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Karen Brown (Acting NIST Director, 2000-2001) receives framed copy of Congressional Record at NIST 2001 Centennial History and Reunion Day
No full textNIST held a number of events to mark its centennial celebration in March 2001. The NIST History and Centennial Symposium-Reunion Day for NIST staff and alumni was held on March 5 AT NIST Boulder and NIST Gaithersburg, pictured here. This image is part of the NIST 2001 Centennial collection. The NIST 2001 Centennial collection consists of images of various celebrations of the 100th anniversary of the National Institute of Standards and Technology (NIST), previously known as the National Bureau of Standards
Karen Brown with time capsule at the grand opening of the Lobby and Information Center during the NIST 2001 Centennial
No full textNIST celebrated the grand opening of its Lobby and Information Center during its March 2001 Centennial Celebration. Attendees at the opening included Acting NIST Director Karen Brown, NIST staff, alumni, and guests. This image is part of the NIST 2001 Centennial collection. The NIST 2001 Centennial collection includes images of various celebrations of the 100th anniversary of the National Institute of Standards and Technology (NIST), previously known as the National Bureau of Standards
Karen Brown (Acting NIST Director, 2000-2001) with framed copy of Congressional Record at NIST 2001 Centennial History and Reunion Day
No full textNIST held a number of events to mark its centennial celebration in March 2001. The NIST History and Centennial Symposium-Reunion Day for NIST staff and alumni was held on March 5 AT NIST Boulder and NIST Gaithersburg, pictured here. This image is part of the NIST 2001 Centennial collection. The NIST 2001 Centennial collection consists of images of various celebrations of the 100th anniversary of the National Institute of Standards and Technology (NIST), previously known as the National Bureau of Standards
Gail Porter in crowd at the grand opening of the Lobby and Information Center during the NIST 2001 Centennial
No full textNIST celebrated the grand opening of its Lobby and Information Center during its March 2001 Centennial Celebration. Attendees at the opening included Acting NIST Director Karen Brown, NIST staff, alumni, and guests. This image is part of the NIST 2001 Centennial collection. The NIST 2001 Centennial collection includes images of various celebrations of the 100th anniversary of the National Institute of Standards and Technology (NIST), previously known as the National Bureau of Standards
Karen Brown and Gail Porter at ribbon cutting of the Lobby and Information Center during the NIST 2001 Centennial
No full textNIST celebrated the grand opening of its Lobby and Information Center during its March 2001 Centennial Celebration. Attendees at the opening included Acting NIST Director Karen Brown, NIST staff, alumni, and guests. This image is part of the NIST 2001 Centennial collection. The NIST 2001 Centennial collection includes images of various celebrations of the 100th anniversary of the National Institute of Standards and Technology (NIST), previously known as the National Bureau of Standards
Karen Brown (Acting NIST Director) and unidentified man at NIST 2001 Centennial History and Reunion Day
No full textNIST held a number of events to mark its centennial celebration in March 2001. The NIST History and Centennial Symposium-Reunion Day for NIST staff and alumni was held on March 5 AT NIST Boulder and NIST Gaithersburg, pictured here. This image is part of the NIST 2001 Centennial collection. The NIST 2001 Centennial collection consists of images of various celebrations of the 100th anniversary of the National Institute of Standards and Technology (NIST), previously known as the National Bureau of Standards
Karen Brown and Gail Porter at ribbon cutting of the Lobby and Information Center during the NIST 2001 Centennial
No full textNIST celebrated the grand opening of its Lobby and Information Center during its March 2001 Centennial Celebration. Attendees at the opening included Acting NIST Director Karen Brown, NIST staff, alumni, and guests. This image is part of the NIST 2001 Centennial collection. The NIST 2001 Centennial collection includes images of various celebrations of the 100th anniversary of the National Institute of Standards and Technology (NIST), previously known as the National Bureau of Standards
Photocurrent measurement of PC and PV HgCdTe detectors
No full textNovel preamplifiers for working standard photoconductive (PC) and photovoltaic (PV) HgCdTe detectors have been developed to maintain the spectral responsivity scale of the National Institute of Standards and Technology (NIST) in the wavelength range of 5 micrometers to 20 micrometers. The linear PC mode preamplifier does not need any compensating source to zero the effect of the detector bias current for the preamplifier output. The impedance multiplication concept with a positive feedback buffer amplifier was analyzed and utilized in a bootstrap PV transimpedance amplifier to measure photocurrent of a 200 Ohm shunt resistance photodiode with a maximum signal gain of 10(8) V/A. In spite of the high performance lock-in used as a second-stage signal-amplifier, the signal-to-noise ratio had to be optimized for output of the photocurrent preamplifiers. Noise and drift were equalized for the output of the PV mode preamplifier. The signal gain errors were calculated to determine the signal frequency range where photocurrent-to-voltage conversion can be performed with very low uncertainties. For the design of both PC and PV detector preamplifiers, the most important gain equations are described. Measurement results on signal ranges and noise performance are discussed
Hysteresis and related error mechanisms in the NIST watt balance experiment
No full textThe NIST watt balance experiment is being completely rebuilt after its 1998 determination of the Planck constant. That measurement yielded a result with an approximately 1 x 10(-7) relative standard uncertainty. Because the goal of the new incarnation of the experiment is a ten-fold decrease in uncertainty, it has been necessary to reexamine many sources of systematic error. Hysteresis effects account for a substantial portion of the projected uncertainty budget. They arise from mechanical, magnetic, and thermal sources. The new experiment incorporates several improvements in the apparatus to address these issues, including stiffer components for transferring the mass standard on and off the balance, better servo control of the balance, better pivot materials, and the incorporation of erasing techniques into the mass transfer servo system. We have carried out a series of tests of hysteresis sources on a separate system, and apply their results to the watt apparatus. The studies presented here suggest that our improvements can be expected to reduce hysteresis signals by at least a factor of 10-perhaps as much as a factor of 50-over the 1998 experiment
