external trigger analog

[steph54]

Hi,

I use  the card PCI 6251 with the connecting box BNC-2110 and Labview 8.5.1

I want to acquire an analogical signal each time that the card recieve an external trigger analog.

1) Can you confirm that I must connect the  external trigger analog on  " AO ext REF " on the box BNC-2110 ?

2) My program does one start trigger and that's it, after I have continuous acquisition but it's not triggered. I precise that I don't want use a counter (internal) to do the trigger. 

I understand that it is a basic question and I'm sorry for that and for my english.

Thank you for your help

[ramses64]

Cf attached files.
If english isn't your native language, please post on your community !;-)

Hope it helps you.
Best regards,
Vincent

Message Edité par ramses64 le 01-15-2009 04:37 AM

[steph54]

Thanh you for your help Vincent, but it doesn't work again.

I don't unterstand. 

Are you sure that we can put in a loop while a start and stop task ? Isn't it too long ?

[TCPlomp]

---

steph54 wrote:

Hi,

I use  the card PCI 6251 with the connecting box BNC-2110 and Labview 8.5.1

I want to acquire an analogical signal each time that the card recieve an external trigger analog.

1) Can you confirm that I must connect the  external trigger analog on  " AO ext REF " on the box BNC-2110 ?

2) My program does one start trigger and that's it, after I have continuous acquisition but it's not triggered. I precise that I don't want use a counter (internal) to do the trigger. 

I understand that it is a basic question and I'm sorry for that and for my english.

Thank you for your help

---

1. No most likely not, I would use something lik AI PFI1 (if available), I think that is the first digital input (TTL).

The way your VI is setup (from the first post) is good!

Ton

[steph54]

Thank you for your help Ton.

Please, I need some precision.

It's right that with the VI of the first post it works when external analog trigger is plugged on  " AO ext REF " on the box BNC-2110 and in continuous mode.

1 ) Why it does'nt work in finite mode ?

2 ) I think that trigger works only one time ( to start acquisition ) but  I would like  that analog trigger work all the time, I mean that each time the level of the analog trigger is "ok" , I have an acquisition of X samples.

I hope that I was clear.

Stéphane. 

[TCPlomp]

Infinite mode let's you get a set number of samples. What happens in a loop:

1. You read sample 0-0.5 seconds (timewise)
2. You process data (takes .1 second)
3. You read data (0.6-1.1 second)

You have a gap.

Continous mode:

1. You read sample 0-0.5 seconds (timewise)
2. You process data (takes .1 second)
3. You read data (0.5-1 seconds) because DAQmx has buffered the data

Just make sure you process the data quick enough to prevent a buffer overflow.

Multiple (external) triggers is something I haven't tried, but there are examples in the examples list, I think they use a counter somehow.

Ton

[steph54]

Well, I'm lost.

For multiple trigger in the examples list, the counter need to be link to a digital trigger ( that's logic ) and the problem for me is that my trigger is analogical.

thanks a lot.

stéphane