Campbell CR9000, Instruction Manual

Page: 149 / 218

Section 7. Measurement Instructions
7-35
Parameter
Enter
FFTFILT PARAMETERS
Excitation
Constant
The continuous, dc, output level for the excitation channel(s). If Reps is greater than one, then
the Filter Module drives the same excitation level on sequential excitation outputs.
Numeric Code Alpha Code Output Level IEPE Freq. Response
CR9052IEPE 605 None Constant 6 mA
0.3 Hz to 20 kHz (
τ
= 5.0 Sec)
CR9052IEPE 405 None Constant 4 mA
0.3 Hz to 20 kHz (
τ
= 5.0 Sec)
CR9052IEPE
205 None Constant 2 mA
0.3 Hz to 20 kHz (
τ
= 5.0 Sec)
CR9052IEPE 600 None Constant 6 mA
3.0 Hz to 20 kHz (
τ
= 0.5 Sec)
CR9052IEPE
400 None Constant 4 mA
3.0 Hz to 20 kHz (
τ
= 0.5 Sec)
CR9052IEPE
200 None Constant 2 mA
3.0 Hz to 20 kHz (
τ
= 0.5 Sec)
CR9052DC 7 V10 Constant 10 V DC
CR9052DC
5 None Constant 5 V DC
CR9052DC 2 None Constant 10 mA
CR9052DC
1 None None
Mult
Constant,Variable,
Array, Expression
A factor by which to multiply the raw time-series voltage measurements. Mult
-1
provides the
reference value for the deciBell (dB) spectral option.
FsampRate
Constant
The sample rate in samples per second, at which the CR9052 will collect time series data
before performing the FFT.
FsampRate must be the same for all channels in a CR9052
module
.
FsampRate Sample Rate Sample Interval
50000 50 kHz 20
µ
s
25000 25 kHz 40
µ
s
10000 10 kHz 100
µ
s
5000 5 kHz 200
µ
s
2500 2.5 kHz 400
µ
s
1000 1 kHz 1 ms
500 500 Hz 2 ms
250 250 Hz 4 ms
100 100 Hz 10 ms
50 50 Hz 20 ms
25 25 Hz 40 ms
10 10 Hz 100 ms
5 5 Hz 200 ms
FFTLen
Constant
FFTLen
65536
32768
16384
8192
4096
2048
1024
512
256
128
64
32
The length of (number of points in) the time series snapshot on which to
perform the FFT. If the scan period equals FFTLen/FsampRate, then the
consecutive time seriessnapshots processed into spectra are “seamless”. If
the scan period is greater than FFTLen/FsampRate, then the time series
snapshots will have gaps between them. A compile error occurs if the scan
Period is less than FFTLen/FsampRate
The FFT throughput for transforms of 2048 points or less is much higher
than the throughput for transforms longer than 2048 points. The
CR9052DC can produce spectra from seamless 50-kHz snapshots on six
channels for
FFTLen equal to 2048 or less. The CR9052DC can produce
spectra from seamless 50-kHz snapshots on two channels for any FFTLen.