NPI SEC-05LX, Руководство по эксплуатации

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The CAPACITY COMPENSATION control on the front panel can be used to improve the
speed of response, it has also an impact on the stability of the feedback circuit. When starting
the LIN VC session this control should be on a low value.
The VC GAIN and INTEGRATOR controls have the same function as in switched VC mode.
When starting the LIN VC session the GAIN control should be on a low value,
INTEGRATOR turned OFF.
Functional description
The series resistance compensation unit is designed to compensate errors induced by the
access resistance during whole cell voltage clamp recordings. It is optimized for access
resistances of below 20 M

( the lower the value the better).
The compensation is based on a shift of the command potential to counterbalance the access
resistance artifact caused by the current flow during the VC recording. It is with respect to the
VC control a positive feedback loop and can cause oscillations if set too high. The maximum
compensation is 90%, in real experiments it is often lower due to uncompensated stray
capacities and nonlinearities of the microelectrode.
For current clamp recordings the amplifier is equipped with a BRIDGE balance circuit which
can fully compensate the access resistance by subtraction of a current proportional voltage
from the recorded electrode signals. In this way the correct membrane potential is displayed
during current injecting protocols. The setting of the BRIDGE balance control depicts the
value of the access resistance in M

.
The R
S
compensation is based on the setting of the BRIDGE balance control. The current
signal recorded by the amplifier is fed via the BRIDGE Balance control into the R
S
compensation control, the signal generated from the R
S
compensation control is summed with
the COMMAND signal and shifts the clamp potential so that the error induced on the access
resistance is reduced.
Important hints

R
S
compensation works correctly ONLY in LINEAR VC operating mode.

Set the BRIDGE BALANCE correctly before using R
S
compensation.

Turn coarse capacity compensation at the headstage to ZERO. CAPACITY
COMPENSATION control on the front panel may be used with care.

Integrator and gain are functional with R
S
compensation