Length of time from Trigger event to Acquisition

[David19]

Dear Sir/Madam,


I am using 5911 digitizer . i want to find out the length of time between the Trigger event to acquire first point of the waveform. In the experiment i 've connect the trigger source PF1 and the Channel 0 to a channel 1 output of the signal generator ,which generator generate onece pulse each time when i push the force trigger buttom.

Attached is the waveform i was captured . As u can see the wavefrom acquires before the trigger event , is that digitzer acquire before the trigger event, doesn't it ??? or Is that my program 've got some bugs??? if not how to solve the problem i want the 5911 acquire/Fetch the signal after the trigger event .

Thx

With regards

david

[Evan R]

Hi David,

After reviewing the .doc file you sent to me (tectronix scope screen capture), it appears that the signal you are sending to the trigger, and the channel 0 input are being generated from the same output.

The 5911 can be configured to collect pre and post trigger data. If it appears as though the digitizer is collecting information before the trigger, then your application is probably set to acquire pre-trigger data. This setting is known as the Reference Position in NI-Scope.

A "Reference Position" input of 0 specifies that you want
the trigger event to happen at the very beginning of your
record. This is the same as saying you want all of your
samples to occur after your trigger is received, or that
all of your samples will be post-trigger samples.

Please refer to the following knowledgebase online to learn more about reference positions and pre-triggered data.

How Do I Configure Pre-Trigger and Post-Trigger Samples Using NI-Scope?
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/1faa0cbd31a841058625697a006af474?OpenDocument

If you have any further questions, please reply with a screen capture of your application program's data so that I can better support this issue.

Best Regards!

Evan R.
Applications Engineer
National Instruments
http://www.ni.com/support

[Evan R]

Hi David,

Additionally, I have included in excerpt from the NI High Speed Digitizers help file in answer to your question regarding the length of time between the application and the acceptance of a trigger:

NI 5911 Triggering and Arming
The NI 5911 has several triggering methods. The trigger can be an analog level that is compared to the input or any of several digital inputs. You can also call a software function to trigger the device.

When you use a digital signal, that signal must be at a high TTL level for at least 40 ns before any triggers will be accepted.

Note The NI 5911 does not support delayed triggering.

Best Regards,

Evan R.
Applications Engineer
National Instruments
http://www.ni.com/support

[David19]

Dear Evan


Thx !!!


With regards

david