Low-Cost, Micromachined Absolute Pressure Sensor

A six-month program in proposed to design and fabricate micropower, absolute pressure sensors micromachined from single-crystal silicon. The sensor utilizes a now capacitive sensing structure developed for micromachined micrometers, seismometers, and differential pressure sensors. The sensor will be housed in a package having a full form, fit, and function compatibility with existing Navy underwater weapons and oceanographic research systems. Based upon measurements with micromachined differential pressure sensors and micrometers, the noise-limited. resolution of the absolute sensor is expected to exceed 0.01" of water at a depth of 600 feet, over a 5 =Hz to 0.25-Hz bandwidth. Micropower, switchedbridge electronics have the capability to detect capacitance changes of 1 ppm. Feedback maintains a linear sensor output over a dynamic range of 120 dB. Acoustic (2 to 500 Hz) and depth sensing outputs (O.to 600 ft.) are also provided. The sensor has a self-calibration capability. The proposed sensor will be designed to the meet the storage, transport, vibration, and shock specifications for Navy airlaunched weapons. A Phase I option is proposed to performance test prototype units at the NSWC, CSS facility in Panama City, FL. Theme units will be available for, environmental testing at the onset of Phase II.