Why the calibration of (force) measuring instruments is important

Everyone involved in 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: It is possible to measure a lot. But the values are only useful if you can validate them. In everyday life, for example, you can be surprised once the scales at home show a big deviation from those at the physician?s or the bicycle speedometer deviates many hundreds of metres from the GPS instrument. The word also often alludes to your tendency to generate more and more data in our modern world, without thinking about its evaluation. As a way 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 best accuracy may not be important. In industrial applications, however, it really is precisely this that can make the crucial difference between rejects and the best quality ? hence the calibration of the measuring instruments. It serves to match the measuring device with the national standard ? in short: to check if the values are correct.
Traceability to the national standard
The keyword here is 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 example, ISO 9000 requires that the deviations of the test equipment used ought to be monitored. Having an up-to-date calibration, passing the audit is not any problem. This avoids the repetition of the audit, production downtime or perhaps a recall ? and thus 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 Silly to possess one?s own measuring devices checked relative to the current standard is the feeling of security: The measuring instruments will continue steadily to supply the correct values!
Certification relative to the German accreditation body
The illustration shows how the four calibration sequences in accordance with DKD-R 3-3 differ.
The highest standard because of this may be 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 example of high-end force transducers, which are used in calibration machines. In 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), the effort is correspondingly high. The purchase price for such a calibration goes together 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 might be selected in line with 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 exemplory case of the usefulness of regular calibration is the checking of hydraulic compression force transducers. Results measure the clamping forces of industrial machines such as for example punches, pneumatic presses, sealing presses, spindle presses, tablet presses and toggle lever presses. Here, calibration provides 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, however they may also be checked at set intervals using a test set for measuring electrode forces (model FSK01). This ensures the standard of the welding points and reduces wear on the electrodes.
For the tension/compression force transducers mentioned, calibration is also 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 easily pay off: If one in that process isn’t noticed immediately (for instance, only if the travel is controlled), several thousand euros in material value could be destroyed within minutes.
Adjustment before calibration can be handy
Depending on the instrument, application and regulation, it might be worthwhile to have an adjustment carried out 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 the own and for third-party products.
Note
On the WIKA website you will discover further information on the individual calibration services as well as on WIKA force measuring instruments (offers may also be available in the web shop). If you have any questions, your contact will gladly help you.
Also read our post
Calibration or adjustment ? Where?s the difference?

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