3-40 Keysight E5260/E5270 User’s Guide, Edition 6
Installation
Connecting Measurement Devices
Guarding
Guarding reduces the leakage current between the measurement points and
instrument. This is important when you measure low current.
The following figure shows the theory of guarding. The buffer amplifier (×1) keeps
the potential of the guard conductor at the same potential as the force conductor, so
current does not flow between the force and guard conductors. Therefore, the
current measured by SMU is same as current at measurement point because no
current is leaked.
To Measure Low Resistance
When you measure a low resistance, high current flows through the DUT. This high
current increases the measurement error caused by the residual resistance of cables.
To cancel the effect of this resistance, you can use Kelvin connections (4-wire),
which means the force and sense lines are extended separately to the DUT.
Connect the probing needles to the terminals of the connector plate by using test
leads or coaxial cables. Following instruction uses the coaxial cables:
1. At end of cable, connect coaxial center conductor to force terminal of connector
plate, and connect coaxial outer conductor to guard terminal of connector plate.
2. At another end, connect coaxial center conductor to tail of the probing needle.
Never connect the outer conductor at this cable end.
Extend the outer conductor as close as possible to the probing needle.
3. Repeat 1 and 2 for the sense terminal of connector plate.
4. Contact the probing needles from force and sense terminals as close as possible
to the DUT.
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