lvm time column negative value

[oliD]

Hi,

I have made a simple data logger to write temperature and pressure values to a lvm file using the write lvm express vi in labview 7. I works ok but the time column in the lvm file does not start at zero but begins with a negative value. There is a difference between the time stamp in the header and the time at the top of each of the columns I am logging which appears to be resposible for the problem. Any ideas how I can solve this.

Cheers,

Oli

[Sarah_Coleman_NIUK]

Hi Oli,

Could you attach your code and some steps to reproduce this as I'm not seeing the same behaviour on my system.

[oliD]

Hi Sarah,

Here is the code. It happens every time i write data to the lvm file. Also tried logging a simulated waveform in the same way and it works fine. Probably a really simple explaination but this is the first time I've used labview so I can't find it.

Oli

[Sarah_Coleman_NIUK]

Hi Oli,

I've had a look at this and am seeing the same behaviour as yourself. I've looked into why this is happening and I think it has something to do with the way the express VI converts data before writing it to file.

When I test this, the time data starts at 0 when I uncheck the Ask User to Choose File option. The issue is worse the longer the file dialog box is open and doesn't seem to appear when you don't have the file dialog box open at all.

If you want to be able to browse for your file, you can use the File Dialog Box VI which is located in File IO >> Advanced File Functions. Place it outside the loop.

I hope this helps.