Collect one sample at a time.

This seems like it ought to be incredibly simple, but I am brand new to labview...
I am acquiring data at a given rate (between 10 and 100 Hz) for the purpose of the read outs in my vi.
What I would like to do is set up the DAQ and the experiement and run it, monitoring at all times my critical variables on gauges, etc.  Then when I have reached the information I need, I would like to click and button and record a single sample.  I would even take just a few samples.
The way I have attempted to do this now is to briefly enable a relay between the signal source and the Write to Measurment File vi.   This kind of works, as long as my sampling rate is low.  With high sample rates (1000 Hz) I end up with a few thousand data points, when all I need is one.
Thus the question:  How do I take a snapshot of my data?

I've seen that Express VI before.  I never use that one because it's useless.  All it is is a fancy wrapper for a very basic True/False Case structure.
What is the mechanical action of that button?  By the picture of the icon, I'm going to guess it is its default value of switched.  That should be Latched action.  With Switch action, you have to click it on and click it off.  At a fast rate, the loop may execute several times while it is True.
Since we are looking at Express VI's, the Write to File function as an Enable input that you can wire the button into.
Message Edited by Ravens Fan on 08-27-2009 05:10 PM
Attachments:
Example.png ‏76 KB

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