Free-falling portable data acquisition

By Lou Kelm KineticSystems

NASA’s Zero-G Research Facility (Zero-G) is the largest microgravity-testing environment in the United States. Payloads fall in simulated weightlessness, and critical test data is captured using a portable data recorder. This article discusses some of the features a recorder needs to survive and meet the data-gathering requirements.

There are a number of portable data recorders available on the market today, and each has its own feature set that makes some units more suitable than others for certain applications. Data recorders for in-vehicle applications have to meet a number of stringent requirements not present in traditional laboratory gear. These applications often expose the recorder to extremes in temperature, humidity, shock, and vibration. The environmental conditions of these applications often preclude the use of a data recorder that requires a physical connection to a computer to function since most standard laptops and PCs do not react well when subjected to these extremes. Other concerns include whether the recorder is capable of supporting the mix of particular sensors that will be used as well as if there is adequate memory/storage to support the test.

The most viable recorders for in-vehicle use are compact, lightweight units that run off of either a self-contained battery or a single DC power source, and require no other connection to function except the connection to the sensors under monitor. Signal conditioning, such as gain and filtering, and high-capacity nonvolatile data storage are other important considerations.

One such demanding application for data recording is found in Zero-G, which allows NASA-funded researchers to simulate the effects of weightlessness on components and hardware designed for flight aboard NASA’s Space Shuttle. On Earth, weightlessness can be modeled in a vacuum chamber by putting an object in a state of free fall.

The Zero-G facility includes a 140 meter-long steel vacuum chamber (Figure 1) that is 6.1 meters in diameter and surrounded by an 8.1-meter diameter concrete-lined shaft extended 155 meters below ground level. An object placed inside a test capsule dropped in the vacuum chamber can obtain a state of near weightlessness for approximately 5.18 seconds as it drops a free-fall distance of 132 meters.

Figure 1

NASA selected KineticSystems’ DAQ532 data recorder (Figure 2) to collect critical data such as voltage, acceleration, and temperature of the free-falling device under test within the capsule. DAQ532 data recorders were mounted into five different free-falling capsules, each required to perform different sets of tests. The DAQ532 data recorder’s performance demonstrated its flexibility, robustness, and ease of configuration.

Figure 2

Any of the DAQ’s 32 differential input analog channels can be activated and assigned a sample rate up to the aggregate maximum of 50 kSps. The DAQ532 provided the most choices of gain/filter combinations via signal conditioning and allowed NASA researchers to easily fine-tune test setups. Data was captured before, during, and after the capsule’s free-fall for a total of approximately 10 seconds. Once the capsule is retrieved by overhead crane, the data is transferred via Ethernet, or via the unit’s CompactFlash, to a PC using KineticSystems’ included VersaDAQ software.

VersaDAQ’s simple, yet powerful user interface, allowed NASA researchers to easily configure channels and sample rates, activate record mode, perform calibration, and control any of the DAQ532’s functionality with a few mouse clicks and pull-down menus. The data conversion utility provided in VersaDAQ allowed collected data to be easily ported to other applications such as MATLAB or LabVIEW for further data analysis or to Excel for report generation or inclusion in other documentation.

The DAQ532 responded to all of NASA’s requirements for a robust and easy-to-use data recorder. It was the only data recorder robust enough to withstand the extreme conditions, such as very high temperature and shock upon impact, of the vacuum chamber in the Zero-G test facility.

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Lou Kelm has maintained the position of eastern regional sales manager, responsible for sales of all product lines in 31 states, at KineticSystems since 2001. Lou has held numerous positions at KineticSystems, including testing group leader, manager of testing and quality control, and field applications engineer. He received his electronics training in the U.S. Air Force and began his career as a testing technician with KineticSystems in 1977.

To learn more, contact KineticSystems Company, LLC at www.kscorp.com.

VersaDAQ is a trademark of KineticSystems Company, LLC in the United States and other countries. Other company product and service names may be the trademarks or service marks of others.