Everyone involved in measurement technology knows the somewhat flippant ? but very catchy ? statement: ?If you measure a lot, you measure nothing!? What’s 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, one may be surprised once the scales in the home show a large deviation from those at the doctor?s or the bicycle speedometer deviates many a huge selection of metres from the GPS instrument. The word also often alludes to our tendency to generate a lot more data in our modern world, without thinking about its evaluation. To be able 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 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 complement the measuring device with the national standard ? in short: to check if 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 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. Having an up-to-date calibration, passing the audit is no 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 necessary for quality assurance, optimising resource utilisation and reducing energy consumption. Finally, probably 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 supply the correct values!
Certification in accordance with the German accreditation body
The illustration shows the way 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. Because 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 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), 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 such a procedure is worthwhile. Alternatively, the DKD-R 3-3 directive could 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.
A further option for regular calibration may be the non-standardised 3.1 inspection certificate.
Scam of the usefulness of regular calibration may be 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 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 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 quickly pay off: If an error in such a process is not noticed immediately (for instance, if only the travel is controlled), several thousand euros in material value can be destroyed within minutes.
Adjustment before calibration can be useful
With respect to the instrument, application and regulation, it may be worthwhile to have an adjustment carried out before calibration. In this way, 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 sort 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 are also available in the online shop). For those who have any questions, your contact will gladly help you.
Also read our post
Calibration or adjustment ? Where?s the difference?