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All about calibration

And why it's so important to keep testing your accuracy

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Calibrationhouse’s business development manager, Andrew Simpson, gives an in-depth look at the importance of maintaining the measurement accuracy of test instruments.

Simpson defines it well when he states that “Accurate measurement is the base factor in all industrial processes and testing systems and is essential for the delivery of high-quality products and services. The calibration of test and measuring instrumentation is therefore vital to ensure that equipment continues to meet its published performance specification.”

Key highlights

Calibration is what assures operators that equipment is measuring correctly, and that the measurement processes can be trusted to be accurate. A full traceable record of calibration for products is one of the requirements for companies that are ISO 9001:2015 accredited.

Original Equipment Manufacturers (OEM) may provide recommendations on calibration for their equipment. This may include different calibration services for different instruments, different types of tests and different measurement applications, as these all undergo different variables.

Simpson gives the example of how “in some cases a simple function or confidence check may be sufficient for certain applications. In others a comparison to the original specification will be required, and any necessary adjustments carried out to rectify ‘out of specification’ performance. Calibration may also need to be tailored to a company’s specific requirements with testing at specific points more suitable for the application.”

Faults that are found during calibration may need to be repaired before calibration can be completed, unless the fault is too serious, in which case the instrument may have to be returned to the manufacturer. Variations discovered during testing should be recorded on calibration certificates, which show both ‘as received’ and ‘post adjustment’ measurement values, as well as details of measuring limits and/or tolerances.

One way that downtimes for vital test equipment can be minimised is by employing the services of ‘mobile calibration personnel’. This means that damage to the instrument during transit is also a risk that is removed, as the machine is calibrated and tested in situ.

In the UK, UKAS is the national body recognised by the government for the accreditation of calibration. ISO/IEC 17025:2017 is the standard for which laboratories must hold accreditation to be deemed technically competent and often suppliers and regulatory authorities will not accept test or calibration results from a lab that does not have this accreditation. This UKAS accreditation confirms the technical competency, impartiality and reliability of a calibration provider to deliver accurate results.

UKAS assessments need to happen regularly to ensure that test procedures, the equipment used and the technical capabilities of test staff are of the highest standards, with assured traceability to national, or in some cases, international standards. From an accountability perspective, many businesses require the UKAS endorsement in order to maintain compliance with their own regulatory authorities and standards bodies.

There is an important difference, though, as Simpson highlights: “Some calibration services may not be accredited to ISO17025:2017, but still be certified to ISO 9001:2015. Although such laboratories can provide traceable calibration, this is a generic standard for quality management systems and does not necessarily demonstrate technical competence to produce valid and accurate data measurement.”

Nonetheless, it’s important to keep in mind that the requirement for calibration certification is based on individual needs, such as the manufacturer or tester’s specifications for accuracy and repeatability, which is also determined by scale of production.

Choosing a service

Those companies that provide an accredited service themselves such as product testing and standards compliance, or are involved in an application that requires greater confidence in the reliability of instrumentation such as electromedical equipment, are more likely to require calibration in ISO17025 accredited laboratories.

Quality assessors may consider that a non-accredited calibration is inadequate, but the broader decision is essentially one of risk management; how important is it that your goods and services are based on measurements taken with fully assessed and correctly calibrated equipment? Can you afford the risk to your market reputation caused by unreliable results?

Choosing the right calibration service for your equipment requires diligent attention in order to ensure a quality service is delivered at the right price, with a lasting guarantee for accuracy. Calibrationhouse is one example of a company that is accredited to both ISO9001 and ISO17025, and is experienced with a wide range of measurement equipment.

Simpson finished by highlighting the importance of accurate calibration, saying that it “cannot be underestimated in ensuring that equipment continues to provide an acceptably reassuring service. Any lack of control or knowledge within the calibration arena not only has a consequent adverse effect on the quality of service provided, but could ultimately lead to a failure to meet regulatory requirements including health and safety regulations. Ultimately, planned and effective calibration ensures long term accuracy, standardisation and repeatability in measurements, providing reliable benchmarks and results, and delivering successful test programmes today and long into the future.”

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