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    Electronically adjustable phase shifter using OTAs
    First-order phase shifter using operational transconductance amplifiers (OTAs) as active elements is presented in this paper. The corner frequency of the proposed phase shifter can be adjusted by electronic means. The purpose of this paper is emphasized on simple configuration and low cost. The phase response between input and output signals against the operating frequency is varied from 180 to 0 degrees of phase lead. The principle of the proposed circuit is confirmed by simulation and experimental results. To verify the proposed circuit performance, the sinusoidal oscillator is provided for circuit application. ©ICROS.
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    Wireless Carbon Monoxide Level Control and Monitoring System
    This paper proposes an online carbon monoxide control and monitoring system. The proposed system comprises an MQ-7 CO gas sensor module, a DHT11 digital temperature and humidity sensor module, an ESP8266 module, and a Relay Module. The ThingSpeak platform is used to create HMI for online monitoring of CO level, temperature, humidity, and status of the ventilation fan. This proposed system can measure CO and monitor all parameters of measurement data, alert users when CO values exceed the set value. In addition, the measured CO values are used to control the ventilation system operation (ON or OFF) to maintain the CO at a non-harmful level. The experiment testing and results with three conditions show that the proposed system can measure and monitor CO level, temperature, and humidity online with satisfying values. The ventilation fan can operate with function as a design procedure and maintain CO at a non-harmful level.
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    Power monitoring circuit using operational amplifiers
    (2010-12-01) ; ;
    Julsereewong, Prasit
    ;
    In this paper presents a power monitoring circuit for battery energy management system using operational amplifiers. The proposed scheme consists of a current sensing circuit with voltage output and an analog multiplier. The voltage output of current sensing circuit is directly proportional to load current. The multiplying result of the load current in the form of voltage signal and the load voltage becomes the load power in term of output voltage of analog multiplier. The configuration of the proposed power monitoring circuit is simple and economically attractive. Simulation and experimental results confirming the performance of the proposed circuit are agreed with the expected values. ©ICROS.
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    Enhanced differential voltage-to-Frequency converter for telemetry applications
    This paper presents an enhanced differential voltage-to-Frequency (dVFC) suitable for telemetry applications. The realization method employs op-amps in conjunction with current conveyors and Set-Reset latch. The converter gain can be easily adjusted through the variation of a single resistor. Compared to the previous dVFC using only current conveyors and Set-Reset latch, the proposed converter offers significant improvements in accuracy and circuit configuration. Its benefits are higher accuracy, simpler structure, fewer components, and lower costs. Experimental results verifying performances of the proposed dVFC are closely agreed with expected values. © 2010 SICE.
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    8-Electrode data collection system for electrical capacitance tomography
    (2006-12-01) ;
    Lertpakdee, Thanakorn
    ;
    Chitsakul, Kitiphol
    ;
    Sangworasil, Manas
    ;
    8-electrode data collection system for electrical capacitance tomography is presented. The system mainly consists of a signal generator, 8×2 multiplexer, detector, amplifier, band-pass filter, rms-to-dc converter, A/D converter circuit and control computer. Experimental results with a circular sensor show that the proposed system is able to collect data with satisfy sensitivities, linearity, resolution and also being insensitive to noise. Reconstructed images from collected data are shown. © 2006 ICASE.
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    Advanced planning for multi-product across a supply chain
    (2009-04-23)
    Masuchun, Ruedee
    ;
    This paper presents a linear integer programming model to plan the production for multiple products. The production is planned using information shared across a supply chain. The advantage of information sharing has been proved from research that it can make the whole supply chain globally visualized and yet decreasing in variability on the supply chain. The objective function of the proposed model is to minimize the total costs involved including the production costs, the distribution costs, the setup costs of manufacturing, and the fixed costs of distributing. From previous research, one more restriction which is limitation of distribution centers has been added to make the model more realistic. Numerical results verify that this model can be used to generate feasible and optimal plans for multiple products across the supply chain. © 2009 IEEE.
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    Simple LVDT signal to DC converter
    A simple technique to produce a linear signal from a displacement transducer, linear variable differential transformer (LVDT), is introduced in this paper. The two-quadrant divider is used to precede the ratio of a different and sum of the two winding signals from the LVDT instead of a four-quadrant divider of a recent approach. The two- quadrant divider is obtained by an operational transcondutance amplifier (OTA) in the form of a voltage-tocurrent converter. The signal from the divider is held by the sample and hold circuit (SHC) controlled by the peak-amplitude finder. As a result, the held signal is achieved without using a low-pass filter. The temperature effect of both OTA and LVDT are compensated. The merit of the proposed technique is that the circuit requires without the low-pass filter. Therefore, the fast response is obtained. The performance of the proposed scheme is confirmed by the experimental results using commercial devices.
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    Simple interface circuit for resistive/capacitive sensors
    (2013-01-01)
    Tongcharoen, Jakkapun
    ;
    ; ; ;
    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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    A current signal CMOS sample-and-hold circuit
    (2007-12-01)
    Luangpol, Amata
    ;
    ;
    Kamsri, Thawatchai
    ;
    This article presents a current signal sample-and-hold (S/H) circuit using 0.5μm CMOS technology. A current minimum circuit is used to sample the input signal in place of a sampling switch used in the conventional S/H circuit. The current peak detector is used to hold the signal from the minimum circuit in the "hold" state. The proposed configuration is adopted effectively to cancel switch feedthrough error. The performances of the proposed circuit are demonstrated using the PSPICE analog simulation program. Simulation results show the sampling frequency up to 100MHz and high accuracy. © ICROS.
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    Simple vector summation circuit using opamps
    (2011-01-01)
    Kamsri, Thawatchai
    ;
    ;
    Keawpoonsuk, Anucha
    ;
    ;
    This paper presents a vector summation circuit using operational amplifiers (opamps) for multiple voltage inputs. The implementation method based on the opamp supply-current sensing utilizes an inherently quadratic characteristic of the opamp class-AB output stage. The distinguishing features of the proposed implementation are simple configuration and low cost. Experimental results verifying the performances of the proposed vector summation circuit are included. © 2011 SICE.