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4. Reduce the loop area of any ground loops that remain by routing cables close
together or twisting wires.
5. Make sure power lines to equipment have a direct, low impedance path to earth
ground so that no voltage is present between equipment grounds.
6. Ground strap the instrumentation chassis to provide low impedance between
components of the system.
2.4.1.3 Shielding
Shielding reduces noise induced in the probe cables by electric fields in the
environment or other equipment in the experiment. The probe station’s vacuum
chamber is the most important part of a shielding system. The electrically conductive
chamber surrounds the sample area and is often connected to the measurement
system’s ground reference as described in section 2.4.1.1. BNC and triaxial signal
connector shells are electrically connected to the chamber to provide a shield contact
for cabling. DC/RF probe cables are all made from cryogenic, coaxial wire so the
shielding can be carried inside the chamber and down the probe arm. Outside the
chamber, shielding is recommended for all signal cables, but the shielding must not
be allowed to create ground loops as described in section 2.4.1.2. It is often necessary
to connect the shield at only one end of the cable.
2.4.1.4 Noise Isolation
Every attempt was made in the design and construction of the Model CRX-6.5K to
isolate potential noise sources so they do not interfere with measurements. It is
important to recognize these features so they are not inadvertently defeated when
the probe station is re-configured or set up for measurements. Non-conductive
components are used to attach the vacuum isolation valve to the vacuum chamber to
prevent electrical noise emanating from the pump from entering through the
vacuum line (bellows).
The temperature sensors and control heaters are electrically isolated from the
sample cooling assembly to prevent interference from the instrumentation. This
isolation is sufficient for most probe station applications. Additional precautions may
be necessary for very low noise measurements; see section 2.4.6.
Содержание CRX-6.5K
Страница 4: ...Model CRX 6 5K Probe Station ...
Страница 52: ...42 CHAPTER 2 System Overview Model CRX 6 5K Probe Station ...
Страница 92: ...82 CHAPTER 3 Installation and Setup Model CRX 6 5K Probe Station ...
Страница 162: ...152 CHAPTER 6 Maintenance and Troubleshooting Model CRX 6 5K Probe Station ...
Страница 166: ...156 INDEX Model CRX 6 5K Probe Station ...