Keithley 237 - Page 83

2.7 HIGH VOLTAGE SWITCHING
CONFIGURATIONS
There are four switching cards available from Keithley
that
can
handle
high
voltages
(>200V)
from
the
Model
237
Source
Measure
Unit
•
Model7154 2-pole
High
Voltage Scanner
Card
•
Model
7054
1-pole
High
Voltage Scanner
Card
•
Model
7070-PCA
Prototype Circuit Assembly
•
Model7072-HV
High
Voltage Semiconductor
Matrix
Card
2.7.1
Model7154 2-pole
High
Voltage
Scanner Card
The Model 7154
is
a 10-channel scanner card
that
can
switch
up
to
1100V.
It
can
be
controlled
by
the
Model
70S
or
706
Scanner. The card uses 2-pole switching
and
ac-
commodates connections
with
screw terminals.
Figure 2-26
shows
how
this
card can
be
used
to
switch
OUTPUT
ill
to
test
up
to
10 OUTs. Notice
that
the
guard
jumpers
on
the
scanner card
are
installed, allowing
the
guard
(G)
circuit
of
the
card
to
be
used.
+
SECTION2
Operation
Connections to
the
Source
Measure Unit requires a triax
cable
that
is
unterminated
on
one
end. The appropriate
conductors
at
the
unterminated
end
of
the cable are
con-
nected directly
to
the screw terminals
of
the
scanner card.
Keep
in
mind
that
the triax connectors
on
the
Source
Measure
Unit
are 3-lug, requiring 3-slot triax cables
such
as the Model7078-TRX cables.
Note
that
cutting
one
triax
cable
in
half results
in
two
cables
that
are unterminated
at
one
end.
Figure 2-27
shows
how
two
Model7154 cards
can
be
con-
nected
to
the
Source
Measure
Unit
and
test fixture for re-
mote
sensing. As
shown
in
the illustration,
guard
can
be
used
but
special connections
and
precautions
are
needed
to extend
the
guard
to
the test fixture.
The
special cable
can
be
a
triax
cable
that
is
unterminated
on
both
ends.
One
end
is
wired
directly
to
the
screw terminals of the
scanner card.
High
(H)
and
low
(L)
at
the
other
end
of
the
cable can
be
terminated
with
banana
plugs
that
will mate
to
banana
jacks
mounted
on
the
test fixture. The
outer
shield
of
the
cable,
which
is
guard,
should
extend as far as
possible
to
the
test fixture.
WARNING
To
prevent
electric
shock
(up
to
llOOV),
make
sure
that
the
guard
path
of
specially
built
cables
is
completely
insulated.
Triax/Unterminated Cable
Output
HI
Guard
Sense
HI
K
Guard
K
K
Sense
LO
Output
LO
236/237/238
Internal
Jumpers
installed
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~~~~
I
I
OUT
I
#1
I
C'h
10
ouio#10.--~">-+-l-l
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~o---o-4-<
L----J
L-------l
7154
Scanner
Card
Test
Fixture
Banana/Banana Cable
WARNING
:
To
avoid
electric
shock,
test fixture chassis
must
be
connected
to
a safety
earth
ground.
CAUTION
:
To
prevent damage,
do
not
"hot•
switch
high
voltage
(>200V).
Figure
2-26.
Using
Model
7154
to
Switch
OUTPUT
HI
(Guarded)
+
2-31