Everyone involved in measurement technology knows the somewhat flippant ? but very catchy ? Vilified : ?In the event that you measure a lot, you measure nothing!? What’s meant by that is: It is possible to measure a lot. However the values are just useful when you can validate them. In everyday activity, for example, one may be surprised when the scales in the home show a big deviation from those at the physician?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 in our modern world, without thinking about its evaluation. So that you can 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 will not be 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 complement 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. Understanding that the respective measuring instrument measures the right value can be of great importance for most applications. For instance, 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 even 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 may 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 in accordance with the current standard is the feeling of security: The measuring instruments will continue to provide 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 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 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 used in calibration machines. Within their case, the test sequence follows the EN ISO 376 standard. At the very 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), the effort is correspondingly high. The purchase price for this type of calibration goes together with this.
Regarding industrial devices, the question arises as to whether this type of procedure is worthwhile. Alternatively, the DKD-R 3-3 directive can be applied. It describes four test sequences that can be selected good requirements. WIKA and tecsis likewise have DAkkS certification for this.
A further option for regular calibration is 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 measure the clamping forces of industrial machines such as 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 is 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 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 can be worthwhile, should they be used for monitoring very precise production steps. When pressing in cellular phone displays, for example, both the measuring instruments and their calibration can easily pay back: If one in such a process is not noticed immediately (for instance, only if the travel is controlled), thousands of euros in material value could be destroyed within minutes.
Adjustment before calibration can be useful
Based on the instrument, application and regulation, it can 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 type and procedure, both for our own and for third-party products.
Note
On the WIKA website you will find further information on the average person calibration services in addition to on WIKA force measuring instruments (offers are also available in the web 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?