Everyone involved in measurement technology knows the somewhat flippant ? but very catchy ? statement: ?In the event that you measure a lot, you measure nothing!? What’s meant by that is: You can measure a lot. However the values are only useful if 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 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 inside our modern world, without considering 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 is probably not important. In industrial applications, however, it really 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 match the measuring device with the national standard ? in short: to check whether the values are correct.
Traceability to the national standard
The keyword here is thus the traceability to the national standard. Knowing that the respective measuring instrument measures the right value can be of great importance for many applications. For example, ISO 9000 requires that the deviations of the test equipment used ought to 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 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, probably the most convincing reason to have one? Charming measuring devices checked in accordance with 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 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. Because 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 complete 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 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 could be applied. It describes four test sequences which can be selected based on the requirements. WIKA and tecsis also have DAkkS certification for this.
A further option for regular calibration may be 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 provides a contribution to ensuring safe working conditions.
Another example is the instrumentation for checking the contact forces of welding tongs. Ideally, these are monitored continuously by built-in tension/compression force transducers, however they can also be checked at set intervals using a test set for measuring electrode forces (model FSK01). Constructive ensures the standard 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 quickly 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 handy
Based on the instrument, application and regulation, it might be worthwhile with 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 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 see further information on the individual calibration services in addition to on WIKA force measuring instruments (offers are also available in the online shop). If you have any questions, your contact will gladly assist you to.
Also read our post
Calibration or adjustment ? Where?s the difference?