HP 740B Operating And Service Manual page 106

Appendix C
DC NULL
VOLTMETER
hp
419A
~II@
~,
0 0
.=
J
IJ
DC STANDARD/DIFFERENTIAL
OIL BATH
\/ II
VOLTMETER
~
OUTPUT CABLE
/L
hp740B
f!
hp
1I055B RI R3
IK IK
@I
11~1
0
~
..
.
R2
R.
@@@@@@@
..
IK IK
U
~ ~
/\
J \
l'4011-.~oeol
Figure C-l. 1 kO Matching Bridge
Model 740B
k. Repeat steps i and j for the remamrng
un-
matched 1 kU resistor. All of the 1 kO re-
sistors are now matched to each other and to
the original reference resistor,
!lx.
C-8. MATCHING THE 10 kO RESISTORS.
a. Rebuild the matching bridge as shown in
Figure C -2.
~
is a series string of the 10
matched 1 kO resistors.
b. Set null voltmeter to the 30
J.l
V range and
check meter zero.
c. Apply 20 Vdc to the bridge from the Model
740B.
d. Adjust R3 for a null indication on the Null
Voltmeter, 30
J.lV
range. Do not adjust any
of the 10 matched 1 kO resistors. If adjusting
R3 does not produce null, adjust R1 or R2 until
null is achieved.
ALWAYS DE-ENERGIZE THE 740B
OUTPUT WHEN MAKING CHANGES
IN THE MATCHING BRIDGE SETUP.
e. Replace R
x
(10 - 1 kO resistors) with one of
the six remaining 10 kO resistors.
DC NULL
VOLTMETER
hp
419A
C-2
~II@
~~
J
J
\ I //
DC STANDARD/DIFFERENTIAL
OIL BATH
V /
VOLTMETER
~
OUTPUT CABLE
/L
hp740B
f!
hp
1I055B
RI R3
10K 10K
@I
II~I
0
~
..
.
R2
:llK
@@@@@@@u~"~
10K
(IO-IK)
/\
J \
1401-1-080.
Figure C-2. 10 kO Matching Bridge
01794-1