Fluke deaver msc01 free download

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PREDICTABILITY OF SOLID STATE ZENER REFERENCES David Deaver Fluke Corporation PO Box 9090 Everett, WA 98206 425-446-6434 [email protected] Abstract - With the advent of ISO/IEC 17025 and the growth in laboratory accreditation, more complete, detailed uncertainty analyses are required. This often points out the need for improved accuracy starting from the top of the traceability chain of a calibration laboratory. This paper describes a program that has been in place for several years to provide better uncertainties for solid state 10V zener references. This program is an on-site calibration service that can model a reference's drift performance resulting in a very predictable projected value. An evaluation of the accuracy of the predictions is presented as well as a description of the tools used to make the predictions. INTRODUCTION Prior to the development of the solid-state zener reference standard (DCVS), standard cells were used by most laboratories to maintain the volt. Pampered, they are quiet and have very predictable drift characteristics. However, they are poor travelers making it very difficult to send them for calibration or to use them to deliver accurate voltages to a production line or remote site. Zener references were conceived as a means to easily transfer dc voltage anywhere that it was needed. For manufacturers of precision calibrators, the need was to deliver 10V accurate to about 1-1.5 parts in 106. Soon, many laboratories wanted to be able to maintain their own zener references so calibration uncertainties were improved to about a part in 107. With multiple standards, some history and the use of regression models, 0.3 parts in 106 can be maintained with annual calibrations [1]. With further characterization and care, zener references can be used for intercomparisons between Josephson Arrays with transfer uncertainties of about a part in 108 [2]. Though zeners travel much better than standard cells, the demand for increasingly better uncertainties also increased the reluctance of some owners to allow them to do so. Many of them use an on-site calibration service that uses a well- characterized zener reference with demonstrated ability to travel well. A proficiency test is performed, then the calibration using a procedure from the calibration service provider. This process was accredited in 1995 by NVLAP and in 1998 by DKD, the German accreditation body. After calibration, users employ a number of methods to re-assign the value throughout the calibration interval. Some use the calibrated value throughout the interval and increase the uncertainty by the drift specification. This works well if the more accurate workload