neuroConn DC-Stimulator, User Manual

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Chapter 4 - Operating Basics
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Please also note the relationship between electrode impedance and maximum stimulation
current, shown in Figure 17.
NB: Impedance warnings also appear if voltage limitation of 22 V is reached or
exceeded. For example, a current of 2 mA at 10 kOhm impedance produces a
voltage drop of 20 V. An impedance of 20 kOhm produces a voltage drop of 40 V,
which is above the limit.
Impedance control is designed for measurements with “real” electrodes. A
comparison with ohmic resistances could lead to divergent values - especially in
all noise modes and with currents < 150 mA at the time of measurement.
Ensure, therefore, that appropriate impedance limits are used. Try to decrease impedance
as much as possible before you raise impedance limit.
A manual check of the electrode impedance can be started by pressing button 2
and 3 simultaneously.
Figure 17: Relationship betw een electrode impedance and maximum stimulation current