Glitches in data when using USB6009 and Labview

[engtech4]

NI Support

We're using a USB-6009(driver:NI-DAQmx Base 1.4) and Labview 7.1 on a P4 WinXPhome system and have encountered a couple of problems

We made a LabView program to acquire data from 8 analog inputs. A "while"loop is used to get data continuously. When the program is running glitches appear on the waveforms and in the data file. The glitches are intermittent and can be triggered when changing the graph scaling, or can occur by themselves (with no user intervention) after a couple of hours...

The second problem is an error 200036 which occurs when I set up the sample rate less than 0.0067Hz from the mxBase Timing module.

We've got a few of these USB6009 modules and are trying desperately to use them...Can you please tell us what we can do to solve these issues....

Thanks Tao Yang / Scott Jackson, UBC Civil Engineering

[Otis]

First I would recommmend upgrading from DAQmx Base 1.4 to DAQmx Base 1.5. Upgrading might help resolve some of the other issues. Also try running an example and see if the same type of behavior is noticed.

The error you are getting is related to the sampling rate. It sounds like you may be sampling so slowly that the device is timing out. Although, the error code you mentioned typically relates to those trying to sample faster than the device is capable of running. What may be the best workaround for your case is to try to oversample and average. Instead of that very slow rate, maybe take a few more samples at a faster rate, then you can simply do some math in your program to average the points acquired. This might also help to eliminate some of the error noticed in the glitches that you originally mentioned.

[samriddh]

hi otis,

I am having the same problem but in my case i am acquiring Digital signal with a sampling rate of the time LabVIEW takes to fire between two successive loop iterations.

There is no Delay between the acquisition loop like wait for miliseconds to wait.

Even DAQ Assistant vi configured for the same acquisition gives glitches.

w 

[JÞB]

Please post your code.

The highest probabilty for these "Glitches" is that an untimed loop is hogging the CPU resources.  Do you have a 'wait until ne mS multiple' in all of your for and while loops?

Other potential issues exist but, we can't check for them either without a vi. 

[Dennis_Knutson]

duplicate post