E9Screen Software EPC9 Manual 45
Delay: This determines how many seconds to wait before the next auto-
compensation is started. With short delays (e.g., 1 ms), membrane capacitance will be
tracked at rates of >10 Hz (depending on the Macintosh model).
Note: You can increase the rate of Cap. Track (about two-fold) when closing the
Oscilloscope.
R
s
-comp: The series resistance compensa-
tion corrects for membrane voltage errors
under conditions of high access resistance between pipette and cell interior (see see
Chapter 7. Compensation Procedures on page 59). The amount of compensation can
be changed by dragging the mouse or typing (range 0-95%). The compensation is
based on the value of R-series and will be effective only when R
s
-comp is not Off, i.e.,
set to a speed value. The following settings determine the speed of feedback
compensation:
• Off - Turns compensation off.
• 100 µs - Slow compensation.
• 10 µs- Fast compensation.
• 2 µs - Very fast compensation.
The choice of speed depends on the recording time constant and the degree of
compensation desired, as described in Chapter 7. Compensation Procedures on page
59. Fast R
s
-compensation requires more critical adjustment of the controls but
provides the maximum voltage-clamp speed. In fast modes, Filter 1 will be
automatically switched to its HQ-30 kHz setting. In Current Clamp mode, R
s
-comp
will act as a bridge compensation.
Test Pulses: Test pulses are added to the holding
potential and applied to the pipette; the current
responses are sampled and displayed. Test pulses are
applied at maximal rates depending on the durations
specified.
Amplitude / Duration: Duration and amplitude of built-in test pulses can be
specified in the dialog. The minimum pulse duration is 1 ms with 100 points
sampled per pulse, i.e., the sampling interval is 1/100 times the pulse duration.
Stimulus: The stimulus can be filtered (2-pole Bessel)
to reduce the amplitude of fast capacitance transients
when the speed of potential changes is not critical.
Two settings are available:
• 2 µs • 20 µs
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