• Journal of Advanced Marine Engineering and Technology
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• v.34 no.6
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• pp.864-870
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• 2010

Air embolism can be a lethal complication of surgical procedures during which venous pressure at the site of surgery is sub-atmospheric or air is forced under pressure into a body cavity. To solve the problem, we developed the air detector using relative dielectric constant change, which is expected to be used broadly in industrial circles. We designed air detection system with air control equipment, detection circuit and LabVIEW system for air sensing. In experiments with a mock system, the proposed system showed a signal difference depending on the amount of air in the Tygon tube of the mock system.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.845-846
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• 2006

In this paper, we describe a capacitive position sensing and motion control scheme of a MEMS scanner used for laser display application. The laser displays can be made by scanning laser beams much the same way a CRT scans electron beams. So the accuracy of the scanner motion determines the quality of the displayed image. The MEMS scanner under consideration is composed of electrostatic comb electrodes with initial gap and requires large driving voltage. Due to the under-damping and nonlinear driving characteristics, the scanner motion is subject to be an unwanted oscillation. For the linear scanner motion, we devise a differential charge amplifier and phase compensator. The experimental results show that the implemented feedback control system provides sufficient electrical damping and improves the dynamic performance of the scanner.

• Smart Structures and Systems
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• v.7 no.5
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• pp.365-378
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• 2011

Piezo-based active structural health monitoring (SHM) requires amplifiers specifically designed for capacitive loads. Moreover, with the increase in number of applications of wireless SHM systems, energy efficiency and cost reduction for this type of amplifiers is becoming a requirement. General lab grade amplifiers are big and costly, and not built for outdoor environments. Although some piezoceramic power amplifiers are available in the market, none of them are specifically targeting the wireless constraints and low power requirements. In this paper, a piezoceramic transducer amplifier for wireless active SHM systems has been designed. Power requirements are met by two digital On/Off switches that set the amplifier in a standby state when not in use. It provides a stable ${\pm}180$ Volts output with a bandwidth of 7k Hz using a single 12 V battery. Additionally, both voltage and current outputs are provided for feedback control, impedance check, or actuator damage verification. Vibration control tests of an aluminum beam were conducted in the University of Houston lab, while wireless active SHM tests of a wind turbine blade were performed in the Harbin Institute of Technology wind tunnel. The results showed that the developed amplifier provided equivalent results to commercial solutions in suppressing structural vibrations, and that it allows researchers to perform active wireless SHM on moving objects with no power wires from the grid.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.986-988
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• 2012

최적의 식물 생장을 위해서는 적절한 수분의 유지가 필수적이며 넓은 지역, 다양한 종류, 고가의 식물의 경우일수록 적절한 수분의 관리를 위한 시스템의 도움이 필요하다. 이를 위해 저가의 센서노드 시스템이 적절한 해결책이 될 수 있으나 일반적인 배터리 기반의 센서노드 시스템을 적용시 배터리 용량 확인 및 교체 등의 유지보수 문제가 대두된다. 본 논문에서는 이러한 유지보수의 문제를 해결하고 식물재배에 도움을 줄 수 있는 자기유지 지원 방식의 정전용량 센싱기반의 수분 모니터링 센서노드를 설계하였다. UHF 기반의 무선 전력 전송의 자기유지 지원 시스템 및 PCB 패턴기반의 정전용량센싱 수분센서와 초저전력 센서노드 시스템으로 구성된다. 센서노드는 한번 송신시 약 0.24 mJ을 소모하며 에너지획득모듈은 에너지 획득 주기마다 약 4 mJ의 에너지를 공급하도록 설계하여 센서동작을 위한 충분한 에너지 마진을 주도록 설계하였다.

• Journal of Sensor Science and Technology
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• v.28 no.1
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• pp.1-6
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• 2019

This paper presents an air flow sensor (AFS) based on a polymer thin film. This AFS primarily consists of a polymer membrane attached to a metal-patterned glass substrate and a temperature-sensing element composed of NiCr. These two components were integrated on a single glass substrate. The AFS measures changes in capacitance caused by deformation of the polymer membrane based on the air flow and simultaneously detects the temperature of the surrounding environment. A readout integrated circuit (ROIC) was also fabricated for signal processing, and an ROIC chip, 1.8 mm by 1.9 mm in size, was packaged with an AFS in the form of a system-in-package module. The total size of the AFS is 1 by 1 cm, and the diameter and thickness of the circular-shaped polymer membrane are 4 mm and $15{\mu}m$, respectively. The rate of change of the capacitance is approximately 11.2% for air flows ranging between 0 and 40 m/s.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.11
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• pp.1-8
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• 2005

In this paper, we present design and prototyping of a low-cost, integrated multi-functional micro health sensor chip that can be used or embedded in widely consumer devices, such as cell phone and PDA, for monitoring environmental condition including air pressure, temperature and humidity. This research's scope includes basic individual sensor study, architecture for integrating sensors on a chip, fabrication process compatibility and test/evaluation of prototype sensors. The results show that the integrated TPH sensor has good characteristics of ${\pm}\;1\%FS$ of linearity and hysteresis for pressure sensor and temperature sensor and of ${\pm}\;5\%FS$ of linearity and hysteresis But if we use 3rd order approximation for humidity sensor, full scale error becomes much smaller and this will be one of our future study.

• Journal of Sensor Science and Technology
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• v.10 no.3
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• pp.173-179
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• 2001

The currently used semiconductor pressure sensors are piezoresistive and capacitive type. Especially, semiconductor micro pressure sensors have a great deal of attention because of their small size. However, its fabrication processes are difficult, so that its yield is poor. For the purpose of resolving the drawbacks of the existing silicon pressure sensors, we demonstrate a new type of pressure sensor using PSFET(pressure sensitive field effect transistor) and investigate its operational characteristics. We used PZT(Pb(Zr,Ti)$O_3$) as a pressure sensing material. PZT thin films were deposited on a gate oxide of MOSFET by an rf-magnetron sputtering method. To abtain the stable phase, perovskite structure, furnace annealing technique have been employed in PbO ambient. The sensitivity of the PSFET was 0.38 mV/mmHg.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.1
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• pp.209-218
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• 2017

Healthcare services can be provided through a number of independent service platforms for measurement of vital signs, diagnosis and prevention of diseases, and Information and communication technology(ICT) such as internet and mobile are converged to provide health information to users at anytime and anywhere, and it is in the center of the IoT(Internet of things). Accordingly, in this paper, we designed IoT based urination management system and evaluate the performance. A low - power Zigbee network was constructed for the configuration of the urination management system. The implemented capacitive diaper sensor was operable for the duration of 2,000 hours. We also built a database server using Raspberry Pi, a tiny embedded device, and stored the collected data to verify the data through an Android-based mobile application. The proposed urination management system can be utilized not only for the older patients, but also for the infants.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.1
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• pp.48-58
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• 1998

For the purpose of designing novel capacitance pressure sensor, several effects on sensitivity such as parasitic capacitance effects, temperature/thermal drift and leakage current have to be eleiminated. This paper proposed the experimental studies on frequency compensation method by electronic circuit technique, C-V converting method with switched capacitor and C-F converting method with schmitt trigger circuit. The third interface circuit by frequency compensation method is composed to eliminate the drift and leakage component by comparision sensing frequency with reference frequency. The signal transmission is realized by digital signal to minimize the influence of noise and high resolution is obtained by means of increasing the number of digital bits. In the fabricated high performance C-V interface, the offset voltage was not appeared, and in case of voltage source, 4.0V, feed back capacitance, 10㎊, the pressure, 0~10 ㎪, the sensitivity of C-V converter is 28 ㎷/㎪.V, the temperature drift characteristic, 0.051 %F.S./$^{\circ}C$ and C-F converter shows -6.6 Hz/pa, 0.078 %F.S./$^{\circ}C$ respectively, relatively good ones.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.412-417
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• 2022

Capacitive-type humidity sensors with a high sensitivity and fast response/recovery times have attracted a great attention in non-contact respiration biological signal monitoring applications. However, complicated fabrication processes involving high-temperature heat treatment for the hygroscopic film is essential in the conventional ceramic-based humidity sensors. In this study, a non-toxic ceramic/metal halide (BaTiO₃(BT)/NaCl) humidity sensor was prepared at room temperature using a solvent-free aerosol deposition process (AD) without any additional process. Currently prepared BT/NaCl humidity sensor shows an excellent sensitivity (245 pF/RH%) and superior response/recovery times (3s/4s) due to the NaCl ionization effect resulting in an immense interfacial polarization. Furthermore, the non-contact respiration signal variation using the BT/NaCl sensor was determined to be over 700% by maintaining the distance of 20 cm between the individual and the sensor. Through the AD-fabricated sensor in this study, we expect to develop a non-contact biological signal monitoring system that can be applied to various fields such as respiratory disease detection and management, infant respiratory signal observation, and touchless skin moisture sensing button.