Larson Davis System 824, Technical Reference Manual

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A-54 824 Reference Manual 9/29/09
History Records
Histories are records of stored data
based on time or a particular event.
One record is available at a time.
The current record number is
selected by using the Advance,
Backup, and Find commands (see
below) or the Setting S211 through
S217.
The various histories of the System
824 are each accessed in a similar
fashion. The Find command is the
primary method of locating a history
record for random (nonsequential)
access. For example, to find the one
hundred twenty-fifth Exceedance
record you send the command
F125,1 <cr> where the [,1] specifies
that it is an Exceedance record to be
found (as defined in the
“history_number” column below).
The Advance and Backup
commands are generally used next.
They extract data after the initial find
command.
The Find command takes longer to
execute as the record number
increases in size, therefore, for
sequential data extraction locate the
first desired record with the Find
command and then use the Advance
command. The [,relative_rec] option
can be used to retrieve data forward
or backward from the current record
number without changing that record
number; it is a signed 8-bit value, i.e.
1 to 127 is positive 1 to 127 while
128 to 255 is -128 to -1 respectively.
Refer to settings 211 through 217 to
query the current record number.
Setting these to a desired record