Skin electrodes

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PB
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Joined: Wed Jan 25, 2006 12:37 pm
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Skin electrodes

Post by PB » Wed Jan 25, 2006 12:46 pm

Hi,

Our Biosemi system came with a little bonus: 2 skin electrodes. Its not the ordinary flat ones. These connects to the aux3 of the AD-box and seems to be passive.

The problem is that I can't get a signal in ActiView. Do I need a modified version of ActiView or what?

Cheers,
P

Coen
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Post by Coen » Wed Jan 25, 2006 5:20 pm

The two extra electrodes are for the GSR (Galvanic Skin Response) measurement. The response is displayed on the "Auxiliary Sensors" tabpage.

For more information, see viewtopic.php?t=79 and viewtopic.php?t=30

Following the discussion on our use of a 512 Hz excitation current, we have conducted further testing with various frequencies. The main reason for using 512 Hz in the original design was to prevent interference to the EEG bandwidth. However, we have now also developed a version of the GSR circuitry with 16 Hz excitation current, which showes no interference problems to the EEG signals. This 16 Hz version of the GSR is reported to produce exactly the same results in terms of waveforms and conductance values as conventional stand-alone GSR devices (with low-frequency excitation currents).

BioSemi is prepared to offer a free upgrade to all customers who have purchased the GSR module in the past. This should not be seen as a product recall, because according to all our tests and customer feedback, the 512 Hz GSR is different (lower impedance values), but not at all worse then the more common low frequency GSR methods. However, for customers wanting better compatibility of the data with traditional low frequency GSR experiments, we offer the option of a free upgrade of their system. Customers who are happy with the 512 Hz GSR as it is now, can keep using it; we will keep supporting the 512 Hz GSR in future ActiView versions.

The upgrade involves sending the AD-box to us for a few days because we need to change the gain of the GSR module (besides the reprogramming with new firmware of course). ActiView version 5.35 and higher are compatible with both 512 and 16 Hz GSR system, the sofwtare automatically detects and switches between the two versions. The 16 Hz GSR data is displayed and saved to file in nanoSiemens (conductance), whereas the 512 GSR data remains displayed and saved to file in Ohm (resistance) as before.

One final note: the 16 Hz GSR can only be used in combination with the USB interface. Customers with an older PCI interface, will have to upgrade to the USB interface first (purchase USB receiver and upgrade to ActiView 5.35 or higher, no further AD-box changes required).

Best regards, Coen (BioSemi)

PB
Posts: 4
Joined: Wed Jan 25, 2006 12:37 pm
Contact:

Post by PB » Thu Jan 26, 2006 6:53 pm

Aah, the reason why it didn't work was because I tried to plug the GSR electrodes to an Mk1 box instead of an Mk2 box. Now everything works fine.

Thanks,
P

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