In metrology, calibration is the process of determining whether the coordinate measuring machine is operating at its respective defined accuracy. Among other things, the measuring machine is tested during calibration according to the manufacturer's specifications, the so-called accuracy specifications. Calibration thus has a significant influence on your production reliability and helps to minimize the risk of complaints and failures.

Accreditation recognizes the technical and organizational competence of a conformity assessment body (= accredited laboratory). For example, a metrological procedure (e.g. length measurement and its deviations) is accredited. Thus, accreditation is the confirmation and recognition of technical competence. Certification confirms that prescribed requirements (e.g. QM systems) are met. It always refers to a management system, i.e. processes, quality inspections or corrective actions.

The conformity assessment is part of the calibration certificate, which is issued by a ZEISS service employee. The confirmation by a third party formally states that a conformity assessment body has the competence to perform certain conformity assessment tasks.

Basically, there are no prescribed time intervals for the calibration of testing equipment. So, users can decide for themselves whether and when to perform a calibration. However, it should be kept in mind that the accuracy of a measuring machine decreases with increasing use. For this reason, calibration is recommended depending on the utilization, but at least every year. Calibration should also be considered whenever there is doubt about the accuracy of the measurement results. For example, after a collision of the sensor system with the component.

Factory calibrations are procedures defined by the manufacturers themselves and are usually based on guidelines or standards. Responsibility for these procedures rests with the manufacturer and are not externally verified. Accredited procedures, on the other hand, are implemented in accordance with ISO 10360 and the VDI/VDE and are monitored at regular intervals by the national accreditation body.

Furthermore, accredited calibration certificates are internationally recognized through agreements with ILAC (MRA). This makes the measurement results internationally comparable and enables metrological traceability to national standards.

Precise measuring instruments and measuring equipment are crucial in industrial production to ensure functionality, quality assurance and comparability. Accredited calibration confirms the metrological procedure by the national accreditation body of the Federal Republic of Germany (DAkkS) or national accreditation bodies in other countries. This is proof that the activities are performed competently, in compliance with legal and normative requirements and at an internationally comparable level. Accreditation according to ISO/IEC 17025:2018 recognizes the technical and organizational competence of a conformity assessment body (= accredited calibration laboratory).

Whether a calibration certificate is ISO-compliant can be identified by the following criteria:

• Complete identification (date, number of the calibration certificate, identification of the measured object, measuring location, client, signature)
• Designation of the documented and validated calibration procedures (in standards, guidelines, work instructions)
• Metrological traceability of the results: The chain of calibration to the pre-standard or accredited calibration certificate must be traceable
• Ambient conditions during calibration
• Documentation of the calibration results and measured values (measurement results) with indication of the unit and measurement uncertainties
• Indication of the specification (in the case of statements on conformity)
• Source of the specification

When you order a coordinate measuring machine from ZEISS, the machine goes through the following stages:

1. The CMM is built for you
2. Acceptance inspection at ZEISS
3. Transport, assembly, and adjustment at your company
4. Calibration on-site
5. Issue of the calibration certificate