Test & Measurement

Differential Nonlinearity in Analog Measurements

By: Jon Titus, Sealevel Systems, Inc. Q: In a previous answer you noted, "... most applications require linearity but not absolute precision..." What does that mean?

Posted in: Briefs, White Papers

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A Portable, Projection Focusing Schlieren System

Heating, ventilation, and air conditioning systems can be monitored using this system, especially those used in commercial kitchens and industrial ventilation. John H. Glenn Research Center, Cleveland, Ohio A new type of projection schlieren camera system (schlierenscope) is more portable, easier to align, and more versatile than existing systems. The schlierenscope is a projection focusing schlieren camera system that can acquire images of shock waves, vortices, gas jets, and other disturbances that create gradients in the refractive index of a transparent medium. These gradients appear as streaks (called schlieren in German) in the resulting image. Thus, a schlierenscope is an apparatus for looking at disturbances in transparent media. The schlierenscope constructed in the project utilizes fast strobes that freeze motion and capture images with a scientific CCD (charge-coupled device) camera. The schlierenscope is unique among schlieren instruments because all of the critical controls are contained within the instrument housing.

Posted in: Briefs, TSP

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Cryogenic and Non-Cryogenic Optical Liquid Level Instrument for Stratified Conditions

Marshall Space Flight Center, Alabama Typical cryogenic tank metering systems use a series of thermocouple, RTD, or other temperature or resistive devices in a rake or array configurations. Since these operate using the thermal change between the liquid and gas fluid phases, they are limited by thermal latency (the time it takes the sensing element to respond to the temperature). In addition, cryogenic fluids often create a volatile boundary or sloshing layer. This layer causes uncertainties of the true fluid boundary in a tank. Finally, accuracy and resolution are determined by the number of sensing segments used. These are typically tied to individual data channels, which puts a strain on data acquisition systems to achieve continuous and high-accuracy values.

Posted in: Briefs

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Low-Pressure Ion Chromatography for Planetary Exploration

NASA’s Jet Propulsion Laboratory, Pasadena, California Ion chromatography is the state-of-the-art technique for anion separation and analysis on Earth, but it typically requires a large, powerful pump to operate at high pressures in order to speed up analysis time. The weight and power requirements of the pump interfere with creating an ideal instrument for flight. The solution is to run the ion chromatography system at low pressure to allow the use of a smaller, lower-power pump for flight, but at the expense of longer analysis time.

Posted in: Briefs

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Imaging Technique Could Detect Acoustically “Invisible” Cracks

It has long been understood that acoustic nonlinearity is sensitive to many physical properties including material microstructure and mechanical damage. The lack of effective imaging has, however, held back the use of this important method. Currently, engineers are able to produce images of the interior of components using ultrasound, but can only detect large problems such as cracks.

Posted in: News

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Webb Telescope’s Heart Survives Deep-Freeze Test

After 116 days of being subjected to extremely frigid temperatures like those in space, the heart of the James Webb Space Telescope, the Integrated Science Instrument Module (ISIM) and its sensitive instruments, emerged unscathed from the thermal vacuum chamber at NASA’s Goddard Space Flight Center.

Posted in: News, Measuring Instruments, Monitoring

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Reverse Engineering Helps NASA Analyze Icing Conditions

ROMER Absolute Arm with integrated laser scanner Hexagon Metrology North Kingstown, RI 800-274-9433 www.hexagonmetrology.us While air travel is considered the safest form of transportation, research continues to better understand ice buildup and its affects on aerodynamics. At NASA’S Glenn Research Center in Cleveland, OH, engineers in the Icing Branch have been studying the mechanics of ice buildup since the 1940s.

Posted in: Application Briefs, Measuring Instruments

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