Molecular Devices Axoclamp 900A, Руководство пользователя

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Installation and Basic Operation
Grounding and Hum
A perennial bane of electrophysiology is line
‐
frequency pickup (noise),
often referred to as hum. Hum can occur not only at the power line
frequency but also at multiples of it.
The Axoclamp 900A has inherently low hum levels (less than 20
μ
V peak
‐
to
‐
peak). To take advantage of these low levels great care must be taken
when integrating the Axoclamp 900A into a complete recording system.
The following procedures should be followed.
1. Only ground the preparation bath by directly connecting it to the
yellow ground connector on the back of the CHANNEL 1 headstage
(or to a virtual
‐
ground headstage if used).
2. Place the Axoclamp 900A in a position in the rack where transformers
in adjacent equipment are unlikely to radiate into its electronics. A
thick sheet of steel placed between the Axoclamp 900A and the
radiating equipment can effectively reduce the induced hum.
3. Initially make only one connection to the Axoclamp 900A: the
oscilloscope from the Scaled Output. Ground the CHANNEL 1
headstage input through a 1 M
Ω
resistor to the yellow ground
connector. After verifying that the hum levels are low, increase the
complexity of the connections one lead at a time. Leads should not be
draped near transformers inside other equipment. In desperate
circumstances the continuity of the shield on an offending coaxial
cable can be broken.
4. Try grounding auxiliary equipment from a ground distribution bus.
This bus should be connected to the Axoclamp 900A via the yellow
0.16” (4 mm) socket on the rear panel. This socket is connected to the
Axoclamp 900A’s signal ground (
i.e.,
the outer conductors of all the
BNC connectors) which is isolated from the chassis and power
ground.
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