Agilent Technologies 6621A, Service Manual

Page: 35 / 156

h. Now observe Channel B on the oscilloscope while
maintaining the trigger on Channel A as in step f. Note
that the diode clamp, used in the test setup of Figure 3-
4, prevents gross overload of Channel B (which is set at
50 mV/div) allowing examination of the "tail" of the
exponential waveform. The output voltage should be
within 20 mV of its final settling value on the bottom
outputs and within 50 mV in less than 6 msec for 40
WHV/80 WHV outputs. Refer to the Channel B
waveform shown in Figure 3-5.
i. Repeat steps a through h for each output in your
supply.
3-17 CV Up Programming Speed. This test measures the
time required for the output voltage to rise to 63% of the
High Range Full Scale Voltage (time constant). Also
measured is the time the output takes to change from .4
volts to full scale and settle within the specified settling
band (response time).
a. Turn off the supply and connect the output to be tested
as shown in Figure 3-6.
b. Turn on the supply and select the output to be tested
(OUTPUT SELECT key on the front panel).
c. First, program the selected output's voltage to its High
Range Full Scale value (see Table 3-3) by sending the
following string:
VSET < ch >, < 20 or 50 >
d. Set the vertical sensitivity switch of Channel A on the
oscilloscope to 5 V/div (40WLV/80WLV outputs) or to
10 V/div (40WHV/80WHV outputs). With the
oscilloscope's input switch in the GND position, adjust
the trace to the bottom horizontal line. Then set the
input switch to the dc coupled position. Set the vertical
sensitivity switch of channel B on the oscilloscope to 50
mV/div and the input switch to the GND position.
e. Adjust the Channel B trace to the top horizontal line of
the oscilloscope and move the input switch to the DC
position.
f. Adjust the bucking supply until the Channel B trace is
as close as possible (within 1 division) to the top
horizontal line and then use the scope vertical adjust to
fine adjust the trace to the top horizontal line.
3-7
horizontal line in less than 2 msec for 40WLV/80WLV