ThinkPulse active electrodes, Q&A [resolved]
Hi there -
I've recently assembled an ultracortex with the thinkpulse active electrodes. As far as I can tell, I have wired them correctly according to the instructional video. Ear clips are connected to SRB2 and BIAS. The ear clips themselves seem good with an ohmeter, showing ~3ohms at most. I am definitely receiving signal from the thinkpulse electrodes, but if the ear clips are connected to the ears, the signals are all railed. If they aren't, the signal values are huge (100s- to 1000s of uV), noisy, and do not seem to reflect brain waves (not surprising, but demonstrates that the signal wires are connected). The normal spiky electrodes that come with the ultracortex seem to work ok and report reasonable values; I'm using a cyton board which has been working fine with a wet electrode EEG cap.
I feel l'm missing something here....the documentation suggests that the thinkpulse electrodes should be drop-in replacements and have similar signal ranges. I've connected the power supplies for the electrodes to AVDD and AVSS as instructed in the video via the power supply header board, so I'm not really sure what I'm doing wrong. I've tried fiddling with the channel gain settings in the GUI but that doesnt help with railing. Is there some other wiring or ref/bias connection detail I'm not seeing?