Occasionally we loose connectivity to a device that is being recorded in a SQL database. I would like to alarm based off of getting a null value returned in a tag. Is this possible?
From my test, when a device lost connection to Gateway, the tags from that device tend to keep the last known value instead of updating to ‘null’. So I think configuring an alarm using
Bad Quality Mode might be more accurate in your case as the tag quality will be updated once the device lost connection. See more information in our User Manual: Configuring Alarms - Ignition User Manual 8.1 - Ignition Documentation
Tag Alarm Properties - Ignition User Manual 8.1 - Ignition Documentation