Echelon i.LON 100 e2 Internet Server - Manual (Page 90)

i. LON 100 Internet Server Programmer’s Reference 7-1
7 Alarm Generator
Use the Alarm Generator application to generate alarms based on the values of the data
points in your network. Each time you create an Alarm Generator, you will select an input
data point and a compare data point. The Alarm Generator will compare the values of these
data points each time either one is updated. You will select the function the Alarm Generator
will use to make the comparison. If the result of the comparison is true, an alarm will be
generated, and the status (UCPTpointStatus) of the input data point will be updated to an
alarm condition.
For example, you could select GreaterThan as the comparison function. The Alarm Generator
would generate an alarm each time either data point is updated, and the value of the input
data point is greater than the value of the compare data point. The Alarm Generator
application includes many other comparison functions like this, such as Less Than, Less
Than or Equal, Greater Than or Equal, Equal, and Null. Each comparison function is
described in detail later in the chapter.
The Alarm Generator application also includes a comparison function called Limits. When
you select this comparison function, you will specify four offset limits for the Alarm
Generator. The four offset limits allow you to generate alarms based on how much the value
of the input data point exceeds, or is exceeded by, the value of the compare data point. If the
compare or input data points are updated, and the difference between their values exceeds
any of the offset limits, an alarm will be generated.
You will define a hysteresis level for each alarm offset limit when you use the Limits
comparison function. After an alarm has been generated based on an offset limit, the value of
the input data point must return to the hysteresis level defined for that offset limit before
the alarm clears, and before another alarm can be generated based on that offset limit. As a
result, the Alarm Generator will not generate an additional alarm each time the input data
point is updated after it reaches an alarm condition, but before it has returned to a normal
condition. The relationship between the offset values, hysteresis levels, and alarm data
points is described in more detail in the following sections.
All of the comparison functions have features like this that will allow you to throttle alarm
generation. You can specifiy an interval (UCPTalarmSetTime) that must elapse between
alarm generations for a data point. You can also define an interval (UCPTalarmClrTime)
that must elapse after an alarm has returned to normal status before that alarm will be
cleared. These features prevent the Alarm Generator from triggering multiple alarms each
time the input data point reaches an alarm condition.
You can optionally select up to two alarm data points for each Alarm Generator, one of type
SNVT_alarm and one of type UNVT_alarm2. The of these data points,
and of the input data point, will be updated to an alarm condition each time the Alarm
Generator generates an alarm. The alarm data points are described in more detail later in
the chapter.
You can use the Alarm Notifier application to generate e-mail messages when the alarm and
input data points are updated to alarm conditions. For more information on this, see Chapter
9, Alarm Notifier.