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Linear-range extension for linear variable differential transformer using triangular signal
(2018-12-10)
Petchmaneelumka, W.
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Koodtalang, W.
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Songsuwankit, K.
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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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Compensation of Temperature Effect for LVDT Transducer
(2018-11-01)
Petchmaneelumka, W.
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Rerkratn, A.
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Luangpol, A.
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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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High-accuracy resolver-to-linear signal converter
(2018-09-02)
Petchmaneelumka, W.
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Mano, P.
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Songsuwankit, K.
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Riewruja, V.
A high-accuracy resolver-to-linear signal converter for the measurement of angular displacement is proposed in this paper. The proposed converter comprises two sections: a demodulator and linear shaper. In the first section, the demodulator makes use of the sample-and-hold circuit (SHC) to sample the peak amplitude of the resolver signal. The control signal of the SHC is provided from the resolver signals instead of the excitation signal used in traditional approaches. The proposed demodulator requires no analogue multiplier and low-pass filter. Therefore, the fast response time of the proposed demodulator is achieved. In the second section, the linear shaper consists of the inverse-sine function scheme together with a switched-gain amplifier to produce the linear signal proportional to the shaft angle. The hyperbolic tangent characteristic of the operational transconductance amplifier is utilised to realise the inverse-sine function scheme. The proposed technique requires one phase of the resolver signal to obtain the linear signal. Therefore, the position error caused by amplitude imbalance between the two resolver signals is avoided. The performances of the proposed converter are discussed in detail and demonstrated by an experimental implementation using commercial devices. The experimental results show that the maximum relative error and response time for the excitation frequency of 3 kHz are measured as 0.06% and 0.11 ms, respectively.
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Linear range extension for LVDT using analog lookup table
(2018-08-13)
Petchmaneelumka, W.
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Koodtalang, W.
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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.
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Square-rooting and absolute function circuits using operational amplifiers
(2009-04-20)
Riewruja, V.
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Kamsri, T.
A method for implementing Square-rooting and absolute function circuits using operational amplifiers (opamps) as only active elements is introduced. The realisation technique is provided through the use of the opamp supply-current sensing, which utilises an inherently quadratic characteristic of the opamp class-AB output stage. The proposed circuits are attractive in terms of simple configuration and low cost. The performances of the circuits are discussed in detail. Experimental results demonstrating the characteristics of the circuits using commercially available opamps are also included. © 2009 The Institution of Engineering and Technology.
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Simple square-rooting circuit using OTAs
(2008-08-28)
Riewruja, V.
A method to implement a square-rooting circuit is described. The proposed circuit employs operational transconductance amplifiers (OTAs) as the only active elements. The implementation technique is based on an electronically variable resistor formed by the OTA, where the magnitude of the resistance is controlled by the output current, to provide the square-rooting function. The proposed scheme can operate with both a voltage input and a current input signal. The purpose of the circuit is emphasised in terms of simple configuration, high accuracy and low cost. Experimental results showing the circuit performance are presented. © 2008 The Institution of Engineering and Technology.
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A CMOS-based algorithmic ADC
(2005-01-01)
Arayawat, S.
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Chaikla, A.
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Petcmaneelumka, W.
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Riewruja, V.
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Julsereewong, P.
This paper presents a one-bit cell of reverse Gray-code algorithmic analog-to-digital converter, which operates in the current mode. The realization method is simple, small in size, and suitable for fabrication using CMOS technology. The design strategy is based on the MOS bias at the edge of conduction to provide a high-speed operation and a low distortion in the transfer characteristic. The N-bit resolution can be achieved by cascading of the N proposed one-bit cells. PSPICE simulation results verifying the proposed circuit performances are agreed with the expected value. ©2005 IEEE.
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High-speed multiple-input maximum and minimum circuits
(2005-01-01)
Yotingoravong, C.
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Kamsri, T.
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Chaikla, A.
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Riewruja, V.
This paper presents the multiple-input maximum and minimum circuits, which operate in the current-mode. The realization methods are suitable for fabrication using CMOS technology. The proposed circuits provide the high operation speed and perform the low-distortion in the transfer characteristics. The performances of the proposed circuits were studied using the PSPICE simulation program. The simulation results show the approval of these circuits that they have adequate basic performances for the real-time systems. © 2005 IEEE.
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Current tunable CMOS operational transresistance amplifier
(2001-01-01)
Riewruja, V.
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Parnklang, J.
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Julprapa, A.
A new signal power amplifier is presented in this paper. The proposed circuit is consisted of the new design of transresistance amplifier cell connecting with the common source negative feedback and the output driver circuit. The input and output impedance of the circuit is low because the negative feedback and output driver circuit are used. The voltage buffer is use for the output driver circuit. The new transresistance amplifier is found to have a constant bandwidth independent of gain in most close-loop configurations. The feedback network particular increased bandwidth and enhances the linearity of the transresistance amplifier. The biasing current of this shunt-shunt common source negative feedback can also tune the gain of the close-loop circuit configuration. In this work has shown an experimental result of the fundamental transresistance amplifier by used the commercial integrated circuits compared to the simulation result. And this confirms that the new design of transresistance amplifier is useable.
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Sinusoidal frequency doubler and full-wave rectifier using translinear current controlled conveyors
(2000-12-01)
Anuntahirunrat, K.
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Tangsrirat, W.
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Riewruja, V.
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Surakampontorn, W.
An alternative technique for realizing both a sinusoidal frequency doubler and a fall-wave rectifier, using translinear current controlled conveyors as active circuit elements, is presented. The frequency doubling and the rectifying action are exploited from the translinear characteristic of the current conveyor. Simulation results are given to confirm the theoretical predictions.

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