Noise digitization

Digital noise-reduction Videonoise is related to tape quality, camera resolution and light conditions. In a video picture, pixels will change their colour ran-... 

Digital noise measurements have been obtained by use of a microcomputer controlling the sampling rate of a sensitive digital voltmeter employed to measure the potential or current fluctuations. The subsequent analysis of the derived time records is described. 

Figure 1. Schematic diagram for digital noise measurements using multiplexed electrodes.

Electrochemical noise can be characterized by some common statistical parameters including the mean, the variance, and the standard deviation. In particular, the standard deviation, o, is used as a measure of the amplitude of the variation in the noise signal. Skew and kurtosis sometimes give indications of the form of corrosion occurring (140). For unfiltered digitized noise data in a time record, the noise resistance, Rn, is... 

Data acquisition is straightforward, while digital noise filtering can improve long-time data [87]... 

SV Vaseghi. Advanced Signal Processing and Digital Noise Reduction. John Wiley Sons, New York, NY, 1996. 

Savitzky, A. and Golay, M.J.E. (1964) Anal. Chem., 36, 1627. Vaseghi, S.V. (1996) Advanced Signal Processing and Digital Noise Reduction, Wiley-Teubner, Chichester - Leipzig. 

The correlation time is 8, where 8 is the single parameter to measure the deviation from the white noise situation. The robustness of white-noise-induced phenomena, at least for small correlation time, are verified by this perturbation expansion method. Slightly different results were obtained by Sancho et al. (1982). They studied the qualitative properties of the stationary distribution as a function of the intensity and correlation time of the noise. Two results of their experiments on an electric circuit with a digital noise generator were not in accordance with the white noise limit theory (i) for higher noise intensity the stationary distribution might be bimodal even for rather small correlation time (ii) the location of the maximum of the stationary distribution depends on the noise characteristics. 

In practice, IRRAS spectra are almost invariably measured with p-polarized radiation. Because IRRAS spectra are usually so weak, the noise on the spectral baseline should be no greater than 1 X 10 AU (lOpAU). To achieve this performance in a reasonable time, the measurement should be made with an MCT detector. However, so little radiation is lost in an IRRAS measurement that the power at the detector is very high. Under these conditions, the response of MCT detectors is usually highly nonlinear so that not only do photometrically inaccurate spectra result (see Section 8.6.1) but the SNR may be limited by digitization noise rather than detector noise (see Section 7.3). It is therefore necessary to attenuate the beam before making the measurement. It is far more efficient to attenuate the beam with a polarizer than with a screen or an iris because not only is the signal reduced... 

The fact that only /7-polarized radiation is absorbed by surface species has been applied by a number of workers to circumvent the problem of digitization noise. These workers have used a photoelastic modulator (PEM) configured to modulate the plane of polarization rapidly between and p, as described in Chapter 12. The Fourier frequencies are removed with a high-pass electronic filter so that the only signal is caused by the difference between the absorption of p- and -polarized radiation, which is caused solely by the surface species. A description of the signal processing and computation was given in Section 12.3. 

---