• Title/Summary/Keyword: Current sensors

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Characteristics of $Ta_{2}O_{5}$ Films by RF Reactive Sputtering (RF 반응성 스펏터링으로 제조한 $Ta_{2}O_{5}$ 막의 특성)

  • Park, Wug-Dong;Keum, Dong-Yeal;Kim, Ki-Wan;Choi, Kyu-Man
    • Journal of Sensor Science and Technology
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    • v.1 no.2
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    • pp.173-181
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    • 1992
  • Tantalum pentoxide($Ta_{2}O_{5}$) thin films on p-type (100) silicon wafer were fabricated by RF reactive sputtering. Physical properties and structure of the specimens were examined by XRD and AES. From the C-V analysis, the dielectric constant of $Ta_{2}O_{5}$ films was in the range of 10-12 in the reactive gas atmosphere in which 10% of oxygen gas is mixed. The ratio of Ta : 0 was 1 : 2 and 1 : 2.49 by AES and RBS examination, respectively. The heat-treatment at $700^{\circ}C$ in $O_{2}$ ambient led to induce crystallization. When the heat-treatment temperature was $1000^{\circ}C$, the dielectric constant was 20.5 in $O_{2}$ ambient and 23 in $N_{2}$ ambient, respectively. The crystal structure of $Ta_{2}O_{5}$ film was pseudo hexagonal of ${\delta}-Ta_{2}O_{5}$. The flat band voltage shift(${\Delta}V_{FB}$) of the specimens and the leakage current density were decreased for higher oxygen mixing ratio. The maximum breakdown field was 2.4MV/cm at the oxygen mixing ratio of 10%. The $Ta_{2}O_{5}$ films will be applicable to hydrogen ion sensitive film and gate oxide material for memory device.

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Analysis of Temperature Characteristics on Accelerometer using SOI Structure (SOI 구조 가속도센서의 온도 특성 해석)

  • Son, Mi-Jung;Seo, Hee-Don
    • Journal of Sensor Science and Technology
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    • v.9 no.1
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    • pp.1-8
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    • 2000
  • One of today's very critical and sensitive accurate accelerometer which can be used higher temperature than $200^{\circ}C$ and corrosive environment, is particularly demanded for automotive engine. Because silicon is a material of large temperature dependent coefficient, and the piezoresistors are isolated with p-n junctions, and its leakage current increase with temperature, the performance of the silicon accelerometer degrades especially after $150^{\circ}C$. In this paper, The temperature characteristic of a accelerometer using silicon on insulator (SOI) structure is studied theoretically, and compared with experimental results. The temperature coefficients of sensitivity and offset voltage (TCS and TCO) are related to some factors such as thermal residual stress, and are expressed numerically. Thermal stress analysis of the accelerometer has also been carried out with the finite-element method(FEM) simulation program ANSYS. TCS of this accelerometer can be reduced to control the impurity concentration of piezoresistors, and TCO is related to factors such as process variation and thermal residual stress on the piezoresistors. In real packaging, The avarage thermal residual stress in the center support structure was estimated at around $3.7{\times}10^4Nm^{-2}^{\circ}C^{-1}$ at sensing resistor. The simulated ${\gamma}_{pT}$ of the center support structure was smaller than one-tenth as compared with that of the surrounding support structure.

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Fabrication and Its Characteristics of Ion Energy Spectrometer for Diagnostics of Plasma (플라즈마 진단을 위한 이온에너지 분석장치의 제작 및 특성 조사)

  • Kim, Kye-Ryung;Kim, Wan;Lee, Yong-Hyun;Kang, Hee-Dong
    • Journal of Sensor Science and Technology
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    • v.7 no.3
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    • pp.163-170
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    • 1998
  • An ion energy spectrometer which has the $45^{\circ}$ parallel electrostatic deflection plate was designed and constructed for measuring ion temperature in high temperature plasma. The energy calibration and the energy resolution were studied in detail for a hydrogen ion at the $0.24{\sim}1.92\;keV$ energy using electrostatic accelerator with a duoplasmatron ion source. The voltage of the deflection plate was linearly increased for the decreased ion detector position at the constant ion energy and decreased for the increased ion energy at the fixed ion detector position. The inclination of the deflection plate voltage to the ion energy was between 0.92 and 1.61, and linearly decreased for the increased the ion detector position. The measured energy resolution, which is $4.2%\;{\sim}\;11.6%$ in this experiment region, was improved for the increased ion dector position and ion energy. The relative efficiency was increased for the decreased the ion detector position. The ion energy spectrum of the DC plasma in the multi-purpose plasma generator was measured using this equipment. The ion temperature was 203-205 eV at the discharge voltage 320 V, discharge current 1.7 A.

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A Study on the Implementation of the 2-Dimension Magnetic Fluxgate Sensor (2차원 Magnetic Fluxgate센서의 구현에 관한 연구)

  • Park, Yong-Woo;Kim, Nam-Ho;Ryu, Ji-Goo
    • Journal of Sensor Science and Technology
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    • v.11 no.2
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    • pp.67-76
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    • 2002
  • We have presented a 2-dimensional fluxgate sensor with ferrite core, excitation, and pick-up coil. This fluxgate sensor system consists of a sensing element, driving circuits for excitation coil and signal processing for detecting second harmonic frequency component which is proportional to the DC magnetic to be measured. The sensor core is excited by a square waveform of voltage through the excitation coil of 80 turns. The second harmonic output of pick-up coil(x and y axis: 100 turns) is measured by FFT spectrum analyzer. This result is compared with output of PSD(phase sensitive detector) unit for detecting the second harmonic component. The measured maximum sensitivity is about 1580 V/T at driving frequency of 1.5 kHz and excitation current of 2 App. The nonlinearity of this system is measured about 2.3%(PSD) and about 1%(second harmonics of the pick-up). The angle error of the system is ${\pm}2$ %/FS.

Pt/AlGaN Schottky-Type UV Photodetector with 310nm Cutoff Wavelength

  • Kim, Bo-Kyun;Kim, Jung-Kyu;Park, Sung-Jong;Lee, Heon-Bok;Cho, Hyun-Ick;Lee, Young-Hyun;Hahn, Yoon-Bong;Lee, Jung-Hee;Hahm, Sung-Ho
    • Journal of Sensor Science and Technology
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    • v.12 no.2
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    • pp.66-71
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    • 2003
  • Pt/AlGaN Schottky-type UV photodetectors were designed and fabricated. A low-temperature AlGaN interlayer buffer was grown between the AlGaN and GaN film in the diode structure epitaxy to obtain crack-free AlGaN active layers. A comparison was then made of the structural, electrical, and optical characteristics of two different diodes: one with an AlGaN($0.5\;{\mu}m$)/n+-GaN(2 nm) structure (type 1) and the other with an AlGaN($0.5\;{\mu}m$)/AlGaN interlayer($150\;{\AA}$)/n+-GaN($3\;{\mu}m$) structure(type 2). A crack-free AlGaN film was obtained by the insertion of a low-temperature AlGaN interlayer with an aluminum mole fraction of 26% into the $Al_xGa_{1-x}N$ layer. The fabricated Pt/$Al_{0.33}Ga_{0.67}N$ photodetector had a leakage current of 1 nA for the type 1 diode and $0.1\;{\mu}A$ for the type 2 diode at a reverse bias of -5 V. For the photoresponse measurement, the type 2 diode exhibited a cut-off wavelength of 300 nm, prominent responsivity of 0.15 A/W at 280 nm, and UV-visible extinction ratio of $1.5{\times}10^4$. Accordingly, the Pt/$Al_{0.33}Ga_{0.67}N$ Schottky-type ultraviolet photodetector with an AlGaN interlayer exhibited superior electrical and optical characteristics and improved UV detecting properties.

Analysis of IoT Open-Platform Cryptographic Technology and Security Requirements (IoT 오픈 플랫폼 암호기술 현황 및 보안 요구사항 분석)

  • Choi, Jung-In;Oh, Yoon-Seok;Kim, Do-won;Choi, Eun Young;Seo, Seung-Hyun
    • KIPS Transactions on Computer and Communication Systems
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    • v.7 no.7
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    • pp.183-194
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    • 2018
  • With the rapid development of IoT(Internet of Things) technology, various convenient services such as smart home and smart city have been realized. However, IoT devices in unmanned environments are exposed to various security threats including eavesdropping and data forgery, information leakage due to unauthorized access. To build a secure IoT environment, it is necessary to use proper cryptographic technologies to IoT devices. But, it is impossible to apply the technologies applied in the existing IT environment, due to the limited resources of the IoT devices. In this paper, we survey the classification of IoT devices according to the performance and analyze the security requirements for IoT devices. Also we survey and analyze the use of cryptographic technologies in the current status of IoT open standard platform such as AllJoyn, oneM2M, IoTivity. Based on the research of cryptographic usage, we examine whether each platform satisfies security requirements. Each IoT open platform provides cryptographic technology for supporting security services such as confidentiality, integrity, authentication an authorization. However, resource constrained IoT devices such as blood pressure monitoring sensors are difficult to apply existing cryptographic techniques. Thus, it is necessary to study cryptographic technologies for power-limited and resource constrained IoT devices in unattended environments.

Application of Automatic Stormwater Monitoring System and SWMM Model for Estimation of Urban Pollutant Loading During Storm Events (빗물 자동모니터링장치와 SWMM 모델을 이용한 강우시 도시지역 오염부하량 예측에 관한 연구)

  • Seo, Dongil;Fang, Tiehu
    • Journal of Korean Society of Environmental Engineers
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    • v.34 no.6
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    • pp.373-381
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    • 2012
  • An automatic flow and water quality monitoring system was applied to estimate pollutant loads to an urban stream during storm events in DTV (Daeduk Techno Valley), Daejeon, Korea. The monitoring system consists of rainfall gage, ultrasonic water level meter, water quality sensors for DO, temperature, pH, conductivity, turbidity and automatic water sampler for further laboratory analysis. All data are transmitted through on-line system and the monitoring system is designed to be controlled manually in the field and remotely from laboratory computer. Flow rates were verified with field measurements during storm events and showed good agreements. Automatic sampler was used to collect real time samples and analyzed for BOD, COD, TN, TP, SS and other pollutant concentrations in the laboratory. SWMM (Storm Water Management Model) urban watershed model was applied and calibrated using the observed flow and water quality data for the study area. While flow modeling results showed good agreement for all events, water quality modeling results showed variable levels of agreement. These results indicate that current options in the SWMM model to predict pollutant build up and wash-off effects are not sufficient to satisfy modeling of all the rainfall events under study and thus need further modification. This study showed the automatic monitoring system can be used to provide data to assist further refinement of modeling accuracy. This automatic stormwater monitoring and modeling system can be used to develop basin scale water quality management strategies of urban streams in storm events.

Detection of Fracture Signals of Low Prestressed Steel Wires in a 10 m PSC Beam by Continuous Acoustic Monitoring Techniques (연속음향감지기법을 이용한 긴장력이 감소된 10 m PSC보의 PS 강선 파단음파 감지)

  • Youn, Seok-Goo;Lee, Chang-No
    • Journal of the Korea Concrete Institute
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    • v.22 no.1
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    • pp.113-122
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    • 2010
  • Corrosion of prestressing tendons and wire fractures in grouted post-tensioned prestressed concrete bridges have been considered as a serious safety problem. In bridge evaluation the condition of prestressing tendons should be inspected, and if corroded tendons are found, the loss of tendon area should be included when we calculate the ultimate strength. In the previous study, it was evaluated that continuous acoustic monitoring techniques could be considered as a reliable non-destructive method for detecting wire fractures of fully grouted post-tensioned prestressing tendons. In the present study, an experimental test was performed for detecting wire fractures of post-tensioned prestressing tendons which are prestressed lower than current design level. A 10 m prestressed concrete beam was fabricated, which included two tendons prestressed 66 percentage and 40 percentage of tensile strength, respectively. The corrosion of two tendons was induced by an accelerated corrosion equipment and the test beam was monitored by using seven acoustic sensors and a continuous acoustic monitoring system. From each prestressing tendon, two acoustic signals of wire fractures were successfully detected and source locations were estimated within 20 mm error. Based on the test results, it is considered that continuous acoustic monitoring techniques can be applied to detect low-prestressed wire fracture in fully grouted post-tensioned prestressed concrete beams.

A dose monitoring system for dental radiography

  • Lee, Chena;Lee, Sam-Sun;Kim, Jo-Eun;Symkhampha, Khanthaly;Lee, Woo-Jin;Huh, Kyung-Hoe;Yi, Won-Jin;Heo, Min-Suk;Choi, Soon-Chul;Yeom, Heon-Young
    • Imaging Science in Dentistry
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    • v.46 no.2
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    • pp.103-108
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    • 2016
  • Purpose: The current study investigates the feasibility of a platform for a nationwide dose monitoring system for dental radiography. The essential elements for an unerring system are also assessed. Materials and Methods: An intraoral radiographic machine with 14 X-ray generators and five sensors, 45 panoramic radiographic machines, and 23 cone-beam computed tomography (CBCT) models used in Korean dental clinics were surveyed to investigate the type of dose report. A main server for storing the dose data from each radiographic machine was prepared. The dose report transfer pathways from the radiographic machine to the main sever were constructed. An effective dose calculation method was created based on the machine specifications and the exposure parameters of three intraoral radiographic machines, five panoramic radiographic machines, and four CBCTs. A viewing system was developed for both dentists and patients to view the calculated effective dose. Each procedure and the main server were integrated into one system. Results: The dose data from each type of radiographic machine was successfully transferred to the main server and converted into an effective dose. The effective dose stored in the main server is automatically connected to a viewing program for dentist and patient access. Conclusion: A patient radiation dose monitoring system is feasible for dental clinics. Future research in cooperation with clinicians, industry, and radiologists is needed to ensure format convertibility for an efficient dose monitoring system to monitor unexpected radiation dose.

A Parametric Study of Pulsed Gamma-ray Detectors Based on Si Epi-Wafer (실리콘 에피-웨이퍼 기반의 펄스감마선 검출센서 최적화 연구)

  • Lee, Nam-Ho;Hwang, Young-Gwan;Jeong, Sang-Hun;Kim, Jong-Yeol;Cho, Young
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.18 no.7
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    • pp.1777-1783
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    • 2014
  • In this paper, we designed and fabricated a high-speed semiconductor sensor for use in power control devices and analyzed the characteristics with pulsed radiation tests. At first, radiation sensitive circular Si PIN diodes with various diameters(0.1 mm ~5.0 mm) were designed and fabricated using Si epitaxial wafer, which has a $42{\mu}m$ thick intrinsic layer. The reverse leakage current of the diode with a radius of 2 mm at a reverse bias of 30 V was about 20.4 nA. To investigate the characteristic responses of the developed diodes, the pulsed gamma-radiation tests were performed with the intensity of 4.88E8 rad(Si)/sec. From the test results showing that the output currents and the rising speeds have a linear relationship with the area of the sensors, we decided that the optimal condition took place at a 2 mm diameter. Next, for the selected 2 mm diodes, dose rate tests with a range of 2.47E8 rad(Si)/sec to 6.21E8 rad(Si)/sec were performed. From the results, which showed linear characteristics with the radiation intensity, a large amount of photocurrent over 60mA, and a high speed response under 350ns without saturation, we can conclude that the our developed PIN diode can be a good candidate for the sensor of power control devices.