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Start date: 2020Subject: search.filters.subject.Capacitive sensor

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    Integration of CCTAO/PDMS composite films into proximity capacitive sensor devices
    (2026-12-01)
    Bongkarn, Theerachai
    ;
    Panpho, Phakakorn
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    Charoonsuk, Thitirat
    ;
    Vittayakorn, Naratip
    ;
    Pakawanit, Phakkhananan
    Flexible capacitive proximity sensors are promising for contactless sensing applications, but their performance is strongly influenced by the dielectric properties and microstructure of the sensing layer. In this work, CaCu<inf>3</inf>Ti<inf>4-x</inf>A<inf>x</inf>O<inf>12</inf>/polydimethylsiloxane (CCTAO/PDMS, A = Nd<sup>3+</sup> or Gd<sup>3+</sup>) composite films were developed as flexible dielectric layers for interdigitated capacitive proximity sensors. Nd- and Gd-doped CCTO ceramics were synthesized by a solid-state reaction method and incorporated into a PDMS matrix at different filler loadings. Structural analysis confirmed that the CCTAO ceramics retained the cubic CCTO phase after rare-earth substitution, while the composite films preserved the characteristic amorphous structure of PDMS with embedded ceramic fillers. The FESEM, EDS mapping and X-ray tomographic microscopy analyses showed that the CCTNdO/PDMS composite had a more uniform distribution of ceramic particles than the CCTO/PDMS system. The dielectric measurements demonstrated the improvement in the dielectric constant of the PDMS-based composites upon CCTNdO incorporation and also indicated that the composites did not exhibit any significant changes in their dielectric properties across the range of frequencies examined. The CCTNdO/PDMS films were found to show the negative capacitance response as a function of distance due to the electric-field shunting mechanism when used in an interdigitated capacitor sensor. The sensor with composition 10 wt% CCTNdO/PDMS had excellent performance with a maximum normalized capacitance change equal to −8.70%, which corresponds to a proximity sensitivity of around 0.42%/mm and an effective sensing range of around 20 mm. It is concluded that the optimization of the loading of the rare-earth material in a flexible PDMS matrix is an effective approach to achieve a compromise between the dielectric enhancement of the sensor and the dispersion of the filler and fringing-field interaction in the contactless capacitive proximity sensor.
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    Estimation of Vertical Jump Height using Capacitive Sensing Method
    (2023-01-01)
    Kaewjumras, Yongyut
    ;
    Klongratog, Bhanupol
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    Inboonma, Weerayut
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    Sukprasertchai, Siwakorn
    ;
    Somdock, Nuttakrit
    This paper presents a low-cost vertical jump height measuring device based on the time-of-flight technique. A capacitive mat was developed and used as a sensing element to sense the athlete's feet. The capacitive mat was made from aluminum foils that dimensions of the capacitive mat ware with a width of 50.3 cm x length of 70.6 cm. The signal conditioning circuitry that was used as an analog front-end for measuring the capacitive was also described. The time difference between when athletes jumped off and reached the ground was calculated by a microcontroller. The jump height was recorded and stored via the computer. A total of 27 athletes, weighted between 48 kg to 115 kg were used as a sample. The testing results have shown that the proposed system has a percentage difference of 18.16%.
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    Capacitive sensor readout circuit based on sample and hold method
    (2022-04-01)
    Petchmaneelumka, Wandee
    ;
    Phankamnerd, Phirapong
    ;
    Rerkratn, Apinai
    ;
    Riewruja, Vanchai
    This paper presents a capacitive sensor readout circuit using sample and hold method. The proposed readout circuit is used to convert capacitance from sensor to DC (direct current) voltage output. The basic structure of readout circuit consists of the pulse generator circuit, differentiator circuit, amplifier circuit, monostable I circuit, monostable II circuit, and sample and hold circuit. The proposed technique is based on the change of time constant from differentiator circuit corresponding to the measurement capacitance. The sample and hold circuit is used for sampling output voltage from differentiator circuit. The output voltage of the proposed readout circuit is proportional to measurement capacitance. The standard capacitors with different capacitance are used to test the proposed converter performance. Experimental results show that the proposed readout circuit can convert measurement capacitance to output voltage with satisfied values, good linearity and high sensitivity.