User
Guide
for
Axoclamp
900A
The
main
advantages
of
the
TEVC
technique
are:
1.
High
current
‐
passing
capacity:
for
larger
cells
single
‐
electrode
clamps
do
not
work
adequately,
if
at
all.
An
Axoclamp
900A
in
TEVC
mode
can
supply
current
in
the
mA
range.
A
common
application
for
two
‐
electrode
voltage
clamps
is
recording
currents
in
amphibian
oocytes.
2.
Excellent
time
resolution:
the
rise
time
for
a
voltage
step
with
a
TEVC
can
be
a
factor
of
3
or
more
faster
than
a
single
‐
electrode
clamp
implemented
using
similar
microelectrodes.
A
high
frequency
response
might
be
required
to
record
very
rapid
tail
currents
or
gating
currents
associated
with
voltage
‐
gated
channels,
for
example.
3.
Low
noise:
current
noise
levels
with
a
TEVC
are
generally
lower
than
single
‐
electrode
voltage
clamps
implemented
using
microelectrodes
of
comparable
resistance,
even
given
the
higher
frequency
response
of
the
TEVC.
The
major
drawbacks
to
TEVC
systems
are
that
two
microelectrodes
must
be
applied
to
one
cell
and
that
there
is
added
complexity.
Configuration
of
the
Voltage
Clamp
System
Before
setting
up
the
voltage
clamp
you
have
to
decide
how
to
record
the
membrane
potential
(V
m
)
and
how
to
measure
the
membrane
current
(I
m
).
The
decisions
you
make
are
determined
by
what
you
want
to
achieve
and
the
particular
characteristics
of
your
preparation
and
bath.
The
brief
discussions
of
the
various
options
that
follow
will
help
you
assess
your
particular
requirements.
Voltage
Recording
and
Series
Resistance
The
reference
point
for
the
voltage
recorded
by
CHANNEL
1
is
the
system
ground
and
under
ideal
conditions
a
bath
ground
electrode
holds
the
extracellular
solution
at
a
constant
voltage
relative
to
the
system
ground.
After
CHANNEL
1
is
offset
to
zero
volts
in
the
bath
and
then
applied
to
the
100
