A Relaxation oscillator-based transformer ratio arm bridge circuit for capacitive humidity sensor

A simple signal conditioning circuit using a transformer ratio arm (TRA) bridge for converting capacitance change into frequency for capacitive sensors is presented. The circuit employs a relaxation oscillator in which the output frequency is linearly related to the capacitive unbalance of a TRA bridge. The design, analysis, and experimental results of the circuit and its application to a thin-film-based humidity sensor are reported. The experimental results confirm the theoretical value predicted. The circuit which offers the minimum parasitic earth capacitance effect has the potential for accurately monitoring measurement parameters, particularly ppm-level humidity. The simulation results for the effect of parasitic earth capacitances and ambient temperature on the output frequency have also been discussed. The pulse wave output of the circuit is interfaced with microcontroller for direct moisture display in ppm. The frequency sensitivity and nonlinearity of the sensor for the 0-110-ppm moisture range are found to be 10.94 Hz/ppm and 1.2%, respectively.9 page(s

Sensitivity Enhancement of Wheatstone Bridge Circuit for Resistance Measurement

Present work deals with the development of a low cost, appreciably accurate and sensitive electronic circuit for resistive sensor. The circuit is based on the modification of the Wheatstone bridge using active devices. It helps measurement of the incremental resistance precisely and linearly. It requires few components for its hardware implementation and found to be suitable in case there is small change in resistance due to change in physical quantity or chemical analytes to be measured. Theory of the proposed bridge circuit has been discussed and experimental results have been compared with conventional full bridge circuit. Experiments have been conducted with metallic strain gauge sensor but it can be utilized to other resistive sensors. Results show that the output of the circuit is almost four times more than usual full Wheatstone bridge circuit. Experimental results show that the errors due to the effects of the ambient temperature and connecting lead resistance are minimized

Performance Evaluation and Robustness Testing of Advanced Oscilloscope Triggering Schemes

In this paper, performance and robustness of two advanced oscilloscope triggering schemes is evaluated. The problem of time period measurement of complex waveforms can be solved using the algorithms, which utilize the associative memory network based weighted hamming distance (Whd) and autocorrelation based techniques. Robustness of both the advanced techniques, are then evaluated by simulated addition of random noise of different levels to complex test signals waveforms, and minimum value of Whd (Whd min) and peak value of coefficient of correlation(COCmax) are computed over 10000 cycles of the selected test waveforms. The distance between mean value of second lowest value of Whd and Whd min and distance between second highest value of coefficient of correlation (COC) and COC max are used as parameters to analyze the robustness of considered techniques. From the results, it is found that both the techniques are capable of producing trigger pulses efficiently; but correlation based technique is found to be better from robustness point of view

Real Time In-circuit Condition Monitoring of MOSFET in Power Converters

Abstract:This paper presents simple and low-cost, real time in-circuit condition monitoring of MOSFET in power electronic converters. Design metrics requirements like low cost, small size, high power factor, low percentage of total harmonic distortion etc. requires the power electronic systems to operate at high frequencies and at high power density. Failures of power converters are attributed largely by aging of power MOSFETs at high switching frequencies. Therefore, real time in-circuit prognostic of MOSFET needs to be done before their selection for power system design. Accelerated aging tests are performed in different circuits to determine the wear out failure of critical components based on their parametric degradation. In this paper, the simple and low-cost test beds are designed for real time in-circuit prognostics of power MOSFETs. The proposed condition monitoring scheme helps in estimating the condition of MOSFETs at their maximum rated operating condition and will aid the system designers to test their reliability and benchmark them before selecting in power converters

Advanced Oscilloscope Triggering Based on Signal Frequency

This paper presents a novel frequency based technique for triggering of the oscilloscope. Fast Fourier Transform (FFT) has the capability of analyzing waveforms in the frequency domain and this has opened up a new set of opportunities in digital oscilloscopes. The proposed FFT based technique can provide stable triggering even in the case of complex periodic signals. In this technique, the frequency of all harmonics present in the test signal is retrieved using FFT and the base repetition rate of the signal is found by selecting the frequency of the lowest harmonic present. This base frequency signal can be used to trigger the oscilloscope to obtain a stable waveform display. The efficacy of the method is evaluated by implementing the technique using DAQ (Data Acquisition) card and LabVIEW ® software. Robustness of the technique is evaluated by simulated addition of random noise. It is found that the proposed technique is quite effective in detecting the base repetition rate of complex as well as simple waveforms and is quite robust

A medium-range hygrometer using nano-porous thin film of gamma-Al2O3 with electronics phase detection

Present work deals with the development of a low-cost prototype RH meter for measuring humidity in the range of 1-10% RH. The sensor working on capacitive technique consists of porous thin film of gamma-Al2O3 formed between the parallel gold electrodes. The film was fabricated by dipcoating of sol solution obtained from the sol-gel method. The pore morphology of the sensor has been characterized by XRD, FESEM and BET analysis. The electrical parameters of the sensor have been determined by Agilent 4294A impedance analyzer. Response (similar to 10 s) and recovery (similar to 16 s) times of the sensor are better than the commercial sensor utilized for calibration (Xentaur, USA, LPDT-100). A suitable signal condition circuit has been developed to convert the capacitance change into voltage signal. For direct display of the humidity, the output of the sensor has been linearized by diode function generation. The prototype instrument has the potential for measuring humidity in different applications

Classification of Cellulosic Insulation State Based on Smart Life Prediction Approach (SLPA)

The state of cellulosic solid kraft paper (CSKP) insulation, to a large extent, is an indication of a transformer’s health. It not only reflects the condition of transformer but also diagnose its residual life. The quantity of 2-furfuraldehyde (2-FAL), carbon dioxide (CO2), and carbon monoxide (CO) dissolved in the transformer oil are useful diagnostic indicators to predict the state of the CSKP insulation. In this work, the current physical state of the CSKP is determined with the help of easily measurable parameters, like temperature, moisture, and the aging time. Here, the degree of deterioration of CSKP insulation has been determined using an integrated insulation health assessment system. This technique integrates a two-stage system comprising of a neural network (NN) model followed by a Smart Life Prediction Approach (SLPA). A thermo-moisture-aging multi-layer feed-forward NN model has been developed to predict the concentrations of 2-FAL, CO2, and CO, which are further correlated to estimate the Degree of Polymerization (DP) values adopting an SLPA. The advantage of the proposed integrated system is that it provides an alternative means of paper health assessment based on Dissolved Gas Analysis (DGA) without estimating dissolved gas concentrations in oil, thereby avoiding the use of sophisticated measuring instruments. The optimal configuration of the NN model has been achieved at minimum iterations with an average cross-validation mean square error of 3.78 × 10−7. The proposed system thereby avoids destructive and offline measurement of DP and facilitates real-time condition monitoring of oil-immersed transformers. The test results of the developed system show considerable reliability in determining insulation health using easily measurable parameters. Furthermore, the system’s performance is compared with reported work and has been found to provide encouraging outcomes

Open Innovation of Institutional Investors and Higher Education System in Creating Open Approach for SDG-4 Quality Education: A Conceptual Review

The introduction of sustainable development goals has made sustainability a top priority for most nations. This has raised the investment into the educational system for potential growth and for creating an innovation culture in any country; the role of institutional investors in the development of financing clean energy infrastructure, entrepreneurial development, poverty reduction, and driving corporate social responsibility and firm development has been found significant. An intensive literature search of Scopus and the web of science database was explored with different relevant sets of keywords “Institutional investors AND Education”, “Institutional investors” AND “Higher education”, which drew 29 final articles between 2010–2021. This scoping review draws a new open approach for creating alternative sustainable funding for the higher education system and investment opportunities for institutional investors with government intervention. This research becomes the first that shows the road map to the higher education system in creating alternative funding through the proposed Institutional Investor & Sustainable University Funding Governance Code, which will make the higher education system independent and ease the burden on the government, as well as create a huge market opportunity for both players. This research model will scope the collaborative approach towards sustainable development goal 4—Quality education