
Section 6. Data Table Declarations and Output Processing Instructions
6-13
Parameter&
Data Type
Enter
NumCov
Constant
The number of covariances to calculate. The maximum number of covariances
is Z/2*(Z+1). Where Z= NumVals. If X(1) is the first specified element of the
source array, the covariances are calculated and output in the following
sequence: X_Cov(1)…X_Cov(Z/2*(Z+1)) = Cov[X(1),X(1)], Cov[X(1),X(2)],
Cov[X(1),X(3)], … Cov[X(1),X(Z)], Cov[X(2),X(2)], Cov[X(2),X(3)], …
Cov[X(2),X(Z)], … Cov[X(Z),X(Z)]. The first “NumCov” of these possible
covariances are output.
FFT (Source, DataType, N, Tau, Units, Option)
The FFT performs a Fast Fourier Transform on a time series of measurements
stored in an array. It can also perform an inverse FFT, generating a time series
from the results of an FFT. Depending on the output option chosen, the output
can be: 0) The real and imaginary parts of the FFT; 1) Amplitude spectrum.
2) Amplitude and Phase Spectrum; 3) Power Spectrum; 4) Power Spectral
Density (PSD); or 5) Inverse FFT.
Parameter
& Data Type
Enter
Source
Variable
The name of the Variable array that contains the input data for the FFT.
DataType
A code to select the data storage format.
Constant
Alpha Code Numeric Code Data Format
IEEE4 24 IEEE 4 byte floating point
FP2 7 Campbell Scientific 2 byte floating point
N
Constant
Number of points in the original time series. The number of points must be a power of 2
(i.e., 512, 1024, 2048, etc.).
Tau
Constant
The sampling interval of the time series.
Units
The units for Tau.
Constant
Alpha Code Units
USEC microseconds
MSEC milliseconds
SEC seconds
MIN minutes
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