16-bit Signed Value

For some time we’ve been seeing an issue where a tag which is set up to get an integer value with “Good” quality suddenly gives up in the GUI (the label construct goes all red and the tag has a yellow exclamation mark glyph attached). Opening the tag shows that the quality has changed to “null” from “Good.”

It has been observed that this apparently happens only when the tag value exceeds 32767. The tag in question is set as an Int8 within Designer. It’s purpose is to monitor a pulse from a water meter that emits a pulse to a secondary piece of equipment that conditions it into a clock edge. Each edge translates into a couple of gallons of water volume. The tag is the keeper of this value and it accumulates just fine until it reaches that magic number then dies.

We’re using Ignition 7.6.4. There are several modules attached including a non-Inductive Automation version of SCADA. If anyone has any suggestions I’m 99.7% ears.


Where’s this value coming from? OPC? Our server or a 3rd party server? What kind of device?

Sorry for the late reply. This value is coming from a third party SCADA server connected to a different third party RTU. I get that the 16-bit value is a Modbus limit but I thought we had it dialed in for extended range.