19
www.warneronline.com
Using the Model Membrance
AC Clamp Test
Adjust the Vm OFFSET control to 0.0 V. Apply a 0.8 V, 100 Hz square wave to the
COMMAND IN ÷10 BNC. Monitor the Vm x10 and I MONITOR outputs on the
oscilloscope.
Switch the CLAMP MODE switch to fast and increase the GAIN until Vm reads 80 mV.
Verify that the Vm x10 BNC reports 0.8 V. As you further increase the GAIN control, you
will see the rise time of the oscilloscope trace become faster since the speed of the
clamp is limited by the resistance of the current electrode and the capacitance of the
oocyte. If ringing (oscillation) is observed, decrease the GAIN setting to obtain the fastest
clean waveform as shown below. (The current signal (I MONITOR) shown in the figure
below displays the high current spikes required to charge the oocyte capacitance.)
Set the HOLD control to a reading of 50 mV and switch the POLARITY toggle to pos. The
square wave will be displaced 50 mV in the positive direction. Switching the polarity to
neg will produce a -50 mV offset.
