| Budget Amount *help |
¥6,000,000 (Direct Cost: ¥6,000,000)
Fiscal Year 2004: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2003: ¥4,500,000 (Direct Cost: ¥4,500,000)
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| Research Abstract |
The proposed sensor is based on a conventional integrated optic pressure sensor using intermodal interference, with an added semi-closed space with a small hole under the bottom side of the diaphragm. By the addition of this semi-closed space, the sensor, unlike conventional sensors, can withstand high static pressure. When there is a sudden change in ambient pressure, pressure within the semi-closed space cannot quickly adjust due to the small hole that restricts fluid flow. So, pressure difference is induced on the diaphragm for a short while. Thus, the sensor shows a response only to changes in pressure, not to static pressure.
In the first year of this research project, we examined the step response of the sensor, that is, the output characteristics for sudden pressure change. The diaphragm dimensions of the fabricated sensor were 14mm×14mm×0.22mm, and the volume of the semi-closed space was 14mm×14mm×1.8mm. The sectional area of a small rectangular hole was 93μm×25μm. In this exper
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iment, the pressure in a 30cm×28cm×30cm closed box, in which the fabricated sensor was placed, was suddenly increased by 0.78 kPa. Due to the pressure change, the output intensity decreased by approximately 20% of the initial intensity level. Approximately 1.4 sec after the step-like change in pressure, output intensity returned to the initial level.
In the second year, it was found from the theoretical analysis that the duration of the induced pressure difference is proportional to the V/A ratio between the volume of the semi-closed space and the sectional area of the small hole, and proportional to the square root of the initial pressure difference. So, the relationship between the duration and the sectional area of the small hole was examined experimentally. The radii of the circular holes were 20μm,25μm, and 40μm. The measured duration of the induced pressure difference was approximately 2 sec when the ambient pressure was suddenly changed by 0.7 kPa, although the duration must be dependent on the hole radius according to the theoretical results. It is attributed to pressure leak from the closed box in which the sensor was placed. Less
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