I do not take time to match data with the PC time

[nanoalberto]

Hi

I have a question and do not know why I did not coincide with the time that stores a data graph with the time at which the data is stored on the PC should be every 0.5s and there values are 0 almost, 46s between data and information.

Attached is a picture and -vi.

By the way why do not load the stage number and always reads 0?

  Thanks for your help.

[nanoalberto]

[VItan]

There are a lot of things wrong in your VI.  You have no data dependency between your simulated signal source and the operations you do with it, you are offsetting the t0 using a constant timestamp, and you are using a local variable to append data to Table Control.  I do not know why you have two tables at all.

However, to address your specific questions:

• Your signal simulation is set for 20 Hz, which means 0.05 s period, NOT 0.5 s period.
• Stage number is always zero because it is the iteration counter of the for loop, which always runs only once since the length of the Y array is always one.
• I do not know what you mean by "46s between data and information".

[nanoalberto]

Hi Vltan.
I modified my vi.la simulation signal at 10 Hz and period 0.1s.
Where I have the problem is that when the pc was not increased in 0.1s.When the while loop period is 0.1s.

You can modify my vi.

[VItan]

Note that with the "Simulate acquisition timing" checked in the Simulate Signal Express VI, you do not need the Wait Until Next ms Multiple in your loop; the Simulate Signal is controlling timing itself.

The loop period is nominally 0.1 s, but it will not be very well controlled on a non-real-time target.  Variations of several milliseconds are expected on a PC, with variations increasing more as depending on the amount of activity (more applications running, lots of GUI interaction and mouse movement, etc.).

[RavensFan]

When you use a PC's time to timestamp values directly, you are at the mercy of the update rate of the Windows/PC clock.  I found that the update rate of that clock is about 1/60th of a second.  The timestamps generally jump about 16-17 millisecond steps.  You are probably seeing that effect here.

[nanoalberto]

Sample 1 sec. an loop T = 1 saves the data well.

Sample 2 sec. an loop T = 0.5 saves the data well.

Sample 4 sec. an loop T = 0.2 saves the data well.

Sample 5 sec. an loop T = 0.25 saves the data well.

It is the problem of PC / Windows clock ?