HP 740B Operating And Service Manual page 43

Section V
Table 5-3. Output Noise and Hum Test Data
DCVM POINTER
ACVM READING
740B RANGE MOVEMENT
(Max. )
(Max. )
1V
±
1
J.lV
100
J.lV
10 V ± 10
J.lV
100
J.lV
100 V ± 100
J.lV
1 mV
1000 V
±
1 mV 10 mV
f.
Connect the ac voltmeter across the + and -
OUTPUT terminals and check the 1 Hz to
1 MHz noise on the 1 V, 10 V, 100 V and
1000 V ranges. Table 5-3 lists the noise
limits for each range.
Model 740B
a. Connect test setup shown in Figure 5-5.
b. Measure the 1 V reference output in
~
VM mode.
Leave the X10 4 SENSITIVITY button depressed.
c. Open the switch to place the 100 kQ resistor
in series with the 740B input. The 740B
meter reading should change less than 10 J.lV
(1 major division).
- - - - - N O T E - - - - -
A change of less than 10 J.l V verifies
the input resistance specification:
greaterthan10 10 Q(1 V range).
In-
put resistance canbe calculated from
the formula:
R.
III
b. Connect + and - OUTPUT terminals to volt-
meter input.
c. Vary 740B ZERO control from one extreme
to the other. Voltmeter indication should
vary from at least -10 J.lVto atleast +10 J.lV.
5-25. DIFFERENTIAL VOLTMETER AND HIGH
IMPEDANCE VOLTMETER PERFORMANCE TESTS.
5-23. ZERO CONTROL LIMITS TEST.
5-24. This test checks the range of the front panel
ZERO control. A sensitive dc voltmeter (-hp- Model
419A DC Null Voltmeter) is required for this test.
a. Set 740B controls as follows:
FUNCTION . .
RANGE . . . .
VOLTAGE SET
STANDARD VERNIER
OUTPUT .
STD
1 V
00000
o
On
where R s
=
input resistance
E a
=
applied voltage (1 V)
~Ea
=
voltage change (less
than 10 J.lV) when
series resistance is
added
5-28. SUPERIMPOSED AC REJECTION TEST.
5-29. This test measures the error introduced when
an ac signal is superimposed on the dc input to the
Model 740B. A 1 V source (-hp- Model 735A DC
Transfer Standard), an oscillator (-hp- Model 651B
Test Oscillator), an ac voltmeter (-hp- Mode1403A),
a 10 kQ ±10% resistor (-hp- Part No. 0684-1031),
and a 2 J.lF ±20%capacitor (-hp- PartNo. 0170-0002)
are required for this test.
a. Connect test setup shown in Figure 5-6. Do
not turn on oscillator yet.
5-26. INPUT RESISTANCE TEST.
5-27. This test measures the Model 740B inputre-
sistance. A 1 V reference supply (-hp- Model 735A
DC Transfer Standard), a 100 kQ ± 1% resistor (-hp-
Part No. 0811-0050) and a solid copper contact knife
switch are required for this test.
b. Measure the 1 V output of the dc transfer
standard in
~VM. Leave the X10 4 SENSI-
TIVITY button depressed.
c. Turn on oscillator; set frequency to 70 Hz;
adjust amplitude for a reading of 1 V on the
ac voltmeter.
IOOKfi!l%
COPPER KNIFE
SWITCH
7C08-8-3OOO2
DC STANDARD/DIFFERENTIAL
VOLTMETER
hp 7408
5-6
Figure 5-5. Input Resistance Test
01794-1