Keithley 237

2.3
BASIC
TEST CONNECTIONS
In order to achieve the best results, the Source Measure
Unit
must
be
used
with
a test fixture to house the DUT.
For optimum performance, the test fixture should
pro-
vide guarding, shielding
and
remote sensing for the
DUT. Also, the test fixture should incorporate a safety in-
terlock to prevent access to live
circuitry
above
42V peak.
WARNING
To prevent
an
electric shock,
do
not
use
test
cables
that
expose voltage. All test cables
must
be
completely insulated.
The following paragraphs
show
how
to make connec-
tions to the Keithley
Model8006
test fixture. Also, infor-
mation for building a custom test fixture is covered.
2.3.1
Interlock
The Source Measure
Unit
is designed to
be
used
with
a
test fixture that incorporates a safety interlock switch,
such as the Keithley
Model8006
test fixture.
By
using the
Interlock feature, the Source Measure
Unit
cannot source
a voltage
or
current
when
the lid of the test fixture
is
open.
The Interlock feature
is automatically enabled
when
an
interlock cable
is
connected to the Source Measure Unit.
+
+
SECTION2
Operation
Connections
When using Interlock with the Model
8006
or
8007
test
fixture, the Source Measure Unit
will
go into standby
when
the
lid of the fixture
is
open
or
ajar. Figure 2-2
shows
how
the Source Measure
Unit
Interlock
is
con-
nected to the
Model8006
test fixture. The interlock cable
is
shown connected to Interlock 1 receptacle of the Source
Measure
Unit.
An
interlock cable is supplied with the
Models 236, 237,
and
238.
If
a custom built test fixture is
going to
be
used, make sure it
has
an
interlock switch. In-
structions to wire
an
interlock switch of a custom built
test fixture to the Source Measure
Unit
are contained in
paragraph 2.3.3.
There are two
INTERLOCK
receptacles
on
the rear panel
of the Source Measure
Unit.
One
is used to connect Inter-
lock to a test fixture as previously explained,
and
the
other
is
used
to connect Interlock to a second Source
Measure
Unit.
In
this configuration,
an
open interlock
switch
at
the
test fixture
will
place both Source Measure
Units
in
standby. Connection information for multi-unit
test systems
is contained
in
paragraph
2.4.
WARNING
When
using
the
INTERLOCK
feature
in
a
multiple
unit
test system,
make
sure
all
the
Model
236/237/238s
remain
powered
up.
Turning
off
one
or
more Model236/237/238s
in
the
test system
may
result
in
erratic IN-
TERLOCK
operation.
That
is,
an
operational
Model236/237/238
may
not
go into
standby
when
the
lid
of
the
system test fixture is
opened. This condition exposes
the
operator
2-7