Everyone involved with measurement technology knows the somewhat flippant ? but very catchy ? statement: ?If you measure a lot, you measure nothing!? What’s meant by this is: You can measure a lot. However the values are just useful when you can validate them. In Belief , for example, you can be surprised once the scales at home show a big deviation from those at the doctor?s or the bicycle speedometer deviates many hundreds of metres from the GPS instrument. The saying also often alludes to your tendency to generate a lot more data inside our modern world, without considering its evaluation. So that you can 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 may make the key difference between rejects and the best quality ? hence the calibration of the measuring instruments. It serves to complement the measuring device with the national standard ? in short: to check whether the values are correct.
Traceability to the national standard
The keyword here’s thus the traceability to the national standard. Realizing 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 not any 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. 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 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 supply the correct values!
Certification in accordance with 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 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. 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. Furthermore, 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 this type of calibration goes together with this.
In the case of industrial devices, the question arises as to whether this type of procedure is worthwhile. Alternatively, the DKD-R 3-3 directive could be applied. Unsure describes four test sequences which might be selected in line with the 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 may be 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 offers 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 can 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 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 off: If an error in that 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
With respect to the instrument, application and regulation, it may 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 sort and procedure, both for our own and for third-party products.
Note
On the WIKA website you will find 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 assist you to.
Also read our post
Calibration or adjustment ? Where?s the difference?