Spider DSA User’s Manual
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Hamming window is optimized to minimize the maximum (nearest) side lobe,
giving it a height of about one-fifth that of the Hann window.
Flattop window is a partially negative-valued window that has a flattop in the
frequency domain. Such windows have been made available for the measurement
of amplitudes of sinusoidal frequency components. They have a low amplitude
measurement error suitable for this purpose, achieved by the spreading of the
energy of a sine wave over multiple bins in the spectrum.
Uniform window is really no window at all. It is sometimes called the “boxcar
function “because it looks like a boxcar, a pulse that is unity for all values of time.
The uniform window provides the best frequency resolution and amplitude
accuracy, but can only be used if the measured signal is periodic in the time
record.
Kaiser-Bessel window is a simple approximation of the DPSS window using
Bessel functions. It approximates the prolate-spheroidal window, for which the
ratio of the main lobe energy to the side lobe energy is maximized.
Blackman window is useful for single tone measurement because it has a low
maximum side lobe level and a high side lobe roll-off rate.
Force window is used for a specific application of computing the transfer
function of a mechanical structure using an impulsive force excitation.
Exponential window increases exponentially towards the center of the window
and decreases exponentially in the second half. Since the exponential function
never reaches zero, the values of the window at its limits are non-zero.
Force-Exponential window is time domain weighting function that has been
developed for impact testing. The principal purpose of the window is to reduce
the effects of leakage on lightly damped response measurements, but it can also
improve the signal-to-noise ratio of heavily damped response measurements. The
purpose of the force is to eliminate the noise on the signal after the impact.
Tukey window, also known as the tapered cosine window, can be regarded as a
cosine lobe of width αN/2 that is convolved with a rectangular window of width (1
− α/2) N.
User window is defined by the user.
Running a Test
When using accelerometers, it is a good idea to do a quick check to verify if they
are working correctly. Tap your finger close to where the accelerometers are
mounted. The input should register a signal between 0.1 and 10 g’s of acceleration.
Anything significantly out of this range can indicate a problem with the
connection or channel setup. The Input Channel Status also provides an overview
of the current input levels. It can be activated from View->Channel Status.
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