Keithley 6487, Справочное руководство

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2-10 Measurement Concepts and Connections Model 6487 Reference Manual
Guard plate
A metal guard plate will provide guarding or noise shielding for the DUT or test circuit. It
will also serve as a mounting panel for DUT or test circuits. The guard plate must be insu-
lated with appropriate spacing from the chassis of the test fixture commensurate with the
external source used.
Connectors, terminals, and internal wiring
Basic connector requirements include a female triax connector and two banana jacks. The
banana jacks provide for connection to the power supply (either the internal voltage source
or an external power supply). The banana jacks must be insulated from the chassis of the
test fixture.
DUT and test circuits are to be mounted on the guard plate using insulated terminals. To
minimize leakage, select terminals that use virgin Teflon insulators.
Inside the test fixture, use an insulated wire to connect the shell of the triax connector to
the guard plate (the guard plate will serve as a noise shield).
Handling and cleaning test fixtures
Dust, body oil, solder flux, and other contaminants on connector and terminal insulators
can significantly decrease the leakage resistance resulting in excessive leakage currents.
Contaminants on DUT and test circuit components can create a leakage path. The leakage
currents may be large enough to corrupt low-level measurements.
Handling tips:
• Do not touch the bodies of DUT or test circuit components. If you can not handle
them by their leads, use clean cotton gloves to install them in the test fixture.
• Do not touch any connector or terminal insulator.
• If installing a test circuit that is on a PC board, handle the board by the edges. Do not
touch any board traces or components.
Cleaning tips:
• Use dry nitrogen gas to clean dust off connector and terminal insulators, DUT, and
other test circuit components.
• If you have just built the test fixture, remove any solder flux using methanol along
with clean foam-tipped swabs or a clean soft brush. Clean the areas as explained in
the next tip.
• To clean contaminated areas, use methanol and clean foam-tipped swabs. After
cleaning a large area, you may want to flush the area with methanol. Blow dry with
dry nitrogen gas.
• After cleaning, the test fixture (and any other cleaned devices or test circuits)
should be allowed to dry in a 122
°
F (50
°
C) low-humidity environment for several
hours.