Agilent Technologies 6621A, Service Manual

Page: 42 / 156

i. Close the short switch and immediately record the
output current.
j. Wait 30 minutes and again record the output current.
The difference in the readings taken in steps i and j
should be less than the values given in step h for the
particular output type being tested.
k. Repeat steps a through j for each output in the supply.
3-33 Long Term Voltage Drift Test. This test measures the
output voltage drift over an 8 hour period. Place the supply
to be tested in a temperature chamber or in a temperature
controlled environment such as a standards room.
a. Turn off the supply and connect the output to be tested
as shown in Figure 3-3 with the DVM connected across
the + S and - S terminals, 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 Low
Range Maximum Programmable Current value and the
output voltage to the Low Range Full Scale value (see
Table 3-2).
d. Adjust the load for slightly less than Low Range Full
Scale Current as read on the display. Check that the CV
annunciator is on.
e. Wait 30 minutes and record the output voltage reading
on the DVM.
f. Observe and record the output voltage reading
periodically over an 8 hour period. The difference
between any two readings should not exceed 1.84 mV
for 40WLV/80WLV outputs or 3.4 mV for
40WHV/80WHV outputs.
g. Repeat steps a through f for each output in your
supply.
3-34 Long Term Current Drift. This test measures the
output current drift over an 8 hour period. Place the supply
to be tested in a temperature chamber or in a temperature
controlled environment such as a standards room.
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 Low
Range Full Scale Current value and the output voltage
to the Low Range Maximum Programmable Voltage
value (see Table 3-2).
d. Adjust the load until the output enters the CC mode
with the displayed output voltage slightly less than the
Low Range Full Scale Voltage value as read on the front
panel display. Check that the CC annunciator is on.
e. Wait 30 minutes and record the output current (DVM
reading X 10).
f. Observe and record the output current reading
periodically over an 8 hour period. The difference
between any two readings should be less than the value
listed below for the particular output type tested.
Output Drift
40WLV 3.6 mA
80WLV 7.2 mA
40WHV 2.64 mA
80WHV 5.28 mA
g. Repeat steps a through f for each output in your
supply.
3-35 TEMPERATURE COEFFICIENT
(TC) TESTS
These tests check certain temperature coefficient
specifications with the supply placed in a temperature
controlled oven that provides an even temperature
distribution. The temperature is varied over the supply's
operating range and changes in output voltage and current
are measured. The supply is left in the oven for 30 minutes
to ensure stability. Note that the test equipment,. e.g.
current monitor resistor, DVM, load, etc., is located outside
of the oven.
3-36 Output Voltage and Readback
Voltage
TC
a. Turn off the supply and connect the output to be tested
as shown in Figure 3-3 with the DVM connected across
the + S and -S terminals, 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 Maximum Programmable Current value and the
output voltage to the High Range Full Scale Voltage
value (see Table 3-3).
d. Adjust the load for slightly less than High Range Full
Scale Current as read on the display. Check that the CV
annunciator is on.
e. Set the temperature chamber to 30 degrees C and allow
30 minutes for the output to stabilize.
f. Record the output voltage on the DVM.
the value.
h. Increase the temperature to 40 degrees C and allow 30
minutes for the output to stabilize.
i. Repeat steps f and g. Note the difference between the
values read before and after the temperature change.
The difference between the output voltage DVM
readings should be less than 16 mV for 40WLV/80WLV
outputs or less than 40 mV for 40WHV/80W`HV
outputs. The difference the readback voltage should be
less than 21 mV for 40WLV/80WLV outputs or less
than 50 mV for 40WHV/80WHV outputs.
3-14
g. Readback the output voltage over the GPIB and record