Agilent Technologies 6621A, Service Manual

Page: 40 / 156

3-25 CC Load Effect.
This test measures the change in
output current for a change in the load from High Range
Full Scale Voltage to short circuit.
a. Turn off the supply and connect the output to be tested
as shown in Figure 3-3 with the DVM connected across
the current monitoring resistor, the load switch closed,
and the short switch opened.
b. Turn on the supply and select the output to be tested
(OUTPUT SELECT key on the front panel).
c. Program the current of the selected output to the High
Range Full Scale Current value and the output voltage
to the High Range Maximum Programmable Voltage
value (see Table 3-3) by sending the following strings:
ISET < ch >, < 2, .8, or 4 >
VSET < ch >, < 20.2 or 50.5 >
d. Adjust the load for High Range Full Scale Voltage as
indicated on the front panel display. Check that the CC
annunciator is on. If it is not, adjust the load so the
output voltage drops slightly.
e. Record the output current reading (DVM reading X 10).
f. Close the short switch and record the output current
reading. The difference in the current readings in steps
e and f is the load effect and should not exceed the
values listed below for the particular output being
tested.
Output CC Load Effect
40WLV 1 mA
80WLV 2 mA
40WHV 0.5 mA
80WHV 1 mA
g. Repeat this test (steps a through f) for each output in
your supply.
3-26 CC Source Effect. This test measures the change in
output current that results when the ac line voltage changes
from the minimum to the maximum value within the
specifications.
a. Turn off the supply and connect the ac power line
through a variable voltage transformer.
b. Connect the output to be tested as shown in Figure 3-3
with the DVM connected across the current monitoring
resistor, the load switch closed, and the short switch
opened.
c. Adjust the transformer to 13% below the nominal line
voltage.
d. Turn on the supply and select the output to be tested
(OUTPUT SELECT key on the front panel).
e. Program the current of the selected output to the High
Range Full Scale Current value and the output voltage
to the High Range Maximum Programmable Voltage
value (see Table 3-3) by sending the following strings:
ISET < ch >, < 2, .8, or 4 >
VSET < ch >, <20.2 or 50.5 >
f. Adjust the load for High Range Full Scale Voltage as
indicated on the front panel display. Check that the CC
annunciator is on. If it is not, adjust the load so that the
output voltage drops slightly.
g. Record the output current reading (DVM reading X 10)
h. Adjust the transformer to 6% above the nominal line
voltage.
i. Record the output current reading again. The difference
in the current readings in steps g and i is the CC source
effect and should not exceed the values listed below for
the particular output being tested.
Output CC Source Effect
40WLV 2.2 mA
80WLV 4.4 mA
40WHV 1.4 mA
80WHV 3.2 mA
j. Repeat this test (steps a through i) for each output in
your supply.
3-27 CC RMS Noise. This test measures the rms noise in the
output when operating in the constant current mode.
a. Turn off the supply and connect the output to be tested
as shown in Figure 3-3 with an rms voltmeter
connected across the output, the load switch closed,
and the short switch opened.
b. Turn on the supply and select the output to be tested
(OUTPUT SELECT switch on front panel).
3-12