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4.4.2.2 D/A & A/D Conversion Circuits
Refer to page 8-12 in Section 8. U30 and U31 are six channel multiplexer/A-to-D converters. Each
multiplexer reads their prospective analog DC voltages and convert it to digital signals. This allows the
microprocessor to read the digital values which represents an analog voltage after it has received the READ/
WRITE signal.
• U30 reads the following analog voltages: ±15VDC signals from U25 pins 1 and 7, +5VDC
from U25 pin 8, TESTDAC signal from U24 pin 7 and WATERTEMP signal from U29 pin 7.
• U31 reads the following analog voltages: SAFETY_ENERGY signal from U21 pin 3, WATER-
RESIST signal from U27 pin 6, MAIN_ENERGY signal from U20 pin 3, TESTDAC signal
from U24 pin 7 and V-F_FEEDBACK signal from U28 pin 7.
U32 is a D/A converter which outputs a signal to test and checks the A/D converters. It is also used to set the
comparator trip levels for the Lamp Volts & Lamp Energy Frequency Generators.
4.4.2.3 DC Power Supply Monitor Circuits
Refer to page 8-12 in Section 8. The low voltage power supply outputs are continually monitored during
operation of the laser to verify that the outputs are within tolerance. Any out-of-tolerance condition results in
a fault code display and laser set in STANDBY.
The microprocessor monitors the actual voltages to the +5, ±15 VDC supply outputs by reading the 12 bit
digital output of the A/D converter U30. Inputs to the A/D converter U30 channels 0, 1 and 2 correspond to
±15 and +5 VDC respectively. Any low voltage output that falls below or goes above a specified voltage sets
the microprocessor to display a fault code on the LCD display.
4.4.2.4 Audio Amplifier Circuit
Refer to 8-9 in Section 8. The Audio Amplifier circuit provides an audio indicator for the system status. An
audio tone from a speaker sounds when the following coditions occur:
• The system has finished its self-test routine during the initial turn-on.
• A tone sounds when a system error occurs.
• A tone sounds anytime a parameter is changed.
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