• Title/Summary/Keyword: Capacitive sensor

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A CMOS integrated circuit design of charge-sharing scheme for a capacitive fingerprint sensor (용량형 지문인식센서를 위한 전하분할 방식 감지회로의 CMOS 구현)

  • Nam, Jin-Moon;Lee, Moon-Key
    • Journal of Sensor Science and Technology
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    • v.14 no.1
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    • pp.28-32
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    • 2005
  • In this paper, a CMOS integrated detection circuit for capacitive type fingerprint sensor signal processing is described. We designed a detection circuit of charge-sharing sensing scheme. The proposed detection circuit increases the voltage difference between a ridge and valley. The test chip is composed of $160{\times}192$ array sensing cells (12 by $12.7{\;}mm^{2}$). The chip was fabricated on a 0.35 m standard CMOS process. Measured difference voltage between a ridge and valley was 0.95 V.

Liquid level measurement system using capacitive sensor and optical sensor

  • Shim, Joonhwan
    • Journal of Advanced Marine Engineering and Technology
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    • v.37 no.7
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    • pp.778-783
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    • 2013
  • Measurement of liquid level in storage and processing vessels, tanks, wells, reservoirs and hoppers is commonly needed. The several different ways to measure the liquid level of oil or water tank have been provided such as an electrostatic capacity, a supersonic waves and an optical science etc. In the study, we have constructed the stable and efficient measurement system to measure the level of liquid at real-time and to get accurate measurement of the maximum and minimum level of the tank. For this purpose, we suggest double sensing methods by adopting both capacitive and optical sensing. The experimental results, presented in this paper, illustrate the effectiveness of the proposed method under different sensing methods.

Precise in situ Measurement using Non-Contacting Capacitive Sensor with 4-Electrodes (비접촉식 4-전극형 전기용량 센서를 이용한 in situ 정밀측정)

  • 이래덕
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 1999.10a
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    • pp.93-98
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    • 1999
  • Non-contacting capacitive sensors, based on principle of the cross capacitor, for measuring small displacement less than 1.95$\pm$0.5 mm have been fabricated and characterized. To overcome disadvantages of the existed capacitive sensors, the new sensor is consisted of 4-electrodes which are formed 2 active electrodes and 2 guard electrodes on a sapphire plate with diameter 17mm and thickness 0.7 mm, and are symmetrically situated with constant gap of 0.2 mm among the electrodes. The sensor is evaluated to be correlation coefficient of 0.9987 for the range of 1.95$\pm$0.5 mm and that of 0.9995 for 1.95$\pm$0.25 mm range. This sensor can be used for in situ measurements in the mechanical mirror polishing with precision less than $\pm$1${\mu}{\textrm}{m}$.

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Design and Fabrication of Capacitive Pressure Sensor (용량형 압력센서의 설계 및 제작)

  • 이승준;김병태;권영수;정귀상
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.07a
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    • pp.561-564
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    • 2000
  • Silicon capacitive pressure sensor has been fabricated by using electrochemical etching stop and silicon-to-glass electrostatic bonding technique. A diaphragm structure is designed to compensate the nonlinear response. A cavity is etched into the silicon to the depth of 2$\mu\textrm{m}$ by anisotropic etching in 20wt.% TMAH solution at 80$^{\circ}C$. A fabricated sensor showed 3.3 pF zero-pressure capacitance, 297 pp.m/mmHg sensitivity, and a 7.4 7%F.S. nonlinear response in a 0-1 kgf/cm$^2$pressure range.

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1.5 V Sub-mW CMOS Interface Circuit for Capacitive Sensor Applications in Ubiquitous Sensor Networks

  • Lee, Sung-Sik;Lee, Ah-Ra;Je, Chang-Han;Lee, Myung-Lae;Hwang, Gunn;Choi, Chang-Auck
    • ETRI Journal
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    • v.30 no.5
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    • pp.644-652
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    • 2008
  • In this paper, a low-power CMOS interface circuit is designed and demonstrated for capacitive sensor applications, which is implemented using a standard 0.35-${\mu}m$ CMOS logic technology. To achieve low-power performance, the low-voltage capacitance-to-pulse-width converter based on a self-reset operation at a supply voltage of 1.5 V is designed and incorporated into a new interface circuit. Moreover, the external pulse signal for the reset operation is made unnecessary by the employment of the self-reset operation. At a low supply voltage of 1.5 V, the new circuit requires a total power consumption of 0.47 mW with ultra-low power dissipation of 157 ${\mu}W$ of the interface-circuit core. These results demonstrate that the new interface circuit with self-reset operation successfully reduces power consumption. In addition, a prototype wireless sensor-module with the proposed circuit is successfully implemented for practical applications. Consequently, the new CMOS interface circuit can be used for the sensor applications in ubiquitous sensor networks, where low-power performance is essential.

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An 0.4nm Resolution Encoder-like Capacitive Displacement Sensor (0.4nm 해상도의 엔코더 타입 전기용량형 변위센서)

  • Kang, Dae-Sil;Kim, Moo-Jin;Moon, Won-Kyu
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.1450-1454
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    • 2007
  • A Contact-type Linear Encoder-like Capacitive Displacement Sensor (CLECDiS) has been developed to measure displacements at high accuracy within a long measurement range. In this paper, we have worked on improving the performance and reliability of the sensor. The performance increase can be done by introducing the smaller electrode patterns of $4{\mu}m$ width. In order to improve the reliability of the sensor we have changed the electrode layers from chrome-gold to chrome-gold-chrome and re-design its supporting structure. The newly-designed sensor is fabricated and tested to show that its sensitivity is $35pF/{\mu}m$, which implies that its resolution may be 0.36nm if SNR (Signal-to-Noise-Ratio) is 80.1dB. It is about ten times of that $(3.14pF/{\mu}m)$ of its previous version with 10${\mu}m$ electrodes. The total measurement range remains the same as the previous one; 15mm. The calibration experiments show its improved performance and reliability.

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Capacitive Humidity Sensor Using Reactive Methacrylate Copolymers (반응성이 있는 메타크릴레이트 공중합체를 이용한 정전용량형 습도센서)

  • 공명선;이임렬
    • Journal of the Microelectronics and Packaging Society
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    • v.10 no.4
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    • pp.21-27
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    • 2003
  • The copolymers with various composition of methyl methacrylate (MMA), ethyl methacrylate (EMA), methacrylic acid (MA) and hydroxyethyl methacrylate (HEMA) were synthesized for capacitive humidity sensitive materials. The capacitive humidity sensor consisted of a polymethacrylate film coated on both sides with gold electrode. Capacitance versus relative humidity increased with HEMA content in the copolymer. In the case of self-crosslinkable MMA/MA/HEHA= 40/10/10, the average capacitance at 30%RH, 60%RH and 90%RH are 102, 134 and 166 pF, respectively. And also, the hysteresis, temperature cycle and long-term stability were evaluated as a capacitance humidity sensor.

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Enhancement in the Performance of Capacitive Sensor for Oily Water Separator (유수분리기용 정전용량형 센서의 성능향상에 관한 연구)

  • Che, Woo-Seong;Kim, Kyong-Woo;Kwon, Hyu-Sang
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.10
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    • pp.1835-1841
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    • 2006
  • Demand of enhanced bilge separation sensor system has been recently increased due to the severe regulation reinforcement of MEPC(Marine Environment Production Committee). Up to date bilge separation sensor has to be extremely accurate and highly reliable. To design and build such a bilge separator. a precise oily water separation level sensor that distinguishes oil from water is critical. Three dimensional simulations have been carried out to figure out the characteristics of capacitive level sensors, which grounds the finding of the parameters required to design the sensors. The parasitic capacitance problem which is inherent to capacitive level sensors has been taken care of. This paper concludes with the future research direction that can be pursued with the newly defined parameters of the capacitive level sensors.

Characteristics of Flexible Transparent Capacitive Pressure Sensor Using Silver Nanowire/PEDOT:PSS Hybrid Film (은나노와이어·전도성고분자 하이브리드 필름을 이용한 유연 투명 정전용량형 압력 센서의 특성)

  • Ahn, Young Seok;Kim, Wonhyo;Oh, Haekwan;Park, Kwangbum;Kim, Kunnyun;Choa, Sung-Hoon
    • Journal of the Microelectronics and Packaging Society
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    • v.23 no.3
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    • pp.21-29
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    • 2016
  • In this paper, we developed a flexible transparent capacitive pressure sensor which can recognize X and Y coordinates and the size of force simultaneously by sensing a change in electrical capacitance. The flexible transparent capacitive pressure sensor was composed of 3 layers which were top electrode, pressure sensing layer, and bottom electrode. Silver nanowire(Ag NW)/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) hybrid film was used for top and bottom flexible transparent electrode. The fabricated capacitive pressure sensor had a total size of 5 inch, and was composed of 11 driving line and 19 sensing line channels. The electrical, optical properties of the Ag NW/PEDOT:PSS and capacitive pressure sensor were investigated respectively. The mechanical flexibility was also investigated by bending tests. Ag NW/PEDOT:PSS exhibited the sheet resistance of $44.1{\Omega}/square$, transmittance of 91.1%, and haze of 1.35%. Notably, the Ag NW/PEDOT:PSS hybrid electrode had a constant resistance change within a bending radius of 3 mm. The bending fatigue tests showed that the Ag NW/PEDOT:PSS could withstand 200,000 bending cycles which indicated the superior flexibility and durability of the hybrid electrode. The flexible transparent capacitive pressure sensor showed the transmittance of 84.1%, and haze of 3.56%. When the capacitive pressure sensor was pressed with the multiple 2 mm-diameter tips, it can well detect the force depending on the applied pressure. This indicated that the capacitive pressure sensor is a promising scheme for next generation flexible transparent touch screens which can provide multi-tasking capabilities through simultaneous multi-touch and multi-force sensing.

A Simple Capacitive Sensor Array Based on a Metal-Insulator-Metal Structure

  • Lee, Hee-Ho;Choi, Jin-Hyeon;Ahn, Jung-Il;Kim, Chang-Soo;Shin, Jang-Kyoo
    • Journal of Sensor Science and Technology
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    • v.21 no.2
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    • pp.83-89
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    • 2012
  • A simple array of metal-insulator-metal capacitive elements was proposed for a potential application in humidity sensing platforms. We fabricated meso-scale sensors with different sizes(large-size: $2.7{\times}2.7mm^2$ ; mid-size: $1.5{\times}1.5mm^2$ ; small-size: $0.7{\times}0.7mm^2$) and characterized the performance of each design. Polyimide films were utilized as a humidity-sensitive layer. Capacitance changes of the polyimide layer were measured with respect to water absorption. The device showed sensitivity in the full range of relative humidity (RH) with excellent linearity(correlation coefficient > 0.994). This array structure exhibits unique advantages including easy fabrication process, high batch productivity, and high structural compatibility with various substrate materials. It is anticipated that this device structure will be potentially useful in unique applications including mapping spatial humidity variations over a meso-scale area and implementing flexible humidity sensing element arrays.