HEKA Elektronik EPC 10 USB, Hardware Manual, Page: 34 / 81

28 The control software
Figure 5.2: Amplifier Selection dialog
Gain: Sets the scaling of the current monitor output. The range is 0.005 to 2000 mV/pA and can be set by dragging
the mouse or by pressing the up- and down-keys on the keyboard. The Gain setting automatically selects one of
the three available current-measuring feedback resistors in the probe (5 M Ω, 500 M Ω, and 50 G Ω), corresponding
to low, medium and high Gain ranges. The table below summarizes the main features and limitations of the Gain
ranges:
Low Medium High
Feedback Resistor 5 MΩ 500 MΩ 50 GΩ
Gain 0.005-0.2 mV/pA 0.5-20 mV/pA 50-2000 mV/pA
I
max
VC
±
2 µ A
±
20 nA
±
200 pA
I
max
CC (out)
±
1 (5
∗
) µ A
±
10 (50
∗
) nA -
C-slow Ranges 30/100/1000 pF 30/100/1000 pF 30/100 pF
Current Clamp yes yes no
R
s
compensation yes yes yes
Note: * When using the
Extended Stimulus Range
.
The lowest range may be used for experiments (e.g., bilayers, loose-patch, or large cells) in which large currents
need to be delivered (up to about 2
µA ). Capacitance compensation of up to 1 nF is available and Rs-compensation
can be used for Rs values down to 10 Ω in this range.
In the medium gain range, the background noise is larger than in the high Gain range, but the full 100 kHz
bandwidth is available. Currents of up to about 20 nA can be recorded. This range is used mainly for whole-cell
recordings, and for this purpose the special features of the 1000 pF transient cancellation range (see C-slow ranges),
series resistance compensation, and the current clamp modes are made available.
The high Gain range is intended for single-channel recording. It has a very low noise level, but this is obtained at
the expense of a maximum current limit of about 200 pA. The maximum available bandwidth is about 60 kHz,
and the special features mentioned above do not function in this range.
Clipping Indicator: A blinking box labeled ”Clip” in the Gain title indicates saturation of amplifiers in the
current monitor circuitry. Like the Clipping LED on the
EPC 10 USB
main unit, this is a warning that excess
artifacts or noise may occur due to the saturation of amplifiers.
Note: This indicator may appear to be more sensitive than the LED on the
EPC 10 USB
. It is not;
it just latches the clipping status longer than the LED light.
Figure 5.3: Gain and V-membrane control
V-membrane: The V-membrane control can be used to set a holding potential in voltage clamp mode or a holding
current in current clamp mode. The software corrects for liquid junction potentials and offsets (provided the zero-
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