Theory of Operation
Chapter 3: Theory of Operation
Page 3 - 28 Isolette® Infant Incubator (Model C2000) Service Manual
The watchdog timer trips in 1 second ± 0.4 second unless the above
sequence is completed. Once the watchdog timer trips, the following
occurs:
• The safety relay turns off, removing power from the heater and the
humidifier.
• The fan control reverts to closed loop control, maintaining a constant
fan speed regardless of the door’s position.
• The oxygen solenoid control from the microprocessor is overridden,
and the oxygen solenoid turns off so that no oxygen enters the
hood.
• A constant alarm sounds for a minimum of 500 milliseconds.
• The system failure indicator illuminates.
The microprocessor resets the watchdog timer after a watchdog trip by
sending the above data sequence.
Factory Defaults
Factory defaults are stored in program memory, flash EEPROM.
System parameters are configured and stored in the real time clock
(RTC) module or serial EEPROM. The RTC memory and random
access memory (RAM) are protected against corruption during power
failures and are battery-backed for a period of time.
The program is stored in reprogrammable memory and may be
reprogrammed through a cable connected to the serial port of a
computer. The program memory is stored in a flash EEPROM. The RS-
232 serial port operates at speeds of 115,200 baud to expedite the
speed of the program download.
Power Supply
The power supply is so designed that 1 second after disconnection of
the plug, the voltage between the supply pins of the plug and between
either supply pin and the enclosure does not exceed 60 V by using a
bleeder resistor across the mains filter capacitor, if necessary.
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