Allen-Bradley 1404-M4, User Manual

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Publication 1404-UM001D-EN-E - October 2004
7-10 Data Logging
Examples
Example 1: A user wants to log kW every 15 minutes and wants to
know how many records the log will contain and how long a time
that will cover. The first formula applies:
Fill and hold mode allows logging the most records. Logging only 1
parameter per record, the formula results in a total of 45,866 records
after rounding down. Logging every 15 minutes, this log configuration
will log 15.8 months of kW data.
Example 2: Another user wants to log several parameters every 5
minutes indefinitely, retrieving the records within one week after the
end of each month. He will save the retrieved data and create trend
graphs on his PC. The question is how many parameters may be
monitored. The second formula applies to this example:
The total log depth of 10,944 is based on the log duration and interval:
(31 days per month + 7 days) * (24 hours per day) * (60 minutes per
hour) / 5 minute logging interval. Overwrite mode (F = 1) allows you
to read the log any time without losing any data.
In this example, P, the number of parameters that may be recorded, is
7, rounded down from 7.48.
From this example, you can see that the trend log can log 7
parameters every 5 minutes in a 38-day sliding window.
D
7 0 –
( )
65524
•
1 4
• ( )
6 +
--------------------------------------
=
P
7 1 –
( )
16381
•
10944
--------------------------------------
1.5 – =