Campbell Scientific CR9000X Measurement and Control System - Manual (Page 353)

Section 9. Program Control Instructions
FILTER MODULE SUBSCAN: This SubScan type was designed for the Filter
module and runs at a faster rate than the main Scan. Its SubInterval must be evenly
divisible by the main Scan interval. The last parameter for this type of SubScan must
be the ratio of the main Scan Interval to the SubScan Interval. Only the VoltFilt or
the FFTFilt measurement instruction along with associated processing should be
placed in one of these SubScans. Multiple Filter SubScans can exist within each
main Scan structure. You cannot run measurements for a single CR9052 module both
inside and outside of a SubScan, as all measurements for a given module must have
the same Scan Interval and Sample Ratio.
It should be remembered that the Scan's buffer parameter sets up both the CPU's
buffer size and the CR9052 memory buffer. The CR9052's internal memory buffer
can accommodate up to 8,000,000 samples. The number of SubScans that will be
buffered is the product of the Scan's Buffer parameter and the SubRatio parameter.
So the limit for the Scan's buffer parameter when using filter modules with SubScans
is 8,000,000 divided by the product of the number of channels used on the modules
and the SubScan's SampleRatio parameter.
Example, if 4 channels were being used on a CR9052 inside a SubScan with a
SampleRatio of 1000, the largest Scan buffer that could be implemented is 2000:
8,000,000/(4 x 1000). . If the main Scan instruction specifies more scans to buffer
than available CR9052 memory, an error message will be returned at compile time.
You cannot mix the VoltFilt or the FFTFilt instructions with any
other type of measurement instruction within a SubScan. NOTE
See Section 7.8 CR9052DC and CR9052IEPE Filter Module for more
information about CR9052 Filter module measurements with SubScans.
ISOLATION MODULE OR SUPER SUBSCAN: This SubScan runs at a slower
rate than the main Scan and will have an interval that is an integer multiple of the
main Scan interval. The syntax for this type of SubScan would be SubScan(0,0,-j),
where j is the ratio of the SubScan Interval to the main Scan Interval.. You cannot
run measurements for a single CR9058E module both inside and outside of a
SubScan, as all measurements for a given module must have the same Scan Interval.
The CR9058E isolation module has a memory buffer that can hold up to 512 values.
Similar to the CR9052, the Scan's buffer parameter sets both the CPU's buffer size
and the CR9058E memory buffer. The number of SubScans that will be buffered is
the quotient of the Scan's Buffer parameter and the absolute value of the SubRatio
parameter. So the limit for the Scan's buffer parameter when using CR9058E
modules with SubScans is 512 divided by the number of channels used on the
module times the absolute value of the SubScan's SampleRatio parameter.
For example, if 8 channels were being used on a CR9058E inside a SubScan with a
SampleRatio of -20, the largest Scan buffer that could be implemented is (512/8) x
20 = 1280. If the main Scan instruction specifies more scans to buffer than available
CR9058E memory, an error message will be returned at compile time.
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