OPC String tag values go blank

Ignition
1

I have some OPC string tags that are subscribed to a Siemens S7-1500 series OPC Server. The tags are defined from a UDT and using the Default Tag Group. For some reason, the value will randomly go blank for about 0.5 seconds, then return. I have monitored the tag value directly in the PLC, and it is not doing the same, the string value remains constant. I have checked that the tag in the PLC is not being overwritten as well. I should mention that the PLC data type in the Siemens CPU is WSTRING, not sure if that makes a difference or not.

Any suggestions would be appreciated. Thanks all!

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2

I found that by changing the data type in the PLC to String resolved the problem.

1 Like
3

Thanks for the update.

If that really fixes it I'm guessing it was some quirk of the onboard OPC server and it was really sending an empty string value on occasion, rather than a UDT or tag problem on the Ignition side.