Agilent Technologies 4339B - Page 118

Theory
of
Operation
4339B
Grounded
and
Ungrounded
DUT
Measurement
Conguration
The
4339B
has
the
capability
to
measure
both
grounded
and
ungrounded DUT
s.
Figure
3-10.
Ungrounded
and
Grounded
DUT
Measurement
In
Figure
3-10
(a),
the
Ground
and
the
Guard
terminal
are
connected
by a
shut connector
.
The
Input
terminal
is
connected
to
one
side
of
the
DUT
,
while the
other side
of
the
DUT
is
connected
to
the
Output
terminal.
In
this
conguration,
the
Output
terminal
supplies
the test
voltage
to
the
DUT
,
and
the
test
current
through
the
DUT
is
input
to the
4339B
through
the
Input
terminal,
which
is
connected
to
the
ammeter
circuit.
In
Figure
3-10
(b),
the
Guard
and
Output terminals
are
connected
by
the
shut
connector
,
and
the
Input
terminal
is
connected
to
the
grounded
DUT.
The
Output
terminal
supplies
the
test
voltage
to
the
DUT
(through
the
ammeter
circuit).
When
you
measure
the
grounded
DUT
,
the
Ground terminal
may be
left
open,
however
,
for
more precise
measurement, the
Ground
terminal
and
the
DUT's
ground
should
be
connected
to
each other
as a
common ground.
Note
The
4339B's
ammeter measures
the test
current
as
a
positive
value
when
current
ows from
the Input
terminal to
the Guard
terminal.
So
,
an
ungrounded
DUT
measurement
results
in
a
positive
current
value
,
and
a
grounded
DUT measurement
results
in
a
negative
current
value
.
(Resistance
,
R,
is
always
a
positive value
.)
3-28 Function Reference