3Brain BioCAM X, User Manual

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Electrodes with no-signal (saturation)
Symptoms
Few electrodes in the array have either persistent or short periods with no visible signal. This effect is
overall called saturation and in this section we will refer to its two possible subtypes: persistent satura-
tion (i.e. a channel is always saturated and no signal is displayed) and jumping saturation (i.e. raw signal is
affected by short periods of saturation typically of tens to hundreds of milliseconds).
In the MEA Viewer control (left image) in BrainWave saturating electrodes show a lowest fixed color
scale value (persistent saturation) or they blink toward the lowest scale value. The lowest color scale
value is typically deep blue but may differ according to the chosen color scale. By displaying the raw
traces of the single electrodes it is possible to see either “jumping” signals disappearing for short pe-
riods of time (right image: top-left, top-right and bottom-left traces) or no signals (right image: bot-
tom-right trace).
Causes
Saturation arises (i) when the input signal amplitude exceeds the operational range of the amplifiers
integrated inside the BioChip’s CMOS or (ii) when the amplifiers working range is not properly set. In the
first case, this could be due to invalid signal input, for instance; in the second case a wrong calibration of
the BioChip could be the cause.
Possible scenarios and remedies
# Scenario Remedy
S1 Electrodes on the BioChip are insulated by
tiny bubbles that form when adding a saline
solution because of the hydrophobicity of the
CMOS surface. Insulated electrodes exhibit
persistent saturation because the input signal
is missing.
This scenario arises only when trying a new
BioChip or a BioChip that has not been used
for a long period. A 2x or 4x magnification
lenses are enough to observe these bubbles.
Use a plastic pipette with a small tip to flow
liquid on the CMOS surface in order to remove
the bubbles. While doing so, be very careful
not to touch the CMOS and to avoid electrodes
damages.