 |
 |
 |
 |
The "Dr. Allen V. Astin" AwardAC-DC Voltage Transfer Standards with Thin-Film Multi-junction Thermal Converters and Planar ResistorsDr. Hector LaizINTI, Argentina This paper discusses recent results of ac-dc voltage standards with thin-film multijunction thermal converters (PJMTC) and planar serial resistors for the frequency range from 10 Hz up to 1 MHz and for the voltage range from 100 mV to 1000 V. The standard PTB/IPHT PJMTC is well established and fabricated on a silicon chip with a thin dielectric membrane on an anisotropically etched window in the silicon. A thin-film bifilar heater and up to 100 thermocouples are sputtered on a Si3N4/SiO2/Si3N4 sandwich membrane. A small obelisk of silicon is left underneath the heater during the etching process to increase the thermal time-constant. |
 |
Applied CategoryBias, Uncertainty and Transferability in Standard Methods of Pipette CalibrationDr. George RodriguesARTEL Inc. This paper presented experimental work to quantify the error contribution from some of the significant sources identified in part one. Regarding the uncertainty of the measurement method, the uncertainty introduced by the various methods of controlling, measuring and compensating for the effect of evaporation are evaluated. Data are presented to quantify the uncertainty in estimates of the evaporation rate, and the bias incurred as a result of neglecting evaporation (permitted by the ISO standard in some situations). The method used here to assess the bias due to imperfect evaporative compensation might also prove useful for those wishing to validate other gravimetric volume measurement methods. |
|
Invited CategoryAC-DC Voltage Transfer Standards with Thin-Film Multi-junction Thermal Converters and Planar ResistorsDr. Hector LaizINTI, Argentina This paper discusses recent results of ac-dc voltage standards with thin-film multijunction thermal converters (PJMTC) and planar serial resistors for the frequency range from 10 Hz up to 1 MHz and for the voltage range from 100 mV to 1000 V. The standard PTB/IPHT PJMTC is well established and fabricated on a silicon chip with a thin dielectric membrane on an anisotropically etched window in the silicon. A thin-film bifilar heater and up to 100 thermocouples are sputtered on a Si3N4/SiO2/Si3N4 sandwich membrane. A small obelisk of silicon is left underneath the heater during the etching process to increase the thermal time-constant. |
 |
Technical CategoryDetermining Consensus Values in Interlaboratory Comparisons and Proficiency TestingHenrik S. NielsenHN Metrology Consulting Inc. Presented an important part of interlaboratory comparisons and proficiency testing is the determination of the reference value of the measurand and the associated uncertainty. It is desirable to have reference values with low uncertainty, but it is crucial that these values are reliable, i.e. they are correct within their stated uncertainty. In some cases it is possible to obtain reference values from laboratories that reliably can produce values with significantly lower uncertainty than the proficiency testing participants, but in many cases this is not possible for economical or practical reasons. In these cases a consensus value can be used as the best estimate of the measurand. A consensus value has the advantage that it often has a lower uncertainty than the value reported by the reference laboratory. There are well known and statistically sound methods available for combining results with different uncertainties, but these methods assume that the stated uncertainty of the results is correct, which is not a given. In fact, the very purpose of proficiency testing is to establish whether the participants can measure within their claimed uncertainty. The paper explores a number of methods for determining preliminary consensus values used to determine which participant values should be deemed reliable and therefore included in the calculation of the final consensus value and its uncertainty. Some values are based on impressive equations and others have curious names. The relative merits of these methods in various scenarios are discussed. |
 |
Quality & Management CategoryAnatomy of an International Peer EvaluationRoxanne RobinsonA2LA This paper presented the International Laboratory Accreditation Cooperation (ILAC) was established in 1978 and has since emerged as the foremost authority on laboratory accreditation issues. ILAC members include laboratory accreditation bodies throughout the world and other interested stakeholders from governments, private organizations, and laboratories. ILAC focuses on the development of harmonized procedures for laboratory accreditation activities and works to bring to the attention of the international community the importance of laboratory accreditation as a tool to facilitate trade, and in particular the acceptance of data from accredited laboratories to reduce or eliminate re-testing and re-calibration. ILAC's greatest achievement in recent history was the October 2000 signing of the first international mutual recognition arrangement (MRA) in laboratory accreditation. Forty-four accreditation bodies throughout the world signed this arrangement and by doing so, agreed to formally recognize and promote the equivalency of the test and calibration reports issued by laboratories accredited by the other signatories. This created the first comprehensive global network of accredited laboratories. Prior to then, two regional networks existed through the European Cooperation for Laboratory Accreditation (EA) MRA and the Asia Pacific Laboratory Accreditation Cooperation (APLAC) MRA. The magnitude of the commitment signatories make is remarkable. By signing the MRA, each signatory is in effect agreeing that organizations that could be potential competitors in the laboratory accreditation market (other signatories) are doing their job at least as good as the signatory accreditation body is doing it. How can these organizations have such confidence in the other signatory accreditation bodies? The answer lies in the peer evaluation process that accreditation bodies are subjected to in order to become eligible for signatory status. The process includes a rigorous weeklong evaluation of the accreditation body's operations, its laboratories, and its assessors by a team of international accreditation experts and a critical review of the evaluation results by established committees before a decision can be rendered. This paper will explore the peer evaluation process as recently experienced by the American Association for Laboratory Accreditation during its March 2002 multi-regional international peer re-evaluation for renewal as a signatory to the MRAs for ILAC, EA, APLAC, and a new regional cooperation, the Inter-American Accreditation Cooperation (IAAC). |
|
NCSL International © 1996-2008 All Content. July 05, 2008 01:30 PM |