Test & Measurement

Rapidly Expanding Array of Test Applications Continues to Drive Source Measurement Unit Instrument Technology

Since their introduction more than two decades ago, source measurement units (SMUs) have evolved into a category of multi-purpose instruments that are regularly called upon to address a rapidly expanding array of electronics industry applications:Semiconductor device fabrication, process development, and product research/design Production verification of electronic products such as portable wireless devices Production and development of new advanced materials for devices such as solar cells and HBLEDs Almost any electronic device test application

Posted in: Test & Measurement, White Papers

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A Mass-Spectrometer System for Detecting Gas Leaks

This versatile, expandable system can be controlled from a safe remote location. The Hydrogen Umbilical Mass Spectrometer (HUMS) consists of an integrated sample delivery system, a commercial mass-spectrometer- based gas analyzer, and a set of calibration gas mixtures traceable to NIST (National Institute for Standards and Technology). The system, except for the calibration gas mixtures and the remote operator display, fits into a standard 24-in. wide, 6-ft high, 36-in. deep (0.61 by 1.83 by 0.91 m, respectively) equipment rack and is powered by 120-Vac, 30-A, 60-Hz source. It was designed to perform leak detection and measurement of cryogenic propellants (oxygen and hydrogen) from a remote location during shuttle-launch countdown. It is used specifically to sample the background gas surrounding the 17-in. (0.43-m) Orbiter-ET disconnect, looking for leakage of gaseous hydrogen. The capability to monitor shuttle purge gases and cryogenic hydrogen fill and drain line T-0 disconnect helium purge gas is incorporated into the shuttle installation on each Mobile Launch Platform (MLP).

Posted in: Test & Measurement, Briefs

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Measuring Contact Angles of a Sessile Drop and Imaging Convection Within It

Ordinary and laser-shadowgraph images yield valuable information. Figure 1 depicts an apparatus that simultaneously and synchronously records magnified ordinary top-view video images and laser-shadowgraph video images of a sessile drop. The real-time values of contact angle and rate of evaporation of the drop as functions of time can be calculated from the apparent diameters of the drop in the sequences of the images. In addition, the shadowgraphs contain flow patterns indicative of thermocapillary convection (if any) within the drop. These time-dependent parameters and flow patterns are important for understanding the physical processes involved in the spreading of evaporating liquids in such diverse technological applications as coating (including painting), film cooling, processing of materials, lubrication, and boiling. Study of the spreading of drops can also contribute to understanding of the spreading of biological cells.

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Simulating the Structural Behavior of Laminated Glass

This report investigates the strength of archi- tectural laminated glass and the viability of its use for window glass in commercial buildings. Some researchers recommend that the structural behavior of laminated glass (typically consisting of two glass layers and a plasticized PVB [polyvinyl butyral] interlayer) is equivalent to the structural behavior of monolithic glass (one solid piece of glass) for most common applications. However, if this monolithic equivalency assumption is not valid, its implementation would result in the unconservative design and use of laminated glass, which could lead to failure of the glass at the design load. Using ALGOR Mechanical Event Simulation (MES) software, laminated and monolithic glass plates were modeled and analyzed to compare their response to a wind load. Stress results for the two plates were very different due to shear deformations experienced by the interlayer of the laminated plate. This research may help to ensure the safe use of laminated window glass.

Posted in: Test & Measurement, Briefs

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Pressure-Application Device for Testing Pressure Sensors

This device generates a pulse of known pressure. A portable pressure-application device has been designed and built for use in testing and calibrating piezoelectric pressure transducers in the field. The device generates pressure pulses of known amplitude. A pressure pulse (in contra- distinction to a steady pressure) is needed because in the presence of a steady pressure, the electrical output of a piezoelectric pressure transducer decays rapidly with time.

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Small Low-Temperature Thermometer With Nanokelvin Resolution

The magnetic field is generated by permanent magnets instead of a solenoid. An improved high-resolution thermometer (HRT) for use in scientific experiments at temperatures

Posted in: Test & Measurement, Briefs

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Optical Measurement of Temperatures in Muscles and Tendons

Small, electrically and chemically neutral sensors would be implanted surgically. Miniature fiber-optic-coupled sensors based on optically excited, self-resonant microbeams have been proposed for measuring temperatures within muscle fascicles and tendons. The proposed sensors could be used in medical and biological research on humans and other animals. The proposed sensors would be variants of those described in several previous articles in NASA Tech Briefs: "Proximity Measurement of Pressure and Temperature" (NPO-20223), Vol. 22, No. 1 (January 1998), page 48; and "Measurement of Stresses and Strains in Muscles and Tendons" elsewhere in this issue.

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