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Near Full Stroke Length Linear Range Enhancement Circuit for Linear Variable Differential Transformer (LVDT)
(2023-01-01)
Wisetphanichkij, Sompong
This paper proposes a linear range enhancement circuit for Linear Variable Differential Transformer (LVDT). The nonlinear is compensated with a signal obtained from an inverse hyperbolic tangent function circuit and with the appropriate gain settings within the circuit. The efficiency of the proposed circuit depends on the accuracy of the signal obtained by the inverse hyperbolic tangent function circuit. The simulation results with Pspice® program demonstrate the efficiency of the proposed circuit for enhancing the linear operating distance of the transducer. Under a relative error a(%) of 2.2%, the linear operating range is improved from ± 9mm to ± 35mm for LVDT Kn=250(kn=0.1) at ± 37mm full stroke length, which is much wider compared to the signal obtained from the transducer before the improvement.
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Linear-Range Extension for Linear Variable Differential Transformer Using Hyperbolic Sine Function
(2022-05-01)
Rerkratn, Apinai
;
Tongcharoen, Jakkapun
;
Petchmaneelumka, Wandee
;
Riewruja, Vanchai
In this paper, a circuit technique to extend the measuring range of a linear variable differential transformer (LVDT) is proposed. The transfer characteristic of the LVDT contains the odd function form of the cubic polynomial. Therefore, the measuring range of a commercial LVDT is linear in a narrow range compared to its physical dimensions. The wide measuring range of the LVDT requires a large structure of the LVDT, which increases the scale and the cost of the measurement system. The measuring range of the LVDT can be linearly extended to the maximum of the stroke range using the proposed technique. The realization of the proposed technique is based on the use of the hyperbolic sine (sinh) function of the electronic circuit building block, named the class AB bipolar amplifier. The class AB bipolar amplifier can be obtained by the current feedback operational amplifier (CFOA). The circuit of the proposed technique requires two CFOAs and an operational transconductance amplifier (OTA) as the active devices and all devices used in the proposed technique to synthesize the sinh function are commercially available. The proposed technique exhibits an ability to compensate for the nonlinear characteristic of the LVDT without digital components. The proposed technique is attractive in terms of its simple circuit configuration, small size, and low cost. The linear range extension of the LVDT used in this paper is significantly increased with a maximum error of about 18.3 µm of 6.2 mm at the full stroke range or the full-scale percentage error of about 0.295%. The results indicate that the proposed technique provides excellent performance to extend the measuring range of the LVDT without modifying the LVDT structure.
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Simple Technique for Linear-Range Extension of Linear Variable Differential Transformer
(2019-07-01)
Petchmaneelumka, Wandee
;
Koodtalang, Wittaya
;
Riewruja, Vanchai
A technique for extending the linear range of a linear variable differential transformer (LVDT) is introduced in this paper. The linear operating range of a commercial LVDT is narrow compared to the full stroke range due to its nonlinear transfer characteristic. The narrow linear range of the commercial LVDT can be extended to maximum stroke range using the proposed technique based on LVDT inverse transfer characteristic. The circuit building block provided the third-order inverse transfer characteristic of the LVDT is established using analog multipliers and operational amplifiers (opamps). The proposed technique requires only commercially available devices, which is attractive in terms of a simple configuration and low cost. Performances of the proposed technique are discussed in detail and confirmed by simulation and experimental results using the commercial LVDT. As a result, the linear range of the LVDT used in this paper can be extended from ±2mm to ±15mm with the maximum absolute error of about 10.23{\mu }\text{m} or the full-scale error of about 0.068%. It is shown that the linear range of LVDT can be extended greater than seven times.
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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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