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    Internet-based conductivity measurement system with self-temperature compensation
    (2019-07-01)
    Katman, Ratchanoo
    ;
    Rerkratn, Apinai
    ;
    Kaewpoonsuk, Anucha
    An Internet-based conductivity measurement system with self-temperature compensation is presented in the paper. In order to get a simple and portable measurement system, a readout circuit in analog part is designed using only two operational amplifiers (opamps) connected with basic electronic components and energized using single supply voltage. An excitation voltage generated by the AD9833 module is applied to a conductivity sensor. The measured output DC voltages are found to be directly proportional to the conductivity of the solution. The NodeMCU ESP8266 WiFi dev board is used to determine the conductivity and measure the temperature whose effect on the conductivity is compensated. The measured results are sent to display on a smartphone by Blynk app. The conductivity measured by the proposed system is in good agreement with that due to the standard EC meter. A maximum error of measuring the conductivity at different temperatures of solution is 4.79% of full scale.
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    Compensation of Temperature Effect for LVDT Transducer
    (2018-11-01)
    Petchmaneelumka, W.
    ;
    Rerkratn, A.
    ;
    Luangpol, A.
    ;
    Riewruja, V.
    In this paper, a circuit technique to compensate the temperature effect in the output signal of the linear variable differential transformer (LVDT) is presented. The realization technique is based on the proposed feedback configuration to minimize the active component used in the circuit. The subtraction and sum schemes are provided instead of the error detector used in the traditional feedback loop. The feedback signal is obtained from two secondary winding signals of LVDT. The proposed feedback technique requires only the proportional control action to minimize the error caused by the variation of the ambient temperature. The sensitivity of LVDT is unaffected from the proposed compensation technique. The performances of the proposed technique are discussed in detail and confirmed by experimental implementation using the commercial devices. The maximum percentage error can be reduced from 6.52% of the LVDT output signal without temperature compensation to 0.05% of the proposed technique for the ambient temperature varied from 25°C to 70°C. The purpose of the proposed technique is emphasized in terms of high performance, simple configuration and low cost.
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    Linear variable differential transformer temperature compensation technique
    (2018-01-01)
    Petchmaneelumka, Wandee
    ;
    Mano, Pitsini
    ;
    Riewruja, Vanchai
    A feedback technique to compensate for the temperature effect on the output signal of the linear variable differential transformer (LVDT) without losing the sensitivity is presented in this paper. The proposed technique is based on the use of a voltage-controlled amplifier to scale the amplitude of the excitation signal for temperature compensation. The proposed feedback technique provides the proportional-plus-integral control action to minimize the error caused by the temperature variation. The proportional-plus-integral action is realized using the integral scheme in the proposed technique. The peak amplitude of the LVDT output signal is sampled by the sample-and-hold circuit (SHC) to obtain the feedback and displacement signals, where the control signal of the SHC is provided by the LVDT output signal. The proposed LVDT temperature compensation technique is emphasized in terms of simple configuration and low cost. Note that the proposed technique is suitable for signal conditioners embedded in smart sensors and smart materials. The performance of the proposed technique is confirmed by experimental implementation using commercially available devices. The maximum error of the core displacement signal can be reduced from 6.52% for the uncompensated scheme to 0.098% for the compensated scheme at the ambient temperature of 70 °C.
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    A Sub-100ppm/∘C Temperature-Compensated High-Frequency CMOS Relaxation Oscillator
    (2016-01-01)
    Sakphrom, Siraporn
    ;
    Georgiou, Pantelis
    ;
    Thanachayanont, Apinunt
    A temperature-compensated high-frequency CMOS integrated relaxation oscillator with low frequency variations is presented. A current-controlled oscillator topology is employed with a resistive source-degenerated transconductor and a current comparator to achieve high oscillation frequency and low power dissipation. The proposed oscillator was designed with process parameters from a standard 0.35-μm CMOS technology and a 2.5-V single power supply voltage. At a nominal oscillation frequency of 21 MHz, the total power dissipation of the circuit was 201 μW. Post-layout simulation results showed that the frequency variations were less than 34.16ppm/∘C over a temperature range of -40 to +120∘C.
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    Inverse sine function circuit with temperature compensation
    (2016-01-01)
    Apisitticharoonlert, Perm
    ;
    Petchmaneelumka, Wandee
    ;
    Riewruja, Vanchai
    A technique to realize inverse sine function circuit with temperature compensation Is presented In this paper. The hyperbolic tangent characteristic of bipolarransistor differential pair existed in operational transconductance amplifier (OTA) is utilized for the proposed realization method. The proposed scheme provides a simple configuration and low cost. Simulation and experimental results confirming the performance of the proposed scheme are agreed with the theoretical values.
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    Simple current-mode square-rooting circuit with temperature compensation using only OTAs
    (2010-01-01)
    Tangsrirat, Worapong
    ;
    Prasertsom, Danucha
    ;
    Pukkalanun, Tattaya
    ;
    Surakampontorn, Wanlop
    A simple current-controlled current-mode square-rooting circuit with temperature compensation employing operational transconductance amplifi ers (OTAs) as active elements is proposed. It has been designed by using only four OTAs, without the employment of additional passive elements. The current gain of the proposed circuit can be electronically controlled, thanks to the tuning property of the OTA. Simulation and experimental results are obtained to verify the theoretical analysis of the proposed circuit technique.