Issue
What is the BACnet attribute COV Increment and how to use it
Product Line
Andover Continuum
Environment
BACnet
Cause
The COV Increment attribute on a BACnet point is equivalent to the Threshold attribute of standard Continuum Infinity inputs. When a Continuum BACnet point is subscribed to by other BACnet devices using COV (Change of Value), its value must change by at least that COV Increment value before a new Value Notification will be sent out. Using this attribute will decrease network traffic especially on the MSTP network when subscribing to frequently changing values.
Resolution
This CovIncrement attribute can be set in the BACnet point's Editor on the Basic Alarms Tab.
If you have a CyberStation prior to Version 1.8, setting this value from the point editor will not stay persistent in the controller after the controller is reloaded, it will default to 0. In order to keep the value after a reload, you will need to write a PE program to set the desired value after a reload. The program should be Autostart and Fallthru.
A sample of the program is below:
Line SetCov
Writeproperty("Full Bacnet Path to Point", CovIncrement, "Desired Value")
Stop
If you have several points that need the CovIncrement set, you would just add the additional lines into this program.
In 1.8 or greater, this program is not needed as these attributes get sent to controller on a reload. Suitable initial CovIncrements still need to be added to each BACnet point however as they default to 0.
