HP 6296A - Page 19

•
•
•
;ramming
voltage
(reference
voltage)
and
the
load
on
the
programming
voltage
source
will
not
exceed
25
microamperes.
Al
46
A2
+
+
G - -
•S
AJ
A4
AS
A6
A7
Al
101~1r1m1
VOLTAGE
SOURCE
Figure
3-4.
Remote Voltage
Programminq
(Constant
Voltage)
3-23
The
impedance
matching
resistors
(Rx)
for
the
programming
voltage
source
should
be
approx-
imately
1000
ohms
to
maintain
the
temperature
and
stability
specifications
of
the
power supply.
3-24
REMOTE
PROGRAMMING,
CONSTANT
CUR-
RENT
3-25
Either
a
resistance
or
a
voltage
source
can
be
used
to
control
the
constant
current
output
of
the
supply.
The
CURRENT
controls
on
the
front
panel
are
disabled
according
to
the
following
pro-
cedures
•
PROGRAMMING
lu:slStoR
Fiqure
3-S.
Remote
Resistance
Programming
(Constant
.Current)
3-26
Resistance
Pn?qrammins
(Figure
3-5).
In
this
mode,
the
output
current
varies
at
a
rate
determined
by
the
programming
coefficient
--
100
ohms
per
ampere
for
Models
6282A
and
6286A,
200
ohms
per
ampere
for
Models
6285A
and
6291A,
and
500
ohms
per
ampere
for
Models
6290A
and
6296A.
The
programming
coefficient
ls
determined
by the
Constant
Current
programming
current
l
mA
for
Models
~282A,
6285A, 6286A,
and
6291A
or
O.
66
mA
for
Models
6290A
and
6296A. This
current
is
adjusted
to
within
10%
at
the
factory.
If
qreater
programming
accuracy
is
required,
it
may
be
achieved
by
changing
resistor
R808
as
outlined
in
Section
V.
3-27
Use
stable,
low
noise,
low temperature
co-
efficient
(less
than
30
ppm/Oc) programming
re-
sistors
to
maintain
the
power
supply
temperature
3-3
coefficient
and
stability
specifications.
A
switch
may
be
used
to
set
discrete
values
of
output
cur-
rent.
A
make-before-break
type
of
switch
should
be
used
since
the
output
current
will
exceed
the
maximum
rating
of
the
power
supply
if
the
switch
contacts
open
during
the
switching
interval.
CAUTION
If
the
programming
terminals
(Al
and
A7)
should
open
at
any
time durinq
this
mode,
the
output
cur-
rent
will
rise
to
a
value
that
may
damage the power
supply
and/or
the
load. To
avoid
this
possibility,
connect
a lK
resistor
(1.
SK
for
Models
6290A
and
6296A)
across
the
programming
terminals.
Like
the
programming
resistor,
this
resistor
should
be
of
the
low
noise,
low temperature
coefficient
type,
3-28
Voltage Programming (Figure
3-6).
In
this
mode.
the
output
current
will
vary
linearly
with
changes
in
the
programming
voltage.
The
pro-
gramming
voltage
should
not
exceed
1. 5
volts.
Voltage
in
excess
of 1. 5
volts
will
result
in
ex-
cessive
power
dissipation
in
the
instrument
and
possible
damage,
VOLtACE
SOURCE
Figure
3-6.
Remote
Voltage Programming
(Constant
Current)
3-29
The
output
current
will
be
the
programming
voltage
divided
by
the
internal
current
sampling
resistance
RSOO.
The
current
required
from
the
voltage
source
will
be
less
than
10
microamperes.
The impedance matching
resistor
(Rx)
should
be
approximately
1000
ohms
if
the
temperature
coeffi-
cient
and
stability
specifications
of
the power
supply
are
to
be
maintained.
3-30
REMOTE
SENSING
(See Figure
3-7)
3-31 Remote
sensing
is
used
to
maintain good
regulation
at
the
load
and
reduce
the
degradation
of
regulation
which
would
occur
due
to
the
voltage
drop
in
the
leads
between
the
power supply
and
the
load.
Remote
sensing
is
accomplished
by
utilizing
the
strapping
pattern
shown
in
Figure
3-7.
The
power
supply
should
be
turned
off
before
changing
strapping
patterns.
It
is
not
required