User manual

Computer Gateway User Manual 4-100 5/96
4.8.2
For Fast Interval Monthly Averages (history type = 7) derived
from 5-, 10-, or 20-second snapshots, each subrecord is 11 words
long.
Form 1
Word 1 =0 (integer)—normal data, or
=1 (integer)—nonstandard, or
=5 (integer)—time change, or
=13 (integer)—time change nonstandard
Words 2..3 process value (real)
Words 4..5 timestamp (unsigned 32-bit integer)
Words 6..7 maximum process value* in period (real)
Words 8..9 minimum process value* in period (real)
Word 10..11 number of samples (32-bit integer)
Form 2
Word 1 =6 (integer)—outage, or
=7 (integer)—no data, or
=12 (integer) not in history
Words 2..3 not used (real, initialized to IEEE NaN)
Words 4..5 timestamp (unsigned 32-bit integer)
Words 6..7 not used (real, initialized to IEEE NaN)
Words 8..9 not used (real, initialized to IEEE NaN)
Word 10..11 number of samples skipped (32-bit integer)
For a Sampling Rate Inquiry (history type = 8), two data words
are returned for each point.parameter defined in the DDT. Note
that no record headers are included with this data.
Word 1 data access status (integer)—See the Messages Directory.
Word 2 sampling rate in seconds (integer)
Use information: There are two limits placed on the amount of history data that can
be returned for each request:
1) There can be no more than 262 data samples for any one
point.
2) The maximum return-message size is 5986 data words.
The return message's contents are truncated at the point where
either of these limits is reached.
The "timestamp" is a count of seconds since January 1, 1979
Digital process values included in Get History returns are reported
as the ordinal values of user-defined enumerations.
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*Because of the storage method used, Minimum/Maximum process values can have up to 1% error (+1% for maximums
and -1% for minimums).