Agilent Measurement Journal - Issue 4 - 2008 - (Page 10)

Over time, an Agilent-internal software application was created to issue the document in a service center or onsite. This was followed by the development of Infoline, an online service that gives our customers access to the archived certiﬁcate, which is stored as a PDF ﬁle. More recently, Agilent has revisited the standardization of measurement reports, addressing the need to update those produced for older or discontinued products. In such cases, the original calibration software from the production period is still in use: our service organization can calibrate a total of 3,000 Agilent models. Customer feedback regarding this important document is constantly monitored using the Agilent Customer Satisfaction Survey: To date, over 5,000 customer responses have been recorded and the average rating is 9.1 on a scale of 10. of two metrics, the Test Accuracy Ratio (TAR) and its successor, the Test Uncertainty Ratio (TUR). These are also called the guardband management process and producer-consumer risk. The graph in Figure 1 shows ﬁve possible outcomes for a measurement, with the arrows showing the uncertainty around the speciﬁcations. Case 1 clearly corresponds to an acceptance situation while Case 5 would be a rejection. Cases 2 and 3 introduce a risk to the consumer (accepting an instrument out of speciﬁcation) and Case 4 presents a risk for the producer (rejecting an instrument within tolerances). During the design of ISO 17025, the relationship between acceptance criteria and uncertainty resulted in multiple versions of the draft standard, ranging from the most stringent (“measurement value extended by uncertainty shall fall within the appropriate speciﬁcation limit”) to a more practical approach (“a statement of compliance should be made only if the ratio of the uncertainty of measurement to the speciﬁed tolerance is reasonably small, e.g., 1:3”) or to the acceptance of an indeterminate status (neither compliance nor noncompliance can be proved). Ultimately, the standard incorporated a realistic conclusion: The uncertainty must be taken into account. Because ISO 17025 is mainly applied to testing, the expectation was to ﬁnd the acceptance criteria explained within the technical standard itself. In the dimensional area, where acceptance criteria determine the acceptance or rejection of a batch of parts without any possible adjustment, the situation is quite critical. This drove the creation of ISO-14253-1, the only standard covering this topic. For calibration, some accreditation bodies have proposed the use of this standard as the default choice if there is no other agreement with a customer. ANSI/NCSL Z540.3 was the ﬁrst standard to introduce a formal maximum allowance for consumer risk. However, the stated two-percent maximum risk is for a population of parameters or instruments, not for a single measurement. Apart from purely textual content analysis and purely theoretical approaches, there is a new trend in quality and metrology in dealing with the tradeoff between risk and cost. Referring back to Figure 1, the expectation behind acceptance criteria is that Cases 2, 3 and 4 could be moved to Case 1 by a simple adjustment. Figure 2 assumes that a calibration alone will Assessing acceptance criteria The objective of calibration is to validate the previous usage of the instrument and to provide proof of ﬁtness for use until the next calibration cycle. This is documented with a statement of conformity on the calibration certiﬁcate. When a conformity statement is required, the presence of uncertainty adds a new element to the decision-making process. This issue came to light with the adoption of Military Standard (MIL-STD) 45662A and has resulted in the deﬁnition Standard requirements Acceptance level Tolerances Case 1: In specification X X Case 2: In specification with a risk to the consumer of accepting an out-of-tolerance instrument Case 3: Grey area of shared risk X X X X Case 4: Out of specification with risk to the producer of rejecting an in-specification instrument Case 5: Out of specification X X X X Figure 1. Each of these ﬁve possible measurement outcomes has consequences for either the customer or the manufacturer. 10 Agilent Measurement Journal

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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