National Instruments Order Analysis Toolset - Manual (Page 44)

Chapter 4 Resampling-Based Order Analysis
LabVIEW Order Analysis Toolset User Manual 4-4 ni.com
Figure 4-2. Original Time Sequence and CIC Interpolation Filter with
an Interpolation Factor of Eight
Resampling Vibration Data
The resampling operation converts a vibration signal from the time domain
into the angle domain. To resample vibration data into even angle spaced
samples, you must be able to calculate the value of the vibration signal at
any time instance.
According to the Nyquist sampling theorem, you can exactly reconstruct
the signal for all time instances using band-limited interpolation if and only
if the original signal is band limited to half of the sampling rate.
For example, a continuous time signal x(t) that is band limited to f
s
/2 Hz and
sampled at a sampling rate of f
s
samples/second yields a discrete sample
given by the following equation.
x
n
= x(nT
s
),
where T
s
= 1/f
s
and is the sampling time interval.