Hi Neuvos,
I'm trying to understand the problem clearly in order to provide proper advice.
The first thing is to understand the constraints..
What do you mean by "specified length of sample"? Do you mean time (ex. 3 sec) or filesize, or something else? It looks like you mean time.
If your vi runs in the background waiting for you to press the "Store" button, then it proceeds to save samples for 3 seconds (continuously), then you can implement something like this:
If you run this for a single event:
Have a loop which monitors for the "store button" action. For instance it can be a while loop which stops when the button is pressed. The vi then goes to another while loop which is initialized by a timestamp and runs until timestamp = timestamp + 3 sec. In this same while loop, you can also initialize a shift register which acts as a buffer for the incoming data. You combine (add) the new data to that from the previous loop by using the appropriate function (concatenate string, build array, etc). When the loop ends, you do what you want to do with the output of the shift register (save to file, etc).
If you run it for multiple events, you could combine the second while loop within the first one.
I'm sure you get the idea.
The above assumes that the length of data was based on time constraints. You can change the constraint by using another constraint to the conditional terminal (loop condition).
The reason I split the single and multiple event is because it looks like you want to change scanrates, etc when running the vi. If that is the case, then you may want to place either a Case Structure that is true if a certain amount of time has elapsed. Within this Case Structure, you can change the instrument settings. This can be inside the second while loop which saves the data.
You also mention "buffer size". If that was the constraint, then replace all refernce to time by buffer size. You can get the size of the data within the second while loop and use that as a condition for loop or for the case structure to change the instrument settings.
Hope this helps...
JLV
