2 integral x(t) – Soft dB Opus Suite Data Logger Module User Manual

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This parameter is used only for the Elliptic and Inverse Chebyshev filter

types. This parameter is the desired attenuation in the stop band of the

filter. It must be greater than zero and you must express it in decibels.

All filter parameters can be saved and recalled using these buttons. Note that the filter interface

automatically creates a .flt file when the filter operation is launched with the Apply Filter and Quit

button. This automatically saved .flt file will have the name of the filtered wave file and it will be in

the same folder. This feature is very useful for following the filtering historic of a wave file.

This control allows selecting the group of channels to which the filter will be applied. Note that the

non-filtered channels will be included in the wave file created by the filter function.

This button launches the filtering operating. The original wave file will be used as a source for the

filter and the filtered signal will be saved in a new wave file. Also, a .flt file containing the filter

parameters is automatically created in the same folder that the filtered wave.

9.2.2

Integral x(t)

This function performs a time-integration on the signal of a group of selected channels. Some

modules in the analysis functions tab allow integration in the frequency domain. This function is

useful for analyzing the signal coming from an accelerometer, especially if the speed and position

must be analyzed in the time domain. There are many available techniques for performing time

integration. We select the filtering approach, which has the advantage of being numerically stable.

So, a simple first order or second order low-pass filter is used to perform a simple or double

integration. The user must specify a cut-off frequency for the filter. We suggest using an Fcut(Hz)

parameter that fits with the sensor used. A typical accelerometer sensor has a flat frequency

response that starts at around 20 Hz. The interface of the Integral x(t) function is shown in the next

figure: