Address:
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100 Bureau Drive, M/S 8171
Gaithersburg, MD, 20899-8171, United States
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Abstract:
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We report on multiple improvements made in the calibration services offered for thermal converters and thermal transfer standards in the AC-DC Difference Standards and Measurement Techniques Project at NIST during the past year. The major improvement in this calibration is the consolidation of three disparate calibration services - low voltage thermal transfer standards, low-frequency thermal converters, and RF-dc difference calibrations - into the AC-DC Project. This consolidation has the immediate benefit of offering NIST calibration customers one source for ac-dc calibrations from 2 mV to 1000 V and from 10 Hz to 1 GHz. In addition, bringing these calibration services together results in a marked improvement in efficiency, allowing us to lower the fees for thermal converter calibrations, and reduce the turnaround time for calibrations. Finally, the new combined calibration service will implement recent technical achievements in the AC-DC Project to reduce the uncertainties offered for thermal converter calibrations. These technical advances include the incorporation of multijunction thermal converters (MJTCs) as working standards from 2 V to 150 mV at frequencies from 10 Hz to 1 MHz (and possibly higher), and the introduction of an intrinsic ac source to provide a voltage reference at 50 mV and 100 mV. Both the introduction of MJTCs as working standards and the inclusion of the intrinsic ac standard will allow us to measure voltages below 1 V without the laborious range-to-range scaling process, and lead to reduced uncertainties at low voltages. In addition, the continuity between the previous low-frequency (up to 1 MHz) calibration service and the RF-dc service will likely lead to reduced uncertainties at frequencies above 100 kHz.
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