Theory of Operation
This chapter describes the electrical operation of the oscilloscope to the module
level. The block diagrams show four-channel and two-channel oscilloscope
module inter
connections. (See Figure 1 on page 5.) (See Figure 2 on page 6.)
Power Supply
The Power S
upply board converts AC line voltage to +12 V to power for all
internal circuits.
I/O Board
The I/O board contains USB ports, an Ethernet port (LAN), a VGA Video port, an
AUX OUT BNC connector, and an EXT REF IN BNC connector.
Main Board and Analog Board
The Main and Analog boards contain the following functions:
Acquisition System
The Ac
quisition system begins with the analog signal path and ends with a
digitized signal in memory. The signal enters a c hannel input, and then passes
through an attenuator and preamplifier. The analog signal from each preamplifier
goes through a digitizer, a time base controller, and then into acquisition memory.
The analog signal from each preamplifier is also distributed to a trigger c ircuit.
Trigger System
The Trigger system processes the analog signals from the preamplifiers and sends
trigger information to the time-base controller. Advanced trigger functions are
enabled only when the appropriate application modules and supporting software
are installed.
Di
splay System
The Display system combines live waveform data from acquisition memory with
menus and text, and stores this information in display memory. It then uses this
data to refresh the XGA display module (LCD).
Processor System
The Processor system contains a 460EX Power PC microprocessor that controls
the entire instrument. The process or system also contains FLASH ROM, system
RAM, and interfaces to USB ports and the Ethernet port.
MSO4000B and DPO4000B Series Digital Phosphor Oscilloscopes Service Manual 3
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