Campbell Scientific RTDAQ Software - Manual (Page 203)

Section 7. Monitoring Data in Real-time
outputs, or in vector form (i.e., dual-valued outputs; two values per frequency
range), such as Real-Imaginary or Amplitude-Phase output pairs.
Campbell Scientific dataloggers can take a selected number of sampled points
in the time domain and calculate the FFT spectrum for that set of points and
store that spectrum into a table record. The number of sampled points in the
time domain must be an even power of 2 (such as 32, 64, 128 and so on up to
65536). Usually the number of bins or bin pairs in the output of the calculation
is about half of the number of time domain input points (N/2 +1). For
example, an FFT spectrum calculated from 2048 time-series points can have as
many as 1025 frequency output points or pairs.
7.8.2 FFT vs. FFTSample
FFT output instruction. When used this way, the table will monitor the
er number of points has been
point the spectrum is calculated and
r
7.8.3 Opening FFT Viewer Windows
sure that a
or,
in one of the tables of the CRBasic
program.
licking on the datalogger’s icon and
Any measured value can be stored into a table as an FFT spectrum using the
specified time domain value until the prop
measured for creating a spectrum. At that
stored within a single record of the table. This spectrum contains one value o
value pair for each frequency bin.
The FFTSample instruction works in a similar manner, except that it outputs
only the results of an FFTFilt CRBasic measurement instruction, which can
only be executed on a CR9000X datalogger equipped with at least one
CR9052DC or CR9052IEPE module.
To view real-time FFT spectra from a datalogger in RTDAQ, first en
proper FFT program is running in the datalogger you wish to monit
including the proper output instruction(s)
Connect to the datalogger in RTDAQ by c
pressing Connect. Now choose the Monitor Data tab to make the real-time
displays available, and choose the FFT/Histo button.
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