On Shaft Data Acquisition System (OSDAS) is a rugged, compact, multiple-channel data acquisition computer system that is designed to record data from instrumentation while operating under extreme rotational centrifugal or gravitational acceleration forces. This system, which was developed for the Heritage Fuel Air Turbine Test (HFATT) program, addresses the problem of recording multiple channels of high-sample-rate data on most any rotating test article by mounting the entire acquisition computer onboard with the turbine test article. With the limited availability of slip ring wires for power and communication, OSDAS utilizes its own resources to provide independent power and amplification for each instrument. Since OSDAS utilizes standard PC technology as well as shared code interfaces with the next-generation, realtime health monitoring system (SPARTAA — Scalable Parallel Architecture for Real Time Analysis and Acquisition), this system could be expanded beyond its current capabilities, such as providing advanced health monitoring capabilities for the test article.

High-conductor-count slip rings are expensive to purchase and maintain, yet only provide a limited number of conductors for routing instrumentation off the article and to a stationary data acquisition system. In addition to being limited to a small number of instruments, slip rings are prone to wear quickly, and introduce noise and other undesirable characteristics to the signal data. This led to the development of a system capable of recording high-density instrumentation, at high sample rates, on the test article itself, all while under extreme rotational stress.

OSDAS is a fully functional PC-based system with 48 channels of 24-bit, high-sample-rate input channels, phase synchronized, with an onboard storage capacity of over ½-terabyte of solid-state storage. This recording system takes a novel approach to the problem of recording multiple channels of instrumentation, integrated with the test article itself, packaged in a compact/rugged form factor, consuming limited power, all while rotating at high turbine speeds.

The hardware components were oriented, secured, and encapsulated by a variety of novel application techniques that allow for the system to continue operation under rotational stress. This full, custom-hardened system was designed to be a comprehensive solution to attaching directly to instrumentation (without external sensor power supplies and amplification). Instead, all instrumentation has a dedicated power supply, integrated inside OSDAS, with the ability to withstand electrical faults (short circuits, etc.) without compromising other sensors. The amplification required for each sensor was configurable at build time to match that of the Kulite instrumentation used in the HFATT article. The entire computing, storage, and acquisition hardware system was custom-encapsulated in a thermally conductive medium that allows heat to passively dissipate by air via the outer shell (indoor/outdoor environmental conditions) or by conduction cooling in space conditions.

OSDAS is a comprehensive, high-capacity acquisition system capable of withstanding extreme rotational forces. The existing products on the market are either limited in channel capacity, bandwidth, or simply not capable of withstanding physical stress. As part of the build process, a variety of mounting and encapsulation techniques was utilized, which ensures the system can withstand harsh rotational stresses. OSDAS employs the use of standard PC technology. The system was built to share a code interface with that of the SPARTAA, otherwise known as the next-generation, real-time vibration monitoring system (RTVMS). This allows OSDAS to be expanded in the future to incorporate real-time health monitoring of the test article hardware.

OSDAS employs a common hardwaremounting interface that allows the acquisition system to be adapted to a variety of test articles and environments. With the use of built-in sensor amplification and independent power supplies, a total sensor acquisition solution was provided. While acquisition storage capacity and channel counts were limited initially by the desire of a small/compact form factor, further expansion beyond 48 channels and multi-terabyte solutions is possible. For the final system checkout, OSDAS was subjected to speeds over 15,000 RPM (maximum facility capability). A continuous Ethernet connection was maintained throughout the checkout and test series.

This work was done by Marc Pedings, Shawn DeHart, Jason Formby, and Charles Naumann of Optical Sciences Corporation for Marshall Space Flight Center. For more information, contact Sammy Nabors, MSFC Commercialization Assistance Lead, at This email address is being protected from spambots. You need JavaScript enabled to view it.. MFS-32908-1

NASA Tech Briefs Magazine

This article first appeared in the September, 2012 issue of NASA Tech Briefs Magazine.

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