Test & Measurement

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: Test & Measurement, Briefs

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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: Test & Measurement, 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: Test & Measurement, Briefs

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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: Test & Measurement, Measuring Instruments, Transportation, Application Briefs

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Researchers Measure Stress in 3D-Printed Metal Parts

Lawrence Livermore National Laboratory researchers have developed an efficient method to measure residual stress in metal parts produced by powder-bed fusion additive manufacturing (AM).The 3D-printing process produces metal parts layer by layer using a high-energy laser beam to fuse metal powder particles. When each layer is complete, the build platform moves downward by the thickness of one layer, and a new powder layer is spread on the previous layer.While the method produces quality parts and components, residual stress is a major problem during the fabrication process. Large temperature changes near the last melt spot, and the repetition of this process, result in localized expansion and contraction.An LLNL research team, led by engineer Amanda Wu, has developed an accurate residual stress measurement method that combines traditional stress-relieving methods (destructive analysis) with modern technology: digital image correlation (DIC). The process provides fast and accurate measurements of surface-level residual stresses in AM parts.The team used DIC to produce a set of quantified residual stress data for AM, exploring laser parameters. DIC is a cost-effective, image analysis method in which a dual camera setup is used to photograph an AM part once before it’s removed from the build plate for analysis and once after. The part is imaged, removed, and then re-imaged to measure the external residual stress.SourceAlso: Learn about Design and Analysis of Metal-to-Composite Nozzle Extension Joints.

Posted in: Cameras, Imaging, Photonics, Lasers & Laser Systems, Manufacturing & Prototyping, Rapid Prototyping & Tooling, Materials, Metals, Test & Measurement, Measuring Instruments, News

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NASA Computer Model Reveals Carbon Dioxide Levels

An ultra-high-resolution NASA computer model has given scientists a stunning new look at how carbon dioxide in the atmosphere travels around the globe.Plumes of carbon dioxide in the simulation swirl and shift as winds disperse the greenhouse gas away from its sources. The simulation also illustrates differences in carbon dioxide levels in the northern and southern hemispheres, and distinct swings in global carbon dioxide concentrations as the growth cycle of plants and trees changes with the seasons.Scientists have made ground-based measurements of carbon dioxide for decades and in July NASA launched the Orbiting Carbon Observatory-2 (OCO-2) satellite to make global, space-based carbon observations. But the simulation — the product of a new computer model that is among the highest-resolution ever created — is the first to show in such fine detail how carbon dioxide actually moves through the atmosphere.In addition to providing a striking visual description of the movements of an invisible gas like carbon dioxide, as it is blown by the winds, this kind of high-resolution simulation will help scientists better project future climate. Engineers can also use this model to test new satellite instrument concepts to gauge their usefulness. The model allows engineers to build and operate a “virtual” instrument inside a computer.SourceAlso: Learn about the NASA Data Acquisition System (NDAS).

Posted in: Electronics & Computers, Environmental Monitoring, Green Design & Manufacturing, Greenhouse Gases, Software, Test & Measurement, Measuring Instruments, Aerospace, News

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Ocean Gliders Measure Melting Polar Ice

The rapidly melting ice sheets on the coast of West Antarctica are a potentially major contributor to rising ocean levels worldwide. Although warm water near the coast is thought to be the main factor causing the ice to melt, the process by which this water ends up near the cold continent is not well understood. Using robotic ocean gliders, Caltech researchers have now found that swirling ocean eddies, similar to atmospheric storms, play an important role in transporting these warm waters to the Antarctic coast—a discovery that will help the scientific community determine how rapidly the ice is melting and, as a result, how quickly ocean levels will rise. "When you have a melting slab of ice, it can either melt from above because the atmosphere is getting warmer or it can melt from below because the ocean is warm," explains lead author Andrew Thompson, assistant professor of environmental science and engineering. "All of our evidence points to ocean warming as the most important factor affecting these ice shelves, so we wanted to understand the physics of how the heat gets there." Because the gliders are small—only about six feet long—and are very energy efficient, they can sample the ocean for much longer periods than large ships can. When the glider surfaces every few hours, it "calls" the researchers via a mobile phone–like device located on the tail. The communication allows the researchers to almost immediately access the information the glider has collected. Like airborne gliders, the bullet-shaped ocean gliders have no propeller; instead they use batteries to power a pump that changes the glider's buoyancy. When the pump pushes fluid into a compartment inside the glider, the glider becomes denser than seawater and less buoyant, thus causing it to sink. If the fluid is pumped instead into a bladder on the outside of the glider, the glider becomes less dense than seawater—and therefore more buoyant—ultimately rising to the surface. Like airborne gliders, wings convert this vertical lift into horizontal motion. Source Also: Learn about Remote Sensing of Ice Sheets and Snow.

Posted in: Batteries, Electronics & Computers, Environmental Monitoring, Green Design & Manufacturing, Motion Control, Test & Measurement, Measuring Instruments, Monitoring, Communications, Machinery & Automation, Robotics, News

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