Maximum sampling rate per channel when all the channels are working?

[ELCA]

I want to measure continous 64-ch EEG signal with the 6033-E-series. The board's maximum sampling rate is written as 100kS/s. Is it possible to measure the 64-ch EEG with sampling rate of 1.5 kS/s(100/64)? How can I decide the maximum sampling rate and the buffer size when all the channels are working simultaneously (continuous measurement)?.

[JustinBritten]

You are correct. The sampling rate specifications given for our MIO boards is the rate for all channels on the board combined. You will be able to sample each of the 64 channels at 1.5kS/s. Additionally, when using the new NI-DAQmx driver you do not have to worry about programming the buffer size. This is handled for you by the driver.

If you choose to manually set the buffer size using a DAQmx property node, or you are using Traditional NI-DAQ, the buffer size is specified in terms of the number of samples the buffer can hold for each channel in the task.

Regards,
Justin Britten

Applications Engineer
National Instruments

[ELCA]

Thank you for your comment. Could you answer me more concretely about the NI-DAQmx? Where can I get the document about that? In using the NI-DAQmx, What I have to do is just to install the driver for my purpose?

Otherwise, Should I use a special VI for that? I am now using AI config, AI start, and AI read. In case of using the DAQmx, what value should be written for the "buffer size" connector of the AI config VI.

'the buffer size is specified in terms of the number of samples the buffer can hold for each channel in the task.' means the "buffer size" is "1500" for my application(continuous 64-ch. aqusition at the rate of 1.5kS/s)?

Best regards,
Kim, Kiwoong

[JustinBritten]

NI-DAQmx is our latest driver and is a complete rearchitecture of Traditional NI-DAQ. You are most likely using a version of NI-DAQ prior to version 7.0 (such as 6.9.x). In the Tradational NI-DAQ driver you will use AI Config, AI Start and AI Read. NI-DAQmx uses different VIs and is much easier to use.

In the NI-DAQmx driver you are not asked to specify a buffer size -- this is now done for you by the driver. If you would like to download and install this new driver, you may do so from our website. Please go to www.ni.com and click the "Drivers and Updates" link.

NI-DAQ Version 7.1 for Windows 2000/98/ME/NT/XP
http://digital.ni.com/softlib.nsf/954feaeea92d90918625674b00658b83/c1f802e457ea042586256dd00001b0c9?OpenDocument

When y
ou download and install NI-DAQ 7.x you can refer to the help files for advice on programming your LabVIEW application.

If you wish to continue using Traditional NI-DAQ, then you will be required to specify a buffer size to the AI Config VI. The buffer size is the number of scans that will be held in the internal memory buffer, and is limited by the amount of memory available. Experiment with the buffer size and the number of scans to read each time. If the buffer is too small or you are not reading data from it fast enough, your data will be overwritten by new data before you have a chance to read it (overwrite error). If the buffer is too big, you will run out of memory (out of memory error).

You may find that it takes some trials to determine the absolute best buffer size for your acquisition. This effort will be eliminated by using NI-DAQmx.

Best Regards,
Justin Britten

Applications Engineer
National Instruments