What is calibration?

Calibration of force transducers involves comparing their measured values with a reference. The force transducer itself is not altered in the process.

During factory calibration, the relationship between the mechanical input variable – for example, a compressive or tensile force – and the electrical output variable – for example, a current signal – is determined and compared with a traceable reference. The results are then documented.

When should a load cell be recalibrated?

When recalibration is required depends on the nature and duration of use, as well as the specific operating conditions.

For example, the following may be considered:

• Continuous operation / number of operating hours
• extreme environmental conditions
• significant fluctuations in load conditions
• safety-critical applications

How is the calibration interval determined?

The appropriate calibration interval depends on the operating conditions and the measurement accuracy requirements. Factors to be taken into account include, amongst others, the duration of use, the operating hours, the frequency and severity of the loads, and the ambient conditions.

Existing quality management guidelines or customer-specific requirements may also dictate a particular calibration interval. In demanding operating conditions – for example, where there are a high number of operating hours, cyclic loading, or significant temperature and environmental influences – a shorter interval may be advisable.

The calibration interval can also be adjusted on the basis of previous calibration results. If the measured values show a stable trend over several calibrations and the variations remain well within the permissible measurement uncertainty, the interval may be extended where appropriate. In the event of significant changes or if the measurements approach the permissible measurement uncertainty, the interval should be shortened accordingly.

There is therefore no universally applicable calibration interval. It should be determined in accordance with the specific application, operating conditions and measurement reliability requirements, and adjusted as necessary.

When is an unscheduled recalibration required?

In addition to the specified calibration interval, recalibration may also be necessary if the load cell has been subjected to particular stresses or if a change in its measurement characteristics is detected.

Additional recalibration is particularly recommended in the following cases:

• noticeable deviation from zero when the product is dismantled
• mechanical stress, for example caused by a fall or incorrect assembly
• exceeding the permissible working load
• exceeding the permissible temperature conditions
• unauthorised tampering, modifications or repairs

For many applications, it is advisable to carry out a functional check or recalibration every two years. However, depending on the operating conditions and measurement accuracy requirements, a shorter or longer interval may be appropriate.

Do you need a calibration?

VELOMAT calibrates force transducers and force measurement systems from various manufacturers in the range from 1 to 500 kN. Other force ranges are also available on request.

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