Time values from DAQ SubVI don't change when there are many shared variables.

[iCat]

Those shared variables are all single processes.

My coworker's program reads from and writes to a lot of single process shared variables in several threads.

He said that when there were a few of such variables, time values from DAQ changed with time, but when there were a lot of them, time values didn't change as time went.

DAQ SubVI and shared variables don't interact, but shared variables somehow affect DAQ time reading.

What is the problem?

[iCat]

Those shared variables are all single processes.

My coworker's program reads from and writes to a lot of single process shared variables in several threads.

He said that when there were a few of such variables, time values from DAQ changed with time, but when there were a lot of them, time values didn't change as time went.

DAQ SubVI and shared variables don't interact, but shared variables somehow affect DAQ time reading.

What is the problem?

[Anjelica-W]

Can you provide some more details on your application?

What hardware are you using?

What is the exact name of the DAQ SubVI you are using?

How many shared variables are you using?

[iCat]

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@Anjelica-W wrote:

Can you provide some more details on your application?

What hardware are you using?

What is the exact name of the DAQ SubVI you are using?

How many shared variables are you using?

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The SubVI he uses is DAQmx Read(Analog 1D Wfm NChan NSample).

NI 9234 is a test device that has 4 channels, and it has the same problem.

The number of shared variables used with NI 9234 is 4.

The error message he got from NI 9234 is as below.

Error -200279 : DAQmx Read (Analog 1D Wfm NChan NSamp).vi:1

Possible Reason:

It tried to read sample that aren't available anymore.

Property : RelativeTo
Value : Current Read Position
Property : Offset
Value : 0

Task name : _unnamedTask<C>

[Anjelica-W]

Usually this error occurs when the Read VI can not acquire all of the samples before the timeout period.

How many samples are are you taking per channel?

What is your sample rate?

What is your timeout value?

Take a look at the following KnowledgeBase article: http://digital.ni.com/public.nsf/allkb/ab7d4ca85967804586257380006f0e62?OpenDocument