Towards digital and machine-readable calibration certificates

The manufacturing and process industry is moving towards production processes where smart sensors and equipment collect and analyse data while controlling the processes automatically based on the measurements. But what if the measurements are not accurate? If more and more decisions are automated and made based on measurements that may not be reliable? And what should be done to avoid human error creeping into the processes?

“Calibration of measuring instruments is a prerequisite for quality-assured production, and this also applies to the automatic production processes of the future. It is important to be sure that you can trust the measurements, measurement errors can have major financial consequences”, says Ove Gunnarsson, TIC engineer who drives the development of digital calibration certificates at RISE.

Manual adjustments

RISE and other calibration laboratories perform a large number of calibrations for industry and business every year. The output from a calibration is a calibration certificate, which shows how the measuring instrument should be handled and adjusted to account for measurement uncertainties. The calibration certificate is often delivered as a digitally signed PDF. The document is indeed digital, but still difficult for machines to read.

“This means that the person who ordered the calibration needs to manually do the adjustments and corrections needed for the instrument, which is often time-consuming. There is also a risk of errors when hundreds or thousands of measurement values are handled manually”, says Ove Gunnarsson.

Machine-readable calibration certificates

To deal with this, the digital – and machine-readable – calibration certificates of the future is now being developed. With machines being able to read and interpret them, new possibilities are created for automated production, with higher efficiency and fewer mistakes when the human factor is rationalized away.

“In the future, the instruments may also be automatically adjusted and updated based on the digital calibration certificate, then we have removed the human completely. At the same time, it is important that the customer also receives a human-readable document so that you can follow-up that the adjustments have been done correctly”, says Ove Gunnarsson.

Common format

Several European and international institutes, accreditation bodies, universities and manufacturers of measuring instruments and organizations are driving the issue. A major challenge is to develop a common format that can be used and accepted by users worldwide.

“The content of the certificate is one important part. There should be no confusion about which measurement units are used for the same type of measurement between different countries. Another important thing is integrations, you should be able to use and share the calibration certificate between different users, systems and measuring instruments, all over the world”, says Ove Gunnarsson.

RISE follows the work of the Physikalisch-Technische Bundesanstalt (PTB) in Germany. Among other things, they have done much of the basic work around a standardized format, based on XML, which is machine-readable and can be shared between different systems and actors all over the world. XML is also easy to convert to other formats, such as JSON.

“Deciding on a format is one important step, so that there are not several different competing formats that make it more difficult for the users. Another important issue that PTB has worked on is safety, you need to be able to trust the digital calibration certificate”, says Ove Gunnarsson.

From above and from below

Many customers request digital and machine-readable calibration certificates. At the same time, it is important not to proceed too quickly.

“You can both increase quality and save money through this. To go all the way, work is required both from above, with common guidelines and formats, and from below, so that the solutions meet the actual needs of the users”, says Ove Gunnarsson.

He attended the first conference on digital calibration certificates in 2020, so development is still in its infancy.

“But things are moving forward quickly. I envision this to be in place and up and running within a five-year period. It is not an optional development; it will happen, and we need to be involved. We know there is a need; for example in medical technology, drug development, and the automotive industry, but we need to have a deeper dialogue about what the needs look like”, says Ove Gunnarsson.