3.5.6 Dressing Cables
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3.5.6 Dressing Cables
Cable dressing is often overlooked in crowded laboratories, but even neatness can
matter when making small signal measurements. Consider the following ideas for
long cable runs outside of the experimental Dewar.
D
Cables with signals sharing the same ground or common should be routed
together to reduce ground loop area.
D
Cables with signals that differ in ground or signal size should be routed sepa-
rately to reduce induced noise.
D
Cables should be kept away from noise generators like fluorescent lights and vac-
uum pump motors.
D
Cables should be supported to minimize stress on connectors and terminations.
Cable support should also limit movement and vibration of the cables during
measurements because cable motion can generate electrical noise.
D
Shielded cables should be used with the shields connected at both the scanner
and Dewar connectors.
Resistor leads from non-selected channels are shorted to measurement common to con-
trol noise in the 3726 scanner. In the 3708 scanners, these are left open. Please take this
into account when installing the Dewar wiring.
Model 372 scanner and measurement circuitry is isolated from the earth ground. There-
fore, connecting shields at both the scanner and Dewar does not result in a “ground loop.”