Alarm values from LonWorks units in TAC Vista

Alarm values from LonWorks units in TAC Vista


Alarm values from LonWorks units in TAC Vista

Product Line

TAC Vista


  • Vista Workstation
  • LON devices
  • ASCs
  • Xenta 102-AX, Xenta 104-A, Xenta 121


Vista Workstation alarm objects can be used to monitor SNVT values from LON devices and alert the user when a value has gone outside of acceptable limits. For example, An alarm in TAC Vista if the nviSetpoint of a Xenta 104-A goes over 75ºF.

This could also be used on programmable controllers -- any point in the database -- to avoid having to make Menta programming changes in order to alarm a point.

The only issue with a Vista Server Change of state object is that the Vista Server will need to be running in order for the alarm to be received and actioned. 

If multiple change of state objects are to be used consideration must be taken into the interface type as these points will be polled every second to check the state so actions can be taken on an alarm condition. This can easily overload a Lonworks interface if it is already managing lots of messages. 


  1. Create an object of the type "Change of state Dynamic SNVT"
  2. Right-click and go to properties. Click on the ALARM tab.
  3. Type in the alarm text for the Alarm.
  4. In this case, the alarm triggers if the temperature is over 75°F, so set the High limit to 75.
  5. Go to the Object tab and browse in the point that you want to monitor.
  6. In reference property select value. Click ok
  7. Go to the monitored point, right-click and select properties, change the watch setting to "watch"
Tags (2)
Labels (1)
No ratings