Guide to Scale Calibration: Understanding Scale Calibration Procedure

Last Updated: 14/10/2022

WHAT IS SCALE CALIBRATION?

Scale calibration is the process of testing your weighing scales or measuring equipment to see if they are providing accurate results. Any scales that are not accurate are then adjusted accordingly to make sure results are within the acceptable tolerances.

Scale calibration can be completed by yourself or your operators internally, or by a professional calibration provider.

WHY IS CALIBRATION IMPORTANT?

Calibration is key to making sure your scales, checkweighers and other weighing equipment are measuring items as accurately as possible. Calibrated weighing scales help to guarantee accurate and consistent use of ingredients or materials to produce high quality products, while limiting wasted stock.

The accuracy of scales can be affected by changes to the environment (temperature, humidity, barometric pressure etc.) as well as damage caused by exposure to dirt or sudden shocks.

Reasons you might need calibration include:

  • You have a new scale.
  • Your existing scale has been repaired.
  • Your scale has been relocated.
  • Your scale has physical damage.
  • There has been a major change in the environmental conditions.

HOW OFTEN SHOULD SCALES BE CALIBRATED?

Scale calibration frequency depends on several factors including your processes and procedures. If your weighing scale is in frequent use, it’s likely to need calibrating sooner than a scale that is only used a couple of times per day. Likewise, if the precision of your scale is critical to your production, in pharmaceuticals for example, then more frequent calibrations might be needed.

Drift analysis is useful for determining calibration frequency. By recording the drift over time, trends can be identified, and calibration frequency can then be set to minimise business risk.

HOW ARE SCALES CALIBRATED?

Scales are first tested to see how accurate they are. In a calibration test, measurements are taken from a scale using standardised test weights. These test weights are verified as per national and international weighing standards and are used to identify any deviation in the scale tested. Any incorrect scales can then be calibrated.

It’s important that when calibrating a scale, the correct class of test weights are used to provide relevant accuracy. This is particularly useful for laboratory balances and other use cases where precision is vital

Your weighing scale might have a built-in calibration mode or process. If so, you should use this and follow it’s steps. A more comprehensive scale calibration procedure will consist of multiple tests to determine linearity, consistency/repeatability and more. If a more robust calibration is required, it is recommended that an accredited service provider performs the calibration.

HOW DO I KNOW IF MY SCALE IS CALIBRATED?

If you’re unsure whether your equipment is calibrated, or if you’d like to confirm for QA reasons, you can test your weighing scales using sample testing. The typical sign that a scale requires calibration is inaccurate measurements, so using products or items that you know are a certain weight can highlight these inaccuracies.

When calibration is carried out by a third-party service provider, you should expect to be given a calibration certificate or have your equipment labelled accordingly as proof. Similarly, when you purchase weighing equipment, many suppliers will give you the option for calibration.

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