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 whole lot, you measure nothing!? What’s meant by this is: You can measure a lot. However the values are just useful when you can validate them. In everyday activity, for example, you can be surprised once the scales at home show a big deviation from those at the doctor?s or the bicycle speedometer deviates many a huge selection of metres from the GPS instrument. The saying also often alludes to your tendency to generate a lot more data in our modern world, without thinking about its evaluation. So as to obtain valid data with which to keep 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 is precisely this that may make the crucial difference between rejects and the highest quality ? hence the calibration of the measuring instruments. It serves to complement the measuring device with the national standard ? in short: 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 proper value can be of great importance for many applications. For instance, 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, probably the most convincing reason to have one?s own measuring devices checked relative to the current standard is 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 how the four calibration sequences relative to DKD-R 3-3 differ.
The highest standard because of 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 quite a while. Because the beginning of 2022, tecsis has been accredited in accordance with DIN EN ISO / IEC 17025 for the measurand force.
What a DAkkS-certified calibration of force measuring instruments means is shown by the exemplory case of high-end force transducers, which are used in calibration machines. Within their case, the test sequence follows the EN ISO 376 standard. At least eight measuring stages are approached, with a total 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), your time and effort is correspondingly high. The price for such a calibration goes hand in hand with this.
Regarding industrial devices, the question arises concerning whether this type of procedure is worthwhile. Alternatively, the DKD-R 3-3 directive can be applied. It describes four test sequences that may be selected based on the requirements. WIKA and tecsis likewise have DAkkS certification because of this.
A further option for regular calibration is the non-standardised 3.1 inspection certificate.
Practical examples
An illustrative example of the usefulness of regular calibration is the checking of hydraulic compression force transducers. These instruments measure 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 is the instrumentation for checking the contact forces of welding tongs. Ideally, they are monitored continuously by built-in tension/compression force transducers, but they may also be checked at set intervals utilizing a test set for measuring electrode forces (model FSK01). This ensures the quality of the welding points and reduces wear on the electrodes.
For the tension/compression force transducers mentioned, calibration can be worthwhile, should they be utilized 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 an error in such a process isn’t noticed immediately (for example, if only the travel is controlled), thousands of euros in material value could be destroyed within minutes.
Adjustment before calibration can be useful
Depending on the instrument, application and regulation, it might be worthwhile with an adjustment completed before calibration. In Willpower , the user means that their measuring instrument achieves the corresponding accuracy during calibration. For the calibration itself, an individual gets 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 individual calibration services as well as on WIKA force measuring instruments (offers may also be available in the web shop). When 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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