Setting Up BACnet Trends and Historical Alarms

You can enable and configure historical alarms and trends in the channel settings. All devices grouped under that channel inherit the settings from the channel configuration. If needed, you can override these settings on individual devices. Learn how

To enable logging historical alarms and trends on a channel:

  1. Open Workbench and in the Project Explorer pane, expand your project > Data Connectivity > BACnet > Channels.
  2. Double-click the desired channel to display the settings.
  3. On the General tab in the History Settings section, select the Enable Trends checkbox to collect trend data, and then select the Enable Historical Alarms checkbox to log past alarms.

  4. In Read Range Type, specify which parameter of the history values is used to determine the starting point of the reading. In the options containing two different read range types (for example Time, Sequence Number), the first type is used for the initial reading and the second one for all subsequent readings.

    • Time: Starts reading from the oldest previously unread value based on their timestamps.
    • Sequence Number: Starts reading from the item with the lowest unread sequence number (if these are supported by the device/trend log object).

    • Buffer Position: Starts reading the buffer from the position specified by the reference index.

      Since the other methods have better optimalization, we do not recommend this option.

  5. In Initial Read Count, set the requested number of values to be read from the object. If the response is too big, this initial count is halved. It may repeat until the response reaches a size that can be processed by both sides. The calculated count is then used for all following reads.

  6. In History Service Type, select one of the options from the drop-down list:

    • Automatic: Uses event notifications if they are supported by the device and configured. Otherwise, it falls back to polling.
    • Event Notifications: Does not read new values until receiving an event notification from the device.
    • Polling: Reads new values periodically at the interval set in the History Polling Period.
  7. In History Polling Period, specify the time interval for reading the data when polling is used.
  8. Select the Log Good Samples Only checkbox if you do not want to collect values that are evaluated as bad, and then click Apply.

What's Next?