Respironics ESPRIT, Руководство по обслуживанию, Страница: 27 / 329

Chapter 3
Theory of Operation
REF 580-1000-02 G Esprit® Ventilator Service Manual © Respironics, Inc.
3-13
Analog PCB
The analog PCB performs a digital-to-analog conversion of signals from the
CPU to the blower controller PCB and analog output port. The analog PCB
connects directly to the system bus on the main PCB, and includes these
functional circuits:
• An eight-bit digital to analog converter (DAC) that converts digital
signals from the CPU to analog for the blower and external devices
such as chart recorders and bedside monitors.
• Clocked serial interface (CSI), a high-speed communication link
between the air, oxygen, and exhalation motor controllers and flow
sensor lookup tables contained on the CPU and the voltage monitor
register.
• A circuit that retrieves converted data from the sensor PCB.
Digital PCB
The digital PCB conditions serial port signals coming from and going to the
CPU PCB. It also contains control circuitry for the power fail alarm, primary
alarm, backup alarm, RS-232 port, and rotary encoder.
Digital inputs include analog-to-digital converter (ADC) out of range,
compressor temperature switch, and oxygen present. Digital outputs include
the alarm silence indicator, 100% oxygen indicator, running on AC indicator,
running on external battery indicator, backup battery status indicators, printer
ready signal, and printer direction.
VGA Controller PCB
The VGA controller PCB contains the date and real time clock and LCD VGA
display controller drivers.
Blower Controller PCB
The blower motor controller PCB controls the speed of the blower motor based
on analog input conditioned by the sensor PCB. It includes a lockup sensing
circuit, which monitors sensors in the blower motor to detect a locked rotor
condition. If the blower motor stops running, the lockup sensing circuit shuts
off power to the blower.