Measurement - Dräger PM 8030 Instructions For Use Manual

Appendix
02 Measurement
Measuring principle and signal processing
The 02 sensor functions according to the galvanic cell principle. Oxygen
molecules from the gas mixiure for measurement diffuse through a plastic
membrane into an electro-chemical cell and are reduced at noble metal
electrodes.
Simultaneously oxidation occurs at a base metal electrode which is eroded as
a result of the oxidation process, and thus the life of the sensor is limited. The
current flowing through the cell is proportional to the oxygen partial pressure
in the gas mixture.
At a constant pressure and temperature of the gas mixture being measured,
the measured value is directly proportional to the oxygen partial pressure.
Particularly characteristic of the 02 sensor are the two electrically separated
cathodes which give two independent redundant measuring signals. Both
measuring signals are evaluated electronically and the mean value of both
individual signals is displayed.
Where the individual signals differ beyond a permissible tolerance due to
external or internal malfunction, the display will switch off automatically. This
prevents faulty displays and subsequent faulty interpretation.
I
Anaesthetic agent measurement
Measuring principle
The
anaesthetic agent measurement works with the Drsger Iris sensor (IRIS
= InfraRed Inhalation Sensor). The anaesthetic agents halothane, enflurane
and isoflurane absorb a pulsed light beam inside the measuring chamber. At
a constant pressure, the reduction of light intensity (compared to a calibration
point) can be described approximately as the sum of two exponential
functions.
In the selected wavelength ranges changes in the composition of the gas
mixture (NzO etc.) give no measurable cross sensitivity at the required
accuracy.
PM 8030 is calibrated by the manufacturer at a temperature of 22°C. normal
pressure of
1013
hPa.
Since measurement depends on gas density, the measured value must be
corrected when there is any significant deviation from normal pressure (1013
hPa) and temperature (22%):
Ckorr. =
c
It?.
273+T
P
295
:a,,. =correct measured value
= measured value
PO
= normal pressure 10 13 hPa
Y
= actual atmospheric pressure hPa
= actual temperature "C
No correction for pressure is required for comparing the concentration set on
the Drsger anaesthetic agent vaporiser Vapor 19.n and the display value on
PM 8030.
See Driger Vapor 19.n Instructions for Use.
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