FAQ: Service and Calibration
- What does calibration entail?
In calibration, the relationship between the measured value of an output quantity and the corresponding value of the measured input quantity is determined under specified conditions. Simply put: comparison with a reference having the same units, which in measurement engineering means determining the measurement deviation returned by measurement equipment. Calibration does not entail technical intervention – such as adjustment – in the measurement equipment. With indicator measurement equipment, calibration determines the deviation between the measured value indicated and the correct value – or the reference value considered correct.
Calibrations are performed in order to ensure that the measurement equipment used indicates values having a known and documented proportionality to an internationally accepted standard for the quantity measured. The goal is that when measurements of the same quantities are performed by different parties, e.g., customer and supplier, comparable results are obtained. The prerequisite for this is that the measurement uncertainty—which is inherent in any measurement—must be known.
Performing calibration leads to results and findings which provide a guide in better understanding and assessing the tolerances of measurement equipment.
- What is an adjustment?
Adjustment refers to the process of adjusting measurement instruments to compensate for known systematic measurement discrepancies. In contrast, then, to calibration, this means manipulating the instrument in a way which produces lasting effects. Note that this renders any previous calibration and its traceability pedigree obsolete! It is then also no longer possible to reconstruct any changes in the instrument's measurement properties.
- What is a legally secure calibration chain?
The process of calibrating a piece of measurement equipment using equipment conformant to a higher standards, which in turn is calibrated using equipment conformant to yet higher standards, is known as the calibration chain.
The purpose of this calibration chain is to trace a piece of equipment’s calibration to the national standard.
Automobile manufacturers and their suppliers, in particular, have been demanding that calibration service providers be accredited in accordance with ISO 17025.
Fundamentally, however, what is required is proof of competence: accredited laboratories are such which have proven their capabilities to an independent assessor.
imc is not an accredited calibration service provider. However, by definition we possess the capabilities and the regulations pursuant to TS16949 / QS 9000 do not apply to us.
imc performs calibration with instruments calibrated to the national standards in accordance with ISO 9001. Our service comes standard with a (manufacturer’s) calibration certificate.
The optional calibration reports which include records of measured values conform to the requirements of ISO 17025.
DIN EN ISO 9001 only requires a declaration (manufacturer’s calibration certificate) of traceability of the reference equipment used to national standards.
By default, we pass the benefit of lower costs to our customers as price savings (extra charge for optional "Certificate with Protocol as per ISO 17025"). The traceability of equipment, archiving of measurement values etc. are governed by ISO 9001:2008, and are regularly monitored by TÜV TÜV Cert Rheinland GmbH.
All calibration reports along with measurement values are automatically archived at imc and are optionally available for release (up to 10 years later).
- How often is calibration necessary?
To get correct measurements in the long term, the test equipment used has to be monitored regularly and calibrated, if appropriate. The time between such calibration treatments is called the calibration interval. We frequently receive questions about the necessary calibration interval for measurement and test equipment.
However, there is no unambiguous answer to this question, since a device's state of calibration is dynamic and depends upon the following factors, to name a few: the input quantity and its permissible tolerances, wear and tear on the equipment, stability of previous calibration procedures, measurement precision required and last but not least a company's quality assurance system policies.
As a matter of principle, a calibration is valid only at the moment it is performed. Setting deadlines for re-calibration is the responsibility of the equipment user. As a rule, the calibration interval should be designed to optimize the balance between risks and costs.
This means that the calibration interval is ultimately the user's own responsibility to determine and monitor. Our recommendation is from 1 up to 3 years. In order to support our customers in determining the calibration interval, we offer consultation from our employees. Our standard statement in our spec sheets is for 1 year.
- What does monitoring of measurement equipment entail?
The goal of a test equipment management system is to ensure the quality of measurements of products and processes. Toward this end, two major issues must be observed:
- The quality of the measurement processes, i.e. how well the measurements are performed,
- The quality of the test equipment, i.e. how well the test equipment is adapted to the measurement task.
To ensure the quality of test equipment, the following must apply:
- Test equipment is clearly labeled
- Equipment performance requirements are stated
- Test equipment is regularly inspected for compliance with defined requirements, i.e. it is calibrated regularly (and adjusted if necessary), (see also Calibration Interval)
- Test equipment used for calibration can be traced to national or international standards (or to documented calibration foundations if no such standards apply)
- Test equipment is treated in such a way as not to compromise its functional properties.
To meet these requirements, a test equipment management system must be introduced which is also compatible with other company goals.
Companies must have test equipment at their disposal for every measurement required, i.e. for every physical unit of relevance. Toward this end, an overview of all test equipment available to the company is needed.
Correct performance of measurements is conditional on all test equipment used being properly calibrated.
- Is monitoring of measurement equipment really necessary?
Management and monitoring of the equipment used serves the following purposes:
- Ensuring the maintenance of measurement equipment
- Use of only appropriate test equipment for the inspection of the conformity of products and processes to requirements
- Ensuring the required precision of test equipment (including of the reference instruments)
- Ensuring the traceability to higher-level calibration standards
- Avoidance of customer complaints due to incorrect measurement results
- Avoidance of rejection of functional products, or of acceptance of defective products for further processing or shipping
- Proof to customers and certification authorities of the conformity of test equipment monitoring systems to requirements
- Overview of all test equipment available/used
- Improvement of employee awareness with regard to performing tests and to treatment of equipment.