Dc Current Test; Dc Common Mode Rejection Test - HP 3478A Technical Manual

3478A
u. (Step #23.) Turn Autozero on by pressing the blue
Shift button and then the INT/TRIG (AUTO/ZERO)
button.
v. (Step #24.) Set the 3478A to the 300V Range.
Check the full scale accuracy by setting the DC Volts
Standard for an accurate output of + 300V. Check and
record the reading.
w. (Step #25.) Turn the DC Standard's output off.
Disconnect the DC Volts Standard and Digital Voltmeter
from the 3478A.
x. (Step #26.) The DC Common Mode Rejection Test
is next. Do the following:
1. Set the 3478A to the 30mV Range.
2. Connect a IK ohm resistor (-hp- Part No. 0698-
1021) between the 3478A's HI and LO INPUT Terminals.
3. Note the 3478A's reading.
4. With the DC Volts Standard's output off, connect
the standard to the 3478A as shown in Figure 4-3.
5. Set the DC Volts Standard for an output of 500V
and then turn its output on. Check and make sure the
3478A's reading is within .O5OmV of the reading noted
in step 3.
y. Turn the DC Volts Standard's output off and then
disconnect it from the 3478A. This completes the DC
Volts Test. If any test fails, try calibrating the instrument
(go to paragraph 4-86). If the test still fails, go to Section
VII of this manual for troubleshooting.

4-54. DC Current Test

4-55. The DC Current Test limits are printed on the DC
Current Test Card and in Table 4-4. Each step on the
test card also corresponds to a step in the procedure
with each step number shown in parenthesis in the
procedure.
4-56. Unless otherwise noted, all test signals are applied
to the 3478A's A (Amps) and LO INPUT Terminals.
4-57. Equipment Required.
required test equipment for the DC Current Test.
The following is the
Table 4-4. DC Current Test Limits
Figure 4-3. DC Common Mode Rejection Test
Digital Voltmeter (-hp- Model 3456A) DC Volts Standard
(Systron Donner Model M107) AC-DC Current Calibrator
(Valhalla Model 2500)
4-58. Test Procedure.
Performance Test has been completed, before doing the
DC Current Test. Also make sure the 3478A has been
warmed up for at least one hour, then do the following:
a. (Step #1.) Reset the 3478A by pressing the blue
Shift button and then the SGL/TRIG (TEST/RESET)
button.
b. (Step #2.) Set the 3478A to the DC Current
Function and short the multimeter's A (Amps) Terminal
to the LO INPUT Terminal. The instrument should now
be on the 300mA Range.
c. Record the displayed reading on the Test Card and
make sure the reading is within the limits shown on the
Test Card and in Table 4-4.
d. (Step #3.) Set the 3478A to the 3A Range. Check
and record the reading.
e. (Step #4.) Remove the short from the INPUT
Terminals and set the multimeter to the 300mA Range.
f. Set the DC Volts Standard for a + IV output,
g. Set the Digital Voltmeter to the DC Volts Function,
IV Range, and 6 Digit Display mode.
h. Set the AC-DC Current Calibrator to the 100mA
Range.
4-7
TM 11-6625-3071-14
Make sure the DC Volts