I'm looking for an aquisition system to record EEG (~15 chanels, differential, sampling rate 500Hz) and single unit activities (~15 channels, single ended, sampling rate >15KHz).Could I use two NI 9205 to do that simultaneously? is there any better ways with any hardward usable in Labview environnement?
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I'm assuming that in both cases you are using EEG amplifiers before the DAQ system for safety and to amplify and filter the signals?
One issue that you will have to consider is how important it is for you to have simultaneous sampling? Due the "round-robin" or sequential sampling of a multiplexed data acquisition system (like the 9205), small phase delays are introduced into the digitized data. This may or may not be important to you, and may be more of a factor in each recording scenario (surface EEG vs. single-unit). The timing engine in the M-series data acquisition products allow you to scan a set of channels at the fastest possible rate (<1 microsecond between channels for the boards that have max sample rates of 1.25Ms/s like the USB-6251) and then wait for the sampling interval appropriate to the sampling rate you need (2 milliseconds for 500Hz) and then do another scan of all channels. This creates a pseudo-simultaneous sample rate. If you want true simultaneous sampling, we also have DAQ boards and C-series modules that have an A/D converter per channel.
Also, please consider joining our new Biomedical User Group at www.ni.com/biomedusers
The USB-6216 don't go into a cDAQ chassis - they are stand-alone devices. If you want the more modular cDAQ chassis with plug-in C-series modules, the modules are synchronized with each other and can run off the same time base. You can choose from a variety of C-series plug-in modules for cDAQ to get a mix of simultaneously sample inputs, lower-cost multiplexed inputs, high resolution inputs (24-bit), etc.
You probably will not need to use any of these DAQ devices in the differential input mode. The outputs from bio-amplifiers are high-level single-ended and can be digitized accurately with our DAQ devices in the single-ended mode, which doubles the number of channels available.
Here's the full link to the user group: http://decibel.ni.com/content/groups/biomedical-user-group