A dynamic reference parameter is a variation of the external reference parameter that lets you define a path to a value that is selected at run-time during execution of the algorithm. The selection is based on information not available at configuration (for example, an operator entry, a recipe parameter passed from batch control, or a run-time value of a control variable).
The best way to configure dynamic references is by using the parameter browser available in all of the expression dialogs. By selecting a parameter from the browser, you can avoid the potential of typographical errors and case sensitivity when referencing block parameters.
Dynamic references are established by assigning a parameter reference path string to the .$REF field of a dynamic reference parameter. For example, if a tank has two input valves, INLETA and INLETB, the value for the dynamic reference parameter, INLET.$REF, can be assigned the setpoint of INLET_A using a statement such as:
'INLET.$REF' := "//INLETA/SP"
Following is an example using a parameter of type string to store the parameter reference path:
'STRINGVAR.CV' := "//INLETA/SP" 'INLET.$REF' := 'STRINGVAR.CV'