Adjustment Location; Dcv Adjustment - HP 3456A Operating And Service Manual

Adjustments
5·9. ADJUSTMENT LOCATION.
5-10. All the adjustments for the 3456A are located
behind a front panel section located at the front input
terminals (see Figure 5-1). This section must be removed
when doing any 3456A Adjustments. A procedure to
remove the section is as follows:
a. Locate the front panel section.
b . Remove the section by loosening the hold down
screws located at the section's left and right side.
c. Once the screws are loosened, remove the front
panel section. One way to do it is to hold both of the
loosened screws and pull the front panel section perpen­
dicular and away from the 3456A's front.
It
STEP 1 ; LOOSEN SCREWS
___
# 2 :
STEP REMOVE PANEL SECTION
CALIBRATION POTS
Figure 5·1. 3456A Adjustment Location.
5·1 1 . DCV ADJUSTMENT.
5-12. The 3456A has to be warmed-up for at least I
hour before doing any adjustments. The test equipment
used for the DCV Performance Test is also used for the
DCV Adjustments. Refer to Section IV, Paragraph 4-6
for the critical specifications and requirements.
5·2
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0
..
.
5·13. Equipment Required.
Reference Divider (Fluke Model 750A)
DC Transfer Standard (Fluke Mode 731 B)
DC Standard (Systron Donner Model M 107)
DC Null Voltmeter (-hp- Model 419A)
5-14. Adjustment Procedure.
a. Press the 3456A's RESET button and set the
instrument to the 6 digit mode by storing "6" into the N
DIG DISP register.
b . Set the DC Transfer Standard for a 10 V output
anrl connect it to the 3456A's VOLTS input terminals.
Make sure the " + " output is connected to the 3456A's
VOLTS HIGH terminal.
c. Adjust the 3456A's calibration potentiometer "B"
+
for a 10.00000 V I count reading on the display. If
±
unable to adjust to the required reading, go to the next
step. If able to adjust to the required reading, go to Step
e .
d. Do the following:
I . Turn calibration potentiometer "B" completely
counterclockwise.
2. Turn adj ustment "A" until the 3456A's reading is
as close to +
10 V
higher than + 10.00000 V , turn adjustment "A"
one position for a less than
3. Adjust calibration pot "B" for a
±
I count reading.
e. Set the DC Transfer Standard to I V.
f. Adjust calibration pot "C" for a + 1 .0000 00 V
± I count reading.
g. Disconnect the DC Transfer Standard from the
3456A's input.
h. Set the 3456A to the 100 mV (100 -3) range and
short the input terminals.
i. Turn on the 3456A's Null math feature, take an
offset reading, and then remove the short.
j. Using short pieces of number 20 A WG (or thinner)
insulated solid copper wires, connect the Transfer
Standard and the DC Null Voltmeter to the Reference
Divider as shown in Figure 5-2 and 5-3.
k. Turn the DC Standard's output off. Using 24 inch
or shorter shielded cables equipped with banana-plug
connectors, connect the DC Standard and the 3456A to
the Reference Divider as shown in Figure 5-2 and 5-3.
Model 3456A
as possible. the reading is
If
+
10 V reading.
+
10.0000 0 V