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104

Temperature Processing

Measurement of patient temperature is accomplished by processing the signal from a

probe containing a resistor whose resistance is temperature dependent. The class of such

components is called thermistor.

Temperature measurement used by the M30 monitor is based on a thermistor whose

resistance is inversely proportional to its temperature. By measuring the thermistor’s

resistance, its temperature can be calculated. The resistance of the thermistor is

measured by passing a current through it and measuring the voltage developed across it.

The M30 monitor is designed to accept the signals from a range of temperature probes

from the YSI-400 and YSI-700 series. The probes may be used for skin or rectal

temperature measurement. Probes are furnished with a standard 10-foot lead; extension

leads are available. The signal from the probe is conditioned by the monitor input circuitry,

processed, and used to drive the numeric display.

Processing

The M30 CO

sensor measures CO

by using the infrared technique. The principle is

based on the fact that CO

molecules absorb infrared (IR) light energy of specific

wavelengths, with the amount of energy absorbed being directly related to the CO

concentration. When an IR beam is passed through a gas sample containing CO2, the

electronic signal from the photodetector (which measures the remaining light energy) is

measured. This signal is then compared to the energy of the IR source and adjusted to

accurately reflect CO

concentration in the sample. The M30 CO

sensor’s response to a

known concentration of CO

is stored at the factory in the sensor’s memory. A reference

channel accounts for optical changes in the sensor, allowing the system to remain in

calibration without user intervention.

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Mediana P10 Manual de Serviço Página 110