Hello chenjy,
In the future, it is recommended that you post your questions to the NI VeriStand Discussion Forum instead of this location. The NI VeriStand Discussion Forum serves as a platform for support from VeriStand users. In addition, the NI VeriStand Add Ons each have their own individual discussion pages that are specific to the add on itself so this forum that you have posted to is not used.
To answer your question, you can treat the signal like a channel and use the IWorkspace2 GetSingleChannelValue method with the correct signal path to view the current value of that signal.
Thank you,
Lynn
National Instruments
Senior Systems Engineer