HP 740B Operating And Service Manual page 44

Model 740B Section V
DC STANDARD/DIFFERENTIAL
VOLTMETER
hp
740B
INPUT CABLE
hp
1I054A @!
)I~I
+INPUT
0
~Fn
AC VOLTMETER
~.
@
.
hp
403A
I'-'
~NPUT
~@@@@ @@0@
B@
2JLF
@
TEST OSCILLATOR
DC TRANSFER
hp
651B
STANDARD
hp
735A
@EJ
IOK!l
11.©2
0
~
II
o
@
@
; 0
®
$
@@
0
' - - IV OUTPUT
4ii (L
'.oe-B-JOOO3
Figure 5-6. Superimposed AC Rejection Test
d. After the initial transient, the 740B reading
should return to within 10 /lV (1 major meter
division) of the initial reading. This verifies
the specification: Less than 0.001% error
for ac voltages above 60 Hz equal to the DC
signal (25 V rms, maximum).
5-30. AC COMMON MODE REJECTION TEST.
5-31. This test measures the error introduced by an
ac signal applied between the + INPUT and ~ termi-
nals with a 1 kn unbalance across the + and - INPUT
terminals. A testoscillator(-hp- Model 651B), anac
voltmeter (-hp- Model 403A), and a 1 kn
±
10% resistor
(-hp- Part No. 0684-1021) are required for this test.
b. Adjust ZERO control to zero the 740B meter.
c. Remove short from input terminals.
d. Construct test setup shown in Figure 5-7.
e. Set oscillator frequency to 60 Hz; :;djustamp-
Utude to 10 V rms as indicated by the ac volt-
meter.
f.
740B meter deflection should be less than
10 /lV (1 major division). This verifies ac
common mode rejection> 120 dB where:
Common Mode Rejection
=
Eosciilator (rms)
740B
5-32. ACCURACY AND LINE REGULATION TEST.
a. Set 740B controls as follows:
t:>.VM mode
VM mode
FUNCTION . .
RANGE . . . .
SENSITIVITY .
INPUT . . . .
. VM
1V
X1Q4
Shorted
5-33. This test compares the measuring accuracy of
the Model 740B with the specifications:
±
(0.005% of reading + 0.0004%
of range + 1 /lV) .
±(2% of end scale + 0.1 /lV)
hp
740B
DC STANDARD/DIFFERENTIAL
VOLTMETER
AC VOLTMETER
hp403A
TEST OSCILLA1DR
hp651B
o@@I~I@
B@
@[
)(~l
0
@
0 0
®
$
@
f--,
@
•
I~~
@ @ @ @ @ @
@
0@
I 8
INPUT CABLE
.- hp
1I054A
*--.~
§"
GUARD
+-'F!DIIl!I(,~-
~
~
7408-8- 30004
Figure 5-7. AC Common Mode Rejection Test
01794-1
5-7