Everyone involved with measurement technology knows the somewhat flippant ? but very catchy ? statement: ?If you measure a whole lot, you measure nothing!? What’s meant by this is: You can measure a lot. But the values are just useful if you can validate them. In everyday activity, for example, you can be surprised when the scales at home show a big deviation from those at the physician?s or the bicycle speedometer deviates many a huge selection of metres from the GPS instrument. The word also often alludes to your tendency to generate a growing number of data in our modern world, without thinking about its evaluation. So as to obtain valid data with which to keep working, it 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 is precisely this that can make the crucial 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 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 most applications. For instance, ISO 9000 requires that the deviations of the test equipment used should be monitored. Having an up-to-date calibration, passing the audit is no problem. In The Zone avoids the repetition of the audit, production downtime or perhaps a recall ? and therefore reduces stress, time and costs. The expenditure on the calibration has thus quickly paid for itself. Many people are 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 is the feeling of security: The measuring instruments will continue to provide the correct values!
Certification relative to the German accreditation body
The illustration shows the way the four calibration sequences relative to DKD-R 3-3 differ.
The highest standard for 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 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 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 that could be selected good requirements. WIKA and tecsis also 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 is the checking of hydraulic compression force transducers. These instruments 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, 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 quality 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 mobile phone displays, for example, both the measuring instruments and their calibration can quickly pay off: If an error in such a process is not noticed immediately (for example, if only the travel is controlled), thousands of euros in material value can 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 manner, the user ensures that their measuring instrument achieves the corresponding accuracy during calibration. For the calibration itself, the user 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 individual calibration services in addition to on WIKA force measuring instruments (offers may also be available in the online shop). For those who have any questions, your contact will gladly assist you to.
Also read our post
Calibration or adjustment ? Where?s the difference?