• Journal of Sensor Science and Technology
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• v.7 no.1
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• pp.31-38
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• 1998

Multi-channel sensors can be used to increase the reliability and remove the random iloise in ion-sensitive field effect transistors(ISFETs). Multi-channel sensors is also an essential step toward potential fabrication of sensors for several ionic species in one device. However, when the multi-channel sensors are separately biased, the biasing problems become difficult, that is to say, the bias circuit is needed as many sensors. In this work, a circuit for biasing the four pH-ISFETs in null-balance method, where bias voltages are switched, was proposed. The proposed concept is need only one bias circuit for the four sensors. Therefore it has advantages of smaller size and lower power consumption than the case that all sensors are separately biased at a time. The proposed circuit was tested with discrete devices and its performance was investigated. In the recent trend, sensor systems are implemented as portable systems. So the verified measurement circuit was integrated by using the CMOS circuit. Fortunately, ISFET fabrication process can be compatible with CMOS process. Full circuit has a mask area of $660{\mu}m{\times}500{\mu}m$. In the future, this step will be used for developing the smart sensor system with ISFET.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.10
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• pp.1833-1841
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• 2000

Microelectrode probe was made and applied to the biofilm in the biological treatment process as the state-of-art technology in order to actually measure the biofilm thickness, ionic concentration gradient, and material transport, etc. instead of classical theoretical approach. The working microelectrode, one of the main components of microelectrode probe, was easily contaminated and broken when determining the differences in the ionic concentrations through the measurement of biofilm's EMF (electromotive force). As a demonstration, two microelectrode probes were constructed in our lab for the measurement of the pH and $NO_3{^-}$ concentration in denitrifying biofilm. The microelectrode probe through the inner biofilm ($350{\mu}m$ from the surface of biofilm) showed that the pH was increased from pH 8 in the bulk solution to pH 8.3, on the other hand, the $NO_3{^-}$ concentration was decreased from 30 fig N/L in the bulk solution to 4 fig N/L.

• Journal of the Korean Chemical Society
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• v.56 no.5
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• pp.571-576
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• 2012

A sol-gel derived carbon composite electrodes (CCEs) were fabricated by mixing horseradish peroxidase (HRP), sol of tetraethoxysilane (TESO), and graphite powder. The HRP solution was added to the sol solution of TEOS, and then graphite powder was added to this mixture. The resulting carbon ceramic network effectively encapsulated HRP and shows a catalytic reduction starting at -0.2 V for $H_2O_2$. The optimum conditions for $H_2O_2$determination have been characterized with respect to the enzyme loading ratio and pH. The linear range and detection limit of $H_2O_2$ detection were from 0.2 mM to 2.2 mM and 0.035 mM, respectively. The common electroactive interferences such as ascorbic acid, acetaminophene, and uric acid were not affected upon the response to $H_2O_2$ at the HRP biosensor due to low detection potential.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.292-297
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• 2005

This paper proposes a simple MPPT control scheme of a Current-Control-Loop Error system Based that can be obtains a lot of advantage to compare with another digital control method, P&O and IncCond algorithm, that is applied mostly a PV system. An existent method is needed an expensive processor such as DSP that calculated to change the measure power of a using current and voltage sensor at the once. Therefore, it is applied a small home power generation system that required many expenses. But, a proposed method is easy to solve the cost reduction and power unbalance problems that it is used by control scheme to limit error of a current control of common sensor. This proposed algorithm had verified through a simulation and an experiment on battery charger using PIC that is the microprocessor of a low price.

• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.280-282
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• 2005

This paper proposes a simple MPPT control scheme of a Current-Control-Loop Error system Based that can be obtains a lot of advantage to compare with another digital control method, P&O and IncCond algorithm, that is applied mostly a PV system. An existent method is needed an expensive processor such as DSP that calculated to change the measure power of a using current and voltage sensor at the once. Therefore, it is applied a small home power generation system that required many expenses. But, a proposed method is easy to solve the cost reduction and power unbalance problems that it is used by control scheme to limit error of a current control of common sensor. This proposed algorithm had verified through a simulation and an experiment on battery charger using PIC that is the microprocessor of a low price.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.447-448
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• 2007

Product development is consisting by trend that accommodate almost function digital cam in camera phone that can speak of Mobile appliance, and competition about number of elemental area of image sensor is consisting for market prior occupation between these. Propose in this research and small size camera phone self-focusing adjustment actuator that do city manufacture is similar with general storehouse pickup actuator drive way, but selected in cylindrical to reduce space that lens holder occupies because there is restriction loading of lens and space enemy. Target number of research established that execute drive displacement more than $600{\mu}m$ in 2.75V that is house voltage that is used in Mobile device that is general. Also, described about maximum transfer displacement characteristic, displacement response characteristic, hysteresis, response characteristic, smallest transfer step characteristic, actuator's drive characteristic that is manufactured to examination item of maximum consumption electric power by special quality estimation system that apply laser displacement sensor that produce itself to evaluate city manufactured actuator's special quality.

• Progress in Superconductivity and Cryogenics
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• v.22 no.4
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• pp.1-5
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• 2020

Heart consists of myocardium cells and the electrophysiological activity of the cells generate magnetic fields. By measuring this magnetic field, magnetocardiogram (MCG), functional diagnosis of the heart diseases is possible. Since the strength of the MCG signals is weak, typically in the range of 1-10 pT, we need sensitive magnetic sensors. Conventionally, superconducting quantum interference devices (SQUID)s were used for the detection of MCG signals due to its superior sensitivity to other magnetic sensors. However, drawback of the SQUID is the need for regular refill of a cryogenic liquid, typically liquid helium for cooling low-temperature SQUIDs. Efforts to eliminate the need for the refill in the SQUID system have been done by using cryocooler-based conduction cooling or use of non-cryogenic sensors, or room-temperature sensors. Each sensor has advantage and disadvantage, in terms of magnetic field sensitivity and complexity of the system, and we review the recent trend of MCG technology.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.247-254
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• 1999

In recent years there has been a steady increase in geoenvironmental engineering projects where geotechnical engineering has been combined with environmental concerns. Many of these projects involve some investigation of contaminant in the ground. There are many techniques such as geophysical, drilling, sampling, and pushing techniques for investigation of contaminated ground. The most rapidly developing site characterization techniques for geoenvironmental purposes Involve direct push technology, that is, penetration tests. In this study, the envi-cone penetrometer system is developed by modification of traditional cone penetration test. The electrical resistivity sensor, pH sensor, thermometer are installed in envi-cone penetrometer system. This envi-cone penetrometer system provides a continuous profile of measurements, and it is rapid, repeatable, reliable and cost effective.

• Journal of Biosystems Engineering
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• v.28 no.5
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• pp.457-464
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• 2003

The purpose of this study was to develop a pilot scale bio-filter system removing ammonia gas with microorganisms. The system consisted of chaff(filter medium), a blower, a temperature sensor, a moisture sensor, a solenoid valve, and a heating system. Temperature and moisture contents were controlled via a PC to provide the microorganisms with proper environment. The microorganisms used in this study were Bacillius. coagulans NLRI T-6 and Pseudononas. putida NLRI S-21 of bacilli. Performance tests were performed to evaluate gas removal rate during 20 days. The result was shown that the removal rate was high in early days and gradually dropped below 90% without injecting the microbes. However, it was shown that when injecting the microbes, the removal rate was almost 100% and pH value was maintained at between 7 and 9 during the whole twenty-day period.

• Transactions of Materials Processing
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• v.15 no.1 s.82
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• pp.47-56
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• 2006

It is well known that the family-mold has an advantage to reduce the cost for production and mold. However, defects are frequently occurred by over packing the smaller volume cavity during molding, especially when the family-mold has a volumetric difference between two cavities. In this study, the cavity-filling imbalance was confirmed by the temperature and the pressure sensors, and a variable-runner system was developed for balancing the cavity-filling. Experiments of balancing the cavity filling was carried out in the family-mold with the variable-runner system, and balancing the cavity-filling was confirmed by changing the cross-sectional area of a runner in the variable-runner system with the temperature and pressure sensors. The influence of the injection speed to the balancing-capability of the variable-runner system was also examined in the experiment.