200279 error appears after a few hours of continous Analog sampling

[Ronm]

Hi,

I am using labview with the DAQPad-6016.

I configured the DAQ assistant to acquire 6 analog signals in continuous sampling mode.

I set the DAQ assistant parameters as follows:

• 6 channels AI
• Rate of 6,000
• "Samples to read" value set to 6,000.

I have been going through the forum's massages and was left with a few questions.

I left my program running for ten hours and found it stopped when I returned. When trying to restart it I received the 200279 error. I had to restart the computer and the DAQ device to successfully restart the program.

When using the DAQmx read property node, I discovered that "samples available per channel" values settle after an initial short period to a range of 100 to 600. The buffer size stays constant on 10,000.

From reading in these forums I understood that it is recommended to set the read samples value to 10% of the value of the rate.

In my application I wish to average the samples from the six channels over a period of 1 second. This conflicts with the mentioned recommendation.

More than that, I placed the DAQ assistant inside of a timed loop and set the loop's rate to 1000ms (run every 1 second). Is there a fault in the logic of doing this?

To clarify my questions:

1. Should I set the DAQ assistant differently(Rate, Samples to read parameters)? Is it causing the 200279 error?
2. Should DAQ assistant NOT be in a timed loop (when in continuous mode)?
3. Should I increase the buffer size? If so, how do I accomplish it with the DAQ assistant? (I don't have a reference task to wire to a property node before it starts running and after it starts running, it is not possible to change the buffer size)
4. Last one, after the buffer overflow error occurs it some times creates a new 50150 error at start task (unknown state). How do I reset the system without restarting the computer and the DAQ?

I hope my questions are clear enough, Thank you,

Ron

[tnek]

Hi Ron,

There are a few things that may need clarification.

When acquiring multiple channels of data, the number of samples to read and the sample rate are per channel. With your settings, you are acquiring 6000 samples per channel at a rate of 6000 samples per second which results in an overall acquisition of 36000 total samples per second if you have 6 channels.

For the application that you are talking about, I would recommend using the DAQmx API instead of the DAQ Assistant. Using these DAQmx functions will give you more control over details such as your buffer. A good place to begin if you are unfamiliar with the API is by right clicking on your DAQ Assistant and selecting Generate Code.  This will take your current configuration and convert it into DAQmx functions.

To answer your questions more specifically:

1. See above for using the DAQmx API. The buffer size seems fine, the reason you are receiving the error is because the samples available per channel reached a value which filled your buffer. At this point, the new data will be written to the buffer which would overwrite the current data in the buffer which was not read yet. To get around this, I would recommend using the DAQmx Read function to retrieve data from the buffer and set the number of samples per channel to      -1. This will tell the driver to get all samples in the buffer which will eliminate any samples left in the buffer after an acquisition.
2. It would not hurt to take your acquisition functions out of the timed loop. As it stands now, there is already hardware timing configured and the timed loop will add software timing. You only need one, and hardware timing is usually more accurate.
3. You do not need to increase the buffer size, see answer to question 1.
4. Another way to reset the device will be to open the Measurement and Automation Explorer (MAX). In the directory structure to the left, navigate to My System » Devices and Interfaces » NI-DAQmx Devices. In that menu, right click on your device and select reset device.

Here are a few links which may help you get started using the DAQmx API:

Complete Data Acquisition Tutorial

Learn 10 Functions in NI-DAQmx and Handle 80 Percent of Your Data Acquisition Applications

Regards,

Kent