to the concentration of oxygen. Humidity and temperature sensors located in the sensor plug are used for
voltage compensation. A fan mounted to the sensor-housing door is activated when the temperature reaches
50 degrees C. This fan circulates air to keep the sensors below the maximum allowable operating temperature,
about 55 degrees C.
The Servo O2 board is located in the Girae controller enclosure. The microcontroller and integrated EPROM on
the board perform the following:
• Convert sensor output from analog to digital
• Activates oxygen alarm conditions.
• Two-way communications via 485 bus with the Girae control board.
• Controls the calibration valve to select calibration mode.
• Controls the two supply valves to maintain the desired oxygen set point.
• Opens the safety relay, which removes power to the three-way valve and the supply valves in case of a
system failure.
The oxygen delivery system consists of two solenoid supply valves, and a regulator assembly. The preset
regulator regulates the oxygen supply to 345 kPa (50 psi). Two supply valves, controlled by the Servo Oxygen
board, control ow to the infant compartment. Both valves are opened until the measured level gets close to
the desired set point then one valve is closed. One valve is then cycled on and o as needed to maintain the
desired oxygen levels in the infant compartment. The valve selected is alternated so both valves cycle about
the same number of times. There are 2 fuses between the Servo O2 board and the supply valves that prevent
high current from the board entering the valve housing should a short occur in the supply valves. A safety
valve that shuts o oxygen ow whenever the canopy is raised actuates mechanically by the movement of
the canopy support rail. When the canopy is down the valve is open (canopy up/valve closed). The safety valve
actuates independently of the solenoid type supply valves.
8 6600-0343-000 104 © 2001 by Datex-Ohmeda, Inc.. All rights reserved.
Chapter 1: Functional Description
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