Need help with 9403 I/O and capturing time sensitive signal

[Christian6112]

Hello all,

I am fairly new to labview so anyone's help would be much appreciated.  I am using a cDAQ- 9172 and NI 9403, and I am trying to capture a time sensitive signal.  The speed of the NI 9403 (32 pin) is 7us so I think it is fast enough to capture the signals I need.  I realize there is probably another card out there that might be better and include a triggering option, but I'm hoping this card will do the job.

Goal - 

I have 8 channel programmed as inputs (to 8 different devices).  Once the NI 9403 sends out the input signal, there are two response signals that I am trying to monitor (200 ms after).  I want to use 8 channels to catch the first signal, and another 8 to capture the second.

One signal (active HIGH) - is 12-17ms long

The other (active LOW) - is only 1 ms.

As of now, I am using the DAQ assitant to select my channels.  Within my labview case, I have the first DAQ assistant send the input signal, and then directly after I have the other two DAQ assitance monitoring the outputs.  These only "see" the response signal every once in awhile (very seldom actually).  Is there anyway to trigger with this module?  Or does anyone have a tip to capture these signals?I have a feeling I am just setting it up wrong in labview, this can't be that complicated 🙂 .  Any help would be appreciated.  thanks!

-Chris

[GarPar]

Hi Chris-

     Just to clarify, it sounds like you have 8 digital outputs sending signals to your device (you called them inputs, for our purposes, we will call them digital outputs since there are signals going out of the module), and 8 digital inputs that read a response signal from your device.

     It is important to note that the 9403's 7us read time is only relevant when it is used in a compactRIO chassis where it can be controlled by the FPGA.  In the compactDAQ chassis, it is software-timed, and thus not capable of the 7us speed.  This information can be found on page 13 of the NI 9403 Operating Instructions and Specifications.

     That being said, it is going to be really tough (or impossible) to read that 1 ms pulse.  The 9403 is also a static digital IO module and is thus not capable of accessing the counters in the 9403 which could be used for triggering.  I would recommend getting a different digital IO module.

     Your best bet is to swet the digital input DAQ Assistant in its own loop with nothing else in the loop so that it can iterate as fast as possible to potentially catch that signal.  The fastest that loop will ever iterate with a DAQ assistant in it is 1-2 milliseconds.

     I hope this helps.  Best of luck with your application!