An alarm
handling is a property
that can be provided per data
point element. A certain
alarm state (continuous or discrete) can be assigned to
a range of values of the element. While binary data point elements
can accept two states, the value range of a analog value can be
separated to endless monitoring
ranges. Accordingly, for binary alarm handlings, an alarm
can be assigned exactly to one of the two possible states. For
an analog value, there are generally 2,3 or 5 ranges in which
the whole value range of the data point element will be divided
(maximum 255).
In order to configure
an alarm handling, select the associated element in the
database editor PARA and add an alarm handling as a config.
This was already described in the chapter Functionality
of the Device Oriented Data Object - Configs.
Figure: Configuration
of an analog Alarm Handling with 3 Ranges
If you work with
master data points, the alarm handling will be added as
a PowerConfig directly
to the respective element of the master data point. You can then
set alarm limits and other settings using "Configure PowerConfig"
on the particular element of a data point instance.
If you work without
master data point, add the alarm handling directly to the
data point element as a normal config "alarm handling" (_alert_hdl).
In case of analog alarm handlings you can specify
hysteresis for each alarm
range so that when thresholds are exceeded or underrun continuously,
new alarms will not be triggered permanently. A number of properties
is additionally assigned to each alarm
range. These properties are, for example:
Priority of the alarm (Priority of the alarm range) State model of the alarm Required authorization
for acknowledging the alarm Standard color that is used to signalize the color Historic recording of the alarm history (storage) Message
actions ...
So that you do not have to define these properties
for each individual alarm range again, alarm
classes exist in WinCC OA.
An alarm class comprises such properties so that you only have
to refer to the associated
alarm class in case of an individual alarm range of a data point
element. In the previous figure, you can see such references to
alarm classes on the right in the "alert
class" column next to the high and low alarms. The
middle row shows the OK range
of the value so that you do not
have to define an alarm class here.
The indication of the alarm class is in the example
"060_alert". This means priority
= "60" and class =
"alert".
Alarm classes are specified in WinCC OA by using a config with the same name. You can find all alarm classes existing by default
in the module PARA through the internal data point type "_AlertClass"
and data points of the same name. In order to view the existing
alarm classes, open the module PARA, activate the check box "Internal
data points" above the tree view and
navigate to the type _AlertClass.
Figure: Summary of Alarm Properties
through Alarm Classes (the DP presents an alarm class)
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