• Journal of Sensor Science and Technology
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• v.11 no.6
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• pp.350-357
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• 2002

Micro gas sensor with single electrode was proposed for improving stability and sensitivity. Generally, metal oxide gas sensors have two electrodes for heating and sensing. This fabricated new type sensor have only a single electrode by forming a sensing material onto heating electrode. Pt as a heating and sensing electrode was sputtered on glass substrate and a $SnO_2$ sensing material was thermally evaporated on Pt electrode. $SnO_2$ was patterned by lift-off process and then thermally oxidized in $O_2$ condition for 1 hr., $600^{\circ}C$. The size of fabricated sensor was $1.9{\times}2.1\;mm^2$. As a result of CO gas sensing characteristics, this sensor showed 100 mV change for 1,000 ppm and linearity for wide range($0{\sim}10,000\;ppm$) of gas concentrations. And the sensor shows a good recovery characteristics of 1% deviation compared to initial resistance.

• Journal of Sensor Science and Technology
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• v.27 no.3
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• pp.192-198
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• 2018

Pulse oximetry is a non-invasive method for monitoring how much oxygenated hemoglobin is present in the blood. The principle of pulse oximetry is based on the red infrared light adsorption characteristics of oxygenated and deoxygenated hemoglobin. Even through the convenience of a pulse oximeter, its weak signal-to-noise ratio against motion artifacts and low perfusion makes it difficult to be accepted by execs devices. Several researchers have suggested the use of an adaptive noise cancellation (ANC) algorithm. They have demonstrated that ANC is feasible for reducing the effects of motion artifacts. Masimo Corporation developed a discrete saturation transformation (DST) algorithm that uses a reference signal and ANC. In commercial devices, it is very hard to escape it because Masimo's patents are very powerful and a better method is yet to be developed. This study proposes a new method that can measure noise saturation as well as accurate oxygen saturation from signals with high motion artifacts without using ANC and DST. The proposed algorithm can extract a normal signal without noise from a signal with motion artifacts. The reference signal from a pulse oximeter simulator was used for the evaluation of our proposed algorithm and achieved good results.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.134-134
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• 2003

SnO$_2$를 모물질로 하는 가스센서는 n형 산화물 반도체로서 공기중의 산소의 흡탈착 및 전자의 수수에 의해 전기전도도의 변화로 특정 가스를 감지한다. 지금까지 반도체식 가스센서의 모물질로 가장 많이 연구되어 왔지만 아직도 선택성, 안정성 등 여러 가지 문제를 안고 있다. 그리고 개선방안으로 귀금속 촉매의 첨가 및 입자의 크기의 조절 등이 흔히 연구되어 왔다. 따라서 본 연구에서는 순수한 SnO$_2$ 를 이용하여 소결 온도 및 입자 크기에 의한 영향을 CO가스 및 수분에 대한 감도, 반응 시간을 통해 알아보았다. 수열 합성 및 침전 법으로 나노 크기의 SnO$_2$ 분말을 합성하여 스크린 인쇄법으로 후막 가스센서를 제조하였다 침전법에서 SnCl$_4$에 암모니아수로 pH=10.5로 적정하여 SnO$_2$ 분말을 얻었다. 그리고 입자 크기를 조절하기 위해 수열 합성 시 autoclave 내의 수열처리 온도를 100, 150, 20$0^{\circ}C$로 조절하여 SnO$_2$ 분말을 제조하고 입자 크기와 성분분석을 위해 XRD, SEM, TEM, BET 측정을 하였다. 그 결과 침전법으로 제조한 입자의 크기는 20nm 정도였으며 수열 처리한 SnO$_2$ 입자는 10nm이하의 미세한 입자를 얻을 수 있었다. 수열 합성 시 온도가 높아질수록 더 작은 입자 크기를 얻을 수 있었고 600, 7()0, 80$0^{\circ}C$ 열처리 후 입자성장이 침전법에 의한 SnO$_2$ 분말보다 더 작게 일어났다. 이렇게 제조한 나노크기의 SnO$_2$ 분말을 이용하여 습도 및 CO 가스에 대한 그 특실을 평가하였다. CO 20ppm에 대하여 40%정도의 감도를 보였으며 입자가 작아질수록 높은 감도를 보이는 것을 확인 할 수 있었다. 반면 CO 가스와 반응 후 회복 시 입자 의기가 작아질수록 회복이 늦어짐을 알 수 있었다. 그리고 15$0^{\circ}C$에서 습도에 대한 반응 후 회복시간을 조사해보니 같은 결과를 얻을 수 있었다. 이것은 입자 필기가 작아질수록 많은 흡착 사이트를 제공함으로써 높은 감도를 가지지만 반면 다량의 흡착된 가스들이 탈착 하는데 더 많은 시간이 소요되었기 때문이다.

• Journal of the Korean Institute of Gas
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• v.5 no.1
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• pp.7-14
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• 2001

In this work, the chemical composition of the exhaust gas from domestic gas boiler has been analysed in the point of thermodynamics and CO sensor has been characterized. We proposed that the combustion condition can be estimated by the exhaust gas composition, i.e., the excess air ratio and combustion temperature can be calculated simply by the measurement of the $O_{2}$ fraction and $H_{2}/CO$ in the exhaust gas. By analyse the on site situation domestic boiler, the excess air ratio is about $55\~110\%$. Therefore, the CO may be produced in domestic gas boiler by luminous(yellow) flames rapidly lose heat by radiation, turbulent flames may be partially quenched by the action of steep velocity gradients, and flames burning very close to a cold wall may be partial1y quenched by heat conductivity to the wall. The output voltage of CO sensor is lineally depend on the CO and $H_{2}$concentration. And the exhaust CO from boiler can be reduced by closed loop control with CO sensor

• Analytical Science and Technology
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• v.7 no.3
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• pp.285-291
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• 1994

A microbial BOD sensor for the continuous estimation of BOD was been developed by immobilizing Trichosporon cutaneum, which was immobilized between a dialysis and a gas-permeable membrane, on an oxygen electrode. The optimum pH and temperature for BOD measurement using this sensor were pH 7.0 and $32{\sim}33^{\circ}C$, respectively. The best result was obtained at 2~3ml/min flow rate in 0.1M phosphate buffer solution. A linear relationship was observed between ${\Delta}DO$ and the concentration of standard GGA solution below 60mg/l(90ppm $BOD_5$). The reproducibility was found to be within 3% for the standard solution containing glucose 30mg/l and glutamic acid 30mg/l. The output DO value of this sensor was almost constant for 30 dalys. The response time and the recovery time were about 5 and 10 min, respectively. This sensor was employed for the BOD measurement of waste pollutants and was compared with $BOD_5$ method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.180-183
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• 2011

Recently, environmental problems have been deteriorating rapidly. Therefore, there is an urgent need to establish policies and research in the conservation of the global environment. Many researchers are studied in environment systems to prevent and reduce pollution of water, air and soil actively. In this paper, several parameters such as temperature, humidity, illumination, barometric pressure, dew point, water quality data, and air conditions are collected and transmitted thorough wireless sensor network. The field server is located in the coastal and marine area so that any abrupt changes can be detected quickly. In addition, WSN based flooding routing protocol for efficient data transmission is designed to support and monitor information of climate and marin factors.

• Journal of the Korean Ceramic Society
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• v.40 no.12
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• pp.1177-1182
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• 2003

The porous sensing materials for BaTiO$_3$ gas sensors were fabricated by adding the graphite powders. The crystalline structure and microstructure of the porous BaTiO$_3$-based ceramics were studied. All the sintered bodies showed a tetragonal perovskite structure. The porosity increased with increasing graphite contents. This is mainly due to an enhanced evolution of CO and $CO_2$ gases resulting from the exothermic reactions of graphite and oxygen during the sintering. It was found that the discrepancy in the resistivities measured in air and CO atmospheres at high temperatures (>∼20$0^{\circ}C$) became remarkable with increasing temperature. The sensitivity of CO gas increased with porosity, since the reactions between CO gas and $O_2$$^{[-10]}$ and between CO gas and $O^{[-10]}$ are active due to the formation of many reaction sites. The porous BaTiO$_3$-based ceramics could be promising as a sensing material for CO gas sensors.

• Journal of Sensor Science and Technology
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• v.25 no.1
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• pp.51-56
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• 2016

This study evaluates the performance of an optical sensor and measurement system (CMA-24) which can analyze the fluctuation of dissolved oxygen and pH simultaneously. In the optical sensor system, the fluorescent materials, Rudpp and HPTS which are sensitive to dissolved oxygen and pH, respectively, are coated on the bottom of a 24-well -plate by the sol-gel technology. The detection times of the emission light of the oxygen sensor were $4,186{\pm}13.90{\mu}s$ and $4,452{\pm}36.68{\mu}s$ for the dissolved oxygen of 17% $O_2$ and 7.6% $O_2$, respectively. On the other hand, the detection times of the pH sensor were $6,699.43{\pm}14.64{\mu}s$, $6,722.24{\pm}6.21{\mu}s$, and $6,748.52{\pm}2.63{\mu}s$ using pH 6, 7, and 8, respectively. When we determined cellular respiration levels of C2C12 myocytes with CMA-24, $O_2$/pH measurement system, the ratio of the uncoupled to coupled OCR (oxygen consumption rate) was 1.41. The results mean that this CMA-24 system shows almost the same sensitiveness as the commercial system.

• Journal of the Korea Society of Computer and Information
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• v.15 no.9
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• pp.129-136
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• 2010

With mobile computing, wireless sensor network and sensor technologies, ubiquitous computing services are being realized and could satisfy the feasibility of ubiquitous healthcare to everyone. This u-Healthcare service can improve life quality of human since medical service can be provided to anyone, anytime, and anywhere. To confirm the vision of u-Healthcare service, we've implemented a healthcare system for heart disease patient which is composed of two components. Front-end collects various signals such as temperature, blood pressure, SpO2, and electrocardiogram, etc. As a backend, medical information server accumulates sensing data and performs back-end processing. To simply transfer these sensing values to a medical team may be too trivial. So, we've designed a model based on context awareness for more improved medical service which is based on artificial neural network. Through rigid experiments, we could confirm that the proposed system can provide improved medical service.

• Applied Chemistry for Engineering
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• v.32 no.1
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• pp.42-48
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• 2021

In this study, a sensor for detection of nitric oxide (NO) gas was developed using petroleum pitch-based activated carbon which was synthesized from pyrolysis fuel oil (PFO). Polyethylene terephthalate (PET) was added to increase molecular weight by stimulating a polymerization of components in PFO during the pitch synthesis process. The increase in the molecular weight of pitch contributed to the improvement of textural properties of activated carbon, such as the specific surface area and micropore volume. It also enhanced the sensitivity of NO gas sensor based on the activated carbon. In addition, the effect of PET addition during the pitch synthesis on the surface oxygen content and conductivity of activated carbon was investigated. Finally, the correlation of the sensitivity with physical properties of activated carbon was analyzed.