synchronising recording of eeg waveforms with stimulus

[Mer]

Hello everybody ,

im working on a VI  to average several EEG waveforms ...which is attached ..

actually each waveform entering this ' waveform averaging' VI  is actually an EEG reponse to each sound click we present to the subject.

so i need each click to trigger or start the recording .. and continue recording for 17 milliseconds.

Thus if i give 1000 clicks, the averaging VI must produce the average of the 1000 waveforms.

the clicks are given as a square waveform , frequency = 10.1 Hz ,  TIMING mode: simulate acquisition timing , samples per second =  44000 , no : of samples = 204000 (or a figure as high)

i used the simulate signal  and play waveform blocks.

for the above problem, i tried to use the trigger and gate block... i thought of connecting the simulate waveform block to the waveform averaging vi using the trigger block...but dont seem to reach anything useful ...

P.S. : this block diagram has sinusoidal signals as the example .. in reality we record EEG  signals .

I wud really be grateful if u cud help me out ...

best regards

Mer

[MQI]

Hi, I'm not LV expert but I think I run into some thing like yours before.  What I did was checking any missing pulse or abnormal in the EEG waveform and set trigger pulse once I found it.  Take a look at your signal amplitude.  If your signal too low (ex: <1.25V), your counter gate won't trigger.  Once you record your EEG, amplified it and use trigger VI (take a look at the LV example) to set your trigger event pulse.

BC