Start and stop data saving while running the vi

Question

Hi everybody!
Maybe someone can help me on this topic:
I
would like to run a vi which displays voltage values on a waveform graph without saving the values automatically. But - while running the vi - I would like to have the option to
save the data. That's why I created a switch (on: save data, off: don't
save data). I wanted to wire the switch to a case structure, but I
don't know where to put the case structure and the "open/create
file-vi". If I put both into the while loop (where I write the data to
the spreadsheet file) then - of course - it asks me with every run of
the loop where to save the data.
If I put the "open/create file-vi"
outside the loop it asks me at the beginning of the application where
to save the data, even though I maybe don't want to save data.
I don't know if it's understandable what I mean:
If
I run then vi I would like to see the data without saving it first
(on the waveform graph), then I maybe would like to save it, so I
want to press a button to save the data. The vi should ask me where I
want to save the data while still running. I would also like to stop
saving data without stopping the run of the vi. Maybe I would like to
save data to another file within the same run.
Do you know what I mean?
Thank you very much.
Kind regards,
Steffi

Answer 1

Hi Steffi,
your first solution was ok as long as you don't restart the vi without removing it from memory before.
When loading the vi into memory the shift register (SR) is reset to zero and is keeping the value from last iteration.
Now you initialized the SR in each iteration to zero, hence the 0-0.250 range of the time scale. To keep the last value you can use another SR as shown in the attachment or use some math based on the iteration count (start time= i * 0.25).
You should only learn from this: initializing SRs makes your vi more reliable... A SR is nothing more than a variable in text based languages, so keep them initialized!
Message Edited by GerdW on 11-07-2007 01:27 PM
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome
Attachments:
ekg2_mod.vi ‏394 KB