Electrical Signal Acquisition Research Articles

Research on Process Characteristics and Properties in Deep-Penetration Variable-Polarity Tungsten Inert Gas Welding of AA7075 Aluminum Alloy

In this study, a new deep-penetration variable-polarity tungsten inert gas (DP-VPTIG) welding process, which is performed by a triple-frequency-modulated pulse, was employed in the welding fabrication of 8 mm AA7075 aluminum plates. The electric signal, arc shape, and weld pool morphology of the welding process were obtained by means of high-speed photography and an electric signal acquisition system under varying parameters of the intermediate frequency (IF) pulse current. The principle of the arc characteristics and the dynamic mechanism of the weld melting during the process are explained. In addition, the macroforming, microstructure, and microhardness of the welded joints were investigated. The results indicate that, with an intermediate frequency pulse of 750 Hz, the arc displayed a higher energy density and a more effective arc contraction, which improved weld appearance and penetration. Moreover, the impact and stirring action of the arc refined the microstructure grains of the weld center. Therefore, this new welding method is feasible for welding medium-thickness aluminum alloy plates without a groove.

Analysis of arc stability of plasma main arc and inter-wire arc in skew-coupling arc welding

By adjusting the inter-wire arc (IWA) posture, the skew-coupling arc (SCA) is proposed to address the polar effect in the cross arc, enabling decoupling control of heat, force, and mass transfer. Despite the advancement, the arc stabilization mechanism in the SCA remains poorly understood, hindering its application as a heat source in welding or additive manufacturing. To elucidate this mechanism, various influencing factors such as power supply characteristics, shielding gas composition, IWA posture, and plasma main arc (PMA) were analyzed. An electrical signal and high-speed camera synchronous acquisition system was utilized to analyze current-voltage waveforms and arc shapes. The results indicate that the arc stability of the SCA can be enhanced by ensuring specific external conditions. Constant voltage power supply enhances the self-regulating effect of the IWA, maintaining the IWA and the PMA in a hybrid state at all times. Introducing an oxidizing gas to the shielding gas can effectively suppress cathode spot climbing and stabilize the IWA. The vertical spacing between wires directly impacts the PMA deflection, while the wire horizontal angle has a lesser effect. The heat-regulating effect of the PMA column boosts the arc length regulation by the IWA. The current and the ion gas flow rate in the PMA minimally influence the SCA stability. These findings can provide a solid foundation for further applications of the SCA as heat source.

Liquid metal neuro-electrical interface

Liquid metal (LM), an emerging functional material, plays increasing roles in biomedical and healthcare areas. It has particular values in neural interfaces as it combines high conductivity, flowability, and biocompatibility properties. Neuro-electrical interfaces (NEIs) are effective tools to provide a bridge between the nervous system and the outside world. The main target of developing neural interfaces is to help disabled people repair damaged nerves and enhance human capacity above normal ability. This article systematically summarizes LM-based neural interface technologies, including neural electrodes for electrical signal acquisition and administration of electrical stimulation and nerve guidance conduits for neural connectivity and functional reconstruction. The discussion begins with an overview of the fundamental properties associated with LM materials involved in the field of neural interface applications. The fabrication methods of LM-based neuro-electrodes and conduits are then introduced, and the current development status of LM-based neuro-electrodes and conduits is elaborated. Finally, the prospects and possible challenges of LM-based neural interfaces are outlined.

AN APPROACH ON THE DESCRIPTION OF A FLAT DRIVING BELT BEHAVIOUR MIRRORED IN TRANSMITTED MECHANICAL POWER

For driving belt condition monitoring, the main interest is the certification of the capacity to keep their qualities unchanged over a long period of time and secondary to detect the imminence of the catastrophic failure. This paper presents a study on the behaviour detection and description of a flat driving belt health condition, used in a rotary machine electrically driven, particularly a lathe headstock gearbox running idle. It was discovered that in the mechanical power transmitted from electromotor to gearbox via a flat belt some specific sinusoidal components (a fundamental and some harmonics) of variable power are generated. The description of these power components (by values of amplitude, frequency and phase at origin of time) is indirectly detectable in the evolution of the active electrical power absorbed by the drive electromotor. Two arguments are available for this approach. Firstly, there is a reasonable assumption that between the mechanical power and the active electrical power there is an approximated proportionality relationship through the power efficiency. Secondly, the evolution of the active electrical power (or mechanical power as well) is a deterministic signal with a low level of noise. A simple computer assisted procedure of active electrical power signal acquisition and data processing was conceived, the detection was done by computer aided curve-fitting procedures in Matlab applied on active electrical power evolution absorbed by the driving motor in stationary working regimes (the electromotor playing the role of a mechanical power sensor). Mainly two ways of graphic representation have been proposed in order to describe the variable power generated by this flat belt (in time and frequency domains). The behaviour of many other types of belts involved in rotary machines driving can be similarly described.

Current materials for 3D-printed flexible medical electrodes

Electrodes serve as essential tools for both acquiring and stimulating electrical signals, pivotal in monitoring human health through electrophysiological signals and playing a significant role in disease management and treatment. Notably, Young’s modulus of flexible electrodes is similar to that of tissues and organs, thereby avoiding tissue or organ damage arising from mechanical mismatch. Thus, flexible electrodes become the fundamental devices for ensuring the stable, long-term acquisition of electrical signals and delivering reversed electrical stimulation to guide disease treatment. Reducing the size of flexible electrodes and increasing the number of electrode channels are significant for improving the sensitivity and accuracy of signal acquisition. In comparison to traditional manufacturing methods, 3D printing technology is able to fabricate products with higher resolution at a much faster speed. It is customizable and provides a novel approach for preparing flexible electrodes. Many conductive materials have been developed and applied to prepare flexible electrodes, and some have been integrated into 3D printing techniques, driving forward the development of 3D-printed flexible electrodes in medical fields. This article reviews recent research advances concerning the combination of these materials with 3D printing technology to prepare flexible electrodes and categorizes the materials into four main groups, namely metallic materials, carbon-based materials, conductive polymers, and other materials. In addition, we outline the future directions regarding the application of 3D-printed flexible electrodes in clinical research and medical translation.

Analysis Of Low Offset Operation Amplifier Principles and Its Application Areas

While the functionality of traditional operational amplifiers today is no longer sufficient in areas that require high accuracy, low offset operational amplifiers are used in a wide range of applications in today's world. Compared with traditional operational amplifiers, low offset operational amplifiers have a series of advantages such as high precision and high signal-to-noise ratio, and are currently used in ECG signal acquisition, laser ranging, and plant electrical signal acquisition. Low offset op amps can amplify the signal with more accurately, which is advantageous in environments where the acquired signal is weak and the noisy is large, It mainly reduces the system offset by adjusting the input stage circuit (using the three-stage amplification circuit as the preamplifier circuit and using the two-stage amplification to prevent saturation of the preop amp), and improves the manufacturing process to reduce the structural offset to ensure the accuracy of the output signal. In the future, high integration and high accuracy will be the main development direction of operational amplifiers.

Development of multifunctional current-carrying friction and wear test machine based on LabVIEW

In order to study the effect of friction wear behavior on electrical signal transmission, a carrier friction wear test machine was developed which can be analyzed under different test conditions (load, speed and current). The testing machine builds a measurement and control system through LabVIEW platform to realize real-time acquisition and synchronous display of electrical signals, friction coefficient and temperature, and control of load size, and uses wavelet decomposition and arithmetic average to process data and PID control algorithm to revise load in real time. The experimental results show that the stability of the test machine and the accuracy of control system meet the test requirements.

STUDY OF DROPLET TRANSFER CHARACTERISTICS AND WELD FORMATION WITH ER430LNb FERRITIC STAINLESS STEEL DURING GAS METAL ARC WELDING

An ER430LNb ferritic stainless steel wire was used for a gas metal arc welding (GMAW) test. The characteristics of droplet transfer and its corresponding voltage and current waveforms were investigated using a high-speed camera and synchronous acquisition of electrical signals. The weld formation, droplet transfer patterns and corresponding microstructures under different welding parameters were observed, and the effect of the current level on the droplet transfer frequency was discussed. As the results show, there were three typical metal transfer patterns during the GMAW using the ER430LNb ferritic stainless steel wire, namely short circuit transfer, mix transfer and spray transfer. With an increase in the welding current, the weld formation is changing constantly, and the droplet transfer frequency increases exponentially. With the change in the transfer pattern, the columnar ferrite structure of the weld is continuously coarsening. In addition, hardness measurements were taken on joints welded at different welding currents for comparison.

Single‐Molecule Electronic Biosensors: Principles and Applications (Adv. Sensor Res. 5/2023)

Single-Molecule Electronic Biosensors In article number 2200084, Jinying Wang, Chuancheng Jia, Xuefeng Guo, and co-workers summarize the working principles, device architectures, and potential applications of single-molecule electronic biosensors for near-field and real-time detection of single biomolecules, and provide a promising optoelectronic integrated system for realizing synchronous acquisition of electrical and optical signals of single biomolecules.

Effect of Process Parameters on Arc Behavior and Weld Formation in Weaving Gas Tungsten Arc Welding

The arc welding with weaving has been used widely to obtain better weld quality by avoiding lack of side wall fusion and improve the weld efficiency by obtaining the wide weld. But the effect of weaving process parameter on the weld is not clear. The aim of this work is to study the effect of process parameters on arc behavior and weld formation in Weaving-Gas Tungsten Arc Welding (W-GTAW), those parameters include welding current, tungsten electrode height from the electrode tip to upper surface of workpiece, weave angle, weave speed, and weave stop time on the left and right sides. The instantaneous arc shape and electrical signal data were collected by high-speed camera and electrical signal acquisition system, respectively. Furthermore, the weld morphology was also systematically analyzed. This result shows that the bottom surface radius of the arc changed with weaving in the W-GTAW. When the weave speed increased to 0.40 × 10−1 rad/s, the change of the radius was the least, with only 0.10 mm drift, and the difference between the arc forces in the middle and the two sides of the molten pool was smallest in all experiments. Compared with the welding stability of each process, decreasing the tungsten electrode height, weave angle and speed could significantly enhance the welding stability. The forming coefficient of weld with a weave angle of 1.9° was 3.11. It shows that increasing reasonably the weave angle and speed can increase the weld penetration and might help reduce stress concentration and hot crack tendency of the weld. When the welding current is reduced to 130 A for W-GTAW welding, the hardness transition from base metal (BM) zone to weld zone (WZ) is more gentle. Furthermore, the W-GTAW technology shows great application potential in weld forming control by adjusting process parameters.

Self-Patterning of Highly Stretchable and Electrically Conductive Liquid Metal Conductors by Direct-Write Super-Hydrophilic Laser-Induced Graphene and Electroless Copper Plating

Stretchable electrodes are desirable in flexible electronics for the transmission and acquisition of electrical signals, but their fabrication process remains challenging. Herein, we report an approach based on patterned liquid metals (LMs) as stretchable electrodes using a super-hydrophilic laser-induced graphene (SHL-LIG) process with electroless plating copper on a polyimide (PI) film. The LMs/SHL-LIG structures are then transferred from the PI film to an Ecoflex substrate as stretchable electrodes with an ultralow sheet resistance of 3.54 mΩ per square and excellent stretchability up to 480% in elongation. Furthermore, these electrodes show outstanding performances of only 8% electrical resistance changes under a tensile strain of 300%, and strong immunity to temperature and pressure changes. As demonstration examples, these electrodes are integrated with a stretchable strain sensing system and a smart magnetic soft robot toward practical applications.

Characterization of the effects of high-intensity negative current pulses on metal transfer and melting rate in the AC-GMAW process

The use of variants of the gas metal arc welding (GMAW) process has become an affordable option in industry. Alternating current–gas metal arc welding (AC-GMAW) arises as one of them, providing additional degrees of freedom for process controllability and versatility. This study focused on the analysis of a complex waveform of the AC-GMAW process for welding stainless steel, employed in modern synergic programs, which has not been widely disseminated in the technical literature and assessed scientifically. The main objective was to characterize the effects of high-intensity pulses in negative polarity over the process and to discuss the potential of this strategy, since it has not been used in conventional AC synergic programs. In order to bring to light information on the phenomena involved, such as the arc climbing on the wire electrode, advanced techniques of high-speed videography were used, synchronized with the acquisition of electrical welding process signals, as well as infrared thermography, to verify the evolution of the cooling of the piece after welding. The results grounded discussions on different AC-GMAW waveforms. The process’ electrical data, along with images of the arc and analysis of the wire melting and workpiece thermal behavior, showed that there was a significant visible increase in wire melting during the negative pulse. In addition, it evidenced how the negative electrode increment contributed to the increase in wire melting even at lower power and also showed the thermal effects on the workpiece.

An antennal electric signal detection system based on template matching

As the most efficient perception system in nature, the perception mechanism of the insect (such as honeybee) antennae is the key to imitating the high-performance sensor technology. An automated experimental device suitable for collecting electrical signals (including antenna reaction time information) of antennae was developed, in response to the problems of the non-standardized experimental process, interference of manual operation, and low efficiency in the study of antenna perception mechanism. Firstly, aiming at the automatic identification and location of insect heads in experiments, the image templates of insect head contour features were established. Insect heads were template-matched based on the Hausdorff method. Then, for the angle deviation of the insect heads relative to the standard detection position, a method that calculates the angle of the insect head mid-axis based on the minimum external rectangle of the long axis was proposed. Eventually, the electrical signals generated by the antennae in contact with the reagents were collected by the electrical signal acquisition device. Honeybees were used as the research object in this study. The experimental results showed that the accuracy of template matching could reach 95.3% to locate the bee head quickly, and the deviation angle of the bee head was less than 1°. The distance between antennae and experimental reagents could meet the requirements of antennae perception experiments. The parameters, such as the contact reaction time of honeybee antennae to sucrose solution, were consistent with the results of the manual experiment. The system collects effectively antenna contact signals in an undisturbed state and realizes the standardization of experiments on antenna perception mechanisms, which provides an experimental method and device for studying and analyzing the reaction time of the antenna involved in biological antenna perception mechanisms.

A 64-Channel Data Acquisition System-Based Ultralow Noise Transimpedance Amplifier for an Ionization Profile Monitor

To meet the high time-resolution requirements of a fast ionization profile monitor (IPM), a 64-channel electrical signal acquisition system with a fast response frequency of 1 MHz has been developed. This article initially describes an ultralow noise transimpedance amplifier, which is an analog front-end (AFE) electronics aiming to achieve a balance between the accuracy and bandwidth, as well as to truly reflect the microstructure of short beam pulses. Subsequently, a synchronized multichannel data transmission system based on field-programmable gate arrays (FPGAs) transmits data streaming with the low latency and high throughput, and meanwhile, it provides data homogeneity in time across channels. The system is designed in a modular way to easily extend up to 128 channels. The nonlinearity of the readout electronics is less than 0.2% in the dynamic range of 15 nA– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$15~\mu \text{A}$ </tex-math></inline-formula> , and the relative resolution is 0.15% at the input current of 15 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> . The spurious-free dynamic range (SFDR) is about 82.43 dB at a fundamental frequency of 1 kHz, and the effective number of bits (ENOB) of the analog-to-digital conversion (ADC) is better than 13 bits. The relative synchronization time discrepancy between channels is better than 2.5% of the sampling cycle. Finally, the system is deployed for the beam profile measurement with an IPM. The obtained peak value shows a good proportionality with the beam intensity increment, and all the electronics properties achieve reasonable and excellent performance.

Research on multi-fault diagnosis method and test platform of main transmission Machinery of wind Turbine based on electrical signal

An optimised design was carried out based on the original semi-physical simulation system for the main drive chain of a wind turbine. The input of upper computer simulating wind condition, the safety control of electrical signal and vibration signal acquisition module, relay and AC contactor and dual motor control were added. Simultaneously, the simulation schemes of some common faults on the main drive of wind turbines were also designed in order to perform the experimental simulation of the single fault and multi fault. The primary purpose of simulation is to use practical approaches(such as FFT,EMD)to analyze the changes of the fault signals based on the collected electrical signals, and to determine whether there is a fault through comparison and theoretical analysis. In addition, it aimed for verifying the feasibility of electrical signals under multi-fault conditions, and discussing advantages of electrical signals over vibration signals.

Analysis of metal transfer and weld forming characteristics in triple-wire gas indirect arc welding

Triple-wire gas indirect arc welding (TW-GIA) has the advantages of low heat input and high deposition rate. However, the simultaneous melting of triple wires makes the metal transfer mode complicated. The unknown of the metal transfer mode restricts the development of this technology. In this paper, high-speed camera systems and electrical signal acquisition sensors were used to explore the TW-GIA metal transfer mode. The static force model and the arc conductive channel model were used to discuss the droplet force and energy conversion characteristics, respectively. Results showed that the TW-GIA metal transfer modes can be divided into the following: short-circuit transfer (SCT), main wire projected transfer + side wire globular transfer (PGT), main wire streaming transfer + side wire projected transfer (SPT), and main wire streaming transfer + side wire streaming transfer (SST). Moreover, the process parameter ranges corresponding to the four modes were summarized. Due to the stable arc and the uniform metal transfer process, SPT and SST can form desirable weld seam. The gravity and z-axis components of electromagnetic force are the main forces that promote metal transfer. The x-axis and y-axis components of the electromagnetic force deviate the metal transfer path from the arc coverage. Due to the change of arc conductive channel, the energy transferred from TW-GIA to the base metal is less than that of gas metal arc welding, showing the advantages of small welding deformation, narrow heat-affected zone, and grain refinement.

A Three-Dimensional-Printed Recyclable, Flexible, and Wearable Device for Visualized UV, Temperature, and Sweat pH Sensing.

Wearable devices are now recognized as a powerful tool to collect physiological and environmental information in a smart, noninvasive, and real-time manner. Despite the rapid progress of wearable devices especially wearable electronic devices, there are still several challenges that limit their further development, for example, a complicated electrical signal acquisition and processing process to eliminate the interference from the surrounding signals, bulky power supply, inevitable e-waste, and environmental pollution. Herein, we report a 3D-printed recyclable, flexible, and wearable device for visualized UV, temperature, and sweat pH sensing. Compared with wearable electronic devices, our visualized wearable device senses environmental (UV light, ambient temperature), biophysical (skin temperature), and biochemical (sweat pH) signals via stimuli-responsive color change, which does not require complicated electronic circuit design/assembly, time-consuming data processing and additional power source. In addition, this visualized wearable device is fabricated via a 3D support bath printing technology by printing UV-, temperature-, and sweat pH-sensing inks containing photochromic, thermochromic, and pH-chromic materials, respectively, into/onto sustainable starch solution, resulting in a multi-functional, recyclable, and flexible sensing device with high reproducibility. Our results reveal that UV light intensities under sunlight (0–2500 μW/cm2), ambient, and skin temperatures (0–38 °C) as well as sweat pH (4.0–7.0) can be successfully monitored.

Research on aluminum alloy welding process based on high frequency and low power pulsed Laser-MIG hybrid welding

Taking 2219 aluminum alloy as the welding research base metal, a high frequency and low power pulsed laser-MIG hybrid welding system was established. When the laser pulse frequency ranges from 500 Hz to 1500 Hz and the laser-wire distance ranges from 1 to 2 mm, the effects of high-frequency and low-power pulsed laser on the arc shape, metal transfer behavior, and weld formation in the hybrid welding process were compared and analyzed by using high-speed camera system and electrical signal acquisition system. The results show that as the pulse frequency increases, the arc is gradually compressed, and the compression reaches the maximum when the frequency is 1500 Hz. In the test, the limit distance of laser attracted arc is 2 mm and the limit distance of laser stabilized arc is 1.5 mm. From the collected electrical signal, it can be seen that the welding current is reduced by 5.8A after adding laser irradiation. Since the welding power source is a constant voltage source, the welding voltage is almost constant, so the heat input of the welding arc to the base metal and droplets is reduced to a certain extent. When the laser is biased laterally along the welding wire, the weld morphology also shifts from the center to the laser irradiation point, which further verifies the guiding effect of the laser on the arc. In addition, the addition of the laser effectively improves the stability of the welding process, the weld seam is formed uniformly, and the oscillation of the molten pool caused by the laser accelerates the discharge of gas in the molten metal, which effectively reduces the pore defects.

Effects of He content in shielding gases on high-efficient hybrid laser arc welding with C-276 filler metal

High-efficient welding technology with rotating arc assisted by laser under shielding gases with different He content was investigated for the application of 9% Ni steel in LNG storage. High-speed image and electrical signal acquisition were adopted to investigate arc stability and metal transfer behavior during hybrid laser arc welding. The results indicated that with increasing content of He, the weld formation became better first and then worse. Ar+30 %He improved the formation of welding seam. The He content had a significant influence on the electric signal waveforms. With the addition of 30 %He, the waveforms had the minimal fluctuation. It was rotating spray transfer with pure Ar, Ar+30 %He and Ar+50 %He. The difference was that with the He content increase, transfer mode shifted from unstable rotating spray transfer to stable rotating spray transfer, to irregular rotating spray transfer. With pure He, it was large droplet transfer, resulting in the formation of large spatters. The research of rotating spray transfer trajectory showed that the rotation velocity was relatively constant and one rotation time was 3.19 ms in one pulse period under Ar+30 %He. The trajectory equation was obtained for describing the rotating spray transfer. This indicated that the addition of 30 %He improved the coupling effect of laser and arc, enhanced the matching degree between rotating spray transfer and arc pulse period. It was meaningful to understand the effects of shielding gases on 9% Ni steel hybrid laser arc welding, providing theoretical basis for LNG storage efficient and reliable manufacturing.

Classification of Stroke Disease Assessment based on Body Surface Electrical Signals at Acupuncture Points

Stroke is a common brain disease with high sudden onset, high lethality, and a single means of rehabilitation assessment. In this paper, we designed a novel stroke condition rehabilitation classification experiment using a 4-channel body surface electrical signal acquisition circuit independently developed by the Integrated Microsystems Laboratory of Peking University to acquire body surface electrical signals from acupoints on both sides of the body meridians of 8 healthy volunteers and 16 stroke patients with different degrees of rehabilitation. The signals were filtered and wavelet transformed to extract features, which were fed into LR, RR, XGBoost, and SVM models for condition assessment and classification (types: healthy, mild hemiplegia, and severe hemiplegia). The results showed that the experimental scheme had strong classification ability for stroke condition recognition, with F1-score of 0.75 for LR, 0.72 for RR, 0.81 for XGBoost, and 0.79 for SVM. Furthermore, the “anti-interference ability of 50Hz” feature was separately introduced for classification, and a better classification effect was obtained. Among them, the F1 score of stroke evaluation and classification based on the SVM model increased by 2.65%, which is helpful to realize the intelligent prediction of stroke disease in clinical practice Diagnostic function.