Filter value

Fig. 2 Water balance of Switzerland. Points are values for the hydrological years the lines are 9-year low-pass Gaussian filtered values...

The term moving is used because the filter software maintains a storage array with the previous n values of the input. When a new value is received, the oldest value in the storage array is replaced with the new value, and the arithmetic average is recomputed. This permits the filtered value to be updated each time a new input value is received. 

FIGURE 15.22 The instantaneous and filtered values for the derivative of a noisy sensor reading. Also shown is the value of the derivative calculated using filtered values of y, t) with a filter factor of 0.08. 

After deciding on the filter width, the filtered value for the Ath data point is calculated by... 

At this point k, the filtered value is calculated up to the second derivative on the basis of a 5-point Savitzky-Golay filter. 

Calculation of the filtered values and their standard deviations by means of the tabulated filter coefficients leads to ... 

The frequency needs to be low enough so that with practical circuit elements in the IF filters, values of Q can be attained that will provide a steep attenuation characteristic outside the bandwidth of the IF signal. This decreases the noise and minimizes the interference from adjacent channels. 

Filtering for filtering, the mean response interval for a Kalman filtered value can be written as... 

FIGURE 4-18 LabVlEW front panel for a data-acpuisition system allows the user to choose parameters such as sampling rate, sample length, and filtering values. (Reprinted with permission ot National Instruments Corporation.)... 

The advantage of this filter is that, because it uses the trend of the unfiltered measurement to predict the filtered value, it has no lag. Indeed its predictive nature introduces lead which partially counteracts the process lag. This effect is shown in Figure 5.21. Both filters have been tuned to give the same level of noise reduction. The least squares filter not only outperforms the exponential filter in that it tracks the base signal more closely but actually overtakes the base signal. 

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