Agilent Technologies 6621A, Service Manual

Page: 38 / 156

Programmable OV Accuracy Test. This test checks the
overvoltage (OV) programming accuracy. Taking the OV
programming accuracy and the voltage programming
accuracy into account, the upper and lower limits of the OV
firing range for each output type are as follows:
Output Lower VSET Nominal Upper VSET
for no OV OV Setting to fire OV
40WLV/80WLV 18.74 V 19.0 V 19.26 V
40WHV/80WHV 48.38 V 49.0 V 49.62 V
a. Turn off the supply and disconnect all loads and test
equipment.
b. Turn on the supply and select the output to be tested
(OUTPUT SELECT key on the front panel).
c. Program the OV to 1 V below the High Range Full Scale
Voltage value: 19 V (40WLV/80WLV outputs) or 49 V
(40WHV/80WHV outputs). Send the following string:
OVSET < ch >, < 19 or 49 >
d. Program the output voltage to the Lower VSET Limit
specified above by sending the following string:
VSET < ch >, < 18.74 or 48.38 >
e. Note that the overvoltage should not trip and the front
panel should display the programmed output voltage
and no current.
f. Program the output voltage to the Upper VSET limit
specified above by sending the following string:
VSET < ch >, < 19.26 or 49.62 >
g. Note that the overvoltage has tripped as indicated by
the display showing "OVERVOLTAGE".
h. Reset the output by setting the OV to the maximum
value (23 V for 40WLV/80WLV or 55V for
40WHV/80WHV) and resetting the OV circuit as
shown below:
OVSET < ch >, < 23 or 55 >
OVRST < ch >
i. Check that the front panel again displays the
programmed output voltage and no current.
j. Repeat steps b through i for each output in your
supply.
External OV Test. This test checks the operation of the
external OV circuit.
a. Turn off the supply and connect the OV terminals of all
outputs in parallel noting proper polarity. Figure 3-11
shows two outputs connected in parallel.
b. Turn on the supply and select the desired (OUTPUT
SELECT key on the front panel).
c. Program the output voltage to 5 V and the OV to 4 V.
OVSET < ch >, 4
d. Note the display should indicate "OVERVOLTAGE" for
all outputs.
e. Reset all outputs by turning the supply off and on
again.
f. Repeat the above tests until all supply outputs have
been checked.
3-21 Constant Current (CC) Tests
3-22 CC Setup. Follow the general setup instructions of
paragraphs 3-5 through 3-9 and the specific instructions
given in the following paragraphs.
3-23 Current Programming and Readback Accuracy. This
and front panel display functions are within specifications.
of the current monitoring resistor must be 0.05% or better.
a. Turn off the supply and connect a 0.1 ohm current
monitoring resistor across the output and a DVM across
the resistor (see paragraph 3-8).
b. Turn on the supply and select the output to be tested
(OUTPUT SELECT key on the front panel).
c. Program the output voltage to 5 V and the current to
VSET <ch>,5
ISET < ch >,0
NOTE
An output channel cannot be programmed to 0 amps. If
the output channel receives a command to go to 0 amps
(or any positive current below the minimum
programmable current), it will set itself to the minimum
value (see Tables 3-2 and 3-3).
3-10
VSET < ch >, 5
the Minimum Programmable Current value by sending
the following strings:
test verifies that the current programming, GPIB readback,
An GPIB controller must be used for this test. The accuracy