In general, this error indicates that you have connected a refnum of one type to a refnum of another type and both types are members of some class hierarchy, but there is neither a simple up cast nor type cast between the two classes. Examples of class hierarchies are VI Server hierarchy and DAQmx refnum hierarchy. You might encounter this error when wiring VISA resource references or VI Server references. VI Server references include application references, untyped VI references, strictly typed VI references, VI Server references, and LabVIEW classes.
If you are wiring VISA refnums, this error means that you have wired two VISA sessions together whose classes do not match, or that the function to which you have wired the VISA session does not accept sessions of the given class.
To correct this error, change the VISA class of the signal input or output terminals to match. You can change the VISA session class of any front panel control or indicator by right-clicking the control or indicator and selecting Select VISA Class from the shortcut menu. If both ends of the signal are wired to functions, you have to break the wire and choose a different function for either input or output.
If you are wiring a VI Server refnum, this error means that you have wired two different types of VI Server references together, or you have wired a VI Server reference to a function that does not accept the server class of the reference.
For example, in the following illustration, an application reference has been wired to a Call By Reference node. However, Call By Reference nodes accept only strictly typed VI references.
To correct this error, right-click the refnum control and select Select VI Server Class from the shortcut menu to select the appropriate class. After selecting the class for this example, make it a strictly typed VI refnum by dragging the connector pane from the block diagram of the VI to the VI refnum control or right-clicking the VI refnum control and selecting Select VI Server Class»Strictly Typed VIs from the shortcut menu. When you resolve the class conflict, the wire appears solid.
The class conflict error also can occur for the following reasons:
To correct this error, change the target class to a data type compatible with the reference.