Multichannel Systems Wireless-System Manual - Manual (Page 23)

19
5 Operating a Wireless System
5.1 Experimental Setup
First step to set up an experiment with the wireless system is to implant an electrode into the
laboratory animal. The electrode has to be fixed, for example with cement used in dental technic,
to guarantee a tight position of the electrode in the desired area of the brain. The electrode
connector must be available on the skin surface of the animal. Implant a ground option
additionally, if necessary.
Use of the Reference and Ground Electrodes
For in vivo experiments it is necessary to provide a good option for grounding (GND) and a well
placed reference (REF) electrode. Therefore all headstages of the Wireless-System are equipped
with electrical isolated pins for a ground and a reference electrode.
Important: For good signal quality you should use dedicated reference and ground electrodes!
The reference electrode is used to measure the relative potential differences in relation to the
recording electrodes. It should be out of a similar or the same material as the recording electrodes
and it should be of comparable size. The reference is ideally placed near the recording electrodes,
but not in active tissue.
The signals from all electrodes are amplified and then each signal from the recording electrodes
is compared to the signal from the reference electrode. The difference is measured by the analog
to digital converter (ADC) and digitized.
When external interferences, for example heartbeats, muscle potentials, breathing, disturb the
measurements, both, the recording and the reference electrodes measure the same disturbance
and the noise signal is removed because only the difference between recording and reference
electrode is digitized and transmitted (Common Mode Rejection).