2680A/2686A
Users Manual
1-16
The internal evaluation algorithm allows data from slower modules to be recorded
regardless of the scan speed of other modules. The measurements made by slower
PAIs well still be recorded even when running in a chassis of FAIs. Only the
fastest modules may experience some loss of data. If the user sets the interval time
of each module to 31 ms or greater, no data will be lost for any number of FAI
channels. In addition, if the total number of scans for all of the modules combined
is less than 1000 scans per second, there should be no problem with losing scans.
Below is a table showing the timing.
Using the DIO for alarms or the totalizer will slow system throughput because of
its 4 ms overhead. DIO data is provided with each module scan. Consequently,
having five modules scanning at the same speed will incur an additional 20 ms
delay if a DIO is active.
Writing to the PC card is more time consuming than writing to internal memory.
This is partly because the 2686A instrument uses a DOS compatible file storage
system that requires additional overhead. As a result, the maximum scan time
while storing data will be slowed.
Table 1-1. Channel Count vs Scan Rate
2680A/2686A Channel Rate With No Lost Data*
Channel Count
Module Count
Typical Total Time (ms)
Typical Scan Rate (ch/s)
1 1
4
250
1 2
4
500
1 3
4
750
1 4
4
1,000
1 5
5
1,000
1 6
6
1,000
20 1
30
666
40 2 30.1
1,329
60 3 30.1
1,993
80 4 30.1
2,658
100 5
30.1
3,322
120 6
30.1
3,990
* Assumes no DIO, no PC card storage, no network communication, and only FAI modules in the
chassis.
Summary of Contents for 2680A
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