time stamp from dynamic data

[stj]

I trying to write dynamic data to a file using Express VI (Write LabView Measurement file). The dynamic data comes straight from a simulated Signal Express VI. The signal part of the dynamic data is written correctly but the time stamp is what appears to be float counting the seconds since the Write LabView Measurement file Express VI was started.

I have configured the Simulate Signal VI Time stamp to absolute data and time option.

This should be dead simple but it just do not work!

Any suggestion to what I might do wrong?
I do expect that the time stamp would be written as two columns one for date and one for time.

Thanks,
Soren T. Jensen

[Bob_Y.]

The timestamp is written in the header of the file. The time and date entered there is the time and date that you are looking for. The timestamp written next to each piece of data is indead a relative value. It is the delta from the timestamp in the header to the time that datum was collected (created). The reason for this is that timestamps are quite large in bytes, especially if you break out the time and date in strings. Just stamping the header and providing the offsets is much more efficient.

If you choose to not provide a header, I think that the timestamp will be lost entirely. I think that this is probably wrong, but I am uunsure what should be done to correct it.

Hope that this helps,
Bob

[DFGray]

You can get the entire spec for LVM at “Specification for the LabVIEW Measurement File (.lvm), Version 1.0”. It also explains some of the rationale that went into the spec.

[stj]

Thanks Bob,
That make sense from a file space point of view and I will not look further for a way to a date and time stamp for each datapoint.

Soren