Agilent Measurement Journal - Issue 4 - 2008 - (Page 11)

satisfy 90 percent of the cases while the other 10 percent will require an adjustment and a second full calibration. The function can be written as P = (1 – x) x Tc + x(Ta + Tc) where P is the price of calibration, x the percentage of equipment initially found in tolerance, Tc the time to calibrate and Ta the time to adjust. Any instrument function with only one point occurring in the grey zone of Cases 2 or 3 will result in an additional adjustment and calibration process. For complex instruments having hundreds of calibration points, this situation has a high probability of occurring up to the point at which the calibration price will more than double. This is why some service providers now invoice for adjustment fees separately. practice, instruments do not stay in a dedicated conﬁguration. Instead, the trend within many industries is toward placing equipment in a shared pool, which can translate into limited knowledge of previous usage. As a result, the manufacturer’s speciﬁcations become the reference. When talking with our customers, we sometimes face questions such as, “How does an accredited calibration that covers 30 percent of the instrument speciﬁcation compare to a commercial calibration covering 100 percent of the parameters?” To address such questions, standards bodies have tried to deﬁne ethical limits such as the minimum number of points to declare a unit in speciﬁcation per family of instrument. Much work remains, however, because this approach must account for over 60,000 instruments on the market classiﬁed in 200 families. This process was expected to publish its ﬁrst technical recommendation — AFNOR FD X 07-25 — in late 2007. Considering technical calibration schedules Another issue associated with the conformity statement relates to the number of points and functions controlled during the calibration. This helps determine how representative the calibration is compared to the overall instrument speciﬁcations. For Agilent instruments, the recommended calibration schedule is included in the product service manual or other similar documents. A “full calibration according to manufacturer speciﬁcations” is the rule for our service operations. Among independent calibration providers, however, the trend is toward reducing the price of calibration services — and this is often accomplished by skipping several measurement points and functions. This may be due to technical infeasibility (e.g., the lack of essential reference equipment) or insufﬁcient accreditation to cover all test parameters. In theory, the end user should know exactly which measurements are performed with the equipment and the technical calibration schedule should cover those traceability points. In Conclusion The panorama of region- and industry-speciﬁc quality and metrology standards is showing signs of convergence, making it possible to address the global market with consistent, transportable certiﬁcation, accreditation and services. In the quality domain, it is possible for multinational companies to achieve global ISO 9000 certiﬁcation, allowing better alignment of internal processes, sharing of best practices, and creation of consistent sets of deliverables for customers worldwide. Greater consistency should ultimately provide greater — and universal — conﬁdence in the precision and accuracy of calibrated test equipment. This will happen only when all service providers adhere to a clear, consistent set of standards — and can achieve and maintain the relevant quality and metrology accreditations and certiﬁcations. Cost of optimization Fast-track normal calibration In Fast-track full calibration Calibration Exception group adjustment Shipment Deliverables: • One calibration report • 10% of cases, two calibration reports plus adjustments Fast-track calibration with optimization In Fast-track full calibration Calibration Exception group adjustment Shipment Deliverables: • Two calibration reports plus adjustments 10% 100% Figure 2. It may be possible to move an instance of Case 2 or 3 into Case 1 with a calibration alone (left) or an adjustment and an additional full calibration (right). Agilent Measurement Journal 11

Table of Contents Feed for the Digital Edition of Agilent Measurement Journal - Issue 4 - 2008

Agilent Measurement Journal - Issue 4 - 2008 Delivering Confidence through Compliance with Standards Contents Emerging Innovations Trying Early Device Implementations at the IEEE 1588 PlugFest Achieving Greater Confidence in Measurement Accuracy through Consistency in Calibration Services Overcoming the Challenges of RFID Component Testing 3GPP LTE: Introducing Single- Carrier FDMA Ensuring Reliable Operation and Performance in Converged IP Networks Testing Storage Area Networks and Devices at 8.5-Gb/s Fibre Channel Rates Choosing an Appropriate Calibration Method for Vector Network Analysis Making Traceable EVM Measurements with Digital Oscilloscopes Exploring Terahertz Measurement, Imaging and Spectroscopy: The Electromagnetic Spectrum’s Final Frontier Interpreting Quoted Specifications when Selecting Digitizers

Agilent Measurement Journal - Issue 4 - 2008

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