Campbell Scientific CR9000X Measurement and Control System - Manual (Page 190)

Section 6. Data Table Declarations and Output Processing Instructions
The following examples show how triggered output, that is capturing pre-
trigger data, can have varying number of records based on when a trigger
occurs.
Chart 6.2-1 Triggered Data Example 1
Triggered Data Example 1: Chart 6.2-1 depicts a signal that is being
conditionally stored to a DataTable with a single trigger condition that is
evaluated as true when the signal is greater than 4 volts. The DataTable is set
to collect 10 records before and 10 records after the trigger (a maximum of 21
records will be stored per event). As can be seen, only 5 records were available
before the first trigger occurred. This resulted in only 16 records being stored
for the first event. In this example, subsequent events had 21 records.
Chart 6.2-2 Triggered Data Example 2
Triggered Data Example 2: Chart 6.2-2 depicts a signal that is again triggering
output at 4 volts. The trigger is set to capture 10 records before and 30 records
after the event evaluates as true. Again, only 5 records were available before the
first trigger occurred. This results in only 36 records being stored for the first
event. The next trigger occurs before 10 records have passed, resulting in 36
records, counting the trigger record, being sorted. In this example, subsequent
events all have 36 records because the signal is synchronised with the triggers,
and there are always only 5 records available for pre-trigger capture.
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