Time axis of data off by 20-30 seconds in beginning of data acquisition.

[MC85]

I'm using a DAQ card to find the crank angle on a stationary bicycle.  When we start acquiring data, the first 10-20 points on the time axis seem normal but the angles are off, then they jump up by ~20, then the data is normal.  There is also a 2 second lag that we need to get rid of if possible, and an error message that pops up telling me to increase sampling (but I'm already sampling at a really high rate ~1000 and really don't want any more data).  Data acquistion doesn't start until this message is ignored, then it collects as described before. 

[MC85]

The error message is 200279 occuring at DAQmx read and says that attempted to read samples that are no longer avaliable.

[Brooks_C]

Hello MC85,

These delays are a little hard to troubleshoot without more information about your setup.  It would be helpful if you can provide answers to the following questions:

1.  What DAQ card are you using?

2.  What driver are you using?  (Probably NI-DAQmx)

3.  What type of sensor are you using?

4.  What type of measurement are you making?  (Voltage, angular encoder, etc.)

5.  What sample mode are you using?  (Continuous, N Samples, On Demand, etc.)

6.  How many samples are you reading at a time?  If you are acquiring at 1 kHz and reading 10,000 samples at a time the graph in LabVIEW will only update every 10 seconds.

In addition to these questions, you may want to try out some the example programs that come with LabVIEW.  To view these examples open LabVIEW and go to Help>> Find Examples.  Assuming you have a DAQ card that uses DAQmx to do a voltage measurement you'll want to go to Hardware Input and Output>> DAQmx>> Analog Measurements>> Voltage.  In this folder you'll see a number of examples that acquire and graph voltages.  Try running some of these because there may already be an example that does what you want.

As far as the error code goes I can't offer a lot of help without knowing some of the above information, however there are a couple of KnowlegeBase articles that explain a couple common causes of this error code:

(DAQmx) Error -200279 During a Continuous, Buffered Acquisition

Common NI-DAQmx Error Codes and Solutions: Codes -200000 to -200299 and -50103

Why Do I Get Error -200279 When Writing Continuously Acquired Data to a File?

I hope this helps, and if not please reply with answers to the above questions.

Have a good night!