using two scxi filter modules

[fabrizioITA]

I need to filter 8 channels and acquire other 8 channels in differential mode using a single DAQ board (16Ch SE).
I have two SCXI modules: 1141 and 1142, is it possible to connect them in 8+8 differential input configuration (parallel mode)?
The problem now is that both the modules use the channels 0-7 of the DAQ bus, leaving unused the remaining 8-15!
I also have the 1346 and 1180 accessories, are they useful?

thanks

[AlessioD]

Hi,

the configuration you are trying to implement is not supported.
When you configure an SCXI module in parallel mode (provided it supports this operation mode) all the channels aboard your DAQ device are used, since the channels are differential and they use up 2 single-ended channels.
There is no possibility of using 16 channels in parallel on the same DAQ Board, you need to have 2 DAQ boards.

With this being said, even this would not allow you for simultaneous inputs on the DAQ Channels.
It does not make any difference between having 16 channels multiplexed by the SCXI bus on a single DAQ channel and 16 channels multiplexed on the DAQ board. It is still multiplexing.

Regards,

AlessioD
National Instruments

[fabrizioITA]

You are right, but...
I need to use matlab, where multiplexing is not supported. The perfect solution should be using two modules in parallel mode, which is trasparent to matlab: matlab must only acquire the voltages on pin 0:15 which are provided by the modules.
The main problem is that each filter module, which is equipped with intrumental amplifier, routes the outputs (+) on pins 0:7 and the corresponded references (-) on pins 8:15. But the te references are all grounded! so why cannot I disconnect the references from pins 8:15 and route them all on AIGND?? in this way I could use only the first 8 channels of the daq in SE configuration, leaving free the remaining 8. In addition I could connect the channels of the second filter module on the pins 8:15 and route their references again on AIGND. To do it I should modify the daq connector phisically.

P.S. from Labview I can measure channels 0:15 in SE mode only if I don't use the daq A/D as a controller for SCXI modules in MAX configuration. In that way I can measure 16 channels in SE configuration in matlab.

thanks

[AlessioD]

Well,
if you are not using the DAQ functions to access SCXI then I don't know how to help you further in what you are trying to do since it seems to be something not supported.
Best Regards,

AlessioD
National Instruments