How to start a task with a specified delay after a trigger using PXI-5152

[tuankietlk]

Hi everyone,

I'm using the PXI-5152 with 2 external triggers as following the sketch below:

 - The external trigger 1 (ET1) is a digital trigger which is connected to PFI 0. I want to use only the first pulse of ET1 as a start trigger to activate the data acquisition (DAQ) process (from channel 0) after X microsecond (X from 1 ms to 300 ms). The DAQ will rely on the external trigger 2 which is connected to the BNC analog external trigger.

I hope my explanation is understandable and I very appreciate if you could suggest me a solution.

Thank you very much.

Kay.

[Salazar.Slytherin]

What do you mean when you say that the DAQ device will rely on the second external trigger? It looks like you want to use the first external trigger to start data acquisition so I'm not sure what the second external trigger is for.

[tuankietlk]

Hi Slytherin,

The first rising edge of Trigger 1 just acts as a start button, and then it has no further use.

But the real DAQ process should start after that X amount of time, 100ms for example. 

That is the delay that I mentioned above.

I have tried to write this VI below, but the delay is not as I expected, sometimes it faster, sometimes is slower. 

Configurate the trigger 1, then record for null data in order to make a delay

DAQ process

 If I made a mistake somewhere or you have a better solution, please help me. 

Thank you very much.
Kay.

[Salazar.Slytherin]

Do you want that delay to be controlled by the second external trigger or do you want it to be software timed?

[tuankietlk]

I want it to be software timed. I think it is the reason while it's not stable. 

Thank you very much.

[Salazar.Slytherin]

If you want to software time and have a bounded execution time, you'll need to be using a real time operating system to have determinism.

I would look into hardware timing if the execution time needs to be more tight.