Environment And Oxygen Sensor Readings; Pressure Changes; Humidity Changes; Temperature Changes - MSA Orion Manual De Operaciones

Chapter 7, Performance Specifications
Table 7-5. OXYGEN - Typical Performance Specifications
RANGE 0 to 25% O
RESOLUTION 0.1% O
REPRODUCIBILITY 0.3% O
RESPONSE TIME 90% of final reading

Environment and Oxygen Sensor Readings

A number of environmental factors may affect the oxygen sensor
readings, including changes in pressure, humidity and
temperature. Pressure and humidity changes affect the amount of
oxygen actually present in the atmosphere.

Pressure Changes

The Orion oxygen sensor is designed to compensate for ambient
pressure changes in the area of instrument operation. If pressure
changes rapidly (e.g., stepping through airlock) the oxygen sensor
reading may temporarily shift, and possibly cause the detector to
go into alarm. While the percentage of oxygen may remain at or
near 20.8%, the total amount of oxygen present in the
atmosphere available for respiration may become a hazard if the
overall pressure is reduced to a significant degree.

Humidity Changes

If humidity changes to any significant degree (e.g., going from a
dry, air conditioned environment to outdoor, moisture laden air),
oxygen levels can change up to 0.5%. This is due to water vapor
in the air displacing oxygen, thus reducing oxygen readings as
humidity increases. The oxygen sensor has a special filter to
reduce the affects of humidity changes on oxygen readings. This
effect will not be noticed immediately, but slowly impacts oxygen
readings over several hours.

Temperature Changes

The oxygen sensor has built-in temperature compensation.
However, if temperature shifts dramatically, the oxygen sensor
reading may shift. Zero the instrument to within 30
temperature-of-use for the least effect.
7-4
2
2
, for 2 to 25% O
2 2
30 seconds (normal temperature
range)*
3 minutes (extended temperature
range)
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