SCXI Multiplexing vs parallel physical channel set up: only getting data by selecting DAQ physical channel

[alitarraf]

Hello folks,

I have an SCXI 1530 in an SCXI-1000 chassis connected to my DAQ M6251.

Issue: in both multiplexing mode and parallel mode I only get data from my pressure sensors if I choose the physical channel of the DAQ. I do not get any readings if I choose the SCXI physical channels.

This is contrary to everything I have read on forum and NI help:

http://digital.ni.com/public.nsf/allkb/6381CF37FB25733386256E5A005DAFB3
http://digital.ni.com/public.nsf/allkb/E3D3723E9D05AB4986256AA9005B5572

Anyone have any ideas why this can happen? I am getting data from selecting the DAQ physical channels, but I am concerned my data might not be accurate since everyone is saying I should pick the SCXI1530 as my physical channel source.

Thanks

Ali T.

[RichieTheBard]

Have you tried reading from the SCXI channels from a task in NI MAX, the behavior is not expected so I'd like to confirm if you are getting the same problem when making a task directly in MAX with one of the channels.

[alitarraf]

Thank you for getting back to me.

MAX test pannels are able to read from DAQ and SCXI with different values for "almost" the same pressure pertubation (my finger blocking an orifice on and off)!

Create a new task reading from SCXI is not reading anything.

Test pannel AI from DAQ

Test pannel AI from SCXI 1530

My VI

[RichieTheBard]

This sounds more like a software problem that hardware, in which first possible problem could be a problem with the DAQmx driver, have you reinstalling or updating the software.

As I mentioned it sounds like this would be mostly a sw problem but are you able to test this with any other SCXI modules it would be worth seeing if you get the same behavior. 

[alitarraf]

Unfortunately I dont have access to another SCXI.

I noticed that I have been using the SCXI 1530 a 4 channel accelerometer with a Voltage  Analog input reading, instead of an Accelerometer reading.

Do you think that is why I cant read an AI from SCXI1530/AI0, but I can from DAQ/AI0?

As an accelerometer reading I can read perfectly from SCXI/AI0. See below.

SCXI/AI0 Accelerometer reading 20psig finger closing orifice

DAQ/AI0 Voltage reading 20psig finger closing orifice