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Digital Interfaces in Measurement Systems
Published in Robert B. Northrop, Introduction to Instrumentation and Measurements, 2018
Now, let us consider the operation of first-order ∆-∑ ADC. If the number of ones in the output data stream (i.e., the DFF’s Q output) is counted over a sufficient number of samples (clock cycles), the counter’s digital output will represent the digital value of the analog input, VX. Obviously, this method of averaging will only work for DC or low-frequency VX. In addition, at least 2N clock cycles must be counted in order to obtain N-bit effective resolution. In the ∆-∑ ADC, the modulator’s DFF Q output is the input to the block labeled digital filter and decimator. The digital LPF precedes the decimator. The digital LPF serves two functions: (1) It acts as an AAF for the final sampling rate, fo, and (2) it filters out the higher-frequency noise produced by the ∆-∑ modulator.
The Effect of Rapid Oscillations in the Dynamics of Delay Equations
Published in Ovide Arino, David E. Axelrod, Marek Kimmel, Mathematical population dynamics, 2020
Jack K. Hale, Sjoerd M. Verduyn Lunel
The classical method of averaging for ODEs is the appropriate tool for understanding the effects of high-frequency perturbations (see Hale, 1969). In a forthcoming paper we have extended the method of averaging to RFDEs and some other classes of infinite-dimensional systems. Here we would like to discuss a special application of these results.
Development of an intervention program to reduce whole-body vibration exposure based on occupational and individual determinants among dumper operators
Published in International Journal of Occupational Safety and Ergonomics, 2023
Rahul Upadhyay, Amrites Senapati, Kenora Chau, Ashis Bhattacherjee, Aditya Kumar Patra, Nearkasen Chau
The vibration evaluation procedure incorporates a method of averaging vibration level over time and frequency band using a one-third octave band. The human response to WBV is not uniform along all axes. Therefore, weighting filters are used to evaluate it. These weightings are based on potentially harmful effects connected to each frequency. For a seated person, two principal weightings are used for the measurement of WBV. These are Wd for the x and y axes, and Wk for the z axis [45,47,54]. For this study, root mean square acceleration (rmsa) along the dominant axis (z axis) was used as the WBV measurement. Daily exposure, A(8), was also calculated to quantify exposure during an 8-h shift [45,47]. In the present study, the daily exposure, A(8), is estimated from the rmsa in the dominant axis (awz).
Improving vibration test methods and profile selection for complex land vehicle payloads
Published in Australian Journal of Multi-Disciplinary Engineering, 2019
During test measurement accelerometer data is collected during vehicle trials. The processing of this data is critical for representative testing as fatigue relevant data can be lost or gained depending on the averaging processes used. Pure time domain data will discriminate between Gaussian, and non-Gaussian as well as stationary and non-stationary. A PSD is a common method of averaging time history data, and presenting it in the frequency domain. Any time waveform can be reduced to a single PSD, however there are limitations in using a PSD as an indicator of vibration severity, especially if the waveform is non-stationary, due to the averaging process. The usefulness of a PSD is significantly limited if it isn’t presented alongside the rms value, frequency step, standard deviation, skewness and kurtosis of the measured signal it is produced from (Lalanne, Random Vibration – Mechanical Vibration and Shock Analysis and Updated 3rd Edition 2014). Even with these parameters, it is not used to model non-stationary behaviour as shown in (Avendano-Valencia and Fassois 2014).
Novel frequency-based approach for detection of steady-state visual evoked potentials for realization of practical brain computer interfaces
Published in Brain-Computer Interfaces, 2022
Mehrnoosh Neghabi, Hamid Reza Marateb, Amin Mahnam
In this study, several frequency domain approaches were evaluated for SSVEP recognition, and a novel frequency analysis method, Spectral Averaging on Resampled Signals (SAoRS), was proposed to improve the performance of SSVEP-based BCI systems in practical use with a minimum number of electrodes.