Table of Contents
Advertisement
Model 722A
Section III
Paragraphs 3-1 to 3-11
SECTION III
OPERATING INSTRUCTIONS
3-1. OPERATION.
3-2. Refer to figure 3-1 for a complete illustrated
description of all operating controls. No preliminary
adjustments are necessary before turning on this in-
strument.
Connect the wires from the load to the
output terminals either in the front or back of the in-
strument.
If
these leads are long or run past a source
of interference, twist them
if
they are open-wire
leads or run a shielded cable.
Figure 3-1 explains
step by step how to operate this instrument.
- SENSE
-POWER
SW
FRONT
RL
REAR
OR
REAR
SW
+POWER
+SENSE
RO
Figure 3-2. Remote Sensing
722A 1*2
CR
CR
-
O~----+lII~ ~ J----l
J
+ 0 - - - - - -
RO
722A
722A .. ,
3-10.
If
the load must be removed with the supply on
be careful where you break the leads going to the load.
Referring to figure 3-2 you may break the circuit at the
point(s) marked SW. Do NOT break the circuit at the
point(s) marked X as the supply will be damaged.
Figure 3-3. Charging Batteries
3-11.
If
this supply is to be connected to an
active
load (one which supplies voltage) further precautions
must be taken.
The load must not be allowed to run
current through the supply in the reverse direction.
WHEN CONNECTI G THIS SUPPLY TO AN ACTIVE
LOAD ALWAYS MAKE SURE THAT THE VOLTAGE
OF THE MODEL 722A SUPPLY IS GREATER THAN
THE VOLTAGE ON THE TERMINALS WHERE THE
SUPPL Y IS TO BE CONNECTED. The recommended
way of protecting the supply is to use diodes. Figures
3-3 and 3-4 illustrate the proper way to connect these
diodes when connecting this supply to a battery or
when connecting two supplies in parallel. These diodes
must be able to carry 2 amperes current and have a
peak inverse voltage greater than 50 volts. A suitable
diode may be ordered from Hewlett-Packard as stock
number 1901-0019.
3-3. CURRENT LIMITING.
3-4. The maximum current delivered by this
sup~ly
may be set to any value between 0.1 and 2 amperes.
This will limit the current to the set value and protect
the equipment under test in addition to protecting the
transistors in the Model 722A from dissipating too
much power.
3-5. Occasionally when the current-limit control is
set to maximum current and maximum current is
drawn the instrument will not adjust down later to
a smaiIer current limit. In this case switch the power
switch to OFF-RESET position momentarily and then
back ON.
The instrument will now be reset and will
limit at lower levels of current limit.
3-8. To minimize this effect a separate set of termi-
nals for the sensing voltage is provided on the rear
of the instrument. These terminals permit a separate
pair of leads to connect at the load to supply the sens-
ing voltage.
These leads carry no load
curre~t.
but
are actually inside the regulating loop of the amplIfIer.
3-9. To use remote sensing run a separate set of
leads from the load to the supply. These leads do not
need to be as heavy as the supply leads but they must
be protected from hum pick-up.
Run either twisted
pair open-wire leads or shielded leads if hum pick-up
is severe. Connect the leads to the terminals marked
REM+ and REM- on the terminal strip on the rear of
the instrument.
At the load connect these leads to
the load (see figure 3-2).
3-6. REMOTE SENSING.
3-7. When the Remote-Local switch on the rear of
the instrument is in the Local position the voltage for
regulation control (sensing voltage) is taken off the
output of the supply at the front panel. This is not
always the best point to obtain this voltage because
there is a drop in the supply leads between the load
and the supply.
CAUTION
Be sure to observe polarity when making
these connections.
Wrong connections may
damage the supply.
+
o---~~---o+
RO
Figure 3-4. Parallel Operation
01155-1
3-1
Advertisement
Table of Contents
