Theory of Operation
Chapter 3: Theory of Operation
Page 3 - 24 Isolette® Infant Incubator (Model C2000) Service Manual
Heater Power
The controller monitors the heater power. A current transformer is in
series with the power to the heater and the humidifier. The output of the
current transformer connects to the A/D converter.
The system enables control of the incubator’s heater. The
microprocessor controls a solid state relay that controls the power to
the heater. The microprocessor and the watchdog circuit control the
safety relay, K3. The release of the safety relay removes power from
the heater regardless of the functionality of the heater triac.
Humidity Heater Power
The controller monitors the humidity heater power. A current
transformer is in series with the power to the heater and humidifier. The
output of the current transformer connects to the A/D converter.
The system enables control of the humidity heater. The microprocessor
controls a solid state relay that controls the power to the humidity
heater. The microprocessor and the watchdog circuit control the safety
relay, K3. The release of the safety relay removes power from the
humidifier heater regardless of the functionality of the humidity heater
triac.
Oxygen Control
The system enables control of the oxygen pneumatics. The
microprocessor provides a PWM signal to the solenoid’s metal oxide
semiconductor field-effect transistor (MOSFET).
The voltage to the oxygen solenoid is monitored and fed into the A/D
converter. This circuit monitors the 12 V power supply and thermal fuse.
Light-Emitting Diodes (LEDs)
The microprocessor drives each light-emitting diode (LED). The
hardware watchdog timer circuit drives the alarm/system fail indicator.
The power fail detection circuitry drives the Power Fail indicator.
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