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Why the calibration of (force) measuring instruments is important

Everyone involved with measurement technology knows the somewhat flippant ? but very catchy ? statement: ?In the event that you measure a lot, you measure nothing!? What’s meant by this is: It is possible to measure a lot. However the values are just useful when you can validate them. In everyday life, for example, you can be surprised when the scales in the home show a big deviation from those at the doctor?s or the bicycle speedometer deviates many hundreds of metres from the GPS instrument. The word also often alludes to your tendency to generate a lot more data inside our modern world, without thinking about its evaluation. As a way to obtain valid data with which to continue working, it really is worthwhile for industrial measuring instruments to be calibrated regularly.
For the individual, the highest accuracy is probably not important. In industrial applications, however, it really is precisely this that may make the key difference between rejects and the best quality ? hence the calibration of the measuring instruments. It serves to complement the measuring device with the national standard ? in a nutshell: to check whether the values are correct.
Traceability to the national standard
The keyword here’s thus the traceability to the national standard. Understanding that the respective measuring instrument measures the right value could be of great importance for most applications. For example, ISO 9000 requires that the deviations of the test equipment used ought to be monitored. With an up-to-date calibration, passing the audit is not any problem. This avoids the repetition of the audit, production downtime or even a recall ? and therefore reduces stress, time and costs. The expenditure on the calibration has thus quickly paid for itself. Everyone is happy.
Besides meeting the audit requirements, traceability can also be required for quality assurance, optimising resource utilisation and reducing energy consumption. Finally, the most convincing reason to possess one?s own measuring devices checked relative to the current standard may be the feeling of security: The measuring instruments will continue steadily to provide the correct values!
Certification relative to the German accreditation body
The illustration shows the way the four calibration sequences in accordance with DKD-R 3-3 differ.
The highest standard for this is the calibration certificate of the German accreditation body (Deutsche Akkreditierungsstelle ? DAkkS). WIKA has offered certification for pressure, temperature and electrical measurands (DC current, DC voltage and DC resistance) for some time. Since the beginning of 2022, tecsis has been accredited in accordance with DIN EN ISO / IEC 17025 for the measurand force.
Just what a DAkkS-certified calibration of force measuring instruments means is shown by the exemplory case of high-end force transducers, which are employed in calibration machines. In their case, the test sequence follows the EN ISO 376 standard. At the very least eight measuring stages are approached, with a complete of five preloads, two upward series and two up-down series. In addition, the force transducers are each rotated by 120�, which results in three installation positions. With 65 measured values (eight stages), the effort is correspondingly high. The price for this type of calibration goes hand in hand with this.
Regarding industrial devices, the question arises as to whether such a procedure is worthwhile. Alternatively, the DKD-R 3-3 directive can be applied. It describes four test sequences which can be selected in line with the requirements. WIKA and tecsis likewise have DAkkS certification because of this.
An additional option for regular calibration is the non-standardised 3.1 inspection certificate.
Practical examples
An illustrative example of the usefulness of regular calibration may be the checking of hydraulic compression force transducers. These instruments gauge the clamping forces of industrial machines such as punches, pneumatic presses, sealing presses, spindle presses, tablet presses and toggle lever presses. Here, calibration offers a contribution to ensuring safe working conditions.
Another example may be the instrumentation for checking the contact forces of welding tongs. Ideally, these are monitored continuously by built-in tension/compression force transducers, however they may also be checked at set intervals utilizing a test set for measuring electrode forces (model FSK01). This ensures the caliber of the welding points and reduces wear on the electrodes.
For the tension/compression force transducers mentioned, calibration is also worthwhile, should they be used for monitoring very precise production steps. When pressing in cellular phone displays, for example, both measuring instruments and their calibration can quickly pay off: If one in such a process is not noticed immediately (for example, if only the travel is controlled), several thousand euros in material value could be destroyed within minutes.
Bona Fide before calibration can be handy
Based on the instrument, application and regulation, it can be worthwhile to have an adjustment completed before calibration. In this way, the user ensures that their measuring instrument achieves the corresponding accuracy during calibration. For the calibration itself, an individual has the option of choosing the type and procedure, both for our own and for third-party products.
Note
On the WIKA website you will see further information on the average person calibration services as well as on WIKA force measuring instruments (offers are also available in the online shop). Should you have any questions, your contact will gladly assist you to.
Also read our post
Calibration or adjustment ? Where?s the difference?

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