Chapter 8: Theory of Operation
Block-Level Theory
150
Power Supply Assembly
The AC input to the power supply is 100–240 VAC ±10%. Maximum input power is 550 W. The
AC input frequency is 47 to 63 Hz.
Filtered voltages of +5.1 V, +12.25 V, 3.3 V, and –12.25 V are supplied and distributed throughout
the oscilloscope.
FPD Monitor Assembly
The Flat Panel Display (FPD) monitor is a thin film liquid-crystal display (TFT-LCD). This FPD
is an 8.4-inch diagonal, 1024 by 768 pixel XGA color monitor. The assembly requires +3.3 V and
+12 V from the power supply.
A twin fluorescent back light provides illumination for the LCD. The Backlight Inverter assembly
converts the +12 V to +300-1000 volts (AC rms) and drives the back light.
Acquisition System
The acquisition circuitry samples, digitizes, and stores the signals for each channel. The graphics
board provides the system control interface from the motherboard, and also interfaces the
acquisition board to the display board for display of the acquired data. More detailed theory on
the acquisition system follows this top-level block theory.
Front Panel
The front panel is read and controlled by a micro controller IC. This device contains a
microprocessor, RAM, ROM, and a DUART for communication with the microprocessor on the
main assembly. The micro controller is located on the keyboard and communicates with the
system control circuitry through an RS-232 cable. It reads the keys and knobs and controls the
LED indicators.
The elastomeric keypad has 22 keys, each dedicated to a single function to improve ease of use.
A conductive element on the inside of each key shorts a gap on the underlying keyboard circuit
board. The keyboard controller detects this short and sends the proper keypress information to
the system controller on the motherboard.
There are eleven dedicated knobs. Each knob controls a mechanical encoder. The output of the
encoder is a 2-bit gray code that is read by the micro controller for direction and distance turned.
A pushbutton controls the power through a Power Control line that is routed to the motherboard.
Disk Drive
The hard disk drive is a high-capacity, shock-resistant unit. It is used to store the oscilloscope
operating system and certain system configuration data.
The drive can also be used to store and recall oscilloscope setups and waveforms.
To Next Page
Loading...
Need help?
General
