• Journal of Sensor Science and Technology
• /
• v.15 no.2
• /
• pp.97-101
• /
• 2006

Silver electrode having a high Electrocatalytic activity is oxygen-permeable electrode, in which oxygen ad-atoms are adsorbed and moved toward YSZ electrolyte by bulk diffusion. It is the different point in comparison to usual porous electrodes, especially platinum, which react with oxygen only in TPBs(Three Phase Boundaries). Also ad-atoms at TPBs of Pt are diffused to YSZ electrolyte by interfacial diffusion mechanism. These properties were used for turning down the operating temperature of YSZ from over $600^{\circ}C$ to below $450^{\circ}C$. The different heat-treatment temperature between a working electrode and a reference electrode suppresses the formation of silver oxides and reduces a volatility of Ag as well. Above all, these own characteristics and special processes of Ag improved a long-term stability of a oxygen sensor.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 1993.11a
• /
• pp.69-71
• /
• 1993

Fluoride compound potentiometric cell oxygen sensors were fabricated for the measurement of oxygen pressure in the low temperature range (300。K-500。K). The disk type sensors consist of a reference Air(0$_2$):Ag, a solid electrolyte SrF$_2$, and a sensing metel Ag electrode. And the buried reference electrode type sensor have a NiO/Ni reference electrode. The open circuit emf of the cell showed high sensivity to oxygen gas (60mv) at the measuring temperature 20$0^{\circ}C$. Also, The buried reference electrode type sensor showed 30mv from 1% to 10% oxygen pressure range.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.28 no.1
• /
• pp.41-50
• /
• 2023

Dissolved oxygen sensors have characteristics in which data drift occurs over time. Therefore, in-situ calibration of the dissolved oxygen sensor is essential to accurately measure the concentration of dissolved oxygen in seawater. In order to provide a method for in-situ calibration, appropriate number of samples for calibration, and laboratory calibration interval of the dissolved oxygen sensor, the dissolved oxygen sensor values were compared with the measured values by titration on a total of 133 samples from three different cruises in the Indian Ocean, Pacific Ocean, and East Sea over a period of about one year. As a result, it is preferable to calibrate the sensor value using the correlation of a straight line obtained by directly comparing the final concentration value given by the sensor and the measured value. For the accurate calibration, at least 30 samples must be used to enable in-situ calibration within an accuracy range of about 1%. In addition, it is recommended that a laboratory calibration should perform within 1 year for the membrane type dissolved oxygen sensor for CTD to achieve a performance of 70% or more.

• Journal of Electrochemical Science and Technology
• /
• v.14 no.3
• /
• pp.215-221
• /
• 2023

A rapid and environment-friendly electrochemical sensor to determine the chemical oxygen demand (COD) has been developed. The boron-doped diamond (BDD) thin-film electrode is employed as the anode, which fully oxidizes organic pollutants and provides a current response in proportion to the COD values of the sample solution. The BDD-based amperometric COD sensor is optimized in terms of the applied potential and the solution pH. At the optimized conditions, the COD sensor exhibits a linear range of 0 to 80 mg/L and the detection limit of 1.1 mg/L. Using a set of model organic compounds, the electrochemical COD sensor is compared with the conventional dichromate COD method. The result shows an excellent correlation between the two methods.

• KSBB Journal
• /
• v.19 no.1
• /
• pp.62-66
• /
• 2004

The oxygen permeation characteristics of BOPP, OPP and CPP membranes were studied against various thicknesses and temperatures. The experimental results showed that the present method of using electrochemical oxygen sensor was a convenient method for measurement of membrane permeability of oxygen and its activation energy, while the thickness dependency on permeability has an order of BOPP ＞ CPP ＞ OPP. And the activation energy of oxygen permeability showed different values for each membrane ranging from 13.1 kJ/mol to 28.5 kJ/mol, without depending on membrane thickness, presumably due to its depending upon membrane material itself.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.67 no.12
• /
• pp.1641-1647
• /
• 2018

In this paper, we describe a portable potentiostat which is capable of cyclic voltammetry(CV) and amperometry for electrochemical dissolved oxygen sensor. In addition, this portable potentiostat can also transmit the measured data wirelessly to android devices such as smart phone, tablet, etc. through Bluetooth. The potentiostat system consists of three parts; a voltage generator circuit which is controlled by Arduino nano and 12-bit DAC(digital to analog converter) to generate necessary electric potential for operating the electrochemical sensor, an oxidation/reduction current measurement circuit, and a Bluetooth module to transmit data wirelessly to an android device. Once measurements are carried out with the android application, the measured data is transmitted to the android device via Bluetooth and displayed using the android app. in real time. In this paper, we report the measured reduction current with a fabricated dissolved oxygen sensor in both saturated-oxygen state and zero-oxygen states. The results of the developed portable potentiostat system are in good agreement with those of the commercial portable potentiostat (${\mu}stat200$, Dropsens inc.). The measured peak reduction currents using the developed potentiostat and the commercial ${\mu}stat200$ potentiostat were $-0.755{\mu}A$ and $-0.724{\mu}A$, respectively. The reduction currents measured at zero-oxygen state were $-0.005{\mu}A$ and $-0.004{\mu}A$. The discrepancy between those two systems seems very small, which implies successful development of a portable and wireless potentionstat.

• Journal of Powder Materials
• /
• v.18 no.3
• /
• pp.250-255
• /
• 2011

The potential application of ultrafine cerium oxide (ceria, $CeO_2$) as an oxygen gas sensor has been investigated. Ceria was synthesized by a thermochemical process: first, a precursor powder was prepared by spray drying cerium-nitrate solution. Heat treatment in air was then performed to evaporate the volatile components in the precursor, thereby forming nanostructured $CeO_2$ having a size of approximately 20 nm and specific surface area of 100 $m^2/g$. After sintering with loosely compacted samples, hydrogen-reduction heat treatment was performed at 773K to increase the degree of non-stoichiometry, x, in $CeO_{2-x}$. In this manner, the electrical conductivity and oxygen-response ability could be enhanced by increasing the number of oxygen vacancies. After the hydrogen reduction at 773K, $CeO_{1.5}$ was obtained with nearly the same initial crystalline size and surface. The response time $t_{90}$ measured at room temperature was extremely short at 4 s as compared to 14 s for normally sintered $CeO_2$. We believe that this hydrogen-reduced ceria can perform capably as a high-performance oxygen sensor with good response abilities even at room temperature.

• Analytical Science and Technology
• /
• v.20 no.1
• /
• pp.1-9
• /
• 2007

The BOD (biochemical oxygen demand) sensor was fabricated by covering a dissolved oxygen (DO) probe with a microbe-impregnated membrane and a dialysis membrane. Various microorganisms isolated from the soils, water and activated sludge have been evaluated for measuring biochemical oxygen demand (BOD); Bacillus species HN24 and HN93 were selected as they exhibited rapid oxygen consumption and fast recovery. Improved BOD sensor could be prepared by using mixed microbes (Bacillus subtilis, Bacillus sp. HN24 and Bacillus sp. NH93) and silicon rubber gas-permeable membrane for DO probe, and by bubbling 50% $O_2$ ($N_2$ valence) through background buffer solution. This system exhibited excellent analytical performance resulting in good linearity ($r^2=0.9986$) from 0 to 100 mg/L level of BOD.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2007.06a
• /
• pp.503-504
• /
• 2007

• 한국생물공학회:학술대회논문집
• /
• 2001.11a
• /
• pp.819-822
• /
• 2001

In this study a fiber optic biosensor has been developed to on-line monitor the concentrations of oxygen and glucose. The oxygen concentrations in solution and gas phase monitored by the fiber optic sensor has been compared with those by a dissolved oxygen electrode and an IR-type $O_2$ analyzer. The fiber optic glucose sensor has been made by immobilizing glucose oxidase on the tip of the optic fiber and used to on-line monitor the concentration of glucose in a fermentation process.