Siemens SC 7000 Service Manual page 45

SC 7000 and SC 9000XL Patient Monitors
10.3 Cardiac Output
11etCO Module
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ASK-T898-03-7600
7k9kXLTM.c2.CD_ROM.fm/04-99/kaupp
The two thermistor signals are connected to a precision resistor network to
linearize voltage vs temp curve of the thermistor. The thermistor signals are
filtered and clamped before amplification. Two calibration voltages are also
sampled by the A/D converter to correct amplifier offset and gain errors.
The catheter also has a reference resistor which is read for calibration.
The front bezel switches on the HemoMed are converted to unique voltages
when pressed, allowing a voltage to be sent to the A/D converter, which can
be decoded by the front end processor into the corresponding switch
closure.
Figure 2-15 etCO Sensing Process Functional Block Diagram
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The etCO module non-invasively monitors end-tidal CO
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that relies on the selective absorption properties of the CO
frequencies of infra-red radiation. See
In the sensor a thick film infra-red source is pulsed at a rate of
approximately 87 Hz, generating a broad- band spectrum of IR. Selective
filtering separates this into two narrow regions, one inside and one outside
the band of CO absorption. The detector associated with the filter outside
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the band of CO absorption records the maximum level of the source
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energy since the signal it receives is not affected by CO
baseline which serves as a Reference for the level of CO
The other detector senses a filtered energy level modified by the presence
of CO . As the level of CO
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absorb more of the light energy and less signal reaches the detector. This
signal, converted by the detector, is referred to as the Data signal. Current
through the thick-film source is bidirectional to offset the tendency of
particles within the source to migrate when exposed to a strong
unidirectional electric field caused by current flow only in one direction. This
keeps the structure of the source uniform and enhances system integrity
and life of the product.
To acquire a precise level of CO
sampled and the level of CO
the Reference channels. The ratio is compared to a look-up table in
memory to establish the correct value in units of mmHg.
The module then sends the results to the host system for further processing
and display.
Siemens Medical Systems, EM-PCS Danvers
NOT A CONTROLLED DOCUMENT
Figure 2-15.
increases, the CO gas molecules in the airway
2 2
, both channels are simultaneously
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is determined from the ratio of the Data and
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Service Manual
using a technique
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to specific
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. It provides a
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in the airway.
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