• Journal of Sensor Science and Technology
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• v.23 no.2
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• pp.110-113
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• 2014

In this paper, we propose and demonstrate a Fabry-Perot interferometer (FPI) optical fiber tip sensor fabricated by a blade-sawing technique using a fiber optic patch cord for high-resolution temperature measurement. The sensor head consists of a short air FP cavity near the tip of a single-mode fiber patch cord tip. The temperature which we can measure is determined through a phase variation of the interference fringes in the reflective spectrum of the sensor. The fiber optic FPI sensor in this work can monitor the environmental temperature very accurately from 40 to $120^{\circ}C$. As a result, the temperature sensitivity is obtained as $38.2pm/^{\circ}C$.

• The Journal of the Acoustical Society of Korea
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• v.34 no.4
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• pp.288-294
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• 2015

The fiber optic Sagnac interferometer is well established as a sensor for detection of physical perturbations such as acoustic and vibration. In this paper acoustic signals generated in the cylindrical cavity submerged in transformer oil were measured by the fiber optic sensor array in one Sagnac loop. Two different external sound frequencies, $f_1$ and $f_2$, were applied to the sensor array simultaneously by using piezoelectric with frequency range from 5 kHz to 90 kHz. Based on the experimental results, fiber optic sensor detected harmonic series of applied sound frequency such as $f_1$, $f_2$, $2f_1$, $2f_2$, ${\mid}f_1-f_2{\mid}$, ${\mid}f_1+f_2{\mid}$. Suggested fiber optic sensor array can be applied to monitor physical quantities such as internal sound pressure and vibration due to partial discharge in the real electric transformer system.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.3
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• pp.45-50
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• 2005

This paper proposed an efficient manufacturing system using the OMM (on-machine measurement) system. The OMM system is software-based 3D modeler for inspection on machine, and it is interfaced with machine tools via RS232C. The software is composed of two inspection modules; one is touch probe operating module, and the other is laser displacement sensor operating module. The module for touch probe needs the inspection feature extracted from CAD data. The touch probe moves to workpiece by three operating modes as follows: manual, general and automatic mode. The operating module of the laser displacement sensor is used to inspect profiles and very small holes. An advantage of this inspection method is the ability to execute on-line inspection during machining or afterward. The efficiency of proposed system which can predict and define the machining errors of each process was verified, so the developed system was applied to inspect a mold-base (cavity, core).

• Journal of the Optical Society of Korea
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• v.18 no.4
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• pp.301-306
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• 2014

A porous silicon microcavity (PSMC) sensor has been made for vapors of solvent solutions, and a method has been developed in order to obtain simultaneous determination of two volatile substances with different concentrations. In our work, the temperature of the solution and the velocity of the air stream flowing through the solution have been used to control the response of the sensor for ethanol and acetone solutions. We study the dependence of the cavity-resonant wavelength shift on solvent concentration, velocity of the airflow and solution temperature. The wavelength shift depends linearly on concentration and increases with solution temperature and velocity of the airflow. The dependence of the wavelength shift on the solution temperature in the measurement contains properties of the temperature dependence of the solvent vapor pressure, which characterizes each solvent. As a result, the dependence of the wavelength shift on the solution temperature discriminates between solutions of ethanol and acetone with different concentrations. This suggests a possibility for the simultaneous determination of the volatile substances and their concentrations.

• Journal of Sensor Science and Technology
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• v.33 no.3
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• pp.158-164
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• 2024

We developed a self-operated paper pump that can maintain a nearly constant flow rate of an aqueous solution along a paper strip channel in paper-based analytical devices (PADs). The quasi-stationary flow rate was controlled by increasing the crosssectional channel area (capillary force) using a fan-shaped absorption pad coupled with a paper strip channel. The flow rate is regulated by varying the fan angle of the circular absorbing pad. Furthermore, the flow rate can be increased by furnishing a hollow cavity at the center of a conventional paper strip channel. The rate was regulated by varying the length of the hollow paper channel in the flow rate range of 5.1-26.4 mm/min. As a preliminary work, a paper-pump-coupled PAD was fabricated, and its CV detection capability was evaluated for the redox reaction of Fe(CN)₆^+4/+3. The combination of a paper pump with a PAD resulted in an ideal CV curve with a higher limiting current and faster response time. These results are interpreted well by the Levich equation, which suggests that the paper pump is a very useful component in paper-based sensors.

• Smart Structures and Systems
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• v.3 no.1
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• pp.1-22
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• 2007

The energy efficiency of a self-powered wireless sensing system for pressure monitoring in injection molding is analyzed using Bond graph models. The sensing system, located within the mold cavity, consists of an energy converter, an energy modulator, and a ultrasonic signal transmitter. Pressure variation in the mold cavity is extracted by the energy converter and transmitted through the mold steel to a signal receiver located outside of the mold, in the form of ultrasound pulse trains. Through Bond graph models, the energy efficiency of the sensing system is characterized as a function of the configuration of a piezoceramic stack within the energy converter, the pulsing cycle of the energy modulator, and the thicknesses of the various layers that make up the ultrasonic signal transmitter. The obtained energy models are subsequently utilized to identify the minimum level of signal intensity required to ensure successful detection of the ultrasound pulse trains by the signal receiver. The Bond graph models established have shown to be useful in optimizing the design of the various constituent components within the sensing system to achieve high energy conversion efficiency under a compact size, which are critical to successful embedment within the mold structure.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1470-1471
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• 2008

We present a front-side micromachined thermopile with high sensitivity in the 3-5${\mu}m$ window, and discuss its application to a novel non-dispersive infrared (NDIR) $CO_2$ gas sensor with a light source emitting collimated light. The micromachined thermopile shows a measured sensitivity of 30 mV/W and a $D^*$ of $0.3{\times}10^8cm^{\surd}Hz/W$. Using this newly fabricated thermopile, we also have successfully developed a small, sensitive NDIR $CO_2$ detector module for accurate air quality monitoring systems in energy-saving building and automotive applications. The novel sample cavity comprising specular reflectors around the light bulb is configured to uniformly emit collimated light into the entrance aperture of the cavity in order to enhance the sensitivity of NDIR $CO_2$ detector.

• The Journal of the Acoustical Society of Korea
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• v.11 no.4
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• pp.31-35
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• 1992

Cavity resonances are caused by combustion such as the rapid of pressure rise that occurs from knock in high power gasoline engines. These resonances generally occur at frequencies greater than 5KHz. Analysis of these resonances is important for knock control system design in high power gasoline engines. In this paper, in order to design knock control system for the high power gasoline engine, knock phenomena that occur in chamber were analized theoretically and resonance frequencies of knock signals were predicted. Also, experiments were performed using Soupe x-engine and non-resonance type knock sensor of Bosch co. in Germany. In the result, good agreement was obtained between theoretical prediction and experimental observation.

• Journal of the Optical Society of Korea
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• v.17 no.5
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• pp.423-427
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• 2013

We present the preparation and characteristics of liquid-phase sensors based on nano-porous silicon multilayer structures for determination of organic content in gasoline. The principle of the sensor is a determination of the cavity-resonant wavelength shift caused by refractive index change of the nano-porous silicon multilayer cavity due to the interaction with liquids. We use the transfer matrix method (TMM) for the design and prediction of characteristics of microcavity sensors based on nano-porous silicon multilayer structures. The preparation process of the nano-porous silicon microcavity is based on electrochemical etching of single-crystal silicon substrates, which can exactly control the porosity and thickness of the porous silicon layers. The basic characteristics of sensors obtained by experimental measurements of the different liquids with known refractive indices are in good agreement with simulation calculations. The reversibility of liquid-phase sensors is confirmed by fast complete evaporation of organic solvents using a low vacuum pump. The nano-porous silicon microcavity sensors can be used to determine different kinds of organic fuel mixtures such as bio-fuel (E5), A92 added ethanol and methanol of different concentrations up to 15%.

• Journal of Sensor Science and Technology
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• v.7 no.3
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• pp.171-178
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• 1998

Silicon piezoresistive absolute pressure sensor for gas leakage alarm system was developed. This sensor must operate normally in the range of $0{\sim}600\;mmH_{2}O$ pressure, and $0{\sim}100^{\circ}C$ temperature. To make the most of this sensor for gas leakage alarm system, gas must not leak from the sensor itself when the diaphragm of the sensor fractures. Thus, the sealed diaphragm cavity was anodically bonded to pyrex 7740 glass under the condition of $10^{-4}$ torr, at $400^{\circ}C$. The sensitivity of developed sensor was $4.06{\mu}V/VmmH_{2}O$ for $600\;mmH_{2}O$ full-scale pressure range. And temperature compensation method of this sensor is to change bridge-in put-voltage linearly in proportion to the temperature variation by using diode(PXIN4001) or Al thin film resistor. By these methods the temperature effect in the range of $0{\sim}100^{\circ}C$ was compensated over 80 % for offset drift, 95 % for sensitivity.