Error -200279 apt

[cantyoudobetter]

I have a Thorlabs APT DC Serve controller rotating a polarizer.  I want to roate it through 360 degrees one degree at a time and then measure the voltage output from the DAQ and output the angle and voltage to a file.  It is all working pretty well, but the system stops about six degrees in when it seems like the voltage reads get out od sync.   I am getting Error -200279.

I think we need some way to sequence the call to the DAQ read once the motor is done rotating.  There has got to be an easy way to do this, but I am new to LabView and can't figure it out.  The VI is attached.

Thanks in advance for any help you can provide.

[Wayne_T]

cantyoudobetter,

What was the following statement after the error code?  For example...

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

    Possible reason(s):
    Measurements: Attempted to read samples that are no longer available. The requested sample was previously               available, but has since been overwritten.

To get started on figuring out what is happening, the following KB has some things to consider.  Remember that you're opening closing the file every iteration, which could take some time to do.  This could lead to samples being lost.

    http://digital.ni.com/public.nsf/allkb/AB7D4CA85967804586257380006F0E62

[cantyoudobetter]

Here is the full error code.

************************************************************

Increasing the buffer size, reading the data more frequently, or specifying a fixed number of samples to read instead of reading all available samples might correct the problem.

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

Task Name: _unnamedTask<0>

**************************************************************

Would a delay after the file write help?  How would you implement that?

Thanks for your help.

[Wayne_T]

cantyoudobetter,

Did you try any of the recommendations?  What are the Samples to Read and Rate fields set to?