HP 740B Operating And Service Manual page 51

Section V
Model 740B
b. Remove instrument top cover.
c. Set front panel controls as follows:
e. Switch RANGE to "Dot" position (fully ccw).
d. Adjust A10R12 (Meter Zero) for zero meter
indication.
There is generally a slight zero
turn-over error between VM and
~ VM modes and this is quite nor-
mal. A10R12 must be readjusted
in
~
VM mode before proceeding
with the following steps.
- - - - - NOTE-----
procedure printed on the guard shield. The
optimum values for these adjustments are
determined at the factory and will vary from
instrument to instrument.
m. Set FUNCTION to STD and RANGE to 1 V. Using
a sensitive dc voltmeter (10
/lV
range) adjust
740B front panel ZERO control for 0 Vdc at
the + and - OUTPUT terminals.
k. Return INTERNAL ALIGNMENT switch to
OPERATE position.
1.
Set FUNCTION to ~VM and check meterindi-
cation. Adjust A10R12 (METER ZERO ADJ. )
for a zero meter indication .
. 100 V
VM
00.000
. X10 4
Shorted
RANGE .
FUNCTION .
VOLTAGE SET.
SENSITIVITY.
INPUT . . .
performed after a normal (60
minute) warmup period. For
optimum instrument accuracy,
this procedure may be repeated
after an eight hour (or longer)
warmup period.
f. Turn INTERNAL ALIGNMENT switch to posi-
tion 1. If meter pointer is off -scale, depress
X10 3 SENSITIVITY.
g. Alternate between positions 1 and 2 adjusting
A1R1 for equal meter deflection (and same
polarity) at both positions.
h. Adjust A1R2 for zero meter indication (X10 4
SENSITIVITY). Positions 1 and 2 should now
both read zero on the meter.
If
not, repeat
steps g and h.
i. Progressively switch to positions 3 through 9
adjusting the corresponding controls (A1R3
through A1R9) for a zero meter indication in
each position.
j. Adjust A9R10, Rll and R12 to the values in-
dicated in step B -6 of the internal alignment
- - - - - N O T E - - - - - -
If
a standard cell is used in the fol-
lowing steps, zero the 740B output
(step m) on the 10 V range.
n. Connect 740B OUTPUT terminals as shown in
Figure 5-13. Set VOLTAGE SET and STD
VERNIER controls to the value of the known
external reference voltage.
- - - - - N O T E - - - - -
If a dc transfer standard is used,
it should be calibrated to 1 V ±2 ppm
according to the procedure in Ap-
pendix C.
DC STANDARD/DIFFERENTIAL
VOLTMETER
hp
7408
@[ ][~l
0
-SENSE
-OUTPUT
~19~~,,--
1408-B-3OO15
NULL DETECTOR
DC NULL
VOLTMETER
hp
419A
REFERENCE
VOLTAGE
SOURCE
DC TRANSFER
STANDARD
hp
735A
Figure 5-13. Reference Supply Calibration
5-14
01794-1