2.1
0.3
Sense
The
Source
Measure
Unit
has
local
or
remote
sensing ca-
pability.
When
using
remote
sensing, sense lines
are
ex-
tended
to
the
OUT.
When
the
Source
Measure
Unit
is
programmed
to
source
V,
sensing
provides
a feedback voltage
that
is
measured
and
compared
to
the
programmed
voltage level.
If
the
feedback voltage is less
than
the
programmed
voltage
level,
then
the
voltage source is increased
until
the
feed-
back
voltage equals
the
programmed
voltage level.
In
lo-
cal, sensing is
performed
at
the
output
of
the
Source
Measure
Unit.
In
remote, external sense
leads
are
con-
nected
to
the
load,
thus,
sensing is
performed
at
the
load.
Remote sensing compensates for test
lead
IR
drop,
ensur-
ing
that
the
programmed
voltage level is delivered
to
the
load.
When
sourcing
I,
local sensing is
used
to
measure
voltage
at
the
output
terminals.
In
remote
sensing, external sense
connections
are
made
across
the
load. Thus,
the
subse-
quent
voltage
reading
is
the
actual voltage
drop
across
the
load. Test
lead
IR
drops
are
not
included
in
the
meas-
ured
reading.
Remote sensing
should
always
be
used
when
sourcing
or
measuring
lmA
or
more. Sourcing
or
measuring
lmA
or
more
indicates
that
the
load
impedance
is relatively low.
Since
this
low
impedance
load
forms a voltage
divider
with
the
test
lead
resistance,
the
IR
drop
across
the
test
leads
becomes significant. Thus,
in
local sense,
the
volt-
age
reading
does
not
reflect
the
true
voltage
drop
across
the
load. Instead,
the
reading
includes
theIR
drop
across
the
test leads.
Remote sense connections
are
covered
in
paragraph
2.3.
WARNING
With
remote
sensing
enabled,
an
open
sense
lead
will
result
in
lethal
voltages
appearing
at
OUTPUT
HI
and
GUARD.
This
voltage
can
cause
injury
or
death,
and
damage
exter-
nal
circuitry.
Always
make
sure
that
the
sense
leads
are
properly
connected
before
enabling
remote
sense.
Never
change
con-
nections
with
power
applied.
Be
sure
to
al-
ways
discharge
and/or
disconnect
external
power
sources.
+
+
SECTION2
Operation
When
sourcing
voltage,
the
output
voltage
is
sensed
(measured)
and
fed
back
to
the
volt-
age
source
(VsoURCE).
If
the
sensed
voltage
is
lower
than
the
programmed
voltage, V
soURCE
is
increased
until
the
sensed
voltage
equals
the
programmed
voltage.
In
the
case
of
an
open
remote
sense
lead,
the
sensed
voltage
(OV)
will
never
equal
the
programmed
volt-
age.
Thus,
to
compensate,
V
soURCE
will
increase
to
its
maximum
leveL
To check
the
status
of
sense
and
other
operation
menu
item
parameters,
simply
enable
MENU
and
use
the
ro-
tary
knob
to
scroll
through
the
menu
items.
If
no
changes
are
to
be
made,
disable
MENU
to
return
to
normal
opera-
tion.
Perform
the
following
steps
to
select
the
alternate sense
setting:
1.
With
MENU
enabled,
turn
the
rotary
knob
until
the
present
sense setting is displayed.
For
example, if lo-
cal sense is currently selected,
the
following will
be
displayed:
SENSE
LOCAL
2.
Use
the
SELECT
buttons
to
select
the
alternate set-
ting. SELECT ...
selects
remote
sense
and
• SELECT
selects local sense.
3.
With
the
desired
sense selected, press
ENTER
The
next
menu
item
will
be
displayed.
4.
If
no
other
menu
actions
are
to
be
taken, disable
MENU
to
return
to
the
source-measure display state.
NOTES
1.
The
unit
powers
up
to local sensing.
2. Factory initialization places
the
unit
in
local sense.
3. Internally,
the
Source
Measure
Unit
will
go
ot
local
sensing
when
it
is
placed
in
standby.
When
operate
is enabled,
the
Source
Measure
Unit
will
go
to
the
programmed
sense selection (remote
or
local).
Source/Sense
Voltage
Differential
When
configured
as
a voltage source,
the
remote
sense
leads
are
typically connected
in
close proximity to
the
source
leads
by
the
OUT.
As
a result,
the
voltage differ-
ence
between
source
and
sense is virtually zero.
The
very
small
difference is
caused
by
the
voltage
drop
in
the
source leads.
2-39
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