Measuring Velocity with Digital Input

Question

I am not very familiar with digital inputs and so am having trouble picturing this system. I will be starting from scratch but will have PXI chassis' available. I will have about 381 events. Event 1 will trigger acquisition, and over the next 10 - 20 ms, I need to capture the next 380 events. I don't need to know how long each event stays high, only the time in relation to the first event. I would like to catch any event that stays high for at least 1 microsecond.
Since it will require multiple chassis, I think I will just wire Event 1 to each chassis and so shouldn't have to worry about any syncing problems? A colleague has been looking at PXIe-6544 and 6545, but I'm not sure this is the right tool, and hoping there is a less costly alternative.
Hopefully someone can give me a kickstart in the right direction.

Answer 1

Hi Deskpilot,
If you're looking at separate lines, then my previous idea would not scale so well (each X Series card only has 4 counters).  I like the idea of using an R Series board to do this and would suggest posting over at the Real Time Measurement and Control forum to double-check the feasibility. 
If you had to do this with M/X Series boards, then the more efficient solution would be to use the Digital Inputs instead of counters.  The R Series should be more elegant but I thought I would type up the suggestion for M/X Series anyway:
We have a few M/X Series Boards that have 32 clocked digital lines (48 digital lines total, but only 32 support HW timing).  Depending on the board selection, you could sample the digital lines at 1 MHz (PXI 6224,  PXIe 6323) or 10 MHz (PXI 6254, PXIe 6353).  Then, in software you could determine which sample the rising edge occurs on and use this to timestamp when the event occurs.  The two options would respectively give you 1us or 100 ns resolution.  
The X Series (623x) cards have built-in timing and triggering for the digital lines.  The M Series cards (622x) need to take in the clock from another source (you can use a Counter Output to create a 1 MHz or 10 MHz clock which can be triggered by your first event).
At 381 lines you'd require 12 boards.  Each board requires 2 terminal blocks for access to all of the lines.
Again, I recommend looking into the R Series board for your task, I just wanted to post another solution in case somebody comes along with a similar issue but with a few less lines.
Best Regards,
John Passiak