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Author: search.filters.author.Karawanich, KhunanonSubject: search.filters.subject.low-cost

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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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    Extracting the Single-Dispersion Fractional Cole–Cole Bioimpedance Model Based on Low-Pass Filter Technique
    (2025-01-01)
    Prommee, Pipat
    ;
    Chimnoy, Jirat
    ;
    Wongprommoon, Natapong
    ;
    Karawanich, Khunanon
    This article presents a simple approach to extracting the parameters of the single-dispersion Cole–Cole bioimpedance model. The main advantage of the proposed technique is that it is low-cost but accurate in identifying the bioimpedance models. The Cole–Cole model is simplified as a fractional low-pass filter (LPF) using a few electronic components. Based on a low-component count, the circuit can be realized using only a single operational amplifier (OPAMP), two resistors, and two potentiometers (POTs). The proposed technique can achieve a minimal error compared to the theory, ensuring accuracy. The Cole–Cole model parameter values can be extracted by measuring the filter magnitude and phase responses. The LPF topology inherently provides a low-noise output signal. Experimental results using different fruits are carried out to verify the method and compared with measurements from a commercial impedance analyzer to confirm the accuracy of the results, with the maximum errors of R<inf>0</inf>,R<inf>∞</inf>, α, and C<inf>α</inf> being 0.94%, 2.41%, 0.85%, and 1.52%, respectively. The proposed new efficient technique provides excellent results in extracting the Cole–Cole parameters and agrees with the theoretical expectations.
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    Low-Cost Linearity Range Enhancement for Linear Variable Differential Transformer
    (2022-02-15)
    Prommee, Pipat
    ;
    Angkeaw, Krit
    ;
    Karawanich, Khunanon
    This research proposes a low-cost and low-complexity technique to enhance the linearity range of linear variable differential transformer (LVDT) using logarithmic approximation and summing/subtracting operation. The proposed technique utilizes the feedforward approach and thus encounters no divide-by-zero behavior from inverse functions. The nonlinearity of LVDT can be counteracted by simply manipulating the parameters of the canceller circuit. Besides, the proposed technique can be applied to various LVDT nonlinearity types. The proposed linear enhancing circuit consists of operational amplifiers and a small number of passive elements. The nonlinearity cancellation could be further enhanced using a temperature-compensation circuit. Simulations were carried out using two different LVDT nonlinearity types: LVDT#1 and #2. The simulation results showed that the linearity enhancing circuit effectively enhances the LVDT linearity range, with the linearity errors of 0.51% and 1.83%, respectively. To validate, experiments were undertaken with the identical LVDT nonlinearity types using a circuit prototype, and the measured linearity errors are around 2.5% and 5.5%, respectively. The simulation and experimental results are agreeable with the theory, indicating that the proposed technique enhances the linearity range.