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: You can measure a lot. But the values are just useful when you can validate them. In everyday life, for example, one may be surprised when 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 growing number of data in our modern world, without considering its evaluation. As a way to obtain valid data with which to continue working, it is worthwhile for industrial measuring instruments to be calibrated regularly.
For the individual, the best accuracy will 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 right value can be of great importance for most applications. For example, 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. 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. Ecstatic 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 in accordance with the current standard may be 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 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. In 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 Lascivious , 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 price for such a calibration goes hand in hand with this.
In the case of 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 that could be selected in line with the requirements. WIKA and tecsis also 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 may be 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 may be 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 using 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 utilized for monitoring very precise production steps. When pressing in cellular phone displays, for example, both the measuring instruments and their calibration can quickly pay back: If an error in such a process isn’t noticed immediately (for example, only if the travel is controlled), several thousand euros in material value could be destroyed within minutes.
Adjustment before calibration can be useful
Depending on instrument, application and regulation, it might be worthwhile with 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, the user has the option of choosing the sort and procedure, both for the own and for third-party products.
Note
On the WIKA website you will see further information on the average person calibration services in addition to 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?