Ok to mix "Switch Connect" and "Switch Close Relays"?

[GSinMN]

Hello All,

  I am developing a test sequence that uses the 2527 multiplexer card to route signals.  To configure the card, I am using the DAQmx Switches functions.  In my particular application, I have a subVI routine that imports configuration data from a spreadsheet, and runs a for loop to set the configuration for each step (each iteration of the loop contains channel information for the 2527 card).  The topology is set on the first iteration, along with the path configuration for the first channel. 

  My concern is this:  I need to close additional channels/relays without changing the topology or resetting the device.  In the first iteration, I use the "Switch Connect" function to set the initial path, (ch0 to com0 for example).  Then in subsequent iterations of the loop, I use the "Switch Close Relays" function to close additional channels individually (k2 for example).  At the end, when the measurement is made, both ch0 and ch2 must be closed, and routed to com0.  So is this implementation safe, or am I somehow effecting the settings from the initial loop? 

  I would test this with the hardware, but it is not yet available. 

  Also, I realize that I could use the independent topology, and configure all of the relays individually for every step, but I am hoping my approach will be easier and safer.

Please advise.  Thanks.

GSinMN     

[LindyHop]

Hello GSinMN,

I simulated a 2527 (which you can do throught NI MAX) and I was able to use a preconfigured topology like 64x1 and still manually close relays so that in the end I would have had Ch1 and Ch2 connected to Com0 so I'm fairly certain you'll be able to do what you're looking for. 

[Jarrod_J · Accepted solution]

Hello GSinMN,

It's OK to mix "Switch Connect" and "Switch Close Relays" if you understand what is happening underneath. "Switch Connect" connects two channels by closing a path of relays between the channels, then "Switch Close Relays" can be used to change the state of individual relays. If you aren't careful you can mess up your channel connection by toggling relays that are part of the path connecting your channels.

"Also, I realize that I could use the independent topology, and configure all of the relays individually for every step, but I am hoping my approach will be easier and safer."

I would recommend the independent topology if you want to stick with channel connections only. http://zone.ni.com/reference/en-XX/help/375472G-01/switch/2527_independent/

Initial connections:

ch0->pcom0

pcom0plus->icom0plus

pcom0minus->icom0minus

icom0->com0

In each future iteration just connect the next channel to pcom0 (which will indirectly connect it to com0):

ch1->pcom0

ch2->pcom0

...

...

Jarrod

[GSinMN]

Hello All,

  Thanks for the responses.  Looks like I should be on the right track.  One clarification though:  What exactly is the purpose of the "Scan" feature?  It is unclear to me if I need to setup a scan list and commit the scan, or if I can simply use the "connect channel" and "relay control" functions.  Please advise.  Thanks.

GSinMN  

[LindyHop]

Hello GSinMN,

Creating a scan list lets you quickly import the settings you want to transition the channels on your device. However, it does not allow you to access the relays so for your application it won't serve you any use. If you'd like some further details about using scan and some examples, check this link out.

[GSinMN]

Thanks for the clarification, Jonathan.  Glad to know I can ignore those functions to avoid confusion.

GSinMN