If your car needed a 10 000 km service you might expect the choice of garage to be somewhat arbitrary. You would probably expect that, wherever you took it, the manufacturer's recommended procedures would always be followed and that recommended tools and parts would always be used. This would be even more likely if the garage had 'Approved Main Dealer' status.
The ISO9000 and ISO/IEC 17025 standard
It seems logical to apply this analogy to 'calibration dealers' with SANAS (ISO/IEC 17025) accreditation, but remember that ISO/IEC 17025 is procedural: a management system. The standard does not define the product in any way, only the checks and measures required to maintain a consistent quality level as defined by that particular supplier.
It does not mean that, for example, all electronic instrument calibration services from different suppliers have the same quality levels, or even provide a sufficient level of calibration to adequately meet the customer's expectations. Whether the service meets the customers' needs is beyond the scope of this certification.
Commercial considerations
Both commercial and technical needs have to be met when seeking a calibration service. Cost and turnaround time are of course two fundamental commercial criteria and it makes good commercial sense if a more comprehensive coverage of any particular instrument can be provided whilst maintaining a competitive price and a rapid turnaround time. Automation means different things to different providers. For Concilium Technologies, it is a means to provide a more comprehensive assurance of an instrument's performance for a competitive price, rather than just automating a basic functionality check.
Calibration can vary from a thorough performance evaluation of every mode and range to a cursory check of basic functionality. While the latter may meet a customer's need for a lower cost service, it implies a higher level of risk in that the equipment has an undetermined performance deficiency with potentially serious consequences.
Technical considerations
The technical need is most appropriately described as 'an adequacy of testing that confirms usage requirements'. In our experience, many users find it difficult to define their testing needs exactly and simply request a 'Calibration to spec'. This can be ambiguous.
In general, test equipment makers design recommended calibration procedures which carefully balance a compromise between expensive over-testing and the increased risk associated with under-testing. Their understanding of how the equipment works and the crucial areas of its performance ensures that reputable service providers following the manufacturers' guidance can maintain confidence in the ability of a unit to fully meet its specification. For example, an instrument may meet a certain specification through an in house adjustment procedure developed by the service provider, or by partially following the manufacturer's recommended procedures. However, by resorting to these 'cost saving' measures, other performance criteria could unwittingly be compromised and may go unnoticed; especially risky when 'partial' calibrations are performed. It is therefore quite possible to provide a certificate that does not necessarily guarantee the methods used are technically sound.
Calibrations reported on a certificate must be performed using methods and equipment which are closely scrutinised by technical experts. Choosing a calibration supplier is not necessarily straightforward. Unlike the car analogy, it is not an arbitrary decision. ISO9000 and ISO/IEC 17025 is certainly one of the prerequisites, as is SANAS accreditation. But beyond this there are still questions to be asked; these are offered for guidance:
* Who defines the testing? Is it less than that suggested by the manufacturer?
* Does the calibration certificate/results include a clear statement about the spec compliance of the item? And is attention drawn to out-of-tolerance measurements so that further action can be taken?
* Are calibration results unambiguously stated on the calibration certificate?
* Is equipment returned in a spec-compliant state, or do you have to specially request adjustment and re-test?
* Are documented procedures followed or do technicians invent 'suitable' testing as they go along, leading to inconsistency and inability to recreate queried results?
* Does the service provider keep current with the investments required to calibrate the latest generations of test equipment?
Whether potential suppliers are ISO9000 certified or SANAS accredited, it is still the case that equipment users seeking support contractors need to investigate the technical breadth (adequacy) of the calibrations provided.
Concilium Technologies, the only authorised service centre for Agilent T&M equipment in Africa, believes that formalised management systems and measurement accreditation gives an excellent foundation on which to develop the credible services demanded by today's quality-conscious market. They will, eventually, lead to the formulation of defined instrument testing criteria. Then users will at last have a level playing field on which to judge service providers, so easing selection.
The importance of thorough calibration
There is considerable debate as to whether the extent and quality of testing carried out during an instrument calibration makes a difference to the bottom-line of the company that owns the instrument. It is quite difficult to find case studies in which it can be conclusively shown that a less thorough testing routine has a direct impact on the quality of the products being tested.
The following examples, which are from Agilent Technologies, help to illustrate that inadequate testing during calibration can lead to erroneous decisions in the production test area. Coincidentally, they both took place in the same week, at the same Agilent Service Centre.
Case study 1: Company A is the leading manufacturer of electronic counter-measures equipment and other secure communications products. Its usual calibration provider is a large, low-cost third party maintainer (TPM).
Suspecting a problem with the marker counter readout accuracy, it sent a 8594E Portable Spectrum Analyser to the TPM advising of their suspicions. The equipment was returned having been 'fully calibrated' - no fault found (the instrument was reported to be entirely within specification). Still suspecting the problem they sent it back, and again it was calibrated and reported to be in-spec.
The Analyser was then sent to an Agilent Service Centre, with the same fault suspected. It was put into the calibration process and the error was clearly identified. It was corrected with appropriate adjustments to the log/lin amplifier and returned to the customer within specification. Obviously the TPM had not tested that part of the instrument - particularly unsatisfactory considering they were told of a suspected problem in that area. The customer is now confident that his instrument is giving trustworthy information... but now has doubts about the other equipment he has calibrated by the TPM.
Case study 2: Company B is a global electronics company serving aerospace, defence, and IT markets worldwide, and uses a major (different) TPM for calibration.
It sent a 11683A power-meter Range Calibrator to the TPM for routine calibration. The device was found to be outside spec on two ranges and a 'Conditional' calibration certificate was issued. The customer knew his equipment well and was in total disbelief that it was out-of-tolerance.
For a second opinion he sent it to an Agilent Service Centre. It was tested manually while cold and after being warmed-up. Both occasions showed the measured values to be in the middle of the specification on all ranges. The conclusion was that the TPM may have been using an intermittent cable or some other poor technique that produced erroneous test results on some ranges. The customer has his confidence restored in his Range Calibrator... but not in his TPM calibration provider.
Conclusions
The two situations were opposite: one instrument was faulty but reported to be good and the other was good but reported to be faulty. In both cases the customer could have incurred significant costs had he not chosen to ask an Agilent Service Centre for a second opinion.
Concilium Technologies has successfully passed stringent Agilent external audits and are proud to have earned the right to display the Agilent Authorised Service Provider logo; the only laboratory in Africa to be awarded this status. This ensures full access to all the calibration procedures developed by Agilent during the development cycle of their products. They are used world-wide to ensure consistency and a high quality standard. Maintaining this high standard requires continuous investment in the latest test equipment and continuous investment in automation to stay commercially competitive. This makes the calibration laboratory at Concilium Technologies one of the most comprehensive electronic test and measurement laboratory in the country.
| Tel: | +27 12 678 9200 |
| Email: | [email protected] |
| www: | www.concilium.co.za |
| Articles: | More information and articles about Concilium Technologies |
© Technews Publishing (Pty) Ltd | All Rights Reserved
printer friendly version