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Switch Executive "Disconnect" or "Disconnect All" Violates Exclusions with SPDT Relay Modules

Primary Software: Switch Executive
Primary Software Version: 1.0
Primary Software Fixed Version: N/A
Secondary Software: N/A
Hardware: Switches>>General-Purpose>>PXI-2566, Switches>>General-Purpose>>PXI-2558, Switches>>General-Purpose>>PXI-2559, Switches>>General-Purpose>>PXI-2549

Problem:
If I make an explicit call to disconnect COM from either NC or NO using the niSE Disconnect VI, NI Switch Executive updates the software connection state such that COM connects neither to NC nor NO, but when I test the hardware it has not disconnected from where I had it previously connected.

Solution:
For switch devices with SPDT (single-pole double-throw) or Form C relays, a physical connection always exists between the common (COM) and normally open (NO) or normally closed (NC) channels. In some cases, the IVI switch driver may not reflect that connection. The following excerpt has been taken from an updated version of the NI Switch Executive Help.

 

Form C Relay

If an explicit call is made to connect COM to either NC or NO using the niSE Connect VI, NI Switch Executive verifies that there are no exclusion conflicts, makes the hardware connection, and updates the software connection state.

If an explicit call is made to disconnect COM from either NC or NO using the niSE Disconnect VI, NI Switch Executive updates the software connection state such that COM connects neither to NC nor NO, but does not change the hardware connection. Thus, the software state no longer reflects the hardware connection, and verification of exclusion conflicts might be inaccurate. In order to accurately reflect the hardware connection in the software state after using the niSE Disconnect VI, you must then connect either NC or NO to COM using the niSE Connect VI.

If an explicit call is made using the niSE Disconnect All VI, NI Switch Executive connects NC to COM for every relay but does not reflect this change in the software state. Thus, verification of exclusion conflicts might be inaccurate. To reflect this change in the software state, you must then connect NC to COM using the niSE Connect VI.



Related Links:

Products and Services: Switch Executive
Products and Services: Switches



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Report Date: 12/16/2008
Last Updated: 12/16/2008
Document ID: 4SFB1OSL

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