Ohmeda Biox 3700 - Functional Components

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FUNCTIONAL COMPONENTS
The Ohmeda Biox 3700 uses electriral M„,„rtnM» *
discussion explains the function ol! C°np0nents ln siS^l processing. This
* the probe
* the analog and digital electronics
* the calculations the microprocessor makes.
TIMING
CONTROL
DIGITAL
PROCESSING
PROBE
ANALOG
PROCESSING
A/D
CONVERTER
DISPLAY
PROBE
The probe consists of: the light source, and the photodetector.
IT Hfm em,ittln* diodes <LEDs> impose the light source of the Ohmeda
Biox 3700 oximeter:
* one Red (R)
* one Infrared (IR).
The photodetector is a photodiode: An electronic device that produces an
electrical current proportional to incident light intensity.
The photodetector sees only light energy and does not distinguish between
light wavelengths. The timing circuitry sequences the Red and Infrared
light sources on and off. The established timing sequence is:
* red LED on
* infrared LED on
* both LEDs off.
This sequence repeats itself. This cycling occurs 480/400 (60/50 Hertz)
times per second allowing the photodetector to quantify the light energy at
the appropriate wavelengths by producing a current at appropriate points in
the cycle. The on/off LED cycling also determines the effect of ambient
light hitting the photodetector. The off point or "dark" portion in the
light sequence is measured and utilized to eventually cancel the effects of
the ambient light. The photodetector produces current and an operational
amplifier in the oximeter converts it to voltage for further processing.
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