Campbell Scientific LoggerNet Datalogger Support Software - Manual (Page 523)

Appendix C. Table-Based Dataloggers
• Instruction 96, Serial Output – Instruction 96 is used to send data in the
active Final Storage area to a storage module, computer, printer, or
alternate final storage area. This instruction is not included in the table-
based programming instructions.
• Instruction 98, Send Printer Character – Instruction 98 is used to send
characters to either an addressed or pin-enabled printer. This instruction is
not included in the table-based programming instructions.
• Conditional Data Output – check to make sure that the output data is not
being output conditionally. Table-based dataloggers require that the size
of the output record is constant. Any instructions that dynamically change
the number of data values in a record or the size of the record need to be
removed. (e.g., don’t change data resolution from low to high based on a
conditional. )
C.3 Table Data Overview
In the datalogger all data is organized into tables with fixed data records. Each
of these tables has a definite number of records that is either fixed by the
datalogger program or allocated when the program is compiled by the
datalogger. Once the maximum number of records for a table have been
stored, the next record stored will overwrite the oldest record in the table. The
record number will continue to increment, and the oldest record will “drop off”
the top.
Tables that are automatically allocated in the datalogger program are allocated
a number of records based on the time interval for the records. The datalogger
attempts to allocate these tables so that all of the automatically allocated tables
fill up at the same time. For example two tables with records stored every 30
minutes and 60 minutes would have twice as many records allocated for the
30-minute table.
Event driven tables should have a fixed size rather than allowing
them to be allocated automatically. If automatically allocated,
event driven tables are assumed to have one record stored per
execution interval in calculating the length.
Since the datalogger tries to make the tables fill up at the same
time, if you let the datalogger automatically allocate table sizes
these event driven tables may take up most of the memory leaving
very little for the other, longer interval, automatically allocated
data tables.
Within a data table, data is organized in records and fields. Each row in a table
represents a record and each column represents a field. To understand the
concept of records it may be helpful to consider an example.
NOTE
C-5