High speed acquisition across multiple PXI modules

[rgehmlich]

Hi, 

I am fairly new to Labview and trying to develop my first application that uses triggering across multiple devices.  I will try to explain in detail what I am trying to do, and I could really use some help trying to figure it out.  I have 2 weeks to make this work and my efforts over the phone with NI engineers have been helpful, but the response time has been slow.

I am trying to acquire:

1.  Ultrasonic sound data (simple voltage readings at a rate of 250 kHz)

2.  Encoder data from two encoders synchronized with the sound data

3.  Thermocouple data at 100 Hz (but synchronized with the sound data)

4.  In the future, I'd like to be able to read 5 other voltage signals at the same rate as the thermocouple data.

To accomplish this, I have the following hardware:

PXI-1052 chassis

Slot 1:  PXI-8310 controller for laptop

Slot 2:  PXI-6602 counter card for encoder measurements

Slot 3:  PXI-6251 card for measuring sound (voltage) at 250 kHz

Slot 4:  PXI-6250 card for measuring thermocouple and other voltage signals

SCXI Slot 1:  SCXI-1102C card for measuring thermocouple readings

I am using Labview 8.0 and MAX 4.0 with Windows XP. 

I am looking for help mainly in routing terminals for triggering.  I would like all my tasks to start at exactly the same time and sample using the same hardware sample clock.  I am getting errors like -89125 and -89126 which both have to do with triggers that are either already in use or routes that are not supported.  I have 2 weeks to come up with a simple program that can acquire a minute's worth of data at this rate, and I am having a hard time getting it to work.  I trying to use a singel pulse counter output generated from the 6251 as the digital edge that starts the acquisition for all the modules.  Right now I am only trying to acquire the data; next week I need to figure out how to write it all to a file after the acquisition is complete (which may be interesting because there are two different sample rates, but they have to be synchronized in time). 

Thanks for any suggestions!  I am posting the vi and my MAX configuration.

[Jesse_O]

Hello,

I have taken a look at your code, and from your explanation it might be over complicated.  I have modified a shipping example that you can use to synchronize two devices.  In order to use this example you must have your PXI chassis configured in MAX.  The routing is done automatically, and you do not need to have another task to generate a start trigger.  Instead you can use the start trigger signal from the last task you start to trigger your other tasks. 

The example I am posting is for two devices, however you could easily expand this for a third device.  I hope you find this code easier to understand to help you build the rest of your program.

Regards,

Jesse O.
Applications Engineering
National Instruments