SC-2345 with SCC-CO20 and dynamic input

[JeroenBK]

Dear all,

I have the following question:

We use a SC-2345 with SCC-CO20 to test valves. Normally we define a test (number of steps, time to wait etc.) and then let the SC-2345 perform this test.

We read-back the results with a SCXI-1102 and plot them in an XY-graph, because we give a predefined frequency we now the time interval.

The result is a graph which gives me the position in % (converted from 4-20mA read-back) versus time in seconds.

Now comes the hard part:

We would also like to "dynamically" send positions to the valve to be able to have a trend.

The problem now is that for some reason the time is not correct, it starts very quick but the longer the trend takes the slower the time is.

In the first situation we let the SC-2345 handle and time the whole test (we read-back live with the 1102).

In the second situation we continually start and stop the task to the SC-2345.

Is there a way to do this correct (with the SC-2345)?

[ThiCop]

Hello Jeroen,

There are a few things unclear to me regarding this post.

If I understand you correctly, then you are using an SC-2345 with one SCC-CO20 (or multiple?) .

Which DAQ-card is connected to the SC-2345?

To get a more complete hardware description I'm also interested in knowing which chassis your SCXI-1102 is inside and how it's connected to your pc.

The slowness could be related to how the code is programmed.

How you start and stop could also make a big difference on the performance.

Can you share the code you're using with me?

[JeroenBK]

I sort of solved it (for now).

When I start the measurement I write the current date/time in seconds to a variable, everytime the data read loop runs it takes a new timestamp and substracts the first one from it. Then I devide it by the number of samples and in that way I manage to have an accurate time.

When I've got more time to spend I will review the whole project and insert a proper timing system in it (including saving this time stamp in the data file).

For now thank you for participating.

[ThiCop]

Hello Jeroen,

Thanks for your feedback!

If there are questions in the future, then please let us know.