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Model 722A
a. Connect voltmeter across output of power supply.
b. Turn COARSE and FINE VOLTAGE controls
fully clockwise.
Voltage out should be greater than
60.0 volts.
c. Turn COARSE and FINE VOLTAGE controls
fully counterclockwise.
Output voltage should go
through zero to 0.05 to 0.2 volts positive (positive
terminal on Model 722A is considered ground).
5-36. CURRENT LIMITING.
5-37. To check current limiting proceed as follows:
a. Connect 25 ohm, 150 watt load in series with a
precision 1%, 1 ohm, 5 watt resistor, to the output
of the Model 722A.
b. Connect a voltmeter in shunt with the precision
1 ohm resistor.
This voltmeter will be called the
shunt voltmeter.
c. Turn CURRENT LIMIT control fully clockwise.
d. Turn COARSE VOLTAGE control clockwise until
current appears to limit (voltmeter on front panel
stops rising). Shunt voltmeter should read 2.3 volts.
e. Adjust the COARSE and FINE VOLTAGE con-
trols until shunt voltmeter reads 2.00 volts.
The
OUTPUT CURRENT meter should read 2 amperes.
f. Tum COARSE VOLTAGE control for 10 volts
out and CURRE T LIMIT control fully counterclock-
wise.
The output voltage should be 0.08 volt or less.
5-38. OPERATION CHARACTERISTICS.
a. With the DC POWER switch turned off, attach
a well-shielded coaxial cable between the OUTPUT
terminals of the Model 722A and an oscilloscope,
such as the r5j) Models 130B/150A with 151B plug-in,
160B or 170A with 162D plug-in.
It is absolutely
essential that this lead be as well-shielded and as
short as possible.
Not only must this lead be well
shielded but it also must be connected to the OUTPUT
terminals as close to the instrument as possible.
Unscrew the plastic ferrules on the OUTPUT con-
nectors and connect bare wire or clip-leads tightly.
b. Connect a voltmeter and load as instructed in
paragraph 5-36, Current Limiting.
This voltmeter
will be called the shunt voltmeter.
c. Turn DC POWER to ON and adjust CURRENT
controls for 2 amperes current (2 volts on shunt
voltmeter).
d. Set oscilloscope for 5 mv /cm sensitivity and a
sweep speed of 5 ms/cm.
e. Plug the Model 722A into a variable transformer
and reduce the input voltage until the output ripple
reaches at least 5 mv peak-to-peak.
This voltage
should be less than 102 volts ac.
01155-1
Section V
Paragraphs 5-36 to 5-40
5-39. RIPPLE CHARACTERISTICS.
Note
The instrument under test must not be lying
on magnetic material for this test.
a. Connect a voltmeter and load as instructed in
paragraph 5-36, Current Limiting. This voltmeter will
be called the shunt voltmeter.
b. Connect an oscilloscope as instructed in para-
graph 5-38, Operation Characteristics.
c. Connect a floating, battery-operated voltmeter,
such as the r5j) Model 403A, to the OUTPUT terminals
of the Model 722A with a short shielded lead.
d. Turn up the COARSE VOLTAGE control until
the shunt voltmeter reads 2 volts (2 amps current).
e. Read the ripple voltage on the Model 403A. This
voltage should be less than 150 microvolts rms. The
peak-to-peak voltage measured on the oscilloscope
should be less than 1.0 millivolt. If not, make sure
the REMOTE-LOCAL switch on the rear of the in-
strument is on LOCAL.
5-40. LOAD REGULATION.
a. With the Model 722A connected as in paragraph
5-39, Ripple Characteristics, tum the DC POWER
switch off and disconnect the load.
Note
In this test we wish to measure voltages
within 3 millivolts.
The resolution of the
Model 405 Voltmeter is not sufficient to mea-
sure this small a voltage at the full output
voltage.
For this reason we will buck-out
almost all of the output voltage with a stable
voltage source, such as another Model 722A,
and then measure only the difference voltage
with high resolution.
b. Connect the load as indicated in paragraphs 5-38,
Operation Characteristics.
Unscrew the plastic in-
sulated ferrules on the two OUTPUT binding posts of
the Model 722A. Attach one end of an alligator clip-
lead to the main body of the negative terminal binding
post in the vicinity of the cross hole. Attach the other
end of this clip-lead to the negative terminal of the
reference voltage supply. Attach one of the alligator
clips of an r5j) AC-16S (shielded dual banana plug to
alligator clips) to the main body of the positive terminal
binding post in the vicinity of the cross hole. Attach
the other alligator clip of the AC-16S to the positive
terminal binding post of the reference voltage supply.
c. Attach the dual banana plug of the AC-16S to the
Model 405 Voltmeter.
d. Turn the CURRENT LIMIT control on the front
panel fully clockwise.
e. Adjust the output current of the Model 722A under
test to 2 amperes on the meter on the front panel.
Adjust the voltage on the reference Model 722A such
5-7
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