Keysight 34401A, Руководство по обслуживанию

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Block Diagram
Referring to the block diagram on page 9-7, you will notice that the
multimeter’s circuitry is divided into two major blocks: the floating
circuitry and the earth (ground) referenced circuitry. All measurement,
control, and display functions are contained in the floating section.
This section contains the input switching, function selection, and
measurement circuitry. It also contains the multimeter’s main
CPU
.
All measurement setup and a-to-d conversion is performed in the
floating section. Each measuring function converts the input to a
dc voltage between
±
12 volts. The
ADC
(a-to-d conversion) changes the
dc voltage into a digital representation. This digital information is used
by the main
CPU
to calculate the reading. Data stored at the time of
calibration is recalled and used to correct the measurement data.
The corrected reading is then formatted and sent to the front-panel
processor for display. The corrected reading can also be sent to the earth
referenced
I/O
processor for output to the remote interface.
The earth referenced circuitry consists of a processor configured as a
slave to the main
CPU
. This processor establishes external
I/O
communications with the main
CPU
through an optically-isolated serial
communication link. The earth referenced processor provides the
GPIB
(
IEEE-488
) and
RS-232
interfaces. It also handles external trigger and
voltmeter complete handshake signaling.
Separate power supplies are provided for the floating and earth
referenced sections. The front panel operates from the floating section
with its logic common different from the floating
CPU
logic common.
5
Chapter 5 Theory of Operation
Block Diagram
93