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Advice on arranging modules in a 2-chassis PXIe system

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Hello,

 

System contents

We have a system that consists of:

  • 2 PXIe-1085 chasses, connected via a PXIe-8384/PXIe-8360
  • 15 FlexRIO cards (PXIe-7962R + NI-5734), to acquire data at 10 MHz
  • 1 function generator (PXIe-5412)
  • 1 timing card (PXIe-6672)
  • Other cards (switches and low-speed I/O)

 

Use cases

  1. In one mode of operation, we need 60 FlexRIO channels to listen at all times. When any one channel exceeds the threshold, all 60 channels must be simultaneously acquired and logged to disk (i.e. every FlexRIO card must be able to trigger acquisition in in all 15 cards)
  2. In the other mode of operation, we need to generate a pulse from the PXIe-5412, and simultaneously acquire from all 60 FlexRIO channels from the instant the pulse fires.

 

Question

Essentially, we have 17 timing-sensitive cards (15 FlexRIOs + 1 function generator + 1 timing card), but only 16 cards can fit in one chassis (because 2 slots are ocupied by the embedded controller and the MXI-Exprress card). So, one of these need to be on the other chassis. The two obvious options then are:

  1. FlexRIOs plus the function generator on the 1st chassis, timing card on the 2nd chassis.
  2. FlexRIOs plus the timing card on the 1st chassis, function generator on the 2nd chassis.

 

Does it matter which option we go for? Do we get any performance benefits and/or ease of coding either way?

 

Thanks in advance!

Certified LabVIEW Developer
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Actually, I just remembered that the timing card will only improve the oscillator of the chassis it's on. So to get the high-stability clock for the FlexRIOs, the timing card needs to be on the same chassis as the FlexRIOs -- is that right?

Certified LabVIEW Developer
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Solution
Accepted by JKSH

If all you care about it the clock accuracy, there is an input on the back of the PXIe-1085 for an external 10MHz clock and an output of the 10MHz clock.  So everybody can use the same clock.

 

But you care more about triggering.  So I see two real options:

1. Put everything that must trigger each other in the same chassis.  This would mean putting the timing source in the second chassis and using the reference clock I/O on the chassis to share clocks.

2. Get a second timing module.  The module should have PFI lines so that you can share trigger signals.  I would still use the refernce clock I/O on the chassis just to make sure everybody is using the same clock.


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