Synchronize a Counter train pulse With an external laser trigger PCI 6602

[mem3nto]

Good evening,

I am using a PCI CARD 6602 for generate a square train pulse that is synchronize with an external laser of 1Khz (for do that i am using an external waveform generator). What i want to do with my program is to synchronize the input signal with the output and, when i want, create a delay beetween this too signal without loosing the synchronizzation.

Unfortunally right now i lose the synchronizzation, because the freqeuncy of the laser isn't exactly 1khz, it has a fluctuation that create a delay between the input and output. For fix the problem i can use the "retrigerable" option with the trigger node using a finite sample. If i do that i can not use the event case for create a delay between input  and output signal (that is a crucial staff because i want to analyze a TA signal). 

i have different question:

1) Is it a problem of the card that can not use an external clock for the syncrhonizzation, or it is possible? Because if i try to  use sample clock i don't have an output. If yes, please help me.

2) Is it possible to measure the time between two different input edge with this card? because in this way i can use this time like input for a second train pulse.

3) there is a way to use an event case with finite sample? Because the event case, in my program, will enter in a loop if i select the finite sample in the clock.

If you have any idea how to fix the problem or have idea about different program, please help me. There is my program attacked. Thank for your help and attention.

Nicolò

[DigDoug]

Hello, 

Please check out the answers and related links below.

1. You can use one of the counters as a clock with the 6602 as your clock, or read in a pulsetrain from an external clock as your source. Here are some documents that go into more detail on Clocks in NI-DAQmx and Counter Synchronization.
2. This KnowledgeBase article discusses how you can measure the time between the rising edges of two digital signals. However, unless the digital signals you want to use are low frequency, this is probably not a good option for you. The software will be much slower than the timebase clock on your 6602.
3. You could use a filter event and implement some logic will check if the sample has been collected and transition to the appropriate state.

[mem3nto]

thank you for the replay,

Right now i tried to synchronize my output signal with a 20MHzTimebase using a counter for generate it, but

i continue to lose my synchronization. I think that the problem is correleted to the CARD, because it can not

support an external trigger, Is it true? 

Because i can generate a counter output with this kind of card with an externl signal, but i can't synchronize

my countinuous pulse train with the external signal when it change his frequency. To be more precise when 

i do that i can't modificate my pulse output and i need it. 

Right now i am rotating in a circle. Please if you can help me will be great.

Thank you for your attention.

[bahannah]

mem3nto,

The PCI-6602 should be able to support external triggers, as it explicitly gives an example of when you would use an external trigger in the NI 660x User Manual. 

To make sure that I am understanding your question right, the problem is that your laser is not operating at a perfect frequency of 1kHz, which causes drifting between the laser and the PCI-6602 and you lose your synchronization.

Retriggering and setting delays can get complicated on the PCI-6602, as a lot of functionality is not configurable in hardware but can be configured in software. If I am understanding your question correctly, it seems that this forum post about changing the delay time between external triggers may be relevant to your application. 

Please let me know if I am completely misunderstanding your application, or if that information helps!

Regards,

Hannah

Applications Engineering 

National Instruments 

www.ni.com/support