Reference Section
•
97
High-pass Filter
The Primary Output and Scope signals can be high-pass filtered by setting the AC
value in the Output Gains and Filters section of the main MultiClamp 700B
Commander panel. This is typically done in order to remove a DC component of
the signal. When the filter cutoff is set to DC this high-pass filter is bypassed.
Command Filter Frequency
Command stimuli applied in V-Clamp or I-Clamp can be filtered at different cutoff
frequencies, selectable in the General tab under the Options button. You might
wish to do this in order to smooth out sharp transitions in the command signal that,
if unfiltered, might produce very large capacitance transients that saturate the
headstage circuitry, even after capacitance compensation. (See Chapter 5,
EXTERNAL COMMAND INPUTS
.)
Grounding and Hum
•
Methods for minimizing line-frequency noise.
•
See also Noise, Power Supply.
A perennial bane of electrophysiology is line-frequency pickup, often referred to as
hum. Hum can occur not only at the mains frequency but also at multiples of it.
In a well-shielded enclosure the MultiClamp 700B has insignificant hum levels
(less than 0.01 pA
p-p
). To take advantage of these low levels great care must be
taken when incorporating the MultiClamp 700B into a complete recording system.
The following precautions should be taken.
•
Ground the preparation bath only by directly connecting it to the gold
ground connector on the back of the headstage.
•
Place the MultiClamp 700B in the rack in a position where it will not absorb
radiation from adjacent equipment. A grounded, thick sheet of steel placed
between the MultiClamp 700B and the radiating equipment can effectively
reduce induced hum.
Chapter 5
