Alarm and event types and buffered data

Data Change Event

Application (data change) Events have the following fields:

• Event type – data change (historized)

• Timestamp – date/time of event (historized)

  When Log Event is checked for the buffered data-enabled attribute, a data change event will be reported for every VTQ in the attribute's buffer property.

Limit Alarm

The limit alarm can provide a buffer of alarms on an attribute with buffered data enabled.

If the base attribute has an associated Buffer property, then the limit alarm calculation is performed for each VTQ in the buffer. This results in a buffer of Boolean alarm conditions with associated time of the VTQ matching the times of the VTQ in input buffer, which is stored in the respective condition attribute’s buffer property.

The order of the condition buffer matches the order of the input buffer. The respective condition value and time reflects the last VTQ in the input buffer.

Value Deadband: If value deadband is configured for limit alarms, then the alarm condition is calculated using VTQs in the input buffer. All VTQs in the buffer are processed. Value deadband is used during execution.

Time Deadband: If time deadband is configured for limit alarms, when the alarm condition is met, the duration of the condition is calculated using the VTQs in the input buffer. If the last condition change remains undecided until the end of processing the current buffer, then a late decision will be made when the next input buffer is processed. If no more input buffer is received, the last alarm condition change is reported when the time deadband has elapsed as engine time.

The time deadband is applied only to the On Rise event of the alarm state. It is not applied when the alarm state falls outside the limit condition.

State Alarm

The state alarm can provide a buffer of alarms on a Boolean attribute when buffered data is enabled.

If the base attribute has an associated Buffer property, then the state alarm calculation is performed for each VTQ in the input buffer. This results in a buffer of Boolean alarm conditions with associated time of the VTQ matching the times of the VTQ in input buffer, which is stored in the respective Condition attribute’s buffer property.

The order of the condition buffer matches the order of the input buffer. The respective condition value and time reflects the last VTQ in the input buffer.

Rate of Change Alarm

If the input has an associated Buffer property, then the Rate of Change (ROC) calculation is performed for each VTQ in the input buffer. Interval is calculated using the difference of two successive VTQs. These calculations result in an array of Boolean alarm conditions with associated timestamps which are stored in the buffer property of the respective condition alarm attribute. The condition value reflects the last VTQ in the respective condition buffer.

Deviation Alarm

If buffered data is enabled for a deviation alarm’s attributes, buffered data is also enabled on the configured condition attributes Dev.Minor.Condition or Dev.Major.Condition or both.

When buffered data is enabled on a deviation alarm’s attributes and the AppEngine goes Off Scan, the buffers for the configured condition attributes, Dev.Minor.Condition or Dev.Major.Condition or both, are cleared of all VTQs.

If the input has an associated Buffer property, then the deviation calculation is performed for each VTQ in the input buffer. These calculations result in an array of Boolean alarm conditions and associated timestamps which are stored in the buffer property of the respective condition alarm attribute. The condition value reflects the last VTQ in the respective Condition buffer.