Waveform Acquisition Research Articles

Advances on the acoustic emission testing for monitoring of granular soils

The application of the acoustic emission (AE) method for granular media has been considered to be challenging and remains limited. Nevertheless, recent successful explorations from different aspects have greatly encouraged people's attempts in this filed. Typical applications concerning geotechnical element testing, the soil-structure systems, as well as the AE source location suggest that the recent studies aim to obtain direct insights into the mechanical behaviors of the granular soils based on AE features, and emphasize on the quantitative relations between them. Future development of the AE method demands further advances in the following aspects: higher performance of AE instrumentation technology enabling high signal-to-noise ratio; full waveform and broadband signal data acquisition; new insights into the source mechanisms of AE by incorporating more comprehensive and in-depth signal analysis and emerging new technologies; higher levels of correlation study between AE signals and the associated physical processes.

The Auxiliary Diagnostic Value of a Novel Wearable Electrocardiogram-Recording System for Arrhythmia Detection: Diagnostic Trial.

Background: AMAZFIT®, a novel wearable electrocardiogram (ECG)-recording system is used for the measurement, acquisition, and storage of single-lead cardiac waveforms for adults. The aim of the study was to evaluate the accuracy of AMAZFIT® for diagnosing arrhythmia in older patients.Methods: From May to December 2019, we recruited 291 elderly individuals with an average age of 78±10 years old, and 41.9% women. All cardiac waveforms were obtained from the AMAZFIT® which included limb and chest leads. Two trained technicians reviewed all ECG data to determine cardiac rhythm using standard diagnostic criteria. We evaluated the accuracy of AMAZFIT® for identifying arrhythmia by comparing the sensitivity, specificity, accuracy, positive predictive value (PPV), negative predictive value (NPV), and positive and negative likelihood ratios with those of a standard 12-lead ECG.Results: Of the 291 participants, 197 older adults had arrhythmias, including AF (n = 119), first-degree AVB (n = 28), PACs (n = 25), and PVCs (n = 28). Three of these participants had arrhythmias of AF and PVCs. Chest lead data from 100% and limb lead data from 4.7% of the participants were analyzed. An evaluation of AMAZFIT® for atrial fibrillation (AF) reported a sensitivity, specificity, PPV, NPV PLR, and negative likelihood ratio (NLR) of 93.28, 95.35, 93.28, 95.35, 20.06, and 0.07%, respectively. AMAZFIT® also demonstrated excellent sensitivity for premature atrial contractions (PACs) (84.00%) and premature ventricular contractions (PVCs) (89.29%). However, the device demonstrated a low sensitivity for first-degree atrioventricular block (32.14%).Conclusions: The AMAZFIT® showed significantly higher sensitivity and specificity for AF, PACs, and PVCs. This portable ECG-recording device based on an algorithm has a potential auxiliary diagnostic value for identifying arrhythmia compared with a standard 12-lead ECG device.

Spark Analysis Based on the CNN-GRU Model for WEDM Process.

Wire electrical discharge machining (WEDM), widely used to fabricate micro and precision parts in manufacturing industry, is a nontraditional machining method using discharge energy which is transformed into thermal energy to efficiently remove materials. A great amount of research has been conducted based on pulse characteristics. However, the spark image-based approach has little research reported. This paper proposes a discharge spark image-based approach. A model is introduced to predict the discharge status using spark image features through a synchronous high-speed image and waveform acquisition system. First, the relationship between the spark image features (e.g., area, energy, energy density, distribution, etc.) and discharge status is explored by a set of experiments). Traditional methods have claimed that pulse waveform of “short” status is related to the status of non-machining while through our research, it is concluded that this is not always true by conducting experiments based on the spark images. Second, a deep learning model based on Convolution neural network (CNN) and Gated recurrent unit (GRU) is proposed to predict the discharge status. A time series of spark image features extracted by CNN form a 3D feature space is used to predict the discharge status through GRU. Moreover, a quantitative labeling method of machining state is proposed to improve the stability of the model. Due the effective features and the quantitative labeling method, the proposed approach achieves better predict result comparing with the single GRU model.

Validation of the BPro radial pulse waveform acquisition device in pregnancy and gestational hypertensive disorders

To validate the BPro blood pressure (BP) wrist device for use in pregnancy and preeclampsia according to the Universal Standard protocol. BP was measured sequentially in 45 pregnant women (including 15 with preeclampsia, 15 with gestational hypertension and 15 who remained normotensive) alternating between a mercury sphygmomanometer and BPro device. The BPro is accurate in pregnancy with a mean device-observer difference of -1.7 ± 6.1 and 0.1 ± 4.6 mmHg for SBP and DBP, respectively. In women with preeclampsia, BPro also met the validation criteria for the Universal Standard protocol with a mean device-observer difference of -2.7 ± 7.1 and 0.3 ± 4.7 mmHg for SBP and DBP, respectively. However, the number of absolute BP differences within 5 mmHg was considerably fewer in those with preeclampsia when compared to the other two subgroups. The BPro device can be recommended for BP measurement in pregnancy but should be used with caution in those with confirmed preeclampsia.

A Review of Streamline Calibration Approaches for Digital Storage Oscilloscopes with Time-Interleaved Channels

The digital storage oscilloscope (DSO) has a vital role in measurement practice, since its resourcefulness fits both general purpose aims and requirements of more specific applications. A deep knowledge of DSO operation principles and available features is fundamental for technicians to best exploit the possibilities of the instrument. Operation principles regard digitization, acquisition, processing and visualization of the input waveform and concern a number of issues. For performant DSO digitizing systems, one of the most relevant issues is the calibration of the time-interleaved structure at the very heart of the instrument. Unfortunately, the calibration techniques adopted by the manufacturers are never disclosed in plain form with application notes or demos, and limited information can be read from patents, if available. In this article, the state-of-the-art of DSO technologies is reviewed; a general framework to face the calibration issue in time-interleaved systems, which is based on the generalized sampling theorem, is presented; and the case of some DSOs, which require special calibration approaches, implemented through the analysis of the input-output crosscorrelation of the individual acquisition channels, is discussed. Concluding remarks underline the value of the contribution, that provides a significant example of how more ideal acquisition channels can be realized by the combination of analog circuitry with digital processors.

Underwater Signal Measurement and Transmission Experiment Equipment Design for LIDAR

When carrying out related test experiments of shipborne LIDAR, it is necessary to launch lasers to areas with different water depths and confirm the working conditions of LIDAR according to the received waveform conditions, to debug the LIDAR. There is no special introduction to the indoor platform for this kind of testing. This article proposes an indoor LIDAR experiment platform, which will focus on the basic settings of the laser, sink, and reflector in the experiment, the design ideas and rationality of the sink and reflector modules, the experimental steps, and how to effectively obtain the waveform. This platform has good applications in parameter correction, waveform acquisition, water depth measurement, and other aspects of LIDAR design.

Comparison of the Use of Arterial Doppler Waveform Classifications in Clinical Routine to Describe Lower Limb Flow.

Background: Characterisation of arterial Doppler waveforms is a persistent problem and a source of confusion in clinical practice. Classifications have been proposed to address the problem but their efficacy in clinical practice is unknown. The aim of the present study was to compare the efficacy of the categorisation rate of Descotes and Cathignol, Spronk et al. and the simplified Saint-Bonnet classifications. Methods: This is a multicentre prospective study where 130 patients attending a vascular arterial ultrasound were enrolled and Doppler waveform acquisition was performed at the common femoral, the popliteal, and the distal arteries at both sides. Experienced vascular specialists categorized these waveforms according to the three classifications. Results: of 1033 Doppler waveforms, 793 (76.8%), 943 (91.3%) and 1014 (98.2%) waveforms could be categorized using Descotes and Cathignol, Spronk et al. and the simplified Saint-Bonnet classifications, respectively. Differences in categorisation between classifications were significant (Chi squared test, p < 0.0001). Of 19 waveforms uncategorized using the simplified Saint-Bonnet classification, 58% and 84% were not categorized using the Spronk et al. and Descotes and Cathignol classifications, respectively. Conclusions: The results of the present study suggest that the simplified Saint-Bonnet classification provides a superior categorisation rate when compared with Spronk et al. and Descotes and Cathignol classifications.

Wideband Active Load–Pull by Device Output Match Compensation Using a Vector Network Analyzer

This work investigates wideband active load-pull (WALP) on microwave electron devices with a standard vector network analyzer (VNA), solely using calibrated frequency-domain relative measurements. Differently from the methods requiring full time-domain waveform acquisition capabilities, this approach removes any instantaneous bandwidth (BW) requirement, allowing to target modulated signals with arbitrarily large BWs. A VNA-based measurement setup is presented, and a novel mathematical framework is developed in order to enable the synthesis of an arbitrary wideband load profile using suitable numerical algorithms. A linear precompensation of the LS output match of the device, here implemented by different methods, is shown to significantly improve the speed and the stability of the basic secants' iterative method used to reach the target. Performance results, investigating the convergence properties of the approach and the effects of the setup dynamic range, are reported for a gallium nitride (GaN) high-electron-mobility transistor (HEMT) for up to 120-MHz output BW in the sub-6-GHz range.

Interpretation of peripheral arterial and venous Doppler waveforms: A consensus statement from the Society for Vascular Medicine and Society for Vascular Ultrasound.

This expert consensus statement on the interpretation of peripheral arterial and venous spectral Doppler waveforms was jointly commissioned by the Society for Vascular Medicine (SVM) and the Society for Vascular Ultrasound (SVU). The consensus statement proposes a standardized nomenclature for arterial and venous spectral Doppler waveforms using a framework of key major descriptors and additional modifier terms. These key major descriptors and additional modifier terms are presented alongside representative Doppler waveforms, and nomenclature tables provide context by listing previous alternate terms to be replaced by the new major descriptors and modifiers. Finally, the document reviews Doppler waveform alterations with physiologic changes and disease states, provides optimization techniques for waveform acquisition and display, and provides practical guidance for incorporating the proposed nomenclature into the final interpretation report.

Interpretation of Peripheral Arterial and Venous Doppler Waveforms: A Consensus Statement From the Society for Vascular Medicine and Society for Vascular Ultrasound

This expert consensus statement on the interpretation of peripheral arterial and venous spectral Doppler waveforms was jointly commissioned by the Society for Vascular Medicine (SVM) and the Society for Vascular Ultrasound (SVU). The consensus statement proposes a standardized nomenclature for arterial and venous spectral Doppler waveforms using a framework of key major descriptors and additional modifier terms. These key major descriptors and additional modifier terms are presented alongside representative Doppler waveforms, and nomenclature tables provide context by listing previous alternate terms to be replaced by the new major descriptors and modifiers. Finally, the document reviews Doppler waveform alterations with physiologic changes and disease states, provides optimization techniques for waveform acquisition and display, and provides practical guidance for incorporating the proposed nomenclature into the final interpretation report.

A Novel Approach to Acquire the Arterial Pulse by Finger Plethysmography Using Fiber Bragg Grating Sensor

Finger plethysmography is a well-known technique for the acquisition of arterial pulse waveforms in the field of cardiology. The technique involves the acquisition of the volumetric variation of the finger due to pulsatile flow of blood in ulnar artery, to obtain the arterial pulse waveform of the subject. Conventionally, finger plethysmography is carried out by pulse-oximetry method which evaluates the blood flow using the oxygen saturation levels in blood. Though this method is widely used, the data acquired from this method is not the actual pulse pressure experienced by the arterial walls. Therefore, in the present work, a novel, non-invasive Fiber Bragg Grating based arterial pulse acquisition device employing finger Plethysmographic technique is designed and developed. The developed Fiber Bragg Grating Plethysmographic Pulse Recorder (FBGPPR) can acquire the volumetric variations of the finger on a beat-to-beat basis, which represents the arterial pulse waveform. Further, Pulse Transit Time (PTT) evaluation is also illustrated employing FBGPPR and an electronic stethoscope wherein both the devices are triggered simultaneously. Furthermore, the acquired pulse waveforms are analyzed to obtain the accelerated pulse plethysmograph (APG) which is noteworthy to observe the minute inflections and vital features of the pulse waveform.

Design and Implementation of a SoC Embedded Waveform Acquisition System for Surveillance and Diagnostics of Pulsed Magnet Power Supplies

Pulsed magnet power supply systems used for electron beam injection and extraction have been developed for the Taiwan Photon Source (TPS) and the Taiwan Light Source (TLS). Control systems for these supplies have been implemented with well-functioning operations interfaces. To accomplish higher reliable operation, advanced real-time diagnostic toolkits for pulsed magnet power supplies had to be developed. A SoC (System-on-Chip) embedded waveform acquisition system has been designed, implemented and applied to inspect pulsed magnet power supplies during routine operation. This waveform acquisition system not only operates at the 125 MS/s sample rate, 50 MHz bandwidth and 14 bits resolution, but supports also the EPICS software framework for complete system integration. The acquired current waveforms can be immediately extracted specific characteristics to examine the status of pulsed magnet power supplies. In this paper, we summarize the design, implementation and real-time data analysis of the SoC embedded waveform acquisition system for the pulsed magnet power supplies.

Classification of VLF/LF Lightning Signals Using Sensors and Deep Learning Methods.

Lightning waveform plays an important role in lightning observation, location, and lightning disaster investigation. Based on a large amount of lightning waveform data provided by existing real-time very low frequency/low frequency (VLF/LF) lightning waveform acquisition equipment, an automatic and accurate lightning waveform classification method becomes extremely important. With the widespread application of deep learning in image and speech recognition, it becomes possible to use deep learning to classify lightning waveforms. In this study, 50,000 lightning waveform samples were collected. The data was divided into the following categories: positive cloud ground flash, negative cloud ground flash, cloud ground flash with ionosphere reflection signal, positive narrow bipolar event, negative narrow bipolar event, positive pre-breakdown process, negative pre-breakdown process, continuous multi-pulse cloud flash, bipolar pulse, skywave. A multi-layer one-dimensional convolutional neural network (1D-CNN) was designed to automatically extract VLF/LF lightning waveform features and distinguish lightning waveforms. The model achieved an overall accuracy of 99.11% in the lightning dataset and overall accuracy of 97.55% in a thunderstorm process. Considering its excellent performance, this model could be used in lightning sensors to assist in lightning monitoring and positioning.

Laser-induced surface acoustic waves for measurement of elastic constants based on mode conversion

The measurement of elastic constants is very important to the study of materials. Laser ultrasonic technology has been widely concerned for its unique advantages and used to measure elastic constants, but the current measurement methods have their limitations. In general, traditional measurement methods require the use of a fatigue tester or measurement of all modal waves during the experiment. It is found that cracks can transform the mode of ultrasonic wave, in other words, the surface acoustic waves can be transformed into shear waves by mode conversion. So, we proposed a new method of measuring elastic constants of materials by laser ultrasound based on mode conversion. Surface acoustic waves are induced by laser ultrasound system, the reflection and mode conversion of surface acoustic waves can be realized by cracks. Therefore, direct waves, reflected waves and mode converted waves are included in the collected surface wave signals, then the wave velocity of surface waves and shear waves are calculated by the surface acoustic waves, and the elastic constants of materials are obtained by the acoustic elasticity equation. Since the experiment and processing are all based on surface acoustic waves, multiple waveform acquisition and processing are avoided. After calculation, the error is kept below 3% compared with the standard measurement value. In order to further confirm the application range of the method, cracks of different depths are used in the experiment, it is further proved that this method has nothing to do with the crack size. The research results of this paper can extend the application range of laser ultrasound. It also provides a new approach to the characterization of materials.

Focus on analytical equipment, sensors, and instrumentation

Focus on analytical equipment, sensors, and instrumentation

Design and implementation of a measurement system for high-speed testing of electromechanical relays

An automatic measurement system has been developed for high-speed testing of the most important magnetic and contact properties for elementary monostable and bistable miniature electromechanical relays. The system design is based on the virtual instrumentation approach, which is a combination of software and hardware. The comprehensive test application was developed using the LabVIEW graphical programming environment, while the used hardware is based on commercial measurement equipment and a custom developed device. The presented measurement methods are based on simultaneous generation and acquisition of analog and digital waveforms with the high-speed data acquisition device. The implemented automatic relay measurement system was validated metrologically and tested successfully with all supported relay types. The results show that the developed system is capable of performing accurate measurements of the coil resistance, contact resistance, time parameters, and operate/release values in less than two seconds.

An Atomic Receiver for AM and FM Radio Communication

Radio reception relies on antennas for the collection of electromagnetic fields carrying information, and receiver elements for demodulation and retrieval of the transmitted information. Here, we demonstrate an atom-based receiver for AM and FM microwave communication with a 3 dB bandwidth in the baseband of ~100 kHz that provides optical circuit-free field pickup, multiband carrier capability, and inherently high field sensitivity. The atom-based receiver exploits field-sensitive cesium Rydberg vapors in a centimeter-sized glass cell, and electromagnetically induced transparency, a quantum-optical effect, as a readout of baseband signals modulated onto carriers with frequencies ranging over four octaves, from C-band to Q-band. Receiver bandwidth, dynamic range and sideband suppression are characterized, and acquisition of audio waveforms of human vocals demonstrated. The atomic receiver is a valuable receiver technology because it does not require antenna structures and is resilient against electromagnetic interference, while affording multiband operation in a single compact receiving element.

Clinical evaluation of an optical fiber-based probe for the assessment of central arterial pulse waves.

The aim of this study, enrolling 118 patients, was to clinically evaluate the accuracy of carotid pulse waveform acquisition with a new non-invasive optical fiber probe using invasive and non-invasive pressure readings as references. Pulse waves were acquired simultaneously in the ascending aorta and right common carotid; for the non-invasive study, the pulses were sequentially acquired using the optical fiber device and the Complior Analyse® (Alam Medical, France) device in the right carotid artery. For all subjects, the pulse waveforms assessed using the optical fiber sensor and the references were superimposed to analyze the deviation and point-by-point correlation. Augmentation index and central pressure were compared using intraclass correlation and Bland-Altman analyses with a confidence interval of 95%. For the invasive study, the acquired waves presented a mean deviation of 11 ± 3% and a mean intraclass correlation of 0.97 ± 0.02. Concerning the augmentation index and central systolic pressure, correlations of 0.79 (p < 0.001) and 0.94 (p < 0.001) were found, respectively. In the non-invasive comparison, the assessed mean deviation between the morphologies of the waves was 13 ± 5%, with correlation coefficients of 0.91 (p < 0.001) for the augmentation index and 0.98 (p < 0.001) for central systolic pressure. The results show that the optical fiber probe results were highly correlated with those obtained using the reference techniques in terms of the pulse waveforms, central systolic pressure (cSP), and augmentation index assessment.

A Fault Diagnosis Method for On Load Tap Changer of Aerospace Power Grid Based on the Current Detection

As one of the key components of aerospace power grid, the performance of on load tap changer (OLTC) of power transformer is very important. So it is necessary to realize real-time monitoring of its status. At present, there is no feasible monitoring scheme to carry out on-line monitoring and fault diagnosis for detecting faults of OLTC. The current waveform of the switching process will be abnormal due to the contact fault, the transition resistance fault, and most of the mechanical faults. This paper presents a fault diagnosis method for OLTC based on the current detection in the process of switching. Through on-line acquisition of current waveform in the switching process, empirical mode decomposition and Hilbert–Huang transform is used to calculate normalized time-frequency spectrum, and extract fault characteristic quantity, which can realize the comprehensive diagnosis of the running state of the equipment, and identify the early fault characteristics, and promote the process of the OLTC’s maintenance, from regular test to condition based maintenance. Experiment results prove that the designed fault diagnosis instrument can effectively monitor the working condition of OLTC during the switching process and make effective fault diagnosis.

A Waveform Archiving System for the GE Solar 8000i Bedside Monitor.

Our objective was to develop, deploy, and test a data-acquisition system for the reliable and robust archiving of high-resolution physiological waveform data from a variety of bedside monitoring devices, including the GE Solar 8000i patient monitor, and for the logging of ancillary clinical and demographic information. The data-acquisition system consists of a computer-based archiving unit and a GE Tram Rac 4A that connects to the GE Solar 8000i monitor. Standard physiological front-end sensors connect directly to the Tram Rac, which serves as a port replicator for the GE monitor and provides access to these waveform signals through an analog data interface. Together with the GE monitoring data streams, we simultaneously collect the cerebral blood flow velocity envelope from a transcranial Doppler ultrasound system and a non-invasive arterial blood pressure waveform along a common time axis. All waveform signals are digitized and archived through a LabView-controlled interface that also allows for the logging of relevant meta-data such as clinical and patient demographic information. The acquisition system was certified for hospital use by the clinical engineering team at Boston Medical Center, Boston, MA, USA. Over a 12-month period, we collected 57 datasets from 11 neuro-ICU patients. The system provided reliable and failure-free waveform archiving. We measured an average temporal drift between waveforms from different monitoring devices of 1 ms every 66 min of recorded data. The waveform acquisition system allows for robust real-time data acquisition, processing, and archiving of waveforms. The temporal drift between waveforms archived from different devices is entirely negligible, even for long-term recording.