NI5911 acquisition

[Magdalena]

Hello,

I use a NI5911 digitizer to acquire signals from an US sensor with extrnal triggering (PFI2) of 20HZ. I use LabView to control the device (Fetch Vi) and I save the data in a SGL file. When I acquire 1,2 and 3 records the file size is 12,24 1nd 36KB respectively, but when I acquire 4 the file size is 47KB instead of 48KB. In case of more than 4 records, I "lose" 1KB every 4 records. Is that a fetching or an on_board buffer problem or something else? Can somebody help me?

Thanks!!

[Alan_L]

Magdalena,

What mechanism are you using to determine the size of your data files? I have a feeling that the "loss" of 1 KB may just be due to rounding. Windows displays the size of a file (in the 'properties' dialog) in two ways: both as a rounded number of KB, and its actual size in Bytes (enclosed in parentheses). I recommend using the raw Byte count in your calculation. Also, you can double-check that all of the data has indeed been written to disk by reading it back into LabVIEW. If you read the file back and are indeed losing data, please let me know.

I hope that you find this helpful!


Thanks,
Alan L.
Applications Engineer
National Instruments

[Magdalena]

Thank you Alan,

you were right about the file size; I read the file back and there no bytes missing.

Magdalena