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.

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Analog Signal Conditioning for Accurate Measurements

By Jon Titus Q: Should I put some sort of circuit between my sensor and an analog-to-digital converter? A:Yes. You probably need some signal conditioning. The explanation below goes on for a bit, but stay with it and you'll understand what you need and why you need it. Before you make any connections, get the electrical specifications for the analog-to-digital converter (ADC) and for the sensor or sensors in your system. Let's assume the data-acquisition module uses a Maxim Integrated Products MAX197 12-bit ADC. This device can accept eight differential (2-wire) inputs or 16 single-ended (1-wire) inputs. Maxim's specifications show an input impedance of 21 kohms for single-ended inputs and 16 kohms for differential inputs.

Posted in: Test & Measurement, White Papers

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High Precision Multi-channel PXIe Systems Realize More Efficient Wind Tunnel Testing

Wind tunnel testing is widely used in large-scale aerodynamic design projects. Even so, the requirement for large numbers of sensors over large areas of the devices to be tested presents major challenges in data acquisition and retrieval. The article discusses use of multi-channel PXIe systems to achieve fully synchronous, high-efficiency, highly precise measurement solutions. Attributes include: PXIe technology providing effective single-system integration with multiple combinations of a wide variety of sensors PXIe platforms’ PC-based structure delivering easily deployed superior computing power along with networking capability, minimizing development time and simplifying setup

Posted in: Test & Measurement, White Papers

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How to Maximize Temperature Measurement Accuracy

Thermocouples are the most versatile and widely used devices for temperature measurements. Most test engineers are aware of the measurement errors caused by thermocouples but not always about the errors caused by the measurement system itself. This technical note will focus on the lesser known and important aspect called "Self-Calibration" and how it can be used to overcome errors in temperature measurement.

Posted in: Test & Measurement, White Papers

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Building a Test System for High-Speed Data Streaming Applications

High-speed data streaming applications typically require maximum accuracy and long sampling times, including such applications as spectral monitoring, signal intelligence, LIDAR testing, optical fiber testing, radar and satellite signal acquisition, and software defined radio systems. These present unique engineering challenges requiring high throughput, and identifying design flaws and problems can contribute to reduced development costs and time to market, avoiding field recalls and costly system redesigns. The white paper discusses techniques for optimizing configuration of systems supporting high-bandwidth applications, by: Enabling high-speed real-time data streaming Designing applications optimizing system streaming performance Furnishing benchmarks that can be achieved in stream-to-disk and stream-to-memory applications

Posted in: Test & Measurement, White Papers

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