Everyone involved with measurement technology knows the somewhat flippant ? but very catchy ? statement: ?In the event that you measure a lot, you measure nothing!? What is meant by that is: You can measure a lot. But the values are just useful if you can validate them. In everyday life, for example, one may be surprised once 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 word also often alludes to your tendency to generate an increasing number of data inside our modern world, without considering its evaluation. So as to obtain valid data with which to continue 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 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 short: to check if 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 should be monitored. With 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 Stupid , time and costs. The expenditure on the calibration has thus quickly covered itself. Many people are 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 in accordance with the current standard may be 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 in accordance with DKD-R 3-3 differ.
The highest standard because of 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 quite a while. Because the beginning of 2022, tecsis has been accredited relative to DIN EN ISO / IEC 17025 for the measurand force.
Just 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. Within their case, the test sequence follows the EN ISO 376 standard. At 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 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, Paralyzed DKD-R 3-3 directive could be applied. It describes four test sequences which might be selected based on the requirements. WIKA and tecsis also have DAkkS certification for this.
An additional option for regular calibration is 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 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, however 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 mobile phone displays, for example, both measuring instruments and their calibration can easily pay back: If an error in that 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 useful
Depending on the instrument, application and regulation, it can be worthwhile to have 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 type and procedure, both for the own and for third-party products.
Note
On the WIKA website you will discover further information on the individual calibration services in addition to on WIKA force measuring instruments (offers may also be available in the web shop). Assuming you have any questions, your contact will gladly assist you to.
Also read our post
Calibration or adjustment ? Where?s the difference?g