| Infrared (IR) technology is becoming increasingly popular in gas detection applications due to accurate identification of gases and reliable concentration measurements. The conventional system is too large to be intelligentized and integrated to network. A fair amount of effort has been made to develop MEMS (Micro Electro-Mechanical System) IR gas sensors. This work is on developing a low-cost MEMS (Micro Electro-Mechanical System) IR pulsed radiation source, applied as one dominating part in the sensor.The thesis completes the developing task from four aspects: working principle and fabrication of the source, power supply mode of the source, characteristic testing of the source, and its application in NDIR gas detection for validation.Based on theoretic analysis, different element structures and incandescent materials were compared. A suspended membrane structure source is fabricated based on silicon substrate, where platinum and nichrome alloy are used as incandescent material respectively. A 1200A layer of silicon nitride is deposited on the platinum microfilament according to the low emissivity of platinum. Source with a silicon nitride layer on surface showed an improved radiation power, with a prolonged response time according to its increased thermal mass. Source with nichrome alloy used as incandescent material, is fabricated to fulfill both the requirement of radiation power and response time.A detailed comparison is made among different power supply modes through a simplified calculation, and constant-voltage supply is found to be more effective in saving response time, thus is better to the dynamic response of the source. And the results is applied both in testing and application process. The influence of emissivity is also studied, and fast modulation could be realized with an enhanced emissivity value. |
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