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8. APPLICATIONS
8.1 Exposure to Anesthetic Gases
Because of the unique chemistry of the oxygen sensors provided with the
MAXO
2 analyzer, there are no significant effects when exposed to
commonly used anesthetic gases, however, the analyzer is not designed
for exposure to flammable gas mixtures. (See WARNING page i)
8.2 Calibration Techniques in Pressurized Systems
Similar to other oxygen sensors, the MAX series sensors measure the
partial pressure of oxygen in a gas stream. This is correlated to read
“percent oxygen” on the MAXO
2 analyzer. It is important to note that the
sensor output is directly proportional to the pressure of oxygen. Thus,
one must take into consideration the effect of exposing the sensor to
various gas sample pressures.
For example, if an analyzer is calibrated to read 20.9% in ambient air
(atmospheric pressure) and then exposed to a pressurized gas sample
containing a known concentration of oxygen, the analyzer will display a
reading greater than the actual oxygen percentage. This is because the
analyzer was originally calibrated at atmospheric pressure (0 psig) then
exposed to a higher pressure sample (eg, 5 psig). The greater the
difference in pressure, the greater the difference in sensor signal (oxygen
reading on the analyzer).
By the same token, if an analyzer is calibrated on a pressurized gas
sample containing a known concentration of oxygen and then exposed to
ambient air (atmospheric pressure), the analyzer will display a reading
less than the actual oxygen percentage.
To avoid confusion, the analyzer can be calibrated at a single point on a
gas stream similar to the application. If, for example, the purpose of the
analyzer is to measure oxygen in a concentrator or anesthesia
application, the optimal results may be attained by calibrating the
instrument on a gas of similar concentration and pressure. This would
typically be done by connecting to a cylinder of a known high
concentration of oxygen calibration gas and adjusting the flow and
pressure to match the application before calibrating the instrument.
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