Keeping Connectors Clean - Keithley 2000-SCAN-20 Instruction Manual

Figure 3-7 shows how to connect several instruments together to eliminate this type of ground
loop problem. Here, only one instrument is connected to power line ground. Ground loops are
not normally a problem with instruments having isolated LO terminals. However, all
instruments in the test setup may not be designed in this manner. When in doubt, consult the
manual for all instrumentation in the test setup.
Figure 3-7
Eliminating ground loops
Instrument 1

Keeping connectors clean

As is the case with any high-resistance device, the integrity of connectors can be compro-
mised if they are not handled properly. If connector insulation becomes contaminated, the insu-
lation resistance will be substantially reduced, affecting high-impedance measurement paths.
Oils and salts from the skin can contaminate connector insulators, reducing their resistance.
Also, contaminants present in the air can be deposited on the insulator surface. To avoid these
problems, never touch the connector insulating material. In addition, only use the scanner card
in clean, dry environments to avoid contamination.
If the connector insulators should become contaminated, either by inadvertent touching or
from air-borne deposits, clean them with a cotton swab dipped in clean methanol. After thor-
oughly cleaning, allow the insulators to dry for several hours in a low-humidity environment
before use, or you can dry them more quickly using dry nitrogen.
Instrument 2 Instrument 3
Power Line Ground
Operation 3-15