Tech Briefs

This passive, low-cost system detects extremely small vibrations.

Researchers at NASA’s Marshall Space Flight Center (MSFC) have developed a novel point mechanic piezoelectric system capable of sensing extremely small vibrations, forces, or strains. The system’s high sensitivity near resonance and low noise floor enable the sensor to detect various low-frequency parameters — such as miniscule changes in the gravity gradient, seismic waves, and acoustics — from minimum detectable signals in the surrounding environment. Traditional piezoelectric systems, such as gravity gradiometers and seismometers, have larger intrinsic noise and smaller signal-to-noise ratio, thus requiring more complex instrumentation (and often larger, more expensive, and more cumbersome instrumentation). NASA’s innovative point mechanic sensor instead uses a simple and unique system to detect minute parameter changes, leading to significantly lower cost and material requirements.

A photo of NASA’s point mechanic piezoelectric system.

The point mechanic sensor system comprises a piezoelectric sensing surface that produces a voltage when subjected to a mechanical force or strain. The system configuration is a piezoelectric plate that is perpendicular to a force-conducting rod via a mechanical interface. Affixed to the opposing end of the rod is a test mass that is subjected to acceleration caused by slight changes in gravitational force, vibrations, seismic activities, acoustics, and other physical phenomena. When vibration or movement occurs, the motion of the test mass is transmitted down the force-conducting rod, which contacts and activates the piezoelectric sensing surface to produce a voltage for processing.

The patent-pending NASA sensor system has been successfully prototyped, and has been tested and benchmarked against several commercially available sensors at a frequency range of 10 Hz to 5 kHz. Initial tests indicate that the NASA sensor has a high sensitivity of ~100 V/g at 100 Hz, which is orders of magnitude better than currently available sensors. Sensitivity can be increased further by varying system materials and component sizes. The sensor’s low noise floor indicates that the system can potentially lead to minimum detectable signals of 1 ng/Hz or lower, potentially at pico-g levels. NASA is conducting additional tests for frequencies below 10 Hz.

This technology is scalable — it can be designed as small as a microelectromechanical system (MEMS) or as large as a water tower. It can be used in geological applications for early detection of seismic activity; oil or mining applications for detection of oil/ore deposits via gravity field sensing; defense applications for early detection of missiles, submarines, land mines, or explosives; aerospace and industrial applications for early detection of microscopic mechanical failures; and education applications for production of a physics or earth science educational kit for in-class demonstrations.

NASA is actively seeking licensees to commercialize this technology. Please contact Sammy A. Nabors at sammy.nabors@ nasa.gov to initiate licensing discussions. Follow this link for more information: http://technology.nasa.gov/patent/TB2016/MFS-TOPS-63.

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