• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.127-128
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• 2008

본 연구에서는 비분산 적외선 방식을 이용한 일산화탄소, 이산화탄소 듀얼 센서 모듈을 실현한다. 비분산 적외건 방식은 가스분자가 특정 파장의 적외선을 흡수하는 특성을 이용하여 가스의 적외선 흡수도를 측정하여 농도로 환산하는 방식이다. 비분산 적외선 방식은 수명이 길고 정밀도가 높아 기존의 접촉식(화학식) 센서에 비해 우수한 특성을 가지고 있다. 중요한 기술은 NDIR의 핵심부분인 광 공동의 설계 기술과 센서의 성능을 최종 결정짓는 농도-온도 교정 기술이다. 현재까지 개발된 광공동 기술은 $CO_2$ 센서의 단일 센서 방식이었다. 본 연구에서는 이 기술을 접목한 일산화탄소까지 동시에 측정할 수 있는 광 공동기술과 교정기술을 연구개발하여 하나의 광 공동으로 이산화탄소와 일산화탄소를 동시에 측정 할 수 있는 고기능 센서를 실현하는 것이다.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.46 no.2
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• pp.36-40
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• 2009

In this paper we discuss about the practical implementation of a combined CO and CO2 dual sensor module that is adapted by NDIR (Non-Dispersive Infrared) method that measures the absorbance of gas like CO and CO2 by using gas particles' characteristics that absorb specific wave lengths of infrared ray. NDIR has a long life time, excellent measurement and precision compared to the existing contact types or chemical types of CO2 sensors. Since optical cavity technology that had been developed until now can measure CO2 only we research and develop an optimal optical cavity design and density-temperature calibration technologies that can measure CO and CO2 at the same time and is important to decide the performance of the sensor module according to well-designed wave guides of the different length.

• Journal of Auto-vehicle Safety Association
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• v.7 no.2
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• pp.39-43
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• 2015

NDIR (Non-dispersive infrared Rays) alcohol sensor has been prototyped and its temperature characteristics were measured. In order to design novel optical alcohol sensor, elliptical structures with one common foci were modeled and analyzed their optical properties. After analyzing elliptic optical structures, a prototype alcohol sensor module was tested according to the temperature variations from $-20^{\circ}C$ to $35^{\circ}C$. The offset voltages of alcohol sensor decreased from 1.1056 V at the temperature $-20^{\circ}C$ to 0.7339 V at $35^{\circ}C$. However, the highest sensitivity of alcohol sensor showed about $303{\mu}V/ppm$ at room temperature.

• Journal of the Korean Institute of Gas
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• v.15 no.4
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• pp.51-55
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• 2011

This paper describes the temperature compensation algorithm using thermopile detector for nondispersive infrared methane gas sensor. From the output voltage of thermistor that is attached onto the infrared detector, the ambient temperature was extracted. The effects of temperatures on the properties of sensor module (the characteristics of narrow bandpass filter, optical cavity and infrared lamp, and gas absorption coefficient times optical path length) have been introduced in order to implement the temperature compensation algorithm. Even though the measurement error of developed sensor module was in the range of $\pm$ 1,500 ppm, after programming the temperature compensation algorithm, the developed sensor module shows a high accuracy less than +180 ppm error within $20^{\circ}C$ temperature variation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1065-1066
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• 2011

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.81-82
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• 2005

본 논문에서는 두 개의 오목 반사경으로 형성된 광 공동 구조의 비문산 적외선 (NDIR) 가스센서를 제작하였다. 증폭비는 18,000 배, 램프 off 시간은 3초로 일정하게 하고 펄스 modulation 시간을 200ms에서 600ms까지 변화시켰을 때. 300ms에서 가장 효율적인 출력신호를 확보할 수 있었다. 그리고 $5^{\circ}C$에서 $45^{\circ}C$까지 $10^{\circ}C$ 간격으로 온도를 변화시키면서 이산화탄소의 농도를 0ppm에서 2000ppm까지 증가시켰다. 이때, 약 400mV의 전압변화가 있었다. 온도가 상승함에 따라 0ppm에서의 출력전압은 감소하는 양상을 나타내었다. 또한 온도변화 대비 출력특성과의 상관성 해석을 통하여 온도 보상 방법을 고안하였으며, 본 연구에서 제작한 센서모듈의 응답시간은 약 30초였다.

• Journal of the Korean Institute of Gas
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• v.11 no.1 s.34
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• pp.40-45
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• 2007

This paper describes NDIR $CO_{2}$ gas sensor that shows the characteristics of temperature compensation. It consists of novel optical cavity that has two elliptical mirrors and a thermopile that includes ASIC chip in the same metal package for the amplification of detector output voltage and temperature sensor. The newly developed sensor module shows high accuracy ($less\;than {\pm}40\;ppm$) throughout the measuring concentration of $CO_{2}$ gas from 0 ppm to 2,000 ppm. After implementing the calculation methods of gas concentration, which is based upon the experimental results, the sensor module shows high accuracy less than ${\pm}5\;ppm$ error throughout the measuring temperature range ($15^{\circ}C\;to\;35$^{\circ}C$) and gas concentrations with self-temperature compensation.

• Journal of Sensor Science and Technology
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• v.30 no.1
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• pp.36-41
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• 2021

The motivation of this paper is to easily analyze the properties of nondispersive infrared gas sensor that has more than two different optical path length and to suggest the criterion and definition of infrared light absorbance in order to minimize the measurement errors. With the output voltage ratios and the normalized derivatives of infrared ray (IR) absorbance, when the normalized derivatives of IR absorbance decreases from 0.28 to 0.10, the lower and higher limits of errors were decreased from -5.62% and 2.39% to -4.27% and 2.78%. When the normalized derivatives of IR absorbance were 0.10, the output voltage could be partitioned into two regions with one exponential equation and the temperature compensation error was less than 5%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1606-1612
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• 2015

In this paper, a portable high efficiency nondispersive infrared(NDIR) $CO_2$ sensor module with a smart device interface is developed. For low power consumption design, an IR LED was used instead of tungsten lamp for light source and an optical waveguide optimized to the sensor module is designed. With the smart device interface, power of the sensor module is applied from the battery of smart phone. The measured data of the sensor module such as $CO_2$ concentration, temperature, and humidity are displayed on the smart phone using android application. From measured results, the developed sensor module shows ${\pm}60ppm$ tolerance error from 0 to 3,000ppm $CO_2$ concentration range among $-10^{\circ}C$ and $50^{\circ}C$ ranges.

• Journal of Sensor Science and Technology
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• v.25 no.2
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• pp.124-130
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• 2016

NDIR $CO_2$ 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 ($CO_2$ 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 $CO_2$ 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 $CO_2$ 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 $CO_2$ gas sensor at zero ppm $CO_2$ 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 $CO_2$ absorption wavelength. The characteristics of output voltages of $CO_2$ 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.