Configure state alarms
- Last UpdatedDec 17, 2024
- 3 minute read
A state alarm set on an attribute of Boolean data type corresponds to a discrete tag with two possible states. When you create a state alarm, you configure whether the active alarm state corresponds to the TRUE or FALSE state of the attribute.
You can set an alarm category. Valid categories are:
|
Category |
Description |
|
Discrete |
A discrete value event or alarm, such as a change of state. |
|
Value LoLo |
A continuous value is significantly below the acceptable range. |
|
Value Lo |
A continuous value is below or is approaching the low acceptable range. |
|
Value Hi |
A continuous value is above or approaching above the high acceptable range. |
|
Value HiHi |
A continuous value is significantly above the acceptable range. |
|
DeviationMinor |
A value has a minor deviation (plus or minus) from the target or setpoint. |
|
DeviationMajor |
A value has a major deviation (plus or minus) from the target or setpoint. |
|
ROC Lo |
The rate of change for a value is too slow. |
|
ROC Hi |
The rate of change for a value is too fast. |
|
SPC |
A value deviates from the SPC target/range. |
|
Process |
An alarm or event associated with the physical process/plant has occurred. |
|
System |
An alarm or event associated with the automation system has occurred. |
|
Batch |
An alarm or event associated with a batch process has occurred. |
|
Software |
An alarm or event associated with a software operation or logic (such as divide by zero in script) has occurred. |
You can set an alarm message and Priority for a state alarm. The time deadband sets the length of time that an attribute value must continuously remain in an alarm or unalarmed state. The time deadband filters out rapid, transitory value spikes.
The timestamp when a state alarm becomes active or inactive is the most current timestamp of the corresponding input value. If there is no timestamp associated with the alarmed value, the AppEngine timestamp is used instead.
You can only configure an external alarm source for use with Historian Clients, not InTouch clients.
To get the alarm history records for an externally detected alarm (from within a PLC), create a reference to the source_processvariable property, as follows:
-
Create a boolean user-defined attribute.
-
Enable I/O and State Alarm features for the boolean.
-
Bind the IO feature for the boolean to a tag in the PLC.
-
Set the I/O to read the PLC alarm bit where the alarm is being detected in the PLC. Note that there is nothing in the boolean attribute definition to indicate it represents an alarm associated with another attribute (like a “.PV” attribute).
-
To establish the alarm association, associate the boolean (created in step 1) with another attribute. At runtime, this association will set the “source_processvariable” in the alarm history event. This allows clients of History Event and Alarms records to correlate externally detected alarms with the attributes against which they are being reported.
See the sample configuration, below, for additional details.
Sample external alarm source configuration
Attribute Name: Pump001.PV
Type: Boolean
IO: Enabled
Points to a tag within the PLC.
State Alarm: Enabled
Alarm For Attribute: me.Pump001.PV
Attribute Name: Pump.PV.Hi
Type: Boolean:
IO: Enabled:
Points to an alarm tag in the PLC.
This tag will be true if there is a high alarm generated by Pump.PV.
State Alarm: Enabled
Alarm For Attribute: me.Pump001.PV
Attribute Name: Pump.PV.HiHi
Type: Boolean:
IO: Enabled:
Points to an alarm tag in the PLC.
This tag will be true if a high-high alarm is generated by Pump.PV.
State Alarm: Enabled
Alarm For Attribute: me.Pump001.PV