. If you weigh the same item repeatedly, the scale should show the same weight each time for it to be precise. Additionally, in order for the weight shown to be the true weight of the item, the resolution of the scale would have to be high enough to weigh in small enough graduations. These two aspects combined contribute to how accurate a scale is for your weighing needs. In order to confirm the accuracy of the scale, it is recommended that the scale be calibrated regularly.

Basic Facts about Weighing Scale Accuracy

  • Readability of the Scales

All weighing instruments have a calibrated range known as the ‘span’ that has a minimum and maximum limit. The range is shown in graduations, where the minimum value of the displayed graduation is the ‘least count’ or ‘resolution’ of the instrument. The higher the resolution the more precise and accurate the scale will be. Higher resolution scales are frequently used in labs where accuracy and precision are essential.

  • Importance of Legal Metrolog

Industrial scales such as weighbridges, bench scales and counting scales are classified into four accuracy classes namely – I, II, III and IV based on the permissible errors for measurement. ‘Class I’ is the most accurate and ‘Class IV’ is the least.

  • Load Cells

Scales have several components, and the most critical part is the load cell. The load cell is the transducer that converts the applied load into a proportionate electrical signal. The scale will not function properly if it has a bad load cell.

  • International Guidelines for Weighing Accuracy

International Organization of Legal Metrology (OIML) is the most followed standard internationally and is subscribed by more than 120 countries. Another standard that is commonly followed by Canada and the USA is the National Type Evaluation Program (NTEP).

OIML requirements attribute 50% of the error in a weighing system to the error in the load cells. The international guidelines on weighing accuracy emphasize the importance to confirm load cell accuracy to ensure that desired overall accuracy is achievable.

Any scales that are used for ‘legal for trade’ purposes have to be certified for a minimum of ‘Class III’. All scales used for trade purposes are required to be verified and sealed each year by the county the scale is located in.

If you are interested in learning more about scales for your weighing needs, contact us at Quality Scales Unlimited.

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