Campbell Scientific CR9000X Measurement and Control System - Manual (Page 186)

Section 6. Data Table Declarations and Output Processing Instructions
6.2 Trigger Modifiers
DataInterval (TintoInt, Interval, Units, Lapses)
The DataInterval instruction is used to set the time interval for storing data to
an output table based on the datalogger's real-time clock.
DataInterval is
inserted into a data table declaration following the DataTable instruction to
establish a fixed interval table and/or to force the tracking of Data Table Lapses
(Skipped Records). The resulting fixed interval table can require less memory
than a conditional table because a Time Stamp and Record number do not
have to be stored with each record.
DataInterval does not override the Trigger in the DataTable instruction. If
the Trigger is not set always true by entering a constant, it is a condition that
must be met in addition to the time interval before data will be stored. If a
record is not written at the programmed interval, the logger recognizes it as a
Lapse and the Skipped record counter in the Status Table is incremented.
Interval determines how frequently data are stored to the table. It must be an
integral multiple of the interval of the Scan that called it. The interval is
synchronized with the real time clock. Entering zero (0) for the Interval sets it
equal to the scan Interval.
TintoInt allows the user to set the time into the Interval, or offset relative to
real time, at which the output occurs. For example, 360 (TintoInt) minutes into
a 720 (Interval) minute (Units) interval specifies that output should occur at
6:00 (6 AM, 360 minutes from midnight) and 18:00 (6 PM, 360 minutes from
noon). Enter 0 to keep output on the even interval.
Lapses is used to allocate additional memory for the tracking of lapses
(skipped records). A Lapse is any discontinuity in the DataTable records’
time intervals. Lapses can be the result of skipped scans, event driven tables,
and/or logic in the calling of the data table from the program. For example, if
the data output is controlled by the Trigger parameter (e.g., a user flag) in the
DataTable instruction as well as by the DataInterval instruction, a lapse
would occur each time the trigger was false at the time of the DataInterval's
output interval. It should be noted that if multiple data storage intervals are
skipped sequentially, it is a single lapse.
The CR9000X stores a timestamp and record number in the header of each of
the Table’s data frames. A data frame is usually around one KByte of memory.
Data tables using the DataInterval instruction allow for a more efficient use of
memory because, instead of storing time stamps and record numbers with every
record, they use the data frame’s timestamp and record number information. As
each new record is written to the data table, the datalogger checks to insure that
a Lapse has not occurred. If a Lapse has occurred, a 16 byte sub-header with
Time Stamp/Record Number information is inserted into the data frame before
the record is written. When the data are retrieved to the computer, the time
stamp and record number are calculated, using the data frame headers (and sub
headers if lapses have occurred), and stored with each record.
The Lapse parameter specifies the number of sub-headers for which additional
memory will be allocated. The allocation is an integral number of data frames.
For example, if the Lapse parameter were set to 400, the minimum memory
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