Intan Technologies CLAMP User Manual page 9

Intan CLAMP System
be used to tune the bridge balance (see below). Multi-Step
generates multiple current clamp steps and superimposes
the plots. Arbitrary generates a waveform specified by a
user file (see Arbitrary Waveform Specification below for
details).
Current Clamp Range: This control allows the user to
select the range and resolution (i.e., step size) of the current
clamp. The current-output DAC that generates the
headstage clamp current has a range of ±127 steps. The
step size can be 5 pA, 50 pA, 0.5 nA, or 1 nA.
Bridge Balance: Series resistance compensation may be
performed in current clamp mode using this control.
Checking this box enables bridge balance, where the
voltage drop across the series resistance of the pipette is
subtracted from the voltage measurements. The default
value of series resistance is the last measurement of R
made in voltage clamp mode (see Cell Parameters above),
but this value can be adjusted here to minimize step artifacts
observed during Tuning current clamp pulses (see the
Bridge Balance section below for more details).
Buzz: This button must be enabled by clicking the lock icon.
Clicking this button modulates
compensation circuitry to produce small AC current pulses
that may assist in forming a membrane seal around sharp
intracellular electrodes. The parameters of the buzz pulse
can be adjusted by clicking on the blue parameter display.
Plot total Iclamp: Checking this box adds a second plot on
the Clamp Current graph in the Data Display Window. The
primary plot shows the current clamp waveform generated
by the Current Clamp Command controls above. The
second plot shows the total current clamp waveform applied
by the headstage, which is a linear superposition of the
software-defined current clamp command and any external
command delivered to an ANALOG IN port, if this option is
enabled (see below).
Other Controls
Display Resistance: Checking this box enables real-time
display of the measured pipette resistance. This can be
used when establishing a gigaseal. Average "best fit" lines
used to calculate resistance are superimposed on the
measured waveform in the Data Display Window when this
feature is enabled.
Analog/Digital I/O Tabs
External Command Tab: Controls in this tab allow the user
to control the voltage clamp or current clamp in real time via
external command signals from any of the ANALOG IN
ports. Voltage clamp and current clamp scaling factors may
be selected for each headstage. The external command is
superimposed on any software-defined clamp command,
and only takes effect when the system is running or
S
the capacitance
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recording. To control headstages using only the external
commands, select Holding Only in the software clamp
commands and run the system.
Multiple headstages may be controlled simultaneously using
external command signals. Voltage waveforms may be
generated using legacy hardware (e.g., NIDAQ boards) and
connected to ANALOG IN ports to generate clamp control.
Signal Out Tab: Controls in this tab allow the user to route
the measured voltage or current signal to any of the
ANALOG OUT ports for monitoring on an oscilloscope or
speaker. (The ANALOG OUT 1 and 2 signals are connected
to the left and right channels of the AUDIO LINE OUT jack
on the rear panel.) Voltage and current scaling factors can
be selected here as well. DACs in the Intan CLAMP
Controller reconstruct an analog waveform from the digital
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