Error_ExpressionEval not allowing me to keep summing values

Ignition
1

I am using an expression tag to sum the value to 4 tags from 4 different PLCs. If any of the PLCs is not connected, then I get this error "Error_ExpressionEval" Which turns the cell red and doesn't keep summing the other values. Is there a way I can give a default value of zero of the value of the last tag read when one of the PLCs is not connected or turned off? This way I can continue to monitor the overall production of the other PLCs.

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2

Possibly via try, but we'd have to see your expression to be sure.

3 
if(isGood({[default]tag0}), {[default]tag0}, 0)
+
if(isGood({[default]tag1}), {[default]tag1}, 0)
+
...

Does that do what you want?

4

I will try this and see.