Amplitude Measurement Accuracy Research Articles

Design, development and multi-scenario application of portable multifunctional test master based on μM-PMU: The case study of Lingang new City Grid, Shanghai

With the large-scale access of new energy generation and electric vehicle charging piles to the grids, power generation and loads are characterized by random fluctuations and intermittency, which affect the stable operation of the distribution network. μM-PMU is capable of realizing the dynamic process monitoring of the grids. In order to solve the function and performance testing problems of multiple application scenarios of μM-PMU, this thesis develops a portable master station based on synchronous phasor measurement system to realize zero drift, voltage amplitude measurement accuracy, voltage phase angle accuracy, current amplitude measurement accuracy, current phase angle measurement accuracy, frequency measurement accuracy, voltage amplitude change with frequency accuracy, and voltage phase angle change with frequency accuracy, Accuracy of current amplitude with frequency change, accuracy of current phase angle with frequency change, active power accuracy, reactive power accuracy, amplitude step response, phase angle step response, frequency step response, a total of 15 test items. It can automatically calculate test results and generate test reports according to different equipment models, reducing the mistakes and calculation errors that may be caused by manually recording test data and improving the accuracy of test results and calculation precision.

Development and Experimental Research of VFTO Measuring Sensor

Very fast transient overvoltage (VFTO) generated by an operating disconnector is one of the main reasons for electromagnetic disturbance in gas-insulated switchgear (GIS) substations. Generally, the amplitude of VFTO can be used as one of the references for the insulation design of GIS primary electric power equipment, so it is necessary to obtain its accurate amplitude. In this study, a new VFTO measuring sensor is developed and its measurement performance is demonstrated through hundreds of operations by a disconnector in a 220 kV GIS test circuit. The validation shows that the low cut-off frequency of the new VFTO measuring sensor has been greatly expanded to 0.01 mHz, which is improved by about 50% compared with the old sensor. The measurement accuracy of amplitude of VFTO micro-pulse improves greatly by about 80% compared with the old one. Thus, the new VFTO measuring sensor can fully meet the measurement needs of trapped charge voltage, power frequency voltage, and high-frequency transient voltage in VFTO waveform. It can be used to provide more accurate data support for insulation design of GIS primary power electric equipment in extra-high voltage (EHV) and ultra-high voltage (UHV) GIS substations.

A Software Digital Lock-In Amplifier Method with Automatic Frequency Estimation for Low SNR Multi-Frequency Signal

In the fault diagnosis field, the fault feature signal is weak and contaminated by the noise. The lock-in amplifier is a useful tool for weak signal detection. Aiming to the amplitude error of the lock-in amplifier caused by frequency deviation between the measured signal and the reference signal, a DFT-based automatic signal frequency estimation method is studied to improve the frequency accuracy of the reference signal. Based on this frequency estimation method, a software digital lock-in amplifier method is proposed to detect the multiple frequencies signals. This proposed method can automatically measure the frequency value of the measured signal without prior frequency information. Then, the reference signals are generated through this frequency value to make the digital lock-in amplifier estimate the amplitude of the measured signal. Moreover, an iterative structure is used to implement the multiple frequencies signal measurement. The frequencies and amplitudes measurement accuracies are tested. Under different SNR conditions, the frequency relative error is less than 0.1%. In addition, the amplitude relative error with different signal frequencies is less than 1.7% when the SNR is −1 dB. This proposed software digital lock-in amplifier method has a higher signal frequency tracking ability and amplitude measurement accuracy.

Comparative Study of AC Signal Analysis Methods for Impedance Spectroscopy Implementation in Embedded Systems

For embedded impedance spectroscopy, a suitable method for analyzing AC signals needs to be carefully chosen to overcome limited processing capability and memory availability. This paper compares various methods, including the fast Fourier transform (FFT), the FFT with barycenter correction, the FFT with windowing, the Goertzel filter, the discrete-time Fourier transform (DTFT), and sine fitting using linear or nonlinear least squares, and cross-correlation, for analyzing AC signals in terms of speed, memory requirements, amplitude measurement accuracy, and phase measurement accuracy. These methods are implemented in reference systems with and without hardware acceleration for validation. The investigation results show that the Goertzel algorithm has the best overall performance when hardware acceleration is excluded or in the case of memory constraints. In implementations with hardware acceleration, the FFT with barycentre correction stands out. The linear sine fitting method provides the most accurate amplitude and phase determinations at the expense of speed and memory requirements.

Study on the Application of Optical Current Sensor for Lightning Current Measurement of Transmission Line.

Accurate and reliable lightning current data are the basis of lightning protection design. To measure lightning current data at different measurement locations in a transmission system, the limitations of traditional lightning current sensors are analyzed, and optical current sensing technology is adopted, which has the advantages of no magnetic saturation and no bandwidth limitation. Compared with traditional application environments, the sensing technology is used in special environments in transmission systems. This paper analyzes the influence of environmental factors on sensors, and combines the extreme environmental requirements, such as temperature and insulation requirements, to study the sensor. Starting from the sensitivity, the sensing characteristics of the sensor are analyzed. The sensor is designed according to three aspects: sensing material selection, spatial measuring position, and sensing material size optimization, such that it can satisfy the different measurement requirements of towers, overhead ground wires, and transmission lines, respectively. The experiments indicate that the developed sensors can meet the measurement sensitivity requirements of different types of lightning strikes. The experimental results of sensors exhibit a reasonable amplitude measurement accuracy, linearity, and waveform measurement capability. These results provide important theoretical and experimental bases for the application of optical current sensing technology to the measurement of the lightning current of transmission systems.

INCREASING THE ACCURACY OF MEASURING AMPLITUDE IN CONTACTLESS CONTROL DEVICES OF THICKNESS POLYMER FILMS

The massive use of polymer films of different types and thickness determines the relevance of measuring their parameters, primarily the thickness, especially in the production process.Methods for measuring the polymer films thickness were analyzed. The most promising ones are acoustic and optical methods, in which one of the main parameters of the output signal of the primary transmitter is an amplitude value. During measuring the thickness of thin and ultrathin polymer films the variation range of signal amplitude decreases, which reduces amplitude measurement accuracy by increasing the impact of noise.The purpose of this work is to analyze and develop methods to improve the accuracy of measuring signals amplitude for control devices of polymer films thickness.The methods to improve the accuracy of measuring amplitude were considered. According to the results of the analysis it is proposed to use the structural method based on the amplitude and averaging coefficients. Their values are known for standard form signal, and can be defined for constant signal shape, typical in measuring the polymer films thickness. In this case, the value of the amplitude is determined by measuring average rectified (ARV) and/or root mean square (RMS) values and related coefficients. It significantly reduces the impact of noise.Structural diagram for the proposed method was developed and model researches on its basis were made. They indicate that when signal/noise ratio is in the range of 100 to 5, amplitude measurement accuracy increases more than 30 times. When signal/noise ratio is less than 5, accuracy decreases, but still 5 times higher than in traditional methods of measuring amplitude.Methods comparison for determining the amplitude by RMS and ARV values shows that when the signal/noise ratio is more than 10 the difference is insignificant. When signal/noise ratio is less than 5, better results can be obtained with ARV values and averaging coefficient. Particularly when the signal/noise ratio is 1, the error is less by almost 7 times.Thus, researches have confirmed the high efficiency of the proposed method under the impact of noise and interference, compared with traditional methods.

A new digital pulse processing method for 2πα and 2πβ emitter measurement

Digital pulse processing has developed rapidly during recent years. Moreover, it has been widely applied in many fields. In this study, we introduce a digital pulse processing method for 2πα and 2πβ emitter measurement. Our digital pulse processing method for 2πα and 2πβ emitter measurement is comprised of a field-programmable gate-array-based acquisition card and a pulse-height analysis routine. We established two channels (one for the α emitter and one for the β emitter) on an acquisition board using an analog-to-digital converter with a 16-bit resolution at a speed of 100 million samples per second. In this study, we used captured and stored data to analyze emission rate counts and spectrums. The method we established takes into account noise cancelation, dead-time correction, background subtraction, and zero-energy extrapolation. We carefully designed control procedures in order to simplify pulse-width fitting and threshold-level setting. We transmitted data and commands through a universal serial bus between the acquisition board and the computer. The results of our tests prove that our method performs well in pulse reconstruction fidelity and amplitude measurement accuracy. Compared with the current standard method for measuring 2πα and 2πβ emission rates, our system demonstrates excellent precision in emission rate counting.

A hydrophysical laser-interference complex

An upgraded laser measurer of hydrosphere pressure variations is described. By mounting new pressure and temperature sensors and optimizing the design of the submersible instrument, it has become possible to considerably increase the measurement accuracy of amplitude−frequency characteristic describing variations in the pressure, aqueous medium temperature, and wave amplitudes at the sea surface in the infrasonic and audio ranges and to correct plotted time dependences of the pressure variations in view of the variations in the interferometer and outboard water temperatures. For long-term (up to 40 h) self-contained operation of the complex to be guaranteed, a versatile floating container has been developed. This container is equipped with high-power batteries and data acquisition systems receiving information from the sensors and can be joined to a hermetically sealed connector of the complex instead of the cable line used for communication between the complex and coast equipment.

The Selection of Online Power Flow Calculation’s Known Quantities

The difference between schedule power flow and online power flow is that the former has no corresponding physical power flow, while the latter is the reappearance of existing physical power flow. Owing to the different premise, the selection of power flow calculation’s known quantities can be different. A schedule power flow schedules physical power flow for power system, so the selection of known quantities has strict requirements, such as active power and reactive power regulation capability. Since the physical power flow exists, the selection of online power flow calculation’s known quantities can be more flexible. For example, we can choose load bus as slack bus or replace PQ bus with PV bus. The example demonstrated that we could locate the stealing electricity buses by choosing load bus as slack bus. Considering that voltage amplitude measurement accuracy is higher than reactive power measurement accuracy, we can replace PQ bus with PV bus and make the power flow calculation results more consistent with the physical power flow. Finally, the examples show that online power flow calculation’s known quantities can be selected flexibly according to the actual situation rather than strictly following the classical power flow calculation requirements.

Measurement of Fetal Heart Rate Variability on an Electronic Monitor Using a Prototype Electronic Ruler

To develop a prototype electronic ruler for assessment of fetal heart rate (FHR) variability on an electronic monitor and test its reliability and accuracy. A prototype electronic ruler was designed and developed for assessment of FHR variability on electronic monitors. The electronic ruler consisted of horizontal bands that were sized and colored to embed the four FHR variability categories. The reliability and accuracy of using the electronic ruler to assess FHR variability was studied with expert clinicians. Intrarater and interrater reliability was moderate for both the electronic ruler and paper strips. The amplitude measurement accuracy of expert variability assessment compared with a gold standard was significantly improved (p < 0.001) with the electronic ruler versus paper strips. The accuracy of subjects' FHR variability category responses compared with the gold standard revealed no significant difference (p = 0.50) using either display type. Performance of the electronic ruler was equivalent to paper strips, which may aid assessment of variability on electronic monitors as paper strips become less prevalent.

Signal processing module for the liquid xenon calorimeter of CMD-3 detector

The coordinate system of a liquid xenon (LXe) calorimeter includes 2112 cathode strips. The charges collected by the strips are to be measured. A special Signal Processing Module has been developed which performs all actions necessary for charge measurement—amplification and shaping of analog signal, digitization, and resulting data transfer to the data acquisition system. In this paper the selected amplitude measurement technique, the estimation of achievable accuracy of amplitude measurement, and the results of module testing are described.

Tides and nutation of the earth: I. Models of an earth with an inelastic mantle and homogeneous, inviscid, liquid core

The use of very-long-baseline radio interferometers during the past 10–15 years has increased the accuracy of amplitude measurements of the Earth’s forced nutation by more than two orders of magnitude (from 3–5 arc ms to 20 arc μs). At the same time, cryogenic gravimeters (which depend for their action on the repulsion of two superconductive rings in a gravitational field) have made it possible to also improve the accuracy of measurements of tidal variations in the gravitational force by two orders of magnitude. This opens up new avenues for the investigation of the mechanical properties of the Earth’s interior at ultralow frequencies. A brief review is given here of the basic results of interpreting astrometric data and measurements of tidal variations in the gravitational force. Problems suggested by the new observational techniques are formulated.

Ultrasonic Detection of Damage in CFRPs

A good knowledge on damage processes in CFRPs can be given by developing non-destructive testing. In order to improve ultrasonic capabilities to detect matrix cracking development, a water tank has been mounted directly on a servo-controlled machine and an automatic scanning by points has been investigated. More accurate testing procedures have been implemented including mechanical improvements, amplitude measurement accuracy, resetting points under loading, comparative evaluation of the attenuation between undamaged and damaged state. A comparison between X-ray and ultrasonic results has been made. Another aim was to control hidden damage due to impact and especially to measure the size and shape of delaminations at each interply location using an improved pulse echo method. Hence, conventional equipment has been modified in order to explore the material by thickness segments. A new procedure has been added to a classical equipment providing in a single scan multiple C-scan images of a coupon with a very limited amount of data. The main purpose of this paper is to describe the methods used and to discuss the original procedures that have been performed. The new capabilities of an improved ultrasonic set-up are going to be examined mainly in relation to crack-density measurement, matrix cracking development under tension and ply by ply delamination sizing and location. With these features, an ultrasonic set-up can find its application in many aeronautical fields: improving composites, moisture influence on damage, detecting of damage resulting from impact, structures lifetime.

Maximum amplitude measurement accuracy with time-variant filtering

The maximum accuracy of amplitude measurements by means of time-variant filters is shown to be the same as for the time-invariant ones.

Improving the accuracy of amplitude measurements by sampling oscilloscopes

Improving the accuracy of amplitude measurements by sampling oscilloscopes