• Journal of Sensor Science and Technology
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• v.15 no.1
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• pp.34-39
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• 2006

This study provides the electrical model of combustible catalytic gas sensor. Physical characteristics such as thermal behavior, resistance change were included in this model. The finite element method analysis for sensor device structure showed that the thermal behavior of sensor is expressed in a simple electrical equivalent circuit that consists of a resistor, a capacitor and a current source. This thermal equivalent circuit interfaces with real electrical circuit using two parts. One is 'power to heat' converter. The other is temperature dependent variable resistor. These parts realized with the analog behavior devices of the SPICE library. The gas response tendency was represented from the mass transferring limitation theory and the combustion theory. In this model, Gas concentration that is expressed in voltage at the model, is converted to heat and is flowed to the thermal equivalent circuit. This model is tested in several circuit simulations. The resistance change of device, the delay time due to thermal capacity, the gas responses output voltage that are calculated from SPICE simulations correspond well to real results from measuring in electrical circuits. Also good simulation result can be produced in the more complicated circuit that includes amplifier, bios circiut, buffer part.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.773-777
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• 2002

In this study, we analyzed the LPG and LNG sensitivity measurement and voltage variation using catalytic type gas sensor characteristics in catalytic combustion type gas detecter sensors. gas detector shall operate as intended when exposed for 24 hours to air having a relative humidity of 0~85 percent at a temperature of $20[{\mu}m]$ and humidity of 45 percent at a temperature of $-10{\sim}40[^{\circ}C]$ the gas detecter sensors are to be subjected to operation for 210 days in an area that has been detemined to be equivalent to a typical residential atmosphere with an air velocity of 50 [cm/sec]. The source of energy for a gas detector sensors employing a supplementary basic circuit is energized from a separate source of supply direct applied voltage 2.1[V], 2.2[V], 2.3[V]. As a result, it was confirmed that the relative humidity and temperature by regression each analysis, compared to the LPG characteristic graph and methane characteristics graph by a relative humidity of 0 ~ 85 [%] at a temperature range of $-10{\sim}40[^{\circ}C]$ show a similar linear pattern on the whore.

• Journal of the Korean Institute of Gas
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• v.13 no.5
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• pp.15-19
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• 2009

In this study, the transient responses of hydrogen sensor against abrupt hydrogen release was experimentally studied for three most common types of hydrogen sensors, i.e. the semiconductor type, electrochemical type, and catalytic combustion type. The experimental study was conducted using a 1% hydrogen - 99% nitrogen mixture gas as the standard gas, while the temperature and relative humidity (RH) of the mixture gas was varied from $25^{\circ}C$ to $50^{\circ}C$ and from 50% to 100%, respectively. The temperature of the mixture gas was found to influence the output signal levels of hydrogen sensors, especially the catalytic combustion type. However, the effect of RH on the sensor response was not noticeable in the present experimental study. Thus, the signal levels of hydrogen sensors, in case of catalytic gas sensor need to be calibrated dependent on gas temperature, when the accurate determination of hydrogen concentration is important.

• International Journal of Automotive Technology
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• v.3 no.1
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• pp.33-40
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• 2002

Increasingly stringent emission regulations of EU and CARB (California Air resource Board) require mandatory OBD (On Board Diagnostics) far the catalytic converters of a vehicle. It demands that MIL(Malfunction Indication Light) should be tuned on to inform the driver of catalytic converter failures. Currently dual oxygen sensor method Is widely used for the converter OBD. However, since it works only alter converter light-off, it has a serious limitation when applied to TLEV or more stringent emission regulations where more than 85% of total emission is coming out before converter light-off. In addition, a recent development in catalyst material. coating technology and additive catalysts leads to a much improved OSC (Oxygen Storage Capacity) after converter light-off, current methods are very difficult to determine levels of converter aging. Therefore, it is desired to develop an OSC detecting method before converter light-off to diagnose converter failures with higher reliability. In this study, OSCs of converters are measured by an absolute measuring method and a dynamic measuring method, and some of fundamental ideas are suggested about converter OBD before converter light-off. The converters are aged with two different aging methods; those are a furnace aging and an engine bench aging: to represent aging conditions in actual field applications. Dual oxygen sensor method at the lower temperature than light-off is also studied at a model gas bench with the converters. It is fecund that there is a certain point in temperature lower than light-off where difference due to aging level becomes maximum, thus a proper dynamic method to effectively monitor catalytic converters could be implemented fur the range lower than light-off temperatures. With this result, the aging level of converters is examined at an engine bench.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.1
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• pp.83-86
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• 2004

A high temperature tolerant microelectronic-based carbon monioxde(CO) gas sensor has been developed. The gas sensing performance has been studied over a wide temperature range$(100-300^\circ{C)}$. The gas sensitivity of the sensor is high, its initial sensing behavior is very fast, and the sensor is reproducible. Pt-SiC and $Pt-SnO_2-SiC$ diodes are fabricated using standard semiconductor processes and their CO gas-sensing behaviors are analyzed as a function of CO gas concentration and temperature by I-V and $\Delta{I-t}$ methods under steady-state and transient conditions. The sensitivity of the device with $Pt-SnO_2$ catalytic gate is higher than that of the Pt gate. The experimental results indicate that $SnO_2$ layer improves the catalytic reaction of the Pt layer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.1
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• pp.87-92
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• 2004

This review focuses on the developed and the being developed environmental sensors in particular biological sensors. As well as discussing the classification and some main principles, presenting current trend of the environmental sensors is given. Two main categories are immunosensors and catalytic sensors. In addition to those. DNA or RNA sensors or protein based sensors are discussed. Some crucial examples of the applications of such sensors are given to show how the sensor technology it used for environmental and biological monitoring, biomarkers of exposure.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2005.11a
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• pp.60-62
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• 2005

• Korean Journal of Materials Research
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• v.24 no.10
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• pp.532-537
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• 2014

In this study, highly sensitive hydrogen micro gas sensors of the multi-layer and micro-heater type were designed and fabricated using the micro electro mechanical system (MEMS) process and palladium catalytic metal. The dimensions of the fabricated hydrogen gas sensor were about $5mm{\times}4mm$ and the sensing layer of palladium metal was deposited in the middle of the device. The sensing palladium films were modified to be nano-honeycomb and nano-hemisphere structures using an anodic aluminum oxide (AAO) template and nano-sized polystyrene beads, respectively. The sensitivities (Rs), which are the ratio of the relative resistance were significantly improved and reached levels of 0.783% and 1.045 % with 2,000 ppm H2 at $70^{\circ}C$ for nano-honeycomb and nano-hemisphere structured Pd films, respectively, on the other hand, the sensitivity was 0.638% for the plain Pd thin film. The improvement of sensitivities for the nano-honeycomb and nano-hemisphere structured Pd films with respect to the plain Pd-thin film was thought to be due to the nanoporous surface topographies of AAO and nano-sized polystyrene beads.

• Journal of Sensor Science and Technology
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• v.3 no.1
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• pp.32-39
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• 1994

Catalytic combustion type sensor was fabricated for alcohol detection, and its characteristics were tested. When the resistance of Pt coil for pellistor is 2.0 ohm, suggestible input power to bridge circuit was about 300 mW for methanol detection, and in the range from 350 mW to 400 mW for ethanol. Pellistors were prepared by means of impregnating Pt or Pd on the ${\gamma}$-alumina bead for sensing element, and transition metals such as $Co_{3}O_{4}$, $Fe_{2}O_{3}$ for compensating element.

• Journal of Sensor Science and Technology
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• v.4 no.4
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• pp.16-22
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• 1995

Catalytic combustion type gas sensor was fabricated by using ${\gamma}-Al_{2}O_{3}$, Pd catalyst and some binders for metane and propane detection. Using the gas sensor, digital gas meter was manufactured and tested for sensing performance. The fabricated sensor had power consumption of 700mW with applied voltage of dc 2V and the output voltage of the sensor was about 700mV for propane of 1,000ppm and 500mV for methane of 1,000ppm. In 10 cycle injection of the gases of 2,400ppm, The digital meter showed good sensitivity, linearity, and reproductivity with precision of ${\pm}25ppm({\pm}1%)$.