Signal Conditioning Circuit Research Articles

Research on Building Gas Pipe Leakage Detection Based on LabVIEW and Multisim

According to the micro energy vibration signal which is generated by the internal gas injection when the building gas pipe leaks, a set of building gas pipe leakage detection and analysis system is designed. The final analysis results of the system can provide the basic analysis data for the timely detection of building gas pipe leakage and the quantitative and qualitative change results caused by leakage. The system selects 801S vibration sensor to extract the vibration signal generated by pipeline leakage, and then amplifies the weak voltage signal converted by vibration signal through signal conditioning circuit. The signal conditioning circuit completes the simulation through Multisim platform and verifies that the expected results meet the requirements. Finally, the signal processing program and detection program based on HHT algorithm are designed and constructed by LabVIEW platform to decompose the data of the conditioned signal and determine whether there is leakage. The results show that the dynamic and static characteristics of the system are fine, and the accuracy is high, especially the effect of the low-frequency and low-pressure (200Hz and below 5V) signal detection is very well.

Real Time PC-Based Flow Measurement Technique Using Optical Channel as a Signal Transmitting Media

A PC based cost effective electro-optic type flow measurement technique is designed and developed. The anemometric principle i.e. the effect of heat loss on a heating element due to flowing fluid is utilized for the measurement of flow rate of liquid in the process industry. A constant voltage p-n junction diode is used as a basic sensing element and the output of the sensing element is amplified and conditioned with the help of the instrumentation amplifier and signal conditioning circuit. Transmission of electrical signals in remote locations suffers from measurement errors due to electromagnetic induction effect, stray capacitance effect etc. The transmission of electrical signal is also not safe for the industries where an inflammable area is present between fields to remote locations and optical transmission is preferred in such areas. To overcome these, an electro-optical system has been developed. The process variable is first sensed electrically. This electrical signal of the transducer is converted into an optical signal using an electro-optic amplitude modulator and then it is transmitted in the form of an optical signal from field to control room through inflammable areas. The modulated signals are demodulated in the control room or remote location and then send to the PC through an optoisolator circuit and DAS card. The experiment has been performed and the theory as well as the mathematical equation has been derived to explain the operation of the proposed system. The overall PC based flow indicator system is also found to have linear characteristics with very good repeatability within tolerable percentage error.The experimental result is reported in the paper.

Design and manufacture of lock-in amplifier

This design realizes the excellent performance of lock-in amplifier in detecting weak signal, which is composed of signal conditioning circuit and MCU control module. The single chip microcomputer is used to control the AD sampling of the filtered DC component after multiplication operation, and the FPGA is used to realize the phase shift control. Finally, the amplitude of the signal to be measured can be obtained by eliminating the gain generated in the whole circuit with the measured amplitude. After testing, it has the advantages of high sensitivity, high input impedance and low noise, and can realize accurate measurement.

Wheelchair for Quadriplegic Patient with Electromyography Signal Control Wireless

<p class="0abstract">Quadriplegia is a paralysis condition in both arms and legs so that the patient is only able to move his neck and head. Manual or electric wheelchairs with joystick or switch control as a tool for people with paralysis certainly cannot be controlled independently by quadriplegia sufferers. This study aimed to help quadriplegia sufferers not to depend on others in carrying out daily activities by developing electric wheelchairs that can be controlled independently. The bioelectric signal which has only been used for diagnostic purposes can be utilized as an electric wheelchair control system for quadriplegia sufferers. In this study, electric wheelchairs were controlled by electromyography (EMG) signals from muscle contractions that can be driven by quadriplegia sufferers, namely the neck and face muscles. The increase in EMG signal amplitude during the muscle contraction is used as a trigger for the electric motor in a wheelchair to move forward, backward, turn right, and turn left. An electronic circuit for signal conditioning was used to amplify the EMG signal leads and filter frequencies that are not needed by the system before being processed by the microcontroller circuit. The use of wireless systems was developed to reduce the use of cables connecting electrodes to patients with electronic devices that will provide comfort to the user. Based on the results of the data collection on the wheelchair system, the detectability and selectivity values were for the 100% and 94% forward commands, 94.33% and 100% reverse commands, 92.31%, and 96% right turn commands and 97.96% and 94.12% left turn commands. The electric wheelchair system with EMG signal control is expected to help the mobility of quadriplegia sufferers.</p>

Design, Assembly and Testing of a Novel Piezoelectric Geophone Based on PVDF Film

A piezoelectric geophone is a vibration transducer that converts mechanical vibrations into electrical signals via the piezoelectric effect. At present, the commonly used sensitive component of the conventional piezoelectric geophone is piezoelectric ceramic (PZT) material, which has low structural flexibility and high natural frequency. This paper reports a piezoelectric geophone based on polyvinylidene fluoride (PVDF) film with a sensitive unit composed of PVDF film and spiral cantilever beam, which can increase the sensitivity and reduce the low-frequency cutoff frequency. Firstly, the PVDF piezoelectric film is introduced, and the sensitive unit with PVDF piezoelectric film and spiral cantilever beam is designed. Secondly, the signal conditioning circuit and the digital module circuit are designed according to the characteristics of the detector and the test environment. Finally, the performance tests and fabrication of the geophone are carried out. The results indicate that the piezoelectric geophone has a stable sensitivity of 230 mV/m/s2 in the range of 4–90 Hz, which are superior to the existing piezoelectric geophone.

Single-photon Counting System Based on a 4H-SiC Avalanche Photodiode

Weak ultraviolet (UV) signal detection systems have broad application prospects in fields such as space science, aerospace, and military communications. 4H-SiC avalanche photodiode (APD) devices have a high internal gain and can be used in single-photon-based UV radiation counting systems when in Geiger-mode operation. The system comprises an APD drive circuit, a passive quenching circuit, a signal conditioning circuit, a counting and control circuit based on a microprogrammed control unit, and a display module, which can perform real-time monitoring of changes in weak UV radiation.

A geophone-based and low-cost data acquisition and analysis system designed for microtremor measurements

Abstract. The commercial data acquisition instruments designed for three-component microtremor measurements are usually very expensive devices. In this paper, a low-cost, computer-aided, and geophone-based system designed to record, monitor, and analyze three-component microtremor data is presented. This proposed system is not a simple data acquisition system. It is also an integrated system developed to interpret the microtremor data using the horizontal-to-vertical spectral ratio (H ∕ V) method without any external software. Therefore, the H ∕ V peak frequency and amplitude can be easily estimated using this system. The proposed system has several features such as a 200 Hz sampling frequency, approximately 72 dB dynamic range, text data format, and data analysis tools. This system consists of a graphical user interface developed by using the .NET Framework 4.5.2 and external hardware that includes signal conditioning circuits, voltage converter circuit, external analog-to-digital converter, and Arduino Uno board. The proposed system uses low-cost vertical and horizontal geophones with a 4.5 Hz natural frequency to measure three-component microtremor data. The developed software undertakes many tasks such as communication between the external hardware and computer, transferring, monitoring, and recording the seismic data to the computer, and interpretation of the recorded data using the Nakamura method. Channel consistency and internal noise measurement tests were performed to demonstrate the accuracy and precision of the proposed system. The proposed system was compared to a commercial triaxial digital seismograph, and satisfactory results were obtained. The developed system is a completely open-source and open-hardware system and can be easily used in academic studies conducted by researchers and university students who are interested in seismic ambient noise analysis.

Improving the energy resolution while mitigating the effects of dark-noise, for a microcontroller based SiPM sensor

We propose a novel design to improve the energy resolution while mitigating the SiPM dark-noise effect of an original SiPM based smart sensor [1]. This improvement then allows the sensor to be used in general purpose particle detector design. It is a low-power, scalable design, suitable for low-cost, self-contained devices, making it attractive for use in various industrial sectors such as mining and infrastructure, as well as, research laboratories. An innovative solution has been realised through the use of an external Track/Hold (T/H) circuit, while leveraging the on-board microcontroller (μC) and signal-conditioning circuit of the existing SiPM smart sensor system. A low sampling/conversion rate analog to digital converter (ADC) minimises the complexity of the design.

Development of an MEMS ultrasonic microphone array system and its application to compressed wavefield imaging of concrete

Although contactless ultrasonic wavefield imaging shows potential for effective nondestructive inspection of various engineering materials, it has been rarely applied to concrete materials owing to technical challenges including low signal-to-noise ratio (SNR) caused by inherent heterogeneity of concrete. This paper presents development of a multi-channel MEMS ultrasonic microphone array system and its application to compressed wavefield imaging of concrete materials. The developed multi-channel MEMS ultrasonic microphone array system contains eight MEMS ultrasonic microphone elements and a signal conditioning circuit that enables measurements of ultrasonic signals with high SNR. A compressed sensing approach, based on the multiple measurement vector (MMV) concept, is applied to reconstruct a full dense ultrasonic wavefield data from sparsely sampled ultrasonic wavefield data. Experiments are carried out on a laboratory concrete sample to verify the performance of the developed MEMS microphone array system and proposed compressed sensing approach and then large-scale concrete samples to demonstrate practical application. The experimental results demonstrate that the developed MEMS microphone array system provides high-quality (SNR > 20 dB) ultrasonic data collected from concrete elements; furthermore, the proposed compressed sensing approach provides accurate reconstruction of dense wavefield data, as determined by peak signal-to-noise ratio (PSNR), from sparsely measured wavefield data with compression ratios up to 85% and PSNR above 25 dB in data collected form realistic large-scale concrete samples. By combining the MEMS array system and compressed sensing approach, the total ultrasonic data acquisition time needed to produce dense wavefield data can be significantly reduced.

Assay of Inductive-Capacitive Probe for the Measurement of the Conductivity of Liquids

The basic principle of a noncontact method of measurement of conductivity of liquids, presented earlier, is analysed to evolve design rules to have minimal error in the measurement. In this method, the current is sent through the liquid whose conductivity is to be measured by induction and the voltage across the liquid column is measured using capacitive coupled electrodes and the conductivity computed therefrom. Hence, problems that arise due to contamination or corrosion of contacting electrodes are eliminated. The signal conditioning circuit is developed such that the measurement of the voltage-drop across the column of the liquid and hence the determination of the conductivity of the liquids unaffected by the coupling capacitances of the potential electrodes. Thus, small deviations that can creep in during manufacturing of the probe (manufacturing tolerances) do not affect the performance. An error analysis of the proposed system was carried out and the practicality of the scheme verified by developing and testing a prototype. The test results showed a worst-case error of 0.82% in conductivity measurements. The facts that the proposed method is unaffected by the coupling capacitors and the presence of materials kept outside of the probe were also verified.

Low-cost capacitive sensor for detecting palm-wood moisture content in real-time

sIn this study, we analyze a non-invasive and low-cost wood moisture meter by means of a capacitive detection circuit. The process of the design and development of an oil-palm-wood moisture meter is described. As part of the study, two electrode structures, i.e., parallel-plate and coplanar electrodes, are tested. The capacitive detection circuit includes a square-wave-generator circuit, low-pass filter circuit, and signal-conditioning circuit. The frequencies of the square-wave excitation signal are in the range of 200 kHz and are analyzed via a microcontroller to interpret the percentage of oil-palm-wood moisture content. The applicability of the capacitive moisture measurement is investigated under various moisture conditions of the oil palm wood i.e., 5%–20%. The experimental results show that the measurement accuracy of the detection circuit is high, with an acceptable measurement error.

A General Embedded Underwater Acoustic Communication System Based on Advance STM32

Underwater acoustic communication (UAC) modem is an important infrastructure of underwater network construction. In recent years, with the performance improvement of the STM32 processor, the realization of reliable UAC through high-performance STM32 processor is conducive to reduce the system power consumption, cheapen the hardware cost, and ease the development difficulty. In this letter, we propose an embedded UAC system with the STM32H743 processor as the core and the peripheral sending/receiving circuit as the signal conditioning circuit module. The system can support a variety of modulation and demodulation methods, including single/multi-carrier frequency-shift keying and orthogonal frequency division multiplexing. Furthermore, in order to reduce the computational cost of the system, a fast and robust frame synchronization algorithm based on the segmented fast Fourier transform is applied. The sea trials show that the system can realize the reliable UAC transmission of 100 b/s-1 kb/s in the distance of 5-8 km in the shallow water area.

Virtual Simulation System with Various Examples and Analysis Tools for Programmable Logic Controller Training

The purpose of this research is to design a virtual educational simulation device as a training aid for the Programmable Logic Controller. This software is equipped with an extensive library of process models to mimic the functional behavior of real factory processes, thus helping students to practice controlling various industrial processes by using various tools from PLC. The advantage of this simulator is that it provides analytical tools to get concise information about the output performance of the controlled system. The method used in this research is the Descriptive Analysis Method which consists of five stages, namely problem identification, literature study, instrument design, implementation, and testing and evaluation. The implementation of this software is based on LabVIEW (Laboratory Laboratory Workbench) on the PC. Exchange of control signals between the actual PLC (any PLC can be used) and the PC via the signal conditioning circuit and the Arduino. The results of this study are that three factory models have been made. The first factory model is a traffic light control system of two adjacent intersections. The second factory model is water level control in the tank. The third factory model is a multi elevator control system. The analysis tools for the first plant is information about the total waiting time of all vehicles passing through the intersection. The analysis tools for the second plant is a system performance graph that is equipped with maximum overshoot, settling time, and steady state error information. The analysis tools for the third plant is the total average floor displacement time of all elevator users. Therefore, this research has succeeded in making a virtual education simulation which, consists of three plant simulations and their analysis tools. The impact of this research is expected to increase students’ understanding of PLC and control techniques.

Design and Implementation of DAC Circuit in Waveform Generator

This article combines the different stages and different levels of various courses such as circuit principle, analog circuit, digital circuit, signal and system, single-chip microcomputer principle, FPGA application and practice, and utilizes the flexibility and interest of the “hardwood classroom” personal multi-functional experimental platform. The simulation design and experimental test of the DAC circuit and signal conditioning and waveform reconstruction circuit in the waveform generator are completed step by step, which fully reflects the process and fun of electronic system design.

High-Performance Analog Front-End (AFE) for EOG Systems

Electrooculography is a technique for measuring the corneo-retinal standing potential of the human eye. The resulting signal is called the electrooculogram (EOG). The primary applications are in ophthalmological diagnosis and in recording eye movements to develop simple human–machine interfaces (HCI). The electronic circuits for EOG signal conditioning are well known in the field of electronic instrumentation; however, the specific characteristics of the EOG signal make a careful electronic design necessary. This work is devoted to presenting the most important issues related to the design of an EOG analog front-end (AFE). In this respect, it is essential to analyze the possible sources of noise, interference, and motion artifacts and how to minimize their effects. Considering these issues, the complete design of an AFE for EOG systems is reported in this work.

Classification of standing and sitting phases based on in-socket piezoelectric sensors in a transfemoral amputee.

A transfemoral prosthesis is required to assist amputees to perform the activity of daily living (ADL). The passive prosthesis has some drawbacks such as utilization of high metabolic energy. In contrast, the active prosthesis consumes less metabolic energy and offers better performance. However, the recent active prosthesis uses surface electromyography as its sensory system which has weak signals with microvolt-level intensity and requires a lot of computation to extract features. This paper focuses on recognizing different phases of sitting and standing of a transfemoral amputee using in-socket piezoelectric-based sensors. 15 piezoelectric film sensors were embedded in the inner socket wall adjacent to the most active regions of the agonist and antagonist knee extensor and flexor muscles, i.e. region with the highest level of muscle contractions of the quadriceps and hamstring. A male transfemoral amputee wore the instrumented socket and was instructed to perform several sitting and standing phases using an armless chair. Data was collected from the 15 embedded sensors and went through signal conditioning circuits. The overlapping analysis window technique was used to segment the data using different window lengths. Fifteen time-domain and frequency-domain features were extracted and new feature sets were obtained based on the feature performance. Eight of the common pattern recognition multiclass classifiers were evaluated and compared. Regression analysis was used to investigate the impact of the number of features and the window lengths on the classifiers' accuracies, and Analysis of Variance (ANOVA) was used to test significant differences in the classifiers' performances. The classification accuracy was calculated using k-fold cross-validation method, and 20% of the data set was held out for testing the optimal classifier. The results showed that the feature set (FS-5) consisting of the root mean square (RMS) and the number of peaks (NP) achieved the highest classification accuracy in five classifiers. Support vector machine (SVM) with cubic kernel proved to be the optimal classifier, and it achieved a classification accuracy of 98.33 % using the test data set. Obtaining high classification accuracy using only two time-domain features would significantly reduce the processing time of controlling a prosthesis and eliminate substantial delay. The proposed in-socket sensors used to detect sit-to-stand and stand-to-sit movements could be further integrated with an active knee joint actuation system to produce powered assistance during energy-demanding activities such as sit-to-stand and stair climbing. In future, the system could also be used to accurately predict the intended movement based on their residual limb's muscle and mechanical behaviour as detected by the in-socket sensory system.

Review on sensitive and selective ethylene detection methods for fruit ripening application

PurposeThis work encompasses the various laboratory-based and portable methods evolved in recent times for sensitive and selective detection of ethylene for fruit-ripening application. The role of ethylene in natural and artificial fruit ripening and the associated health hazards are well known. So there is a growing need for ethylene detection. This paper aims to highlight potential methods developed for ethylene detection by various researchers, including ours. Intense efforts by various researchers have been on since 2014 for societal benefits.Design/methodology/approachThe paper focuses on types of sensors, fabrication methods and signal conditioning circuits for ethylene detection in ppm levels for various applications. The authors have already designed, developed a laboratory-based set-up belonging to the electrochemical and optical methods for detection of ethylene.FindingsThe authors have developed a carbon nanotube (CNT)-based chemical sensor whose performance is higher than the reported sensor in terms of material, sensitivity and response, the sensor element being multi-walled carbon nanotube (MWCNT) in comparison to single-walled carbon nanotube (SWCNT). Also the authors have developed infrared (IR)-based physical sensor for the first time based on the strong IR absorption of ethylene at 10.6 µm. These methods have been compared with literature based on comparable parameters. The review highlights the potential possibilities for development of portable device for field applications.Originality/valueThe authors have reported new chemical and physical sensors for ethylene detection and quantification. It is demonstrated that it could be used for fruit-ripening applications A comparison of reported methods and potential opportunities is discussed.

Excitation module for orthogonal fundamental mode fluxgate sensor

A fluxgate is a device that has important applications in weak magnetic field measurements. Compared with the second harmonic mode, the orthogonal fundamental mode fluxgate exhibits a better performance in terms of lower noise and wider bandwidth, making it popular among researchers in this field. An amorphous wire is a vital part of any orthogonal fundamental mode fluxgate, and its excitation parameters determine the performance of the sensor (especially the noise level). For different structures and sizes of amorphous wires as probes, the optimal excitation parameters of orthogonal fundamental mode fluxgate are different. The conventional excitation module development scheme suffers from problems such as a complicated structure and low flexibility. To overcome these problems, a simple, compact, and effective excitation module is proposed, which is composed of a waveform generator, signal conditioning circuit, and voltage-controlled current source. Owing to the high flexibility, the frequency of the direct digital frequency synthesis is fully programmable. We tested the design performance indexes of key parameters, such as excitation signal waveform, amplitude, noise level, and bandwidth. The excitation current noise level is as low as 12.42 nA/sqrt (Hz) @ 20 kHz without Iac and 17.35 nA/sqrt (Hz) @ 20 kHz with Iac. The effective bandwidth of the alternating current output is 10–200 kHz. Moreover, a system test platform was developed, and this module was used to analyze the variation trend of the noise level of the fluxgate sensor under different excitation parameters (such as Iac, Idc, and excitation current frequency). It has been proved that the excitation module helps in effectively and quickly selecting the best excitation parameters to improve the performance of orthogonal fundamental mode fluxgates and shorten their development cycle.

A Low-Cost Surge Current Detection Sensor with Predictive Lifetime Display Function for Maintenance of Surge Protective Devices.

In this study, a low-cost surge current detection sensor (SCDS) that can measure high current surges using a low-current toroidal coil is proposed for maintenance of a surge protective device (SPD). The proposed SCDS is designed to display the predicted lifetime of the SPD based on the magnitude of surge current and number of surges. In addition, a method for measuring high surge current using a toroidal coil that can usually measure only low current is proposed. A lightning strike counter consists of a microcontroller with a low-power liquid crystal display (LCD) driver, 3 VDC lithium battery, and signal conditioning circuit that converts amplitude information of the surge current into duration information of a negative pulse to facilitate processing in the microcontroller. In this paper, we propose a software algorithm that can calculate the remaining lifetime of SPD based on the amplitude and number of surge currents. There is also an option to select the capacity of the surge protective device and the number of phase lines, allowing it to assess the predicted lifetime for various types of Class II SPDs. The proposed SCDS is measured as 7.2 μA from the battery power consumption test, and the service life is calculated to be 11.1 years. It meets the International Standard IEC62561-6 test conditions of the lightning strike counter and is expected to be useful in the maintenance of SPDs and lightning protection systems.

Piezoelectric geophone: a review from principle to performance

Real-time monitoring of seismic information is important, a wide variety of geophones have emerged to achieve this goal. According to the principle of transforming seismic signals, the geophones can be classified into electromagnetic geophones, piezoelectric geophones, electrochemical geophones, fiber optic geophones and so on. Among them, piezoelectric geophones have been widely used in seismic detection. In this article, the piezoelectric material is briefly introduced at first, and then the piezoelectric seismic detector with piezoelectric ceramic and polyvinylidene fluoride as a sensitive material is involved. After analyzing the electrical equivalent model of the piezoelectric sensitive unit, the signal conditioning circuit of the piezoelectric geophone is summarized as well. After that, the promotion of MEMS technology to piezoelectric geophones is discussed. Finally, a summary of all the work listed in this article is given and an outlook of combining MEMS and PVDF to improve the performance of geophones is proposed.