how to save dynamic data to a spreadsheet with only two columns

[steffi.kono]

Hi,

I have a problem with saving dynamic data to a spreadsheet file. I want to save voltage values every second for example. So I would like to have a spreadsheet file afterwards with two coulmns, one for the time values and one for the voltage values. Maybe you could have a look at my attached vi? In the way I did it I get a spreadsheet file with voltage values placed all over the screen and I don't get what the order is, but I don't know why.

I also tried it with the open file, write to file and close file vi's, but then I get files which I can't read afterwards??

Maybe you can help me. That would be great!

Thanks a lot!

[chilly_charly]

If you wire a TRUE to the transpose input of write to spreadsheet, you'll get a single column file. That will not solve your problem entirely since you lack the time column.

For that you'll need some programmation : get the t0 and deltaT values from your waveform data, then calculate all the time values, and concatenate  with the signal values before feeding the write to spreadsheet subvi.

[steffi.kono]

Hi CC,

thank you very much for your help. To transpose the matrix makes sense, thank you!!

But do you know how exactly to get the t0 and delt T from the waveform? Is there a special VI for it? And how do I exactly concatenate it, so that I get the correct value for the according time? Shall I merge the signals? Maybe you can add an example? That would be really great!

I'm sorry, this stuff is new for me...

THANKS!

Steffi

[chilly_charly]

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steffi.kono a écrit: ... But do you know how exactly to get the t0 and delt T from the waveform? Is there a special VI for it? And how do I exactly concatenate it, so that I get the correct value for the according time? Shall I merge the signals? Maybe you can add an example? That would be really great!

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Should be the "Get Wfm comp" function in the waveform subpalette. Get t0 and delta t, then calculate all the t values in a loop as t(i)= t0 + deltat * i. Use the Build array function  (in the array sub-palette) to associate the time and signal value.

[chilly_charly]

I hope this can work...

Message Edité par chilly charly le 11-02-2007 02:31 PM

[steffi.kono]

Hi CC,

thank you very much, it helped a lot! Now I get the data the way I wanted to.

Maybe I can ask you another question:
Do you know how I can write a header to the spreadsheet file? If I use the "write to file"-vi, there is a boolean constant for the header. But I don't find it for the spreadsheet file.
I would like to have a header at the beginning of every test, means when I append data to an existing file, too.

THANK YOU!!
Steffi

[chilly_charly]

Outside the while loop, insert a write operation after the open/create file. Or replace it. Use the write character to file vi. It accepts a string as input. Use the tab separator to separate the columns, and return for the lines.

A nice operator is the Array to Spreadsheet string (in the string subpalette)

`

Message Edité par chilly charly le 11-05-2007 11:43 AM

[steffi.kono]

Thanks a lot, CC!

Do you also know how to save the data with a "." instead of a ","? For example 3 Volts and 100mV: LabVIEW saves the value as 3,1V. I would like to have it as 3.1V.

Steffi

[steffi.kono]

Hi CC,

got another problem:

I would like to run the vi which you already know ; ) without saving data. But - while running the vi - I would like to have the option to save teh 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 (e.g. 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

[chilly_charly]

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steffi.kono a écrit: ... I would like to run the vi which you already know ; ) without saving data. But - while running the vi - I would like to have the option to save teh 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 (e.g. 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?

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Not sure 😄

There are probably several ways to deal with this problem : I believe the simplest would be to use an uninitialized shift register to store the pathname. That way, on the first access only, the write.vi will ask for a file name.

There is also a "First call"function, that could be used to detect the first run, in the data communication>Synchronization subpalette.

I think the point/comma question can be solved at system level, by changing the numeric separator in Windows