HP 740B Operating And Service Manual page 107

Model 740B
Appendix C
IK IK
H
IK
G
IK
F
IK
E
IK
o
IK
c
IK
A B
IK
7408-8 -0802
K L M
.....1N'o-......1N'o-......1N'o-...... 'IMr__ 'lMr__'lMr__'lMr...... 'IMr__ 'lMr......
-w........
~----
-
~
- - -
--~
IK " - - - - 9 -10K ----.J '-----9 -IOOK----.J
190K) (900K)
Figure C -3. Assembling the Divider
r
f. Adjust R x for a null indication on the Null
Voltmeter, 30
Il
V range. This matches R
x
to the series string of 10 previously matched
1 kO resistors.
g. Repeat steps e and f for the five remaining
10 kO resistors. Thismatches the remaining
five resistors to the original
R,r
(series
string of 10 matched 1 kO resistors).
h. Rebuild the matching bridge using any three
of the matched 10 kO resistors for Rl, R2 and
R3. Do not adjust the matched resistors. Use
one of the three remaining unmatched 10 kO
resistors for
R,r.
1.
Adjust
Rx
for null on the Null Voltmeter, 30
IlV range.
j. Repeat steps h and i for the two remammg
unmatched 10 kO resistors. All of the 10 kO
resistors are now matched to each other and
to the series string of 10 matched 1 kO re-
sistors.
3. Use a series string of 10 matched 1 kO re-
sistors and 9 matched 10 kO resistors (total
100kO) for the initial
R,r.
C-l1. ASSEMBLING AND USING THE DIVIDER.
a. Connect the matched resistors as shown in
Figure C-3.
b. The divider is now ready for use. Maintain
constant oil temperature whenever using the
divider.
C-12.
CALIBRATING THE
-hp- MODEL 73SA TO 1 V 2 PPM
C-13. The following procedure can be used to cali-
brate a Model 735A DC Transfer Standard to 1 V ± 2
ppm. Table C-2 lists the required test equipment.
a. Turn on the Transfer Standard and allow
it
to warm up for at least 30 minutes.
C-9. MATCHING THE 100 kO RESISTORS.
C -10. The 100 kO resistors can be matched using the
10 kO matching procedure with the following exceptions:
1. Use 200 Vdc to drive the matching bridge.
b. Construct the calibration setup shown in Fig-
ure C -4. Make connections with insulated
solid copper wire, 20 gauge or larger. Omit
one connection to the standard cell.
c. Zero the Null Voltmeter on the 3
IlV
range.
Return range to 300
Il
V.
2. Set null voltmeter to the 300 Il V range to read
null.
d. Set Transfer Standard Function switch to 1. 018
+ t::..
for saturated or 1. 019
+ t::..
for unsaturated
Table C-2. Required Test Equipment
ITEM
REQUIRED RECOMMENDED
CHARACTERISTICS MODEL
Standard Cell NBS Calibrated Eppley Laboratory, Inc.
MIN type
6 Dial Kelvin-Varley Accuracy: 0.0001% full scale Julie Research Labora-
Divider Resistance: 100 kn tories Model VDRI06
DC Null Voltmeter Range: 3 Il V full scale
-hp- Model 419A
Fixed Resistors 1000 n ±0.05% 1/4
W
-hp- Part No. 0811-0936
low TC wirewound
8543.50 ±0.1% 1/4
W
-hp- Part No. 0811-0125
low TC wirewound
Power Supply Output:. 8 to 10 V adjustable
-hp- Model 740B
Resolution: 1 ppm of range
Noise:
<
1 ppm of range
01794-1 C-3