Plotting amplitude of one spectral peak over time

Question

Hi,
    I am trying to create a VI where the DAQ continually aquires, plots and saves a waveform in millisecond timeframe (which is already done in this instance), then takes that waveform, finds a specific peak (most likely the first one), and plots the amplitude of that peak over time (30+ minutes, one point every scan that is obtained). Essentially, I have a very fast detector attached to a Gas Chromatograph, and I want to select a single ion and monitor the amplitude of that ion. I can plot the waveforms over time and do this in post processing, but what I would like to do is have the "slow" plot continuously update and display as it moves through time. Attached is the VI this will go into, using IMS Software V1.3.vi,  the subsection is the "GC Mode" it seems like I should be using the "peak detect.vi.", but I am unfamiliar with how this works, and so I do not know how to show a continuously updating graph or pull the amplitudes out and plot them. Thank you for your help,
<>< Eric
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IMS Software v1.llb ‏612 KB

Answer 1

Eric-WSU wrote:
i get an amplitude over time plot, but it does not appear until after all of the iterations have stopped
I have not looked at your VI (because I am in a previous version of LabVIEW), but this is probably because your graph is outside of the loop.
Here is how you can get a graph of the peaks (all of the peaks, per iteration):
Or if you only wanted a certain peak (and how that peak changes over many iterations):
Message Edited by Cory K on 01-21-2009 05:51 PM
Cory K
Attachments:
simple.PNG ‏3 KB
pick peak.PNG ‏7 KB