Keithley 237

SECTION2
Operation
Connectors,
Internal
Wiring
and
Test
Sockets
The
type
of
input
connectors
to
use
on
the
test fixture is,
of
course, influenced
by
the
type
of
connectors
used
on
other
equipment.
If
the
test
fixture
is
going
to
be
con-
nected directly
to
the
Source
Measure
Unit,
use
3-lug
triax
bulkhead
connectors to eliminate
the
need
for
adapters.
The
outer
shell
of
the
triax
connectors
must
be
referenced
to chassis
ground,
thus
DO
NOT
insulate
the
outer
shells
of
triax
connectors
from
the
metal
chassis
of
the
test fix-
ture.
Inside
the
chassis
of
the
test fixture
you
may
use
coaxial
cables
to
extend
guard
from
the
OUTPUT
HI
and
SENSE
HI
triax
connectors
to
the
OUT.
The
shields (guard)
of
the
cables
should
extend
as far
as
possible
to
the
OUT. Ferrite
beads
on
the
cables
may
be
necessary
if
the
OUT
is
an
ac-
tive device (such
as
a
bipolar
transistor
or
MOS/GaAs
Transistor).
To
minimize
leakage (for
pA
levels),
only
use
test
sockets
that
have
excellent
insulation
resistance.
If
terminals
and/
or
standoffs
are
going
to
be
used,
make
sure
they
use
virgin Teflon®.
+
2.4
MUL Tl UNIT CONNECTIONS
For
many
test
configurations,
two
or
more
source
meas-
ure
units
will
be
required. Figure 2-12
shows
how
a
com-
plete
stand-alone
(no controller)
two
Source
Measure
Unit
system
could
be
connected together.
The
following
paragraphs
cover
these connections
in
more
detail.
NOTE
For
rack
mounted
systems,
always
install
high
power
instruments
at
the
top
of
the
rack.
2.4.1
Interlock
Connections
WARNING
To
prevent
electrical
shock
that
could
result
in
injury
or
death,
the
interlock
feature
of
the
Source
Measure
Unit
must
be
used.
The
interlock feature places
the
Source
Measure
Unit
in
standby
whenever
the
lid
of
the
test fixture
is
opened.
The
interlock feature
is
enabled
when
an
interlock cable
is connected
to
the
Source
Measure
Unit.
Complete
infor-
mation
on
the
interlock feature
is
located
in
paragraph
2.3.1.
Model
8006
Test
Fixture
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Source
Measure
Unit
#1
Source
Measure
Unit
#2
Fi
re
2-12.
Two
Source
Measure
UnitS
stem
2-16
+