Calibrating industrial scales – A guide to accurate measurements

Regular calibration of industrial scales is crucial for accurate measurements, compliance with industry standards and regulations, and to avoid costly mistakes. This guide will take you step by step through the process of calibrating your industrial scale, maximising the efficiency and reliability of your weighing processes.

Why does an industrial scale need to be calibrated?

An industrial scale must be calibrated to ensure accurate and reliable measurement results, as numerous factors can affect accuracy. These include environmental conditions such as temperature and humidity fluctuations, placement of the scale on an unstable surface, and the condition of the load cells. Regular calibration is also necessary to correct for deviations due to wear and tear. Other factors such as vibrations and mechanical disturbances can also affect the accuracy of measurements, which is why regular maintenance is essential.

What are the signs that a scale needs to be recalibrated?

Signs that a scale needs to be recalibrated include:

• Inconsistent or fluctuating readings
• Readings that do not return to zero when the scale is empty
• Discrepancies when weighing known weights
• Physical damage to the scale or its components

Regular checks with known weights can help to identify these problems at an early stage

Types of Calibration

Industrial scales can be calibrated either manually by in-house personnel or an external service provider, while modern scales often have an internal automatic adjustment feature that allows for automatic calibration without human intervention.

Step-by-step guide to calibrating an industrial scale

1. Prepare the scale

• Cleaning and levelling: Thoroughly clean any dirt, dust or debris from the weighing platform. Use a spirit level to ensure that the scale is perfectly level. This is important to avoid measurement errors caused by incorrect alignment of the scale.
• Check the ambient conditions: Make sure that the environment is stable and free of vibration, strong air currents and temperature fluctuations.
• Check the GEO value: The GEO value takes into account the influence of geographical location on the accuracy of the scale. Since gravity varies slightly at different locations on Earth, the GEO value must be set correctly to ensure accurate results. Check that the GEO value of your scale is set to the correct geographical region to avoid calibration errors.
• Follow manufacturer’s instructions: Always follow the manufacturer’s specific calibration instructions to ensure that the calibration is carried out correctly and to the required standards.

2. Calibration process

• Select test weights: Use certified, traceable test weights that cover the entire weighing range of your balance.
• Zero the scale: Switch on the scale and allow it to stabilise. Zero the scale to ensure that no tare weights are included in the calculation.
• Loading Weights: Place the test weights on the platform in increments, waiting for the scale to stabilise before adding the next weight. Test various load points, such as 25%, 50%, 75% and 100% of capacity. To check the uniformity of the measurements, also place the weights in the four corners of the weighing platform.
• Unload weights: Remove the weights in reverse order, allowing the scale to stabilise at each step.

3. After calibration

• Check accuracy: Recheck the measurement results using known weights. The measurement values should be within the acceptable tolerance range of the scale.
• Make adjustments: If the scale is outside the tolerance range, adjust the settings according to the manufacturer’s instructions.
• Documentation: Record the date, time, test weights used, and any adjustments or deviations in the calibration record.

4. Maintenance and inspection

• Regular maintenance: Check the scale regularly for wear and tear and carry out scheduled calibrations to ensure long-term accuracy.

Further tips for calibrating and maintaining your industrial scale

• Timing of calibration: Create a fixed schedule based on frequency of use and environmental conditions. Typically, an industrial scale should be calibrated at least once a year. With frequent use or extreme conditions such as dust or temperature fluctuations, calibration every six months may be advisable. Also, follow the manufacturer’s recommendations for calibration intervals to ensure long-term accuracy.
• Appropriate use: Always use the scale within its specified weighing range. Overloading or weighing objects that exceed the maximum capacity of the scale can damage the load cells and other sensitive components, which can affect accuracy and cause expensive repairs. Make sure that the material to be weighed always remains within the permissible range.
• Careful Handling Avoid shock loads caused by the sudden dropping of heavy objects onto the scale. Such impacts can damage the scale’s mechanical and electronic components and lead to inaccurate measurements. Use lifting devices or transport aids to carefully place heavy loads on the weighing platform.
• Cleaning the weighing platform: Regular cleaning of the weighing platform is essential to ensure the function and accuracy of the balance. Remove dirt, dust and debris from the platform, as these can affect the weighing result. Use mild detergents and a soft cloth to avoid damage to sensitive parts. Ensure that the scale is completely dry before using it again to prevent corrosion or short circuits.
• Checking load cells: Load cell inspections should be carried out regularly to ensure that they show no physical damage or wear. Defective or dirty load cells can significantly affect the accuracy of the scale.
• Protect from extreme conditions: Keep the scale away from extreme temperatures, humidity, dirt and chemical substances that could damage the electronics and mechanics. A well-protected working environment extends the service life of the scale and reduces maintenance costs.
• Calibrate under stable working conditions Temperature changes can affect the weighing accuracy of scales. Therefore, calibration should be carried out under stable temperatures that correspond to the actual working conditions. A significant temperature increase or decrease between calibration and use can lead to measurement errors and affect the accuracy of the scale.
• Digitise calibration records: Integrate digital recording systems to efficiently store calibration and maintenance data. This not only facilitates traceability, but can also improve efficiency during audits and compliance with standards such as ISO 9001.
• Training for calibration personnel: Regular training of personnel is essential to ensure that calibrations are carried out correctly and that new technologies or methods are incorporated into practice.

When should calibration be carried out by specialists?

On the other hand, more complex and high-precision scales are often better calibrated by specialists. These include scales used in industries such as pharmaceuticals, aerospace and manufacturing, where extreme accuracy is essential. Also, industrial scales, vehicle scales, crane scales and other large scales usually require specialist calibration due to their size and the complexity of the calibration process.

Calibration vs. verification – what’s the difference?

• Calibration is the process of checking the accuracy of a scale by comparing its readings to a known reference weight. This determines whether the scale is measuring correctly and adjustments are made as needed. It can be done regularly and as needed to ensure that the scale is providing accurate results, but it is not a legal requirement.
• Verification is a legally required process in which the scale is inspected by an official body to ensure that it meets legal standards and requirements. During verification, not only is the accuracy checked, but it also determines whether the scale is approved for trading. After passing the verification, the scale receives an official seal that confirms its compliance. Unlike calibration, verification may only be carried out by authorised auditors.

Calibrating verified Scales

There is no difference in the calibration process between verified and non-verified scales. In both cases, the check is carried out using test weights. While there are no legal requirements for calibration, verification is mandatory by law. Calibration is recommended but not legally required.

In practice, industrial scales should be calibrated at least once a year. For heavy use or challenging environments (e.g. dust, temperature fluctuations), calibration every six months is advised. Always follow the our manufacturer’s calibration guidelines.