Switch executive wont disconnect

[lstein]

LabVIEW 2014

MAX 15.3.0f0

SCXI-1166 32 SPST card

PXI interfaced via MXI, PXI-4072 card is interface to SCXI chassis

I have my channels and routes aliased in MAX for use in TestStand. The problem I am having is that I can connect a route and any of the channels used in the route, but I cannot disconnect them unless I use the Disconnect All button. I have watched the activity in NI I/O Trace and see the disconnect message being sent using the Disconnect Single Channel button, but the switch is not opening. Clicking the Disconnect All button sends the disconnect all message and the swtich opens.

How do I get the single disconnect function to work?

[Danny_Kaps · Accepted solution]

Hello bobblob,

The SCXI 1166 is actually a SPDT card, as listed on the product page: https://www.ni.com/en-us/support/model.scxi-1166.html

With Double Throw relays, disconnecting the channel in hardware does not actually correspond to a change in physical state until you connect to the NO terminal. In general, when using DT relays, every disconnect should be immediately followed with a connect. Please reference the following document on Exclusions with SPDT relays:

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000001DdA5SAK&l=en-US

Best,

Daniel

[lstein]

Great writeup. I hadn't come across that yet in my search. Thanks for the pointer!