Thanks again for you quick reply.
I confirm that PV_Path is data type String; the value source is expression.
I have updated the expression to get the value that you indicated:
"tag('"+ {[.]TankPath} + "/" + {[.]Probe} + "/01_Inputs/PV')"
PV_Path.value = tag('[default]Probes/Probe1/01_Inputs/PV')
I confirm that:
PV in the CoolTank _UDT is data type Float and value source Reference
PV in the probe type is data type Float and value source Memory
If I hardcode the Source Tag Path to PV in the CoolTank_UDT:
[default]Probes/Probe1/01_Inputs/PV
it works:
I don't know it doesn't work when I add the string value from PV_Path