Configuring Analog Voltage Measurement Using USB 6008 and DAQ Assistant

[schmiggy1279]

hi,

I'm using Labview 8.6 with a windows 7 PC. I am using a USB 6008. I have 4.5V input to AI0  and grounded AI0- from a battery source. I have configured the DAQ assistant in Labview. Signal input range is -12 to  12V. Terminal Configuration is differential. Acquisition mode is N samples. Samples to read is 5 and rate is 1KHz. The data output from the DAQ assistant goes to a waveform graph. However, no matter how I change the sample number or rate the program bombs out with the following error.

Error -200361 occurred at DAQmx Read (Analog 1D Wfm NChan NSamp).vi:3
Possible reason(s):
Measurements: Onboard device memory overflow. Because of system and/or
bus-bandwidth limitations, the driver could not read data from the device
fast enough to keep up with the device throughput.Reduce the sample rate,
or reduce the number of programs your computer is executing concurrently.

[David. B]

Hi Schmiggy,

Thanks for posting in the forums.

There are a fews steps that I would recommend trying to resolve this error:

• Reset the device in MAX.
• Try using a different USB port.
• Ensure that no other unnecessary deviced or programs are running.
• Although you have changed the sample rate I would recommend checking how often you are writing to the graph as this is a memory intensive operation. Is your CPU usage in task manager near it's limit when you run the program?
• Another option could be to try it on a different PC to try to replicate the problem.

Also when does this error occur? Is it as soon as you run the program or after a matter of time?

More information on why this error occurs with you device can be found here. You have to be careful about what else the PC is doing when using these devices due to the size of the FIFO they contain on board.

I hope this helps and would very much like to know the outcome.

Kind Regards

[johnsold]

I would also try reading a larger number of samples each time.  At 5 samples per read you need to read 200 times per second. If your program starts to slow down, for example because of writing to the graph, the buffer in the USB-6008 may soon overflow.  According to the specifications the AI FIFO (on board buffer) is 512 bytes.

Lynn