Campbell Scientific CR9000X Measurement and Control System - Manual (Page 274)

Section 7. Measurement Instructions
7-50
Parameter
& Data Type Enter FFTFILT PARAMETERS
FiltOption
Constant The sample ratio for the measurement (how many measurements are made within one cycle of the
highest frequency in the pass band). The sample ratio determines the top of the pass-band (F
PASS
)
and the beginning of the stop-band (F
STOP
) of the anti-aliasing low-pass filter relative the sample
rate (F
SAMPLE
). The sample rate is the inverse the scan interval in the CRBASIC program.
FiltOption must be the same for all channels of a single CR9052DC Filter Module. The CR9052
normally replaces out-of-range measurements with not-a-number (NaN) which is displayed in
RTDaq's realtime windows as Range?. Out-of-range measurements may be replaced by the
analog-to-digital converter saturation value by adding 1000 to the FiltOption codes shown
below.
Numeric Code Sampling Ratio F
PASS
F
STOP
2 2.5 F
SAMPLE
/2.5 F
SAMPLE
/2.01
5 5 F
SAMPLE
/5 F
SAMPLE
/3.37
10 10 F
SAMPLE
/10 F
SAMPLE
/5.08
20 20 F
SAMPLE
/20 F
SAMPLE
/6.81
1* 2.155 23.2 Khz 26.8 kHz
FiltOption 1 is available only when FsampRate is 50 kHz. At this sample rate, no additional
filtering beyond that provided by the CR9052DC hardware is required to anti-alias the data.
Because the CR9052DC processor is not performing additional anti-alias filtering, this
FiltOption increases the CR9052DC’s FFT throughput. To achieve spectra from seamless
snapshots with FsampRate equal to 50 kHz on six channels, FiltOption must be 1.
Excitation
Constant
The continuous, dc, output level for the excitation channel(s). If Reps is greater than one, then the
CR9052 Module drives the same excitation level on sequential excitation outputs.
Numeric Code Alpha Code Output Level IEPE Freq. Response
CR9052IEPE 900 (905) None None τ = 0.5 Sec ( τ = 5.0 Sec)
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 . Some
of the available rates are shown below:
FsampRate Sample Rate Sample Interval
50000 50 kHz 20 μs
25000 25 kHz 40 μs
10000 10 kHz 100 μs
5000 5 kHz 200 μs
2500 2.5 kHz 400 μs
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