Hi,
I want to aquire data with a PCI-6023 card from NI and write them with
time stamps to a file. The problem is that the coordination of time
stamp to the acquired data must be very exact.
For the realization I used a counter which I initialized at the
beginning of the acquisition to the actual system-time. I set the
samplerate for the "AI start.vi" to 10 (per second) and incremented the
counter by 1 second after the "AI read.vi" read 10 samples.
Since the PCI-card uses a 20MHz oscillator I thought that my counter had
an accuracy of 50 ns. I tested my program for several hour and noted
that after 3 hours the difference between my counter and the system-time
had grown up to 400 ms. Since I want to aquire data over a periode of 24
hours the inaccuracy at the en
d would be more the 3 seconds........
I hope this explanation of my problem is not too circumstantial, so that
somebody could tell me, want's wrong with my considerations.
thanks,
hans
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Johann Gimpl
Student at Graz University of Technology
http://www.sbox.tu-graz.ac.at/home/h/hons
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