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CAUTION
Turn-off power
supply before rearranging strap-
ping pattern at the power supply rear terminal
strip.
If
the current programming terminals are
opened
while
the power supply is on,
the
out-
put
current will
exceed its maximum rating and
may result in
damage to the load. The power
supply will
not
be damaged. The constant volt-
age
programming
terminals have a zener diode
connected internally across them to
limit
the
programming voltage
and thus prevent excessive
output voltage.
3-19.
CONSTANT
VOLTAGE. In
the constant voltage
mode
of operation,
either
a
resistance or voltage
source
can
be
used for remote programming
.
For resistance
programming. the programming
coefficient
(fixed by the programming current) is
300
ohms
per
volt
(output
voltage increases
1
volt for each 300 ohms in series with
programming terminals). The programming
current is
adjusted to within 1
%
of 3. 33ma
at the factory. If
greater
programming accuracy is required, change R39 (shunt).
The programming resistance should be a stable,
low
noise, low-temperature (less
than 30 ppm
per
0
c)
resistor with
a power rating at least
10 times
its actual dissi-
pation.
3-20.
The
output voltage of
the
power supply should be 0 +20 mv,
-100 mv when
the programming resistance
is zero
ohms. This tolerance can
be improved
by chang-
ing R6.
For
further information
on improving this tolerance, refer to paragraph 5-63
and
to H-Lab 'l'ech Letter #1.
3-21.
If
the resistance programming device is controlled by a
switch,
make-before-
break contacts should
be
used in order to avoid momentary opening of the program-
ming terminals.
To connect
the remote programming resistance, arrange
rear
terminal strapping pattern as shown in figure 3-4.
The
front-panel VOLTAGE
controls are disabled when the strap between A6 and A7 is removed.
3-22.
If
a voltage
source
is used as the remote programming
device,
the output
voltage of
the
power
supply will
vary in a 1 to 1 ratio
with the programming
voltage.
The
load
on the voltage source will not exceed 25
microamperes.
To connect the
programming
voltage,
arrange rear terminal strapping pattern as shown in
figure
3-5.
3-23.
CONSTANT
CURRENT. In
constant current operation,
resistance
program-
ming
is
used.
The resistance
programming coefficient (fixed
by
the programming
current)is
lOOohms
per ampere
(output
current increases 1 ampere for each 100 ohms
in series
with
programming terminals). The programming current is adjusted to
within approximately
10% of
..
4i
ma at the factory. If greater programming accuracy
is required, change
R41 (shunt).
The programming
resistance should
be a stable,
low noise, low-temperature (less than 30 ppm per
0
c)
resistor
with
a power rating
at least 10
times
its actual dissipation.
3-4
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