Apinai Rerkratn

A novel resolver-to-DC converter based on OTA-based inverse-sine function circuit

A new technique for realizing the resolver-to-DC converter using the OTA-based inverse-sine function circuit is presented. The proposed converter comprises the demodulator, absolute detector, minimum detector, plusmn unity-gain amplifier, controlled signal logic circuit, and OTA-based inverse-sine function circuit. The output voltage is linearly proportional to the resolver angle with maximum absolute error of about 0.195%, which is less than the error from the conventional resolver-to-DC converter based on the similar OTA-based inverse-sine function circuit. PSPICE simulation and experimental results verifying the performances of the proposed circuit are in close agreement with the expected values.

Four-quadrant analogue multiplier using operational amplifier

A method to realise a four-quadrant analogue multiplier using general-purpose operational amplifiers (opamps) as only the active elements is described in this article. The realisation method is based on the quarter-square technique, which utilises the inherent square-law characteristic of class AB output stage of the opamp. The multiplier can be achieved from the proposed structure with using either bipolar or complementary metal-oxide-semiconductor (CMOS) opamps. The operation principle of the proposed multiplier has been confirmed by PSPICE analogue simulation program. Simulation results reveal that the principle of proposed scheme provides an adequate performance for a four-quadrant analogue multiplier. Experimental implementations of the proposed multiplier using bipolar and CMOS opamps are performed to verify the circuit performances. Measured results of the experimental proposed schemes based on the use of bipolar and CMOS opamps with supply voltage ±2.4 V show the worst-case relative errors of 0.32% and 0.47%, and the total harmonic distortions of 0.47% and 0.98%, respectively.

A simple amplitude detector-based demodulator for resolver converters

This paper presents a simple method based on sinusoidal-amplitude detector for realizing the resolver-signal demodulator. The proposed demodulator consists of two full-wave rectifiers, two ±unity-gain amplifiers, and two sinusoidal-amplitude detectors with control switches. Two output voltages are proportional to sine and cosine envelopes of resolver-shaft angle without low-pass filter. Experimental results demonstrating characteristic of the proposed circuit are included.

Front-end interfacing circuit for capacitive sensor

This paper presents an interfacing circuit for capacitive sensor using charge amplifier formed a capacitance-to-voltage converter. The proposed circuit is suitable for the front-end analog-to-digital converter (ADC) and wide variable range of sensing capacitance. The achieved output voltage provides a linear transfer characteristic and fast response. The circuit configuration is implemented using only commercially available devices. The performances of proposed circuit are confirmed by experimental results.

An accurate CCII-based voltage controlled current source

In this paper, a voltage controlled current source (VCCS) providing low distortion in output signal and wide output current range is introduced. In order to obtain the high accuracy, the proposed technique employs the designed scheme to connect in feedback loop of the basic VCCS based on second generation current conveyor (CCII). This scheme consists of instrumentation and differential amplifiers and one resistor. The performances of the proposed circuit were studied through the use of PSPICE simulation program. Simulation results are agreed with the expected values.

High current low frequency eddy current imaging system

Eddy current technique plays an important role in non destructive test. Based on the principal of electromagnetism. We introduce, in this paper our new eddy current imaging system for flaw detection in aluminium plate. The propose system using high current and low frequency with single coil. Results of some preliminary experiments have been shown satisfy sensitivities, resolution and stability of the proposed system.

Integration of WirelessHART and ISA100.11a field devices into condition monitoring system for starting IIoT implementation

This paper presents a technique to integrate wireless field devices using WirelessHART and ISA100.11a technologies into a condition monitoring system based on Wonderware InTouch software. The proposed integration brings the data from a field site with digital multi-device networking for automatic data collection to support the condition monitoring of instruments or smart connected equipment in preparation of the Industrial Internet of Things (IIoT) implementation. Data including process variables and diagnostics from WirelessHART and ISA100.11a devices are buffered and mapped into Modbus/TCP registers for real-time monitoring at the operator workstation. Experimental results confirm that the proposed integration functions correctly.

Characterization and Dielectric Properties of Nanocomposite Made of Lead Zirconate Nanofibers and Polyvinylidene Fluoride Improved with Carbon Nanotubes

A three-phase PZ/CNT/PVDF nanocomposite comprising lead zirconate (PZ) nanofibers, polyvinylidene fluoride (PVDF) and a small volume fraction of carbon nanotubes (CNT) was prepared by the solvent casting technique followed by composite heating at 80°C. The PZ/CNT/PVDF composites were characterized by X-ray diffraction, FT-IR and scanning electron microscopy (SEM). The dielectric properties of the composite were studied as a function of the frequency by an LCR meter. The dielectric constant of the PZ/CNT/PVDF nanocomposite was found to be in the range of 18–61 within the measurement frequencies from 100 Hz to 2 MHz. This value is higher than the dielectric constant of the PZ/PVDF nanocomposite. The measured dielectric properties demonstrate that the addition of CNT can improve the dielectric property appearance of the composite.

Simple level control plant model using labVIEW

This paper presents a design and implementation of water level control plant model used as learning aid in the level control process. The plant model consists of a differential pressure transmitter, Frequency Inverter and Proportional-Integral-Derivative (PID) Controller. The differential pressure transmitter is used for measuring liquid level in process tank, and Inverter is employed to adjust the inlet flow of the tank. The PID controller can be configured by a PID function of LabVIEW program. In addition, two flow transmitters and solenoid valve are also installed to monitor the flow rate and/or cascade additional control loop in the future. The procedure to implement the plant model are divided into 5 steps: controlling liquid level in cylinder tank with 10 cm in diameter and 40 cm in height were specified, sizing and selecting instruments needed, implementing the plant model according to the designed Piping & Instrument (P&I) diagram and Solid Work drawing, designing the control program and human machine interface (HMI) screen in LabVIEW program and the control parameters for single-loop controller modeled TTM-007, and evaluating the performances of implemented plant model. The experimental results of step changes of set point are also included and compared to the result from the plant using a commercially available single loop controller.

Compensation of Temperature Effect for LVDT Transducer

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 t...