Adjustments; Introductions; Equipment Required; Adjustment Interval - HP 3455A Operating And Service Manual

Model 3455A Section V
SECTION V
ADJUSTMENTS
5-1. INTRODUCTION.
5-2. This section contains complete adjustment procedures
for the Model 3455A Digital Voltmeter. After the instru-
ment is adjusted according to the procedures given in this
section, it should meet the 24-hour accuracy specifications
listed in Table 1-1.
§-3. EQUIPMENT REQUIRED.
54. The test equipment required for the adjustments is
listed at the beginning of each adjustment procedure and
in the Recommended Test Equipment table in Section I.
If the recommended equipment is not available, use sub-
stitute equipment that meets the critical specifications
given in the table.
6-5. ADJUSTMENT INTERVAL.
5-6. The 3455A adjustments. should be performed at 90-
day or 6-month intervals depending on the environmental
conditions and your specific accuracy requirements. Adjust-
ments should also be performed after the instrument has
been repeaired.
5-7. ADJUSTMENT SEQUENCE.
5-8. The 3455A Adjustments must be performed in the
sequence in which they are presented. If the dc and ohms
accuracy of the instrument are'satisfactory, the DC Zero
Adjustments and Reference Adjustments can be omitted
and the RMS or Average Converter adjustments can be
performed to optimize the ac voltmeter accuracy.
5-9. TEST POINT AND ADJUSTMENT LOCATIONS.
5-10. Test points and adjustments are labeled on the top
inner cover and rear panel (Reference Module) of the
instrument or are shown in figures designated in the adjust-
ment procedures.
§-11. DC ZERO ADJUSTMENTS.
Equipment Required:
DC Digital Voltmeter (-hp- Model 3490A or 3455A)
a. Remove the 3455A top outer cover and top inner
cover to gain access to the Al0 (Mother) board.
b. Set the 3455A controls as follows:
FUNCTION | 2. oe cccee Se tea a DCV
RANGE) 5.032 dod wae aris aia a 10V
HIGH RESOLUTION. .............. ON
AUTO CALS fice o2.8 Maret aieonne OFF
GUARD» 225.5, 5.8008 pe Besreitune donc betes ON
TRIGGER v2 ee tg ta ee ak jes INT
MATH en 80 32.5 seen nar oe oa OFF
c. Set the test DVM to measure dc volts (autorange).
Connect the DVM's low input to the Al0 board ground test
point and the high input to ALOTO1 (Figure 5-1).
d. Adjust A10R66 (Figure 5-1) for a DVM reading of
0 V + 50 microvolt. Disconnect the test DVM.
e. Set the 3455A RANGE to 100 Vand AUTO CAL to
ON. The 3455A Reading should be 0.0000 V + | count. If
it is not, repeat Steps b through d. If this does not correct
the problem, refer to Section VIII for troubleshooting
information.
f. Reinstall the top inner cover with two or three screws
and reinstall the top outer cover (bottom covers must be
installed).
g. Set the 3455A RANGE to 1 V. Connect a copper
shorting strap across the 3455A INPUT terminals.
h. Allow the 3455A to run at room temperature for
at least 30 minutes.
- i. The 3455A reading should be 0.000000 V + 4 counts.
If it is, proceed to the DC Reference Adjustments (Para-
graph 5-12). If it is not, it will be necessary to change the
value of padding resistor A1OR11O as outlined in the
following steps.
j. Record the 3455A reading: : .
5-1