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    Grounded Capacitive Sensor Readout Using Improved Guard Driving Circuit
    (2025-01-01)
    Chimnoy, Jirat
    ;
    Karawanich, Khunanon
    ;
    Prommee, Pipat
    A remote capacitive sensor is necessary in hazardous locations such as liquid boilers and chemical facilities. The connection of the capacitive sensor and coaxial cable is integrated with the readout circuit, encompassing intrinsic noise and parasitic capacitance limitations. This work presents a grounded capacitive sensor with an economical architecture incorporating an RC lowpass filter and an enhanced guard driving circuit. The proposed technique effectively achieves minimal parasitic capacitance and reduced noise at the output. The sensor capacitance can be readily calculated by measuring the output signal's amplitude at the cutoff frequency. Both simulation and experimental findings corroborate its efficacy and precision. The capacitance range can be quantified between 1-100 pF with less than 2% relative errors.
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    Linear-range extension for linear variable differential transformer using triangular signal
    (2018-12-10)
    Petchmaneelumka, W.
    ;
    Koodtalang, W.
    ;
    Songsuwankit, K.
    ;
    Riewruja, V.
    This paper presents a linear range extension technique for the linear variable differential transformer (LVDT). The technique is based on a signal conditioning circuit using the analog lookup table, which provides very high resolution of resulting signal. The analog table which is obtained by the triangular signal generator, which has the frequency equal to the excitation frequency. Meanwhile, the referenced signal is obtained by the comparison between the excitation signal and the output signal of LVDT. It is used to synchronize with the triangular signal. The proposed technique is simply circuit configuration and it can be implemented using available commercial devices. The experiment shows that the performances of the proposed circuit can be extended from the normal operating range of LVDT to the maximum stroke range. In addition, the response time of the proposed techniques can be approximated as half period of the excitation signal.
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    Linear range extension for LVDT using analog lookup table
    (2018-08-13)
    Petchmaneelumka, W.
    ;
    Koodtalang, W.
    ;
    Songsuwankit, K.
    ;
    Riewruja, V.
    A technique to extend the operating range of the linear variable differential transformer (LVDT) is presented in this article. The realization method is based on the analog lookup table achieved by the ramp signal generator where the frequency of ramp signal is equal to the excitation frequency. Therefore, the resolution of the resulting signal is very high. The output signals of the LVDT are provided to generate the reference signal to synchronize with the ramp signal. The proposed technique can extend the operating range of the LVDT from a normal operating range provided by the specification of the LVDT to maximum stroke range of the LVDT. The circuit of the proposed technique is simple and can be implemented using the commercial devices. The experimental results confirmed that the circuit performance are good agreement with the expected results. The response time of the proposed technique is about two periods of the excitation frequency.