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Linear Variable Differential Transformer Signal Conditioning Circuit Based on Phase-Locked Loop
(2024-01-01)
Songsuwankit, Kanoknuch
;
Petchmaneelumka, Wandee
;
Riewruja, Vanchai
;
Rerkratn, Apinai
The purpose of this paper is to propose a novel technique for extracting the position signal from an inductive displacement transducer named a linear variable differential transformer (LVDT). In general, the movement of the LVDT core causes its primary inductance change in linear form. The primary winding of the LVDT is used as a time-dependent element for the triangular and square wave generator, which can be called self-oscillation, to generate frequency. The advantage of the proposed technique is that it can measure the displacement using the LVDT without an external oscillator. The change in primary inductance causes the frequency deviation generated by the oscillator. The deviated frequency is captured and converted into a voltage signal using the principle of the phase-locked loop. All the components used in this study are commercially available. The merits of this proposed technique are simple configuration, small size, and low cost. Moreover, the operating range of the LVDT can be extended without the limitation of the nonlinear transfer characteristic. The performance of the proposed technique is discussed in detail and confirmed by experimental implementation. Experimental results show that the maximum error from the proposed technique is about 0.42% and the operating range of the LVDT can be extended to more than 200%. It can be seen that the proposed technique is suitable for embedded measurement in small or micro robots.
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Temperature Compensation for Transformer-type Transducer
(2021-01-01)
Songsuwankit, Kanoknuch
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Riewruja, Vanchai
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Watanachaturaporn, Pakorn
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Rerkratn, Apinai
;
Petchmaneelumka, Wandee
A novel technique to compensate the temperature effect of a transformer-type transducer is proposed in this paper. The effect of the ambient temperature on the transformer-type transducer is investigated from a primary-winding current. The advantage of the proposed technique is that the temperature effect is compensated without requiring a temperature sensor, making it suitable for applications in robotic and automation systems operated in harsh environments. The primary-winding current of the transducer is generated using a second-generation current conveyor (CCII). The excitation signal of the transformer-type transducer is driven by the CCII and the current flowing through the primary winding is transferred to an output signal of the CCII. The deviation of the primary-winding current due to the temperature effect is evaluated from the output signal of the CCII. The temperature effect on the transducer is manipulated by a closed-loop principle using a subtract-and-sum action instead of a traditional proportional-plusintegral action to eliminate the deviation of the primary-winding current. Therefore, the temperature effect on the transducer is compensated. A linear variable differential transformer (LVDT) is used to demonstrate the proposed technique, whose performance is discussed in detail and confirmed experimentally. All devices used in this experiment are commercially available. Experimental results show that the measured error of the output signal from the LVDT at 70 C can be reduced from 6.2% without temperature compensation to 0.06% by using the proposed technique, which has the advantages of a low cost, simple configuration, and high performance.
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Position signal detector for linear variable differential transformer
(2020-12-01)
Rerkratn, Apinai
;
Luangpol, Amata
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Petchmaneelumka, Wandee
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Riewruja, Vanchai
This paper presents the position signal detector for linear variable differential transformer (LVDT) based on RMS-to-DC converter. The proposed detector consists of the differential amplifier, the comparator, the phase detector, the controllable unity-gain inverting/non-inverting amplifier and the RMS-to-DC converter. The proposed technique provides a simple scheme and uses the low cost commercial available devices such as opamp, transistor and digital logic gate. The experimental testing with the commercial LVDT model OP12.5G from Solartron Metrology showing the proposed position signal detector can produce the output voltage corresponding to the measured displacement with satisfactory values and good linearity.
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Simple LVDT demodulator
(2020-10-13)
Rerkratn, Apinai
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Luangpol, Amata
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Riewruja, Vanchai
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Petchmaneelumka, Wandee
A simple technique to realize demodulator for linear variable differential transformer (LVDT) is presented in this paper. The proposed LVDT demodulator is based on sample and hold technique. The proposed scheme consists of peak detector, phase detector, monostable circuit, sample and hold circuit, and controllable unity-gain inverting/noninverting amplifier. The presented technique employs the simple and low-cost devices such as op-amp, and digital logic gate. Experimentation with the commercial LVDT model OP12.5G from Solartron metrology shows that the proposed LVDT demodulator provides the output voltage corresponding to the movement of LVDT core with satisfactory values and good linearity. The maximum error of the proposed demodulator is about 1.5%. In addition, the output magnitude of proposed LVDT demodulator can be adjusted by variable resistor (VR1) without the external circuit requirement.
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Linear variable differential transformer temperature compensation technique
(2018-01-01)
Petchmaneelumka, Wandee
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Mano, Pitsini
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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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Simple LVDT signal conditioner
(2017-06-07)
Petchmaneelumka, Wandee
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Songsuwankit, Kanoknuch
;
Rerkratn, Apinai
;
Riewruja, Vanchai
A method to implement a signal conditioning circuit for a linear variable differential transformer (LVDT) is proposed in this article. The proposed signal conditioner can be used instead of a synchronous demodulator in the tradition approaches. The output signal of the signal conditioner is linearly proportional to the moving core of the LVDT with fast response. The realization technique is based on the use of an analog integrator to determine the LVDT signal at the half period of the excitation signal. The proposed signal conditioner provides without low-pass filter in the signal path. Therefore, the response time of the proposed technique is settled within half period of the excitation signal. The devices used in the proposed signal conditioner consist of basic commercially available devices such as operational amplifier (opamp), comparator, analog switch and one-shot timer. Experimental results demonstrated the performance of the proposed conditioner are included. The proposed technique is attractive in terms of simple configuration and low cost.
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Simple LVDT signal to DC converter
(2017-02-18)
Petchmaneelumka, Wandee
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Songsuwankit, Kanoknuch
;
Riewruja, Vanchai
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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Accurate LVDT signal converter
(2016-01-01)
Petchmaneelumka, Wandee
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Songsuwankit, Kanoknuch
;
Riewruja, Vanchai
A novel technique to implement a signal converter for an inductive displacement transducer, a linear variable differential transformer (LVDT), is proposed in this paper. The technique is based on the use of the proposed peak-amplitude finder and the zero-order sample and hold circuit (ZSH) instead of the synchronous demodulator used in traditional approach. The advantage of this technique is that the phase shift due to the dominant pole of the low-pass filter used in the traditional synchronous demodulator is avoided. Therefore, the fast response time of the proposed LVDT signal converter is achieved. The core displacement signal, which is varied in proportion to the position of the moving core of the LVDT, is accurately extracted to directcurrent (DC) voltage signal. The reference signal used to generate the control signal for the ZSH is directly provided by the output signal of the LVDT to prevent the phase shift caused by the LVDT structure. Performances of the proposed technique are discussed in detail and confirmed by the experimental demonstration using commercial devices. The purpose of the proposed technique is emphasized in terms of high accuracy, fast response, simple configuration and low cost.

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