Why the calibration of (force) measuring instruments is important

Everyone involved with measurement technology knows the somewhat flippant ? but very catchy ? statement: ?If you measure a whole lot, you measure nothing!? What is meant by that is: It is possible to measure a lot. But the values are only useful if you can validate them. In everyday activity, for example, you can be surprised when the scales in the home show a large deviation from those at the physician?s or the bicycle speedometer deviates many a huge selection of metres from the GPS instrument. The saying also often alludes to our tendency to generate progressively more data inside our modern world, without thinking about its evaluation. So as 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 best accuracy is probably not important. In industrial applications, however, it is precisely this that can make the key difference between rejects and the highest quality ? hence the calibration of the measuring instruments. It serves to match 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 is thus the traceability to the national standard. Realizing 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 no problem. This avoids the repetition of the audit, production downtime or even a recall ? and thus reduces stress, time and costs. The expenditure on the calibration has thus quickly covered itself. Many people are happy.
Besides meeting the audit requirements, traceability can also be necessary for quality assurance, optimising resource utilisation and reducing energy consumption. Finally, the most convincing reason to have one?s own measuring devices checked in accordance with the current standard is the feeling of security: The measuring instruments will continue steadily to provide the correct values!
Certification in accordance with 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 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. Since the beginning of 2022, tecsis has been accredited relative to DIN EN ISO / IEC 17025 for the measurand force.
What a DAkkS-certified calibration of force measuring instruments means is shown by the example of high-end force transducers, which are employed 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. Furthermore, 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 this type of calibration goes together with this.
Regarding industrial devices, the question arises concerning whether this type of procedure is worthwhile. Alternatively, the DKD-R 3-3 directive could be applied. It describes four test sequences which might be selected in line with the requirements. WIKA and tecsis also have DAkkS certification for this.
An additional option for regular calibration may be 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. These instruments gauge 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, these are monitored continuously by built-in tension/compression force transducers, but 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 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 easily pay back: If an error in such a process isn’t noticed immediately (for example, if only the travel is controlled), several thousand euros in material value could be destroyed within minutes.
Adjustment before calibration can be handy
According to the instrument, application and regulation, it could be worthwhile to have an adjustment carried out before calibration. In this manner, the user means that their measuring instrument achieves the corresponding accuracy during calibration. For the calibration itself, the user gets the option of choosing the sort and procedure, both for our own and for third-party products.
Note
On Snotty 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). In Satisfied 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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