June E. Sims

Complete characterization of Zener standards at 10 V for measurement assurance program (MAP)

A complete characterization of Zener standards for temperature, pressure, and humidity is being performed to improve the uncertainty of a MAP that uses 10 V Zeners as travelling standards. The procedure and equipment used for this work are briefly described. We will report results of evaluating our available pool of Zener standards.

Characterization of RF–DC Transfer Difference for Thermal Voltage Converters With Built-in Tees in the Frequency Range 1 MHz to 1 GHz

We describe the construction of thermal voltage converters (TVCs) with built-in tees and the characterization of their RF-dc differences in terms of power and impedance using thermistor mounts at frequencies greater than 100 MHz and in terms of conventional TVCs at lower frequencies. We also present a description of the measurement system and an uncertainty analysis

New Technologies to Improve AC-DC Difference Measurements at NIST

Abstract: Determination of ac-dc difference of thermal voltage converters has traditionally been done by range-to-range scaling techniques, beginning at the voltage level and optimal frequencies of the primary standards, and continuing until the parameter space has been completed. Range-to-range scaling propagates uncertainties of the measurement process at each step, so that the uncertainties become larger at values away from the primary standards, with the magnitude determined largely from the number of scaling steps. At the National Institute of Standards and Technology (NIST), we have recently fabricated multijunction thermal converters with exceptional properties over a large range of voltages and frequencies. Coupled with the use of an ac voltage standard based on quantum effects, we have reevaluated the NIST uncertainty matrix for ac-dc voltage transfer difference, and have made significant reductions in the uncertainties at all voltage and frequency levels.

Advanced Sensors for Accurate, Broadband AC Voltage Metrology

We report on advances in ac voltage metrology made possible by a new generation of Multijunction Thermal Converters (MJTCs). Although intended for use primarily in high-frequency (1 MHz to 100 MHz) metrology, their exceptional low-frequency qualities, combined with a large dynamic range, makes these MJTCs excellent devices for the frequency range 10 Hz to 100 MHz at voltages from 1 V to 20 V, depending on the design. We anticipate that these devices will form the future basis for ac voltage metrology at the National Institute of Standards and Technology (NIST).

Advanced thermal sensors for precision AC voltage metrology

We describe a new generation of thermal sensors for the measurement of ac voltages at frequencies up to 100 MHz. Electronics grade fused silica has been selected as a substrate material because it is significantly more robust than the previous generation of crystalline quartz, yet retains excellent dielectric properties. We report the design and fabrication of the new sensors, including the method of forming thin membranes, and present results for two sensor designs. Our latest devices show a reduction in the RF-DC of more than an order of magnitude over traditional high-frequency thermal sensors. We anticipate that the new sensors will enable significant reductions in the uncertainties in the NIST calibration service for RF-DC thermal converters.

10 V programmable Josephson voltage standard and its application in direct comparison with conventional Josephson voltage standard

This paper briefly describes the working principle of the 10 V programmable Josephson voltage standard (PJVS) that was developed at the National Institute of Standards and Technology (NIST) and how to use it in a direct comparison with a conventional Josephson voltage standard (JVS). Manual and automatic comparison methods were investigated to verify the agreement between the two types of Josephson standards. The 10 V PJVS will be used as a transfer standard in the 2014 JVS Interlaboratory Comparison (ILC) that is organized by the National Conference of Standard Laboratories International (NCSLI).

Advanced Thermal Sensors for Broadband AC Voltage Metrology

Abstract: We report on the development and application of a new generation of multijunction thermal converters (MJTCs). These devices, fabricated on fused silica substrates, show exceptional performance over the frequency range from 10 Hz to 100 MHz over input voltages ranging from 1 V to 30 V, depending on design. We anticipate that these devices will form the future basis for ac voltage metrology at the National Institute of Standards and Technology (NIST).

Comparison of two Josephson array voltage standard systems using a set of Zener references

It is possible to compare Josephson-array voltage systems to parts in 10/sup 9/ via multi-Zener reference interchanges and ultra-low thermal-emf switching. These techniques were used to achieve a Type A uncertainty of 6 nV/V (k=2) at the 1.018 V level, and to establish that the agreement between the two systems fell within the estimated 4 nV/V Type B relative uncertainty (k=2). The method is useful in checking system operation under normal measurement configurations and programmed control. Data also indicated that thermal-emfs greater than 25 nV have fluctuations that are not perfectly cancelled by either of the two differing measurement algorithms.

IMPROVEMENTS IN THE NIST CALIBRATION SERVICE FOR THERMAL TRANSFER STANDARDS

Abstract: We report on multiple improvements made during the past year in the calibration services offered for thermal converters and thermal transfer standards in the AC-DC Difference Standards and Measurement Techniques Project at the National Institute of Standards and Technology (NIST). The major improvement in this calibration is the increased efficiency made possible by the consolidation of three disparate calibration services – low voltage thermal transfer standards, low-frequency thermal converters, and RF-DC difference calibrations – into a single service. This consolidation immediately benefits NIST calibration customers by offering one source for AC-DC calibrations from 2 mV to 1000 V and from 10 Hz to 1 GHz. Additional benefits include lower calibration prices and reduced uncertainties at many points.