Owner’s Guide
46
‘Active’
microelectrode
Reference
electrode
To Ground/
Reference
electrode
Motion Eff ects
A common source of artifacts when recording neurological signals is motion of the
subject or equipment. For example, muscular activity generates its own electrical
signals, which may interfere with the neuronal signal, depending on the location of the
electrodes.
If the subject is going to move during recording, then special care needs to be taken
when positioning electrodes and securing leads.
Electrode Contact
Occasionally during measurement of a neurological signal, one of the lead wires
connecting the source to the front-end may become disconnected, or electrode contact
may become poor. If this should happen, relatively high voltages (potentials) can be
induced in the open wire, due to electric fields caused by the power line or other sources
close to the front-end or to the subject. These induced potentials result in a constant
amplitude disturbance in the recorded signal at the mains frequency, causing masking
or loss of the desired signal. If the problem is a recurring one, one of the leads may be
faulty. Check connections and replace faulty leads, if necessary.
Figure 4–8
The active
microelectrode is
inserted over the
common peroneal
nerve at the
fibular head.
The reference
electrode is
inserted under
the skin.
The ground (Ag/
AgCl) electrode is
attached to the
surface of the skin
with the green
lead.
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