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Author: search.filters.author.Rerkratn, ApinaiSubject: search.filters.subject.Interface circuit

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    OP-AMP based interface circuit for resistive sensor with lead-wire-resistance compensation
    (2019-04-01)
    Kaewpoonsuk, Anucha
    ;
    Katman, Ratchanoo
    ;
    Rerkratn, Apinai
    This paper presents a simple technique to implement the resistive sensor interface for remote measuring. The circuit is designed using a relaxation oscillator to generate a square wave signal. The time difference during charging and discharging a capacitor is directly proportional to the sensor’s resistance. The structure of the circuit is composed of two op-amps, three bipolar junction transistors, a capacitor, four fixed resistors and a variable resistor. Features of the proposed circuit are single-supply operation and direct interface with a microcontroller without an analog-to-digital converter. In addition, the lead-wire resistance is automatically compensated. When the resistance values of the sensor are varied in the range of 500-1500 O with lead-wire resistance values of 0-100 ω, the result of the circuit testing is found that the maximum error is approximately equal to 1.15% of full scale. The performance of the circuit is in accordance with principles proposed.
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    Simple and low-cost readout circuit for differential resistive sensors
    (2018-09-01)
    Katman, Ratchanoo
    ;
    Rerkratn, Apinai
    ;
    Kaewpoonsuk, Anucha
    In this paper, a simple and low-cost readout circuit for differential resistive sensors is presented. The realization method is based on the relaxation oscillation technique, which utilizes the operational amplifiers (op-amps) with a single supply voltage. The oscillating output Duty-Cycle is proportional to the difference of two sensing resistances. In comparison with the traditional voltage divider circuit or the Wheatstone bridge circuit or the previously reported readout circuit based on CCIIs, the proposed circuit can be interfaced with microcontroller without using an analog-to-digital converter. Theoretical predictions are supported by the PSPICE simulation results and the experimental data. In applying a slide potentiometer with changes of slider positions of ±15 mm, it is found that the maximum error of the proposed circuit is approximately-2.90% of full-scale. Copyright © 2018 Praise Worthy Prize S.r.l.-All rights reserved.
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    Simple interface circuit for resistive/capacitive sensors
    (2013-01-01)
    Tongcharoen, Jakkapun
    ;
    Petchmaneelumka, Wandee
    ;
    Cheypoca, Thepjit
    ;
    Rerkratn, Apinai
    ;
    Riewruja, Vanchai
    This paper presents a method to realize interface circuit for resistive and capacitive sensors. The proposed circuit employs commercially available devices to generate the output signal in form of time period, which is linearly proportional to the both of sensing resistance and capacitance. Circuit configuration is simple and small in size. Experimental results verifying the performances of the proposed circuit are also included.
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    Simple resistance-to-period converter for resistive sensors
    (2012-12-01)
    Tongpakpanang, Jaturon
    ;
    Rerkratn, Apinai
    ;
    Kaewpoonsuk, Anucha
    ;
    Riewruja, Vanchai
    ;
    Petchmaneelumka, Wandee
    A method for realization of resistance-to-period converter is introduced in this article. The principle of converter utilizes the behavior of designed astable multivibrator, which is implemented using commercial available and low cost devices. The operation of proposed converter circuit is in current mode. Therefore, the resistance is linearly converted to period and also converted to frequency with invert proportional relationship. The conversion gain of the proposed converter can be adjusted by electronic means. The configuration of the proposed converter is simple and small in size. Experimental results verifying the proposed converter performance are included in detail. The relative error of about 0.8 % is observed. © 2012 ICROS.
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    Synthesis of simple interface circuit based on time-period detection technique for capacitance measurement
    (2011-01-01)
    Kaewpoonsuk, Anucha
    ;
    Rerkratn, Apinai
    This paper presents a synthesis simple method using time-period detection technique for use in capacitance measurement. The proposed scheme consists of a square wave generator, an integrator, a sample-and-hold circuit, and a designed logic circuit. Output signals of logic circuit are used to control the integrator followed by sample-and-hold circuit in sequential operation. The proposed circuit provides measuring capacitance in 4 ranges; 0.1-1 nF, 1-10 nF, 10-100 nF, and 100-1000 nF. Each range has output voltage signal proportional to the sensing capacitor from 0.5 V to 5 V. Performances of the proposed circuit were experimentally verified. Results are in good agreement with expected values. © 2011 SICE.