Analog Input data by Trigger, but some data before and some after the trigger

[mrBelyash]

Hello everyone!🖐

Equipment and SW:

1. LavView 2021;
2. DAQmx driver;
3. ADC NI USB 6212

I have a goal to acquire analog input data, bit it must start read data by trigger impulse. And by the trigger i want read some data before and after it. I created VI where i use DAQmx blocks:

1. For AI signal:
   • Virtual Channel;
   • Timing;
   • Start Task
   • Read
   • Clear Task
2. For trigger
   • Triggering

 Also I used Property Nodes for:

1. Timing
   • SampMode (idk really i need it btw);
   • SampPerChan (in docs this property uses in Trigger property "PretrigSamples");
2. Trigger
   • PretrigSamples

For example I put params Samples, Rate And PretrigSamples 100000, 200000 and 5000 respectively, and when I give trig impulse I get some chart. But if i change PretrigSamp to 10000, the chart doesn't any change

Pls, could yall help me and explain how to work with samples and rate and etc in LabView

[Tom_Powers]

Can you please save your example as 2019 or earlier.

[Bob_Schor]

I was able to open this VI, which was difficult to read because the Original Poster had turned off "View as Icon", which really messes up the view on the Block Diagram.  I turned View as Icon back on and tried to arrange the wires in an Easy-to-View order, which I'm posting here as a 2019 VI Snippet, and also attaching.  I've not actually done pre-triggering, so I'll defer to those who have used this feature.

Bob Schor

[mcduff · Accepted solution]

Don’t have LabVIEW on this iPad, but will assume @Bob_Schor’s snippet is correct.

I believe you are using the wrong trigger type; you need to use a reference trigger. See the following link for suggestions 

https://www.ni.com/en/support/documentation/supplemental/21/ni-daqmx-data-acquisition-triggering-tec...