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Vibrational Spectroscopy
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Peter Fredericks, Llewellyn Rintoul, John Coates
The layout of a traditional FTIR instrument is shown in Figure 7.10. Relating to this figure, the modulator (interferometer), which is composed of the IR beamsplitter, the fixed mirror, and the moving mirror, has been covered. A further important item, which is integral in the operation of the modulator, is the helium-neon (HeNe) reference laser. Most commercial FTIR instruments incorporate a HeNe, which serves a critical function in the data acquisition, providing a very accurate trigger or clocking signal for the digitization of the interferogram. The critical issue in the acquisition is the accurate location of all acquired data points, in terms of time or distance from ZPD. A high level of signal repeatability is necessary to gain full advantage of noise reduction by signal averaging. In a perfect spectrometer the random noise in the spectrum is reduced by the square root of the number of co-added scans. The perfect situation only occurs for highly reproducible spectral data, where there is exact registration between interferograms—for most signal averaging, it is normal to co-add interferograms, but co-addition of transformed transmission spectra can yield a comparable result.
Signal processing
Published in D.A. Bradley, N.C. Burd, D. Dawson, A.J. Loader, Mechatronics, 2018
D.A. Bradley, N.C. Burd, D. Dawson, A.J. Loader
Where a repetitive signal Is subject to random noise, signal averaging can be used to recover the signal from the noise. Consider such a signal to which has been added a Gaussian noise signal with a mean value of zero and a standard deviation of σn. If N successive sets of data each made up of n samples and containing the signal and noise are summed on a sample by sample basis, the average value of the rth sample is then () rav=(1/N)∑i=1Nri
S
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
time signal, in control and filtering applications. For example, f [k] could represent the above voltage sampled every 0.5 seconds, as shown in the figure. signal averaging an averaging process which is used to enhance signals and suppress noise, thereby improving the signal to noise ratio. See averaging. signal conditioning a process which is used to improve the appearance or effectiveness of a signal, either by suppressing noise or by transforming the signal into a more suitable form. This latter category includes image enhancement. Signal conditioning is often appropriate in preparing signals for recognition. signal decimation signal detection nal in noise. See decimation. detecting the presence of a sig-
Nozzle zone agglomeration in spray dryers: Process dependency of the fines mass flow and its importance for agglomerate formation
Published in Drying Technology, 2023
Jakob Alfons Fröhlich, Maren Spiess, Jörg Hinrichs, Reinhard Kohlus
The maximum absorption of the colorant was determined at 507 nm whereby an AvaLight-HAL Tungsten Halogen Light Source (Avantes BV, Apeldoorn, Netherlands) and an AvaSpec-ULS2048 UV/Vis spectrometer with AvaSoft 8.11 Basic Software was used as detector. Integration time was set to 1.05 ms and signal averaging with 100 scans was performed to reduce measurement noise. Measured absorption signals were correlated to powder mass using a calibration curve from After cooling, the particle-free air was fed to the air flow meter (Mass-View, Bronkhorst High-Tech B.V., Ruurlo, Netherlands) which ensured the isokinetic extraction velocity. The air flow was extracted by means of a liquid ring pump. The measuring time per measuring point in steady-state operation was at least 10 minutes. In another study[19] the identical measuring system was used for residence time measurements in spray dryers, whereby a response time of the measurement set-up of approx. 10 s was determined. This is thus sufficiently small compared to the measurement duration.
A Functional BCI Model by the P2731 working group: Physiology
Published in Brain-Computer Interfaces, 2021
Ali Hossaini, Davide Valeriani, Chang S. Nam, Raffaele Ferrante, Mufti Mahmud
Event-related potentials (ERP) are voltage fluctuations generated when regions of the brain respond to stimuli, prepare for a movement or perform mental operations such as imagining movement. When sensed by EEG, ERPs are detected as consistent changes in micro-voltage levels on the scalp, but these changes are usually masked by higher amplitude background noise. To compensate, ‘time locked signal averaging is necessary to extract ERPs from the raw data’ [85]. This method requires researchers to segment a recording into a series of ‘epochs’ that begin with the stimulus that causes the ERP [86]. ERPs are time-locked to stimuli, so an epoch should be long enough to include the stimulus, a precursor period of background data, and sufficient time to capture the ERP under scrutiny. Averaging a set of epochs allows the time-locked signal to emerge by decreasing the relative amplitude of noise [87]. ERPs have been identified for different sense modalities, but localizing their neural generators has proven difficult because of the head’s conductive properties [88,89]. ERP names are created by combining their polarity – P for positive, N for negative – with their peak latency, namely the time between a stimulus and their maximum amplitude measured in milliseconds (e.g. N250, P300) or the order in which they appear (e.g. P1, N2, P2). Note that both the onset and the maximum amplitude of an ERP are in reality variable, and it is the stereotypical waveform combined with temporal proximity to an hypothetical post-stimulus peak that enables researchers to categorize it [90–93].
Tunable sonar transducer
Published in Instrumentation Science & Technology, 2019
Hasan A. Alwi, Roslan Abd-Shukor, Shahriman M. Ghazali
The receiving sensitivity SR of the tunable transducer was then determined by measuring the echo of a 1-inch steel sphere obtained from a local hardware store which was located at a distance of 3.7 m. The steel ball was suspended from a buoy by a nylon net. The separation of the steel sphere target was fixed by anchoring the buoy to two weights at the bottom of the pool. The free-field acoustic pressure near the transducer face was measured using a hydrophone (Bruel & Kjaer 8103) and a charge amplifier (Bruel & Kjaer 2635). The pulse duration was fixed to 1 ms which is the shortest pulse the transmit/receive circuit can provide to avoid the echo overlaps with reverberations. During the testing and sensitivity measurements, signal averaging function of the oscilloscope was used to get clean echo voltages.