scholarly journals High-Resolution Multi-Channel Frequency Standard Comparator Using Digital Frequency Measurement

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5626
Author(s):  
Bo Xiao ◽  
Ya Liu ◽  
Xiaohui Li ◽  
Zhifeng Deng ◽  
Yanrong Xue
Keyword(s):  
Measurement Method ◽  
Measurement Accuracy ◽  
Frequency Standard ◽  
Frequency Measurement ◽  
Low Noise ◽  
Measurement Technology ◽  
Zero Crossing ◽  
Noise Floor ◽  
Digital Frequency ◽  
Atomic Frequency

The rapid improvement accuracy of the atomic frequency standard puts forward higher requirements for the measurement resolution of the atomic frequency standard comparison system. To overcome the defect that the single zero-crossing point detection is sensitive to noise in the traditional dual mixer time difference measurement method, a digital frequency measurement method is proposed. This method combines sinusoidal beat technology, multi-channel synchronous acquisition technology, and digital frequency measurement technology, and uses differential compensation of system error to realize the precision measurement of atomic frequency standard. The frequency measurement accuracy is less than 2.5 × 10−14 and the noise floor is better than 6.5 × 10−15/τ = 1 s. The system has a high frequency measurement accuracy and a low noise floor, which can realize the precise measurement of a highly stable frequency source.

scholarly journals A Real-Time Measurement Method of Air Refractive Index Based on Special Material Etalon

2018 ◽  
Vol 8 (11) ◽  
pp. 2325 ◽  
Author(s):  
Guo-Ying Ren ◽  
Xing-Hua Qu ◽  
Shuang Ding
Keyword(s):  
Refractive Index ◽  
Real Time ◽  
Direct Measurement ◽  
Measurement Method ◽  
Measurement Accuracy ◽  
Laser Interferometry ◽  
Measurement Technology ◽  
Measurement Principle ◽  
Environmental Responses ◽  
Realization Process

In the precise displacement measurement based on laser interferometry, the measurement technology for the refractive index of air is widely used to improve the measurement accuracy. However, the existing measurement method of the refractive index of air based on direct measurement is not easy to realize in practical work because of its complex measurement principle and the huge volume of the measurement device; while the measurement accuracy and speed based on the indirect method cannot adapt to the real-time, fast and accurate measurement requirements of industrially changing environments, resulting in distortion of the results. In this study, a measurement method of the refractive index of air based on a special material etalon is proposed. The method enables rapid and direct measurement of the air refractive index when the environment changes and it is given the realization process. Finally, the experimental results show that the deviation between this method and the modified Edlen formula is about 2.5 × 10−7, and that this method can quickly reflect the changes of the environment, which prove the correctness of this method and its ability manage rapid environmental responses. This method is worth popularizing in industrial measurement.

Research of Non-Contact Stiffness Measurement Technology

2014 ◽  
Vol 621 ◽  
pp. 331-336
Author(s):  
Wen Xuan Liu ◽  
Hui Feng Wang ◽  
Guang Lin Wang ◽  
Dong Xiang Shao
Keyword(s):  
Measurement System ◽  
Elastic Element ◽  
Measurement Method ◽  
Measurement Accuracy ◽  
Contact Stiffness ◽  
Test System ◽  
Measurement Technology ◽  
Servo Valve ◽  
Stiffness Measurement ◽  
Definition Of

This article describes the elastic element of the servo valve, elaborates the definition of the stiffness of elastic element, analyzes the characteristics of existing rigidity measurement system, points out the limitations of the existing rigidity measurement system when it measures the large-stiffiness elastic element, utilizes a new measuring principle based on the existing stiffness test systems, uses the more accurate laser displacement measurement method to overcome the weaknesses of the existing stiffness test system, improves the measurement accuracy, makes stiffness measurements more accurate and promotes the stiffness measurement technology of the servo valve elastic element.

scholarly journals Frequency synchronization detection method based on adaptive frequency standard tracking

Open Physics ◽  
2021 ◽  
Vol 19 (1) ◽  
pp. 434-438
Author(s):  
Xin Geng ◽  
Baoqiang Du ◽  
Jianwei Zhang ◽  
Erlin Tian
Keyword(s):  
Detection Method ◽  
Wide Band ◽  
Frequency Standard ◽  
Frequency Measurement ◽  
Measurement Range ◽  
Period Change ◽  
Measured Signal ◽  
Frequency Synchronization ◽  
Measured Frequency ◽  
Field Programmable

Abstract In order to achieve wide-band high-resolution frequency measurement, a frequency synchronization detection method based on adaptive frequency standard tracking is proposed based on the quantized phase processing. First, the nominal value of the measured frequency signal was obtained from the rough frequency measurement module. Then, the field programmable gate array generated the nominal value of the measured frequency. After that, the direct comparison between the tracking frequency and the measured signal was carried out. Finally, the group quantized processing module gave the final result according to the phase full-period change time. Experimental results showed that the method has a wide frequency measurement range and high accuracy and can obtain frequency stability of the order of 10−13/s.

scholarly journals Performance Analysis of Surface Reconstruction Algorithms in Vertical Scanning Interferometry Based on Coherence Envelope Detection

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 164
Author(s):  
Dongxu Wu ◽  
Fusheng Liang ◽  
Chengwei Kang ◽  
Fengzhou Fang
Keyword(s):  
Surface Reconstruction ◽  
Measurement Accuracy ◽  
Experimental Studies ◽  
Reconstruction Algorithm ◽  
Low Noise ◽  
Surface Measurement ◽  
Reconstruction Algorithms ◽  
Centroid Method ◽  
Envelope Detection ◽  
Vertical Scanning Interferometry

Optical interferometry plays an important role in the topographical surface measurement and characterization in precision/ultra-precision manufacturing. An appropriate surface reconstruction algorithm is essential in obtaining accurate topography information from the digitized interferograms. However, the performance of a surface reconstruction algorithm in interferometric measurements is influenced by environmental disturbances and system noise. This paper presents a comparative analysis of three algorithms commonly used for coherence envelope detection in vertical scanning interferometry, including the centroid method, fast Fourier transform (FFT), and Hilbert transform (HT). Numerical analysis and experimental studies were carried out to evaluate the performance of different envelope detection algorithms in terms of measurement accuracy, speed, and noise resistance. Step height standards were measured using a developed interferometer and the step profiles were reconstructed by different algorithms. The results show that the centroid method has a higher measurement speed than the FFT and HT methods, but it can only provide acceptable measurement accuracy at a low noise level. The FFT and HT methods outperform the centroid method in terms of noise immunity and measurement accuracy. Even if the FFT and HT methods provide similar measurement accuracy, the HT method has a superior measurement speed compared to the FFT method.

scholarly journals Non-Contact Respiration Measurement Method Based on RGB Camera Using 1D Convolutional Neural Networks

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3456
Author(s):  
Hyeon-Sang Hwang ◽  
Eui-Chul Lee
Keyword(s):  
Measurement Method ◽  
Respiratory Diseases ◽  
Region Of Interest ◽  
Average Error ◽  
Measurement Technology ◽  
Altman Analysis ◽  
Clinical Scenarios ◽  
Actual Environment ◽  
Error Bias ◽  
Robust To Noise

Conventional respiration measurement requires a separate device and/or can cause discomfort, so it is difficult to perform routinely, even for patients with respiratory diseases. The development of contactless respiration measurement technology would reduce discomfort and help detect and prevent fatal diseases. Therefore, we propose a respiration measurement method using a learning-based region-of-interest detector and a clustering-based respiration pixel estimation technique. The proposed method consists of a model for classifying whether a pixel conveys respiration information based on its variance and a method for classifying pixels with clear breathing components using the symmetry of the respiration signals. The proposed method was evaluated with the data of 14 men and women acquired in an actual environment, and it was confirmed that the average error was within approximately 0.1 bpm. In addition, a Bland–Altman analysis confirmed that the measurement result had no error bias, and regression analysis confirmed that the correlation of the results with the reference is high. The proposed method, designed to be inexpensive, fast, and robust to noise, is potentially suitable for practical use in clinical scenarios.

Detection and Analysis of Rats’ Bioelectromagnetic Signal

2014 ◽  
Vol 536-537 ◽  
pp. 13-17
Author(s):  
Hong Long Cao ◽  
Fen Ju Qin ◽  
Xue Guan Liu ◽  
He Ming Zhao
Keyword(s):  
Standard Deviation ◽  
Automatic System ◽  
Measurement Method ◽  
Measurement Accuracy ◽  
Biological Activities ◽  
Measurement Data ◽  
Measured Data ◽  
The Mean ◽  
Frequency Window ◽  
Window Effects

In this paper, we designed an automatic system and automatic test software, and they can carry out Kunming rats bioelectromagnetic measurement in standard status and anesthesia automatically in anechoic chamber where the electromagnetic field outside is shielded, the reflection wave is absorbed, and the measurement accuracy will be improved. We get a great number of measurement data with frequency-sweep measurement method. The mean and standard deviation of amplitudes vs. frequencies is calculated and analyzed. The results show the measurement method is feasible. We have plotted the means of measured data as multiple sets of Y values in a series of bars with standard deviations bars included and distributed in the frequency axis of X. It is found that the fluctuation of the mean and standard deviation in some frequencies is not evident which may explain frequency window effects, while in other frequencies, such a fluctuation can be obviously observed, which may suggest that bioelectromagnetic signal is influenced by biological activities (standard and anaesthesia status) in these frequency points.

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