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실내 공기질 향상을 위한 비분산 적외선 이산화탄소 가스센서
이승환,박정민,박영환,한승오,Yi, Seung-Hwan,Park, Jeong-Min,Park, Young-Hwan,Han, Seung-Oh 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.7
We have simulated and proposed novel optical cavity, which has two elliptical mirrors, for NDIR gas sensor module and have tested it from 0 ppm to 2,000 ppm $CO_2$ concentration. The proposed sensor module shows the maximum peak voltage at 500 ms pulse modulation time, however, it shows a maximum voltage changes at 200 ms pulse duration with 18,000 times amplification gain. From 0 ppm to 2,000 ppm, the voltage difference of sensor module $({\Delta}V)$ shows 360 mV at 200 ms pulse duration and 3 sec turn-off time. The response time of designed sensor module is about 30 seconds.
C-축 배향된 ZnO 박막을 이용하여 제작한 압전형 마이크로 스피커의 특성 평가
이승환,서경원,유금표,권순용,Yi Seung-Hwan,Seo Kyong-Won,Ryu Kum-Pyo,Kweon Soon-Young 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.6
A micromachined piezoelectric microspeaker was fabricated with a highly c-axis oriented ZnO thin film on a silicon-nitride film having compressive residual stress. When it was measured 3 mm away from the microspeaker in open field, the largest sound pressure level produced by the fabricated microspeaker was about 91 dB at around 2.9 kHz for the applied voltage of $6\;V_{peak-to-peak}$. The key technologies to these successful results were as follows: (1) the usage of a wrinkled diaphragm caused by the high compressive residual stress of silicon-nitride thin film, (2) the usage of the highly c-axis oriented ZnO thin film.
李承煥(Seung-Hwan Yi),鄭暻湜(Kyung-Sick Jung),金東其(Dong-Kee Kim),愼廣縡(Gwang-Jae Shin) 대한전기학회 2007 전기학회논문지 Vol.56 No.8
This paper reports the piezoelectric micro speakers that are audible in open air with high quality piezoelectric AIN thin film deposited onto Mo/Ti electrode. This successful achievement, compared to the previous results, is followed by manipulating two material properties: the one is to use a compressively stressed silicon nitride film as a supporting diaphragm (even tensile stressed, around +20 ㎫) and the another is to use high quality AIN thin film with compressive residual stress (less than -100 ㎫). With these materials, the Sound Pressure Level (SPL) of the fabricated microspeakers shows more than 60 ㏈ from 100 ㎐ to 15 ㎑ and the highest SPL is about 100 ㏈ at 9.3 ㎑ with 20 Vpeak-to-peak sinusoidal input and with 10 ㎜ distances from the fabricated microspeakers to the reference microphone (B&K Type 2669 & 4192L).
보상용 적외선 센서를 사용한 비분산 적외선 이산화탄소 센서의 온도특성
이승환 ( Seung Hwan Yi ) 한국센서학회 2016 센서학회지 Vol.25 No.2
NDIR CO2 gas sensor was built with ASIC implemented thermopile sensor which included temperature sensor and unique elliptical waveguide structures in this paper. The temperature dependency of dual infrared sensor module (CO2 and reference IR sensors) has been characterized and its output voltage characteristics according to the temperature and gas concentration were proposed for the first time. NDIR CO2 gas and reference IR sensors showed linear output voltages according to the variation of ambient temperatures from 243 K to 333 K and their slopes were 14.2 mV/K and 8.8 mV/K, respectively. The output voltages of temperature sensor also presented a linear dependency according to the ambient temperature and could be described with . V(T) = -3.191+0.0148T(V) The output voltage ratio between CO2 and reference IR sensors revealed irrelevant to the changes of ambient temperatures and gave a constant value around 1.6255 with standard deviation 0.008 at 0 ppm. The output voltage of CO2 gas sensor at zero ppm CO2 gas consisted of two components; one is caused by the HPB (half pass-band) of IR filter and the other is attributed to the part of CO2 absorption wavelength. The characteristics of output voltages of CO2 gas sensor could be accurately modeled with three parameters which are dependent upon the ambient temperatures and represented small average error less than 1.5% with 5% standard deviation.