Calibration with computed uncertainty and verifiable certificates.

Calibration inside the work order

Calibration is a separately licensed module. With it enabled, any work order can be flagged as a calibration — always of an asset — and the calibration sheet is filled in during execution, in the app, in the dashboard or through the web completion link.

You decide whether a work order can close with an open calibration. With the requirement on, a calibration job only completes once its sheet has a result.

Traceable standards and point templates

The standards used for measuring are registered with type, manufacturer, model, serial number, calibration certificate number, calibration date, due date, calibrating body and attachments. That is what makes the measurement printed on the certificate traceable.

Standard templates define how a calibration is done: method and procedure references, the points to measure and each point's tolerance — as an absolute value, a percentage of nominal or an asymmetric range. When the procedure calls for it, the template requires ambient conditions — temperature, humidity and pressure — with nominal and uncertainty. Templates are versioned, and the sheet copies the points at calibration time, so revising a template next month never rewrites a sheet already filled in.

Uncertainty that explains itself

Expanded uncertainty and coverage factor are not typed-in numbers: they are computed from four sources, following the GUM.

• Type A — the scatter of the readings actually taken, u = s/√n, with n − 1 degrees of freedom.
• Type B — the standard's certified uncertainty at that point, u = U/k.
• Resolution — the finest division the standard and the equipment can display, u = d/(2√3) for each — the term that stops a measurement from claiming zero uncertainty.
• Welch–Satterthwaite and Student's t — combine the sources into effective degrees of freedom and reach the k factor for 95.45% coverage.

The number the technician saw is the number on the certificate

A signed, verifiable certificate

When the work order completes, the certificate is issued from a frozen copy of the calibration data. A SHA-256 hash of the content is printed on the document itself, and the PDF receives a PAdES digital signature applied by the platform. Corrections produce new certificate revisions.

Every certificate carries a QR code leading to a public validation page, where whoever received the paper can check the issuer, the equipment, the date, the hashes of the content and of the signed file, and the details of the digital certificate used to sign it.

The certificate is honest about what the signature proves: that the file has not changed and who signed it — not that the measurement is right, which rests on the procedure, the standards and the responsible engineer.

Evidence of who took part, and a trail of every change

The certificate freezes participant evidence: who opened the work order, who was assigned, who took the measurements, who reviewed and who signed — with the channel each one was authenticated through. Every write to a calibration records the prior state first, including re-syncs from the app.

For companies following the amendment path in ISO/IEC 17025 clause 7.8.8, a preference allows correcting the sheet from the dashboard after the work order is completed. It is off by default, and every correction preserves what the certificate said when it was issued.