30
c
HAPTER
2:
Installation
MeasureReady™ M91 FastHall™ Measurement Controller
2.4.1 Triaxial Sample
Connectors
The rear panel has six triaxial connectors to connect to your sample. For a van Der
Pauw measurement, use terminals 1-4. For a Hall Bar measurement, use all 6 termi-
nals. If using a triaxial to BNC adapter, the following configuration must be used:
D
Center conductor between the BNC and triaxial connected
D
Shields tied together
D
Triaxial guard floating
See section 5.3 for a list of accessories which can be purchased from Lake Shore.
FIGURE 2-4
Triaxial
sample connectors
2.4.1.1 Triaxial Sample Connectors
D
Center conductor:
signal.
D
Inner shield:
attached to the driven guard.
D
Outer shield:
attached to the return signal.
For best performance, it is recommended to leave the guard signal unattached at the DUT
end of the triaxial cable.
Never connect the guard to any other output, including output low. Doing so may cause
damage to the MeasureReady™ M91 FastHall™ measurement controller.
2.4.1.2 Cabling Considerations
The M91 FastHall™ measurement controller was designed to use triaxial cabling to
connect the instrument to the DUT. If the user wants to make their own cabling, the
following items should be kept in mind in order to maintain signal quality and keep
noise to a minimum:
D
The M91 has two “grounds”. The first and most obvious is the chassis which is
power line ground for safety to the user. The second is output low, which is also
referred to as “source common.” It is isolated from the chassis ground. However, a
1 M
)
resistor and 22 nF connect the two together, loosely.
D
It is optional whether or not to connect output low to chassis, depending on the
application. In many cases, connecting output low to chassis is the simplest way
to use the device. However, the isolation allows for a grounding scheme that
avoids ground loops from multiple connections with other equipment such as
the single point ground method for elimination of ground loops.
D
When using the output for either voltage or current, the current return path for
the signal must always be to output low and never to the chassis itself, regardless
of the grounding scheme, to reduce noise to the lowest level.
Содержание Measure Ready M91 FastHall
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