HP 740B Operating And Service Manual page 9

Section I
The output voltage is accurate to within ± (0.002% of
setting
+
0.0004% of range). Output voltage is indi-
cated on digital readout tubes (first five digits) and
the meter (sixth digit). Maximum output current is
50 mA on the 1 V range decreasing linearly to 20 mA
at full output voltage on the 1000 V range. The front
panel CURRENT LIMIT control allows adjustment of
the maximum output current from approximately 10%
to 100% ofthe available output current at each voltage
setting. Remote sensing allows the output voltage to
be regulated at the load, eliminating the effects of
lead resistance. The output circuit is floating and
guarded. A pushbutton switch allows the output volt-
age to be switched on and off without resetting the
voltage dials.
1-7. DIFFERENTIAL VOLTMETER.
1-8. Used as a differential voltmeter, the Model
740B measures dc voltage on seven decade ranges
from 1 mVto 1000 V. Voltage measurements are ac-
curate within ± (0. 005% of reading + 0.0004% of range
+
1 jlV). The measured voltage is indicated on five
digital readout tubes (first five digits) and the meter
(sixth digit). High input resistance (> 10 10 S1 on all
ranges above 10 mY) is maintained regardless of
whether or not the voltage dials are nulled. The input
circuit is floating and guarded, allowing accurate
measurements to be made under conditions where
ground loops are a problem.
1-9. mGH IMPEDANCE VOLTMETER.
1-10. The Model 740B can also be used as a ± 2%
floating and guarded dc voltmeter with 10 voltage ranges
from 1 jlvto 1000 v. Input resistance is
>
10 10 S1 on
all ranges above 10 m V. The measured voltage is
indicated on the meter.
1-11. AMPLIFIER.
1-12. The Model 740B canbeused as a dc power amp-
lifier in the Voltmeter and Differential Voltmeter
modes of operation by connecting the source to the
input terminals and taking the output from the output
terminals. Voltage gain is unity on the 1 V range and
higher, but increases in 20 dB steps on the lower
ranges to a maximum of 60 dB on the 1 mV range.
Output current characteristics are the same as the
DC Standard mode and the high input resistance char-
acteristics of the Voltmeter and Differential Voltmeter
modes are retained. Voltage gain accuracy is ±(O. 01 %
+
5 ppm of range
+
2
/lV).
1-13. The Model 740B can also be used as a voltage
amplifier in the Voltmeter and Differential Voltmeter
modes with up to 120 dB of voltage gain available at
the rear panel RECORDER OUTPUT terminals.
Voltage at these terminals is directly proportional to
meter deflection and is 0 to ± 1 V on all ranges,
l/J,V
to 1000 V.
1-14. INTERNAL ADJUSTMENT.
1-15. An internalbridging arrangement, requiring no
external equipment, allows resistors in the first and
second decades and the range divider to be ratio
matched to compensate for long term aging effects.
The front panel meter serves as a bridge null indi-
1-2
Model 740B
cator and an internal alignment switch sets up the
bridge. A total of 12 adjustments match the re-
sistors. The only other adjustment affecting basic
instnm1ent accuracy can easily be made with a stan-
dard cell or other known voltage source. The internal
alignment procedure is outlined on the instrument in-
ternal guard cover and described in detail in Section V
of this manual.
1-16. SPECIFICATIONS.
1-17. Table 1-1 lists the specifications for the Model
740B. Specifications are listed by instrument func tion.
Those specifications listed with a function apply Lo
that function only.
1-18. INSTRUMENT IDENTIFICATION.
1-19. Hewlett-Packard uses a two-section eight-digit
serial number (000-00000). If the first three digits
of the serial number on your instrument do noL agree
with those on the title page of this manual, a Manual
Change Sheet supplied with this manual will define
differences between your instrument and the Model
740B described in this manual.
If
a letter prefixes the
serial number, the instrument was manufactured out-
side the United States.
1-20. ACCESSORY EQUIPMENT SUPPLIED.
1-21. The accessory equipment supplied with the
Model 740B is listed in Table 1-2.
Table 1-2. Accessory Equipment Supplied
-hp- Part No. Quantity Description
ll054A 1 Input Cable Assembly
11055B 1 Output Cable Assembly
5000-4932 1 Printed Circuit Board
Extractor
5060-0776 1 7 inch Rack Mounting
Kit
8120-0078 1 AC Power Cord
00740-66535 1 Printed Circuit Board
Extender
00740-90002
1 Operating and Service
Manual
1-22. ACCESSORY EQUIPMENT AVAILABLE.
1-23. Accessory equipment available for the Model
740B is listed in Table 1-3.
Table 1-3. Accessory Equipment Available
-hp- Part No.
Description
llOOOA Test Cahle: dual hanana plug-
to dual banana plug- (44 in.)
l1002A Test Cable: dual banana plug-
to alligator clips (60 in.)
l1003A
Test Cahle: dual hanana plug-
to prohe and alligatur clip
(60 in.)
01794-1