Read from measurement file time error?

[scrook]

I have a measurement file that I would like to read via the Read From Measurement File express VI. My small example application will read the file OK but there is an error that I can't figure out how to fix.

When I took the measurements via a DAQmx task it was set to take one sample every 10 seconds. This is reflected in the measurement file. If you open it you see that the Delta X is set to 10 for all channels and also the time column values are all 10 seconds apart. Now when I load this file up, the graph shows that the measurement time has been compressed.

I took the measurements a few days ago starting at 11:27 AM and ending sometime around 4pm. When the VI reads the file back it shows the correct start time, but the measurements end around 11:54 am (according to the graph). The graph also shows the channel labeled AMB (in white) going to 0 after measurements end and there is no data in the file at all showing that this signal was ever 0.

I've uploaded the data file (had to change from LVM to txt extension so that the board would let me upload it), a small VI to read from the measurement file then display to a mixed signal graph, and an image of the front panel output after I had ran the VI using this data file.

[Pie56694]

Hi Scrook,

Please tell me what version of LabVIEW you are using.  Thanks.

[scrook]

I am using Labview 8.6

[scrook]

Forgot to update this post with some additional information I found out after my initial post.

I found the reason why the values go to 0 after a certain time. It is because I have the read to measurement files set to read a  fixed number of samples (13000) which is far more samples than exists in the file. I have tried setting the VI to read all samples in the file and this solves the problem provided that I change the number of samples data in the header of the LVM file to match what is actually there. (I am getting the data from a DAQmx task which is taking a timed sample every 10s in a while loop so the header only says 1 sample by default).

I still am not sure about why it compresses my time scale by a factor of 10. For some reason the read from measurement file seems to be assuming a delta T of 1s even though the time column in the lvm file shows that the samples are 10s apart.

[Pie56694]

Hi Scrook,

This was reported to R&D (# 53026) for further investigation.  A possible workaround is to use Build Waveform to manually set the dt values to the appropriate value.  Thank you for your feedback.