Testing the EPC9 EPC9 Manual 25
values – again by clicking and dragging the mouse upwards. Since there are two
variables to adjust this is more difficult than the C-fast compensation. However, with
some praxis you will get a better feeling for these parameters and how they effect the
recording. With increasing quality of the compensation you should approach the real
values of the model circuit and the transients should disappear (red line). Instead of
compensating C-slow “by hand” you can also press the Auto button (7) in the CSlow
section of the amplifier control panel for an automatic compensation of C-slow and R-
series. If the compensation fails, the E-field (8) in the Auto button becomes black.
When this happens, you should repeat the auto-compensation, until it succeeds and
the E-field becomes normal again.
Note: The speed and success of automatic C-slow compensation depends on the actual
values of C-slow and R-series. These two values should be reasonably near to the
real values. Therefore, you should always check, whether the values are reasonable
before executing the automatic compensation. It is much better to have too large
estimates than too small ones.
Clicking the Cap Track button (9) does this automatic compensation repetitively after
a delay you specify in the Delay field (10). With a delay of 1 ms and a contemporary
computer (Pentium II, 300 MHz) this feature allows you to measure the membrane
capacitance at a rate of 15 Hz. You can output the results of the Cap-Track mode into
the notebook window, if you activate the option Log Tracking from the EPC9 menu.
Note: If you are a novice to patch-clamping it is useful to perform the C-fast and C-slow
compensation at least a couple of times manually before getting used too much to the
convenience of the automatic routines. Doing so you will get a better feeling for the
quality of a recording and how it is affected by the various parameters, especially the
input resistance R-series.
In a similar way as you explored the C-slow compensation, you could now have a
closer look into the Rs-Compensation. Turn the compensation on by setting an
appropriate compensation speed, 2, 10 or 100 µs (11), and gradually increase the
percentage of compensation from 0 to 95% by clicking and dragging the mouse
upwards (12). As soon as you are overcompensating the series resistance typical
oscillations will occur in the oscilloscope. Series Resistance Compensation is a more
complicated topic and is therefore treated in more detail in the EPC9 Manual.
The steps listed above can be automatically executed by clicking the WHOLE-CELL
button or pressing the ‘3’ key on the numerical keypad. This will execute the
following macro that sets the right gain, does a C-Slow compensation with
reasonable values:
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