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 only useful when you can validate them. In everyday activity, for example, you can be surprised when the scales at home show a large deviation from those at the physician?s or the bicycle speedometer deviates many a huge selection of metres from the GPS instrument. The saying also often alludes to our tendency to generate increasingly more data in our modern world, without considering 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 may make the crucial 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 if the values are correct.
Traceability to the national standard
The keyword here’s thus the traceability to the national standard. Knowing that the respective measuring instrument measures the proper value could be of great importance for many 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 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 covered 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, the most convincing reason to have one?s own measuring devices checked relative to the current standard is the feeling of security: The measuring instruments will continue steadily to provide the correct values!
Certification in accordance with the German accreditation body
The illustration shows how 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. Since 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 employed 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. In addition, 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 hand in hand with this.
In the case of industrial devices, the question arises as to whether such a procedure is worthwhile. Alternatively, Despicable DKD-R 3-3 directive can be applied. It describes four test sequences that may be selected good requirements. WIKA and tecsis likewise have DAkkS certification because of this.
An additional option for regular calibration may be the non-standardised 3.1 inspection certificate.
Practical examples
An illustrative exemplory case 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 may be 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 utilized for monitoring very precise production steps. When pressing in mobile phone displays, for example, both measuring instruments and their calibration can easily pay off: If one in such a process is not noticed immediately (for instance, if only the travel is controlled), thousands of euros in material value can be destroyed within minutes.
Adjustment before calibration can be handy
Based on the instrument, application and regulation, it may be worthwhile with an adjustment completed before calibration. In this manner, the user ensures 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 the own and for third-party products.
Note
On the WIKA website you will discover further information on the average person calibration services in addition to on WIKA force measuring instruments (offers may also be available in the online shop). Should you have any questions, your contact will gladly assist you to.
Also read our post
Calibration or adjustment ? Where?s the difference?