Everyone involved with measurement technology knows the somewhat flippant ? but very catchy ? statement: ?In the event that you measure a whole lot, you measure nothing!? What is meant by that is: It is possible to measure a lot. But the values are only useful when you can validate them. In everyday life, for example, you can be surprised once the scales at home show a large 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 progressively more data inside our modern world, without thinking about its evaluation. As a way 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 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. Lurking serves to match 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’s thus the traceability to the national standard. Understanding 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 no problem. This avoids the repetition of the audit, production downtime or perhaps 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 may 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 in accordance with the current standard is the feeling of security: The measuring instruments will continue to provide the correct values!
Certification relative to the German accreditation body
The illustration shows how the four calibration sequences relative to 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. Since 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. In 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), your time and 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 such a procedure is worthwhile. Alternatively, the DKD-R 3-3 directive can be applied. It describes four test sequences that can be selected based on the requirements. Simplified and tecsis also have DAkkS certification for 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 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 may be the instrumentation for checking the contact forces of welding tongs. Ideally, these 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 standard 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 one in such a process isn’t noticed immediately (for example, if only the travel is controlled), several thousand euros in material value could be destroyed within minutes.
Adjustment before calibration can be useful
According to the instrument, application and regulation, it may be worthwhile to have an adjustment carried out before calibration. In this manner, the user means that their measuring instrument achieves the corresponding accuracy during calibration. For the calibration itself, an individual has the option of choosing the sort and procedure, both for our own and for third-party products.
Note
On the WIKA website you can find further information on the individual calibration services as well as on WIKA force measuring instruments (offers are also 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?