Displaying The Alarm History - Omron NT30 Operation Manual

Alarm List & History Display Functions

4-11-2 Displaying the Alarm History

Recording Format of Alarm History
Maximum Number of Alarms to be Recorded
Reference
How to Make Sure of Alarm History
184
The alarm history constantly monitors the status of the bit for which Alarm is
turned ON under Function in the bit memory table and records the date and time
at which it changes to 1 (i.e., turns ON).
The bits recorded in the alarm history are always monitored irrespective of the
display screen of the NT30/30C. If the number of bits are increased excessively,
the processing speed of the NT30/30C may become slower.
The alarm history is common to all bit memory table entries. Unlike the message
display, it cannot deal with only a part of bit memory table entry.
For the alarm history, the following data is recorded in the memory concerning
the bit that turns 1 (ON).
• Bit address
• Date and time of occurrence
• Message set in the bit memory table entry (the contents of the character string
memory table entry)
The maximum number of alarms that can be recorded is 256 when they are re-
corded in the order of occurrence, and 255 for each alarm message when they
are recorded in the order of frequency.
Data recorded is backed up by a battery, so it is not lost even when the power
supply is turned OFF.
If the battery in the PT loses voltage, recorded data cannot be retained correctly.
When recording in the order of occurrence, the way alarms are recorded when
the number of alarms capable of being recorded is exceeded is determined by
the Alarm (Use Ring Buffer) under System (Alarm First-in First-out setting of the
System Memory with DOS version) on the NT-series Support Tool as follows:
ON: Old history is cleared and new history is recorded.
OFF: Alarms in excess of 256 are not recorded (new alarms are discarded).
In order to clear (initialize) the alarm history, the memory is initialized (see page
82). It is also possible to clear (initialize) the alarm history using bit 11 (display
history initialization) of the PT status control bits.
The alarm history can be displayed by the NT30/30C during operation by setting
an area and displaying method when creating a screen data with the NT-series
Support Tool.
There are two displaying methods: in the order of occurrence and frequency.
Section 4-11