Power Supplies
Referring to the schematic shown on page 9-15, the multimeter uses two
types of power supplies: floating supplies and earth referenced supplies.
The floating supply outputs are
±
18 Vdc, +5 Vdc, and a 5 Vrms center
tapped filament supply for the vacuum fluorescent display. The earth
referenced circuits are powered from a 5 Vdc supply.
The ac mains are connected by module
P1
. This module includes the
functions of mains connection, on/off switching, and line voltage
selection (100/120/220/240). The multimeter automatically configures
for the applied line frequency by counting the frequency of the output of
clamp circuit
CR554
,
R555
,
C555
(
LSENSE
).
The 5 volt floating supply is produced by bridge rectifier
CR552
, filter
capacitor
C556
, and regulator
U553
. The reset output of
U553
will change
to logic
LO
when the unregulated dc input to the regulator falls below
5.5 volts.
XPONRST
is the instrument master hardware reset signal.
This supply powers all floating logic. Relay drive circuits are also
powered from this supply.
The floating
±
18 volt supplies are produced by bridge rectifier
CR551
,
filter capacitors
C551
and
C553
, and regulators
U551
and
U552
. These
supplies are used to power all measuring circuits. In addition, the
vacuum fluorescent display is driven from the
±
18 volt supplies. A
separate winding of T1 provides a center tapped 5 Vrms filament supply
for the display. Bias circuit
CR556
,
R556
, and
C559
generates the
required cathode dc bias for the display filament supply.
The 5 volt earth referenced supply is produced by rectifier
CR751
,
C752
,
and regulator
U751
. This supply is earth referenced by the screw which
mounts the
PC
board to the instrument chassis. The
GPIB
(
IEEE-488
)
and
RS-232
interfaces along with other input/output circuits are powered
from this supply.
Chapter 5 Theory of Operation
Power Supplies
106
Содержание 34401A
Страница 1: ...Keysight 34401A 6 Digit Multimeter Service Guide ...
Страница 2: ......
Страница 17: ...Contents 10 ...
Страница 18: ...1 Specifications 1 ...
Страница 33: ...26 ...
Страница 34: ...2 Quick Start 2 ...
Страница 54: ...3 Menu Tutorial 3 ...
Страница 65: ...58 ...
Страница 66: ...4 Calibration Procedures 4 ...
Страница 98: ...5 Theory of Operation 5 ...
Страница 115: ...108 ...
Страница 116: ...6 Service 6 ...
Страница 132: ...7 Replaceable Parts 7 ...
Страница 143: ...136 ...
Страница 144: ...8 Backdating 8 ...
Страница 147: ...34401 66522 Display Assembly Component Locator Chapter 8 Backdating Agilent 34401A Multimeter 140 ...
Страница 149: ...9 Schematics 9 ...
Страница 165: ...This information is subject to change without notice Keysight Technologies 1991 2014 Edition 9 August 2014 34401 90013 ...