How does the WriteLVM vi time information compare with that in a DAQ task?

[brinda]

Hi

My setup is as follows :
I use the DAQmx assistant to configure my data acquisition. The signals are availible from the DAQmx Read vi in the form of a task.
This task is then fed into a Sample Compression vi. The output of this is then split and after some manipulation merged again.
The final values are then logged using a WriteLVM vi.

I gather that the DAQ task already has timing information associated with it, My concern is how does this timing information relate to what is logged by the WriteLVM vi. Does this signal manipulation actually impact the accuracy of this timing information? What happens to the timing information when I split the signals?

Thanks
Brinda

[AlanArmstead]

Brinda,
When you acquire data with the Daq Assistant, the data is in the waveform data type. A waveform has 3 components: a time stamp, a delta T (change in time), and an array of Y values. So, regardless of what signal manipulation you do to that waveform, it will still contain the timestamp it was given when the acquisition was performed. The time that prints in the file will be the time that it was acquired, not the time it was written to the file. Note: this time stamp is taken from the computer's system time. Therefore, the accuracy of the timestamp will be dependent on the operating system (i.e. when the OS tells the LV thread to run, what other processes are running concurrently, etc). I hope this helps!