12-01-2008 07:58 PM
12-02-2008 10:00 AM
You cannot connect this electro-cap (or any biopotential electrodes) directly to a cRIO system. Currently, there are no suitable modules for cRIO to allow direct recording of biosignals like EEG or ECG. You must use an amplifier like the ADInstruments ML138 Bioamp to provide the differential inputs, isolation, high gain, and filtering needed to successfully and safely acquire biosignals. Unfortunately, the ADInstruments amplifer is computer controlled and it looks like they have a proprietary interface to control the settings, so you must use their software for setup/configuration of these amplifiers. However, these amplifiers do have analog outputs that are ready to be digitized by a cRIO analog input module so you could use cRIO (or any NI DAQ card) to record the data and use LabVIEW for on-line and/or off-line monitoring and signal processing. There are other sources for bioamplifiers that have either manual controls (or computer controls that use a standard RS-232 interface). Google Grass Instruments, Harvard Apparatus, World Precision Instruments for some ideas.
12-02-2008 07:38 PM
Hi Steve, Thank you for the explaination. I've already figure out on this too. Yes, I knew that the EEG sensor/electrode requires a bioamplifier. But then, we still can connect them through any NI analog input module, aight, as long as the electrode output (after being amplified) is a voltage.Am I right? I am thinking of using a USB-DAQ or maybe a expresscard since the client has a small budget, but all this still under consideration. The client also requires a module to control a joystick which I trust also analog input will be enuff.
Anyway, if there is any other brilliant suggestion, please do advice me. thanks ya!!!!!
12-03-2008 08:36 AM
That's right - as long as the output of the amplifier is a voltage proportional to the EEG signal and it's large enough to be digitized with the precision that you require, then you should be all set. EEG is typically digitized at rates of about 400-500 samples/sec (per channel) which is pretty slow, so almost any NI DAQ product will work. 12-bit resolution is fine as long as the range of the output matches the input range of the DAQ product closely (for instance, if the output of the EEG amplifier is +/-1 volts, then you would want to set the input range of the DAQ product to match as closely as possible. The other consideration is how many channels you plan to record and whether you want the channels digitized simultaneously (not scanned in sequence). Our lower cost products have multiplexed inputs that scan the channels by switching the A/D converter from one input channel to the next in sequence (very quickly). This is fine for many situations (and most EEG) but some applications require that all channels are sampled at exactly the same time to preserve channel to channel timing relationships. Our S-series DAQ products have simultaneous sampling (a separate ADC for each channel).
For your joystick, you can definitely use A/D inputs to measure the joystick position (one channel for each axis).
12-03-2008 07:11 PM
Good day to you. Thank you again for your advice. I will now ready to explain and suggest to the user on what modules and DAQ that is suitable with her application. Thank you very much!!!!!
12-03-2008 09:37 PM
New information that I need advice from you Steve
I am going to use a electro-cap (as I mentioned last time, by ADInstruments) with National Instruments AI module.
The ADInstruments supplier sent me this email
"The electrocap picks up electrical properties of brain cells. This is shown in mill volts or micro volts in our software. The adapter for this electrocap is suited only to attach to our MLA2540 - 5 lead shielded bio amp cable. You may need to re-configure the adapter to suit your system. "
My concern here now is the adapter. From my understanding, adapter is just an adapter, right? It provides a better signal that suit your data logger as long as both connector at the adapter and data logger suit each other,right? So, by right there is no problem to use their electro-cap and adapter with NI data logger, right? Please advice.
Lots of thanx