HP 4155A, Руководство пользователя по задачам

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Making a Measurement
Connection to Device Under T est (DUT)
K elvin Connection
Kelvin connections give good measurement results when you force high-current. The following gure
shows the equivalent circuits for Kelvin and non-Kelvin connections.
F or the non-Kelvin connection, the voltmeter measures the voltage drop of resistances r
F1
,
R
DUT
, and r
F2
.
F or the Kelvin connection, the voltmeter measures the voltage drop of resistance R
DUT
only . The
impedance of the voltmeter is very high, so the voltage drop of resistances r
S1
and r
S2
is very
small.
The Kelvin connection is eective even when forcing voltage . The voltage drop due to the residual
resistance of the force line wiring is fed back to the voltage source via a comparator in the sense line ,
thereb y ensuring the specied voltage output at the sense point (point where force and sense lines
intersect). The input impedance of comparator is high, so current ow into the sense line is very low .
Therefore , output error is not signicant if the sense line wiring has a residual resistance of 10 or
less.
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