Waveform Chart Refresh

[Davefryx]

Hello,

I'm new of the forum.

I'm working on an Eagle PCI-703 Acquisition board.

My target is to obtain a program to realize data acquisition for static tests. So I need to acquire data and at the same time to display numeric value of the acquired channels on my PC.

I'm working on the example program attached.

My problem is that if I set a number of samples equal to the acquisition frequency, I have a refresh of 1 s that it could be too much slow.

Instead If I set a lower number of samples, the refresh of the chart becomes faster, but I accumulate time by time a delay in the displayed data that become unacceptable after a while.

In an example like this:
Acquisition frequency: 10000 Hz
Number of samples: 1000

I think that the program acquires the data in a correct way but for displaying it works in the following way:

It acquires 10000 samples in 1 s (from 1 to 10000);
It takes the 1000 samples (from 1 to 1000) and sends them to the display;
It acquires 10000 samples in 1 s (from 10001 to 20000);
It displays the samples from 1001 to 2000 to the display;
etc...

In this way it accumulates the delay in the display.

Do you have any suggestion to solve the problem?

Thanks in advance,
Davide.

[altenbach]

How old is this VI? Why the stacked sequence? You did not attach the subVIs, so it is not clear what kind of drivers these are. Seems proprietary, so anything can go wrong. Are you aware that your program uses 100% of a CPU code when it is not doing anything?

First let's clarify that you use a graph, not a chart.  Big difference.

I don't understand the rest of your problem description. How do you determine that the display slows down and how do you conclude that the graph is to blame?

[Davefryx]

Thanks for your reply.

The drivers are proprietary of the hardware manufacturer (Eagle Technology) and this code is just an example code of data streaming included in the documentation. I don't know how old can it have.

I don't know if my problem is really related only to the graph or there are other problems in the code.

I'm just trying to understand what can be wrong without success until now.

[altenbach]

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Davefryx wrote:

The drivers are proprietary of the hardware manufacturer (Eagle Technology) and this code is just an example code of data streaming included in the documentation. I don't know how old can it have.

I don't know if my problem is really related only to the graph or there are other problems in the code.

---

Does the code slow down equally of you don't use the graph? Add some code to display the actual loop rate in both cases.

The sad story is that just by looking at their provided example code, we can tell that this compny did not spend any effort employing experienced LabVIEW programmers. Chances are that the drivers are equally bad so anything can go wrong. Looking at their website, the LabVIEW drivers were updated last in 2005.