IX2-700 Dual Intracellular Preamplifier
7
OPERATION
Each of the two independent channels in the IX2-700 can be used as a
bridge Channels 1 and 2 have Bridge Balance and Holding Current
controls.
PROCEDURE
When beginning, ascertain that the system is grounded properly and that the
noise is low. Connect the current and voltage outputs to an oscilloscope. Set the
gain on the oscilloscope to yield 10mV/div. (i.e., 1mV/ div for the 10V output; also
scale Imon by headstage N). Turn the capacity compensation and bridge balance to
the minimum, and the offset voltage and holding current to zero. Make sure that
the step command and the Z test are also off.
ADJUST DC OFFSET
Insert the electrode tip into the bath solution. Adjust the DC offset control so
that the voltage is at ground potential (ground voltage trace, adjust position on
oscilloscope to desired position, uncouple voltage channel, and return trace to the
same position using the DC offset control).
Z TEST
The Z Test can now be used to determine the resistance of the electrode.
Depress the Z test button. There should be a square wave on the oscilloscope
voltage trace of 1mV/megohm of electrode resistance. This measurement is
obtained by passing a 1nA square wave through the pipette. Note that this
resistance test (scale by headstage multiplier N) disables the bridge balance
control. Providing the electrode resistance is within the range you are interested in
working with, you can proceed to balancing the bridge.
BALANCE THE BRIDGE
The bridge must be balanced to effectively “subtract out” the effect of the
potential drop across the microelectrode, allowing you to record only the events at
the cell membrane. The procedure is as follows:
Содержание IX2-700
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