Problem with TTL trigger

[Travis-E]

Hello Oleks,

We have to make sure you are using the correct reference for your signal. You said you are connecting the CTR 0 OUT signal to the Oscilloscope but you also need to make sure you are connecting the negative portion of the scope probe to the ground of the BNC-2110. You can use the DGND pin the is in the same bank as the CTR 0 Out signal.

Regards,

-Travis E

[Oleks]

Hi Travis,

Thank you very much! I'll give it a try tomorrow in the lab. Just out of curiosity, if the reference is not correct can it lead to both Low/High pulse from CTR0 OUT rather then just High?

[Travis-E]

Hey Oleks,

If the ground of your oscilloscope is different from the ground of the our device then both the high and low signals will be affected.

Regards,

-Travis E

[Oleks]

Hi Travis,

I found the problem today. The scope was set to AC coupling instead of DC coupling... I switched it back to DC and everything looks and works correct now.

Thanks for your help!!!

[bsunny]

Hello Oleks/Travis

I am currently trying out to do the same task (phase locking) as described by the vi that u have posted. I am really greatful for that. The code generates a TTL at each zero crossing of the sine wave. What if i want to have other locking phase angels (such as 45, 90 dergees etc) ? Please guide me as to how to modify the VI. Thanks in advance.

[bsunny]

Hello again Oleks/Travis

I am unable to apply corrections that Travis suggested to the second VI uploaded (Zero_crossing_AI.vi 50 KB). I have added a DAQmx control task vi as suggested but i don't know how to "start the task in the true state in order to have it pick up again" as quoted by Travis.

It may be trivial but i am not able to figure it out.

Pl help.

[Burrito]

Hi bsunny,

In the VI you linked, there is a boolean which controls whether the program enters a "true" case statement or a "false" case statement. In the "true" case, you need to place a Start Task.vi to restart the task.

[bsunny]

Thank u very much Burrito.I will look into it. Another thing is how do i start a trigger at various phase angles of a sine wave?

[Oleks]

Hi bsunny,

In the code that I was using in this thread, there is a DAQmx Create Channel.vi, to which counter channel is connected. In that VI, you can wire an "Initial Delay"(see contex help, Ctrl+H). You can use initial delay to set which phase you are trigering at.

Hope that helps