SECTION2
Operation
+
Model8006 Test Fixture
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236-ILC-3
Interlock
Cable
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WARNING
:
To
avoid
electric
shock,
test
fixture
chassis
must
be
connected
to
a
safety
earth
ground.
Source Measure Unit #2
Figure
2-2.
Interlock
Connection
to
Model8006
to potentially lethal voltages
that
could
re-
sult
in
injury
or
death.
As a general
rule
of
safety
for
multiple
unit
interlocked
test
systems,
either
keep
all
Model
236/237/238s
powered
on,
or
turn
them
all
off.
WARNING
To
prevent
electrical shock, refer to
the
test
fixture
instruction
manual
for
proper
con-
nection
and
operation procedures.
Connecting
more
than
one
test fixture
to
the
test
system
defeats the
purpose
of
Interlock. As
long
as
one
test
fix-
ture
lid
remains closed,
the
lid
of
another
test fixture can
be
opened
without
interrupting
power,
thus
exposing
the
user
to
potentially
hazardous
voltage.
Special
cables
must
be
made
to
put
the interlocks
in
series
when
using
multiple fixtures.
2.3.2 Guarding,
Shielding
and Sensing
rations
are
shown
in
Figure 2-3.
The
driven
guard
is
al-
ways
enabled
and
thus, always available
at
the
rear
panel
of
the
Source Measure
Unit.
The
guard
potential (equal to
the
potential
of
OUTPUT
HI) is connected
to
the
inner
shells
of
the
triax connectors
that
surround
OUTPUT
HI
and
SENSE
HI. Since
the voltage potential
on
the
inner
shells (guard)
and
center conductors (OUTPUT
HI
and
SENSE
HI)
are
the
same, virtually
no
leakage current can
flow from
OUTPUT
HI
or
SENSE
HI
to
low
(or chassis),
and
the
capacitance effects
of
the triax cable
are
reduced.
When
the
Source
Measure
Unit
is
properly
connected to a
test fixture (such as
the
8006),
guard
is extended to
that
test fixture. Inside the test fixture, coaxial cables are
used
to extend
the
guard
all
the
way
to
the
DUT.
WARNING
Hazardous
voltages
that
are
present
on
OUTPUT
HI
and
SENSE
HI
also
appear
on
the
GUARD terminals.
Guarding
NOTE
The
Source
Measure
Unit
provides
a
driven
guard
for
OUTPUT
HI
and
SENSE
HI.
The
basic
guarded
configu-
2-8
+
Guard
is
not
connected directly
to
OUT
leads.
A small potential difference exists
that
could
cause erroneous readings.