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Session:
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2B - Resistance Metrology
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Date & Time:
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Monday August 7, 2:30 PM - 4:00 PM
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Paper Title:
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Temperature and Pressure Coefficients of Thomas 1 Ohm Resistors
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Speaker:
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George Jones, Physicist
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CoAuthors:
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George R. Jones, Randolph E. Elmquist
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Speaker Info
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Company:
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National Institute of Standards and Technology
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Department:
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Quantum Electrical Metrology Division
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Address:
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100 Bureau Drive
, Mail Stop 817-01 Gaithersburg, MD, 20899, United States
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Phone:
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301-975-4225
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Fax:
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301-975-2115
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Email:
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george.jones@nist.gov
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Abstract:
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In preparing to move the precision 1 ohm measurement service to the new Advanced Measurement Laboratory (AML) in the spring of 2004, NIST first assembled a second precision 1 ohm measurement system in the AML using a new type of precision 1 ohm ?resistors as the working standards. This allowed for the NIST calibration service to continue uninterrupted during the transition. This year, in 2006, NIST is providing traveling standards for an international comparison in which two well characterized precision Thomas 1 ohm resistors will be sent to various national laboratories in the western hemisphere. For the best possible inter-comparison both the thermal and the pressure characteristics of these resistors need to be determined so that any effects of temperature or pressure variations on the test resistors can be corrected. Over the past year additional components have been added to these two systems which enable NIST to measure the temperature and pressure coefficients of precision 1 ohm ?resistors. These modifications include an auxiliary thermal oil bath. In addition, a pressure chamber has been constructed in which three precision resistors can be placed. The chamber is partially filled with oil and is then submerged in an oil bath whose temperature is maintained at 25 °C. The internal pressure of the chamber is measured and can be increased or decreased using the vacuum and pressure lines of the AML. Over ten resistors have gone through a battery of thermal and pressure tests at temperatures from 20 to 26 °C and at pressures from 80 to 110 kPa. The two Thomas 1 ohm ?resistors with the best performance have been chosen to participate in the international comparison. The determination of the thermal and pressure coefficients of precision 1 ohm resistors has been offered in the past by NIST as a special test. However, the new capabilities of the systems will increase the accuracy of these measurements. Further, since all the necessary components are permanently in place and new control software has been written to include the temperature and pressure tests, these measurements now can be performed at any time without prior arrangements.
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