MSA SIRIUS Manual De Instrucciones página 51

RESPONSE NOTES:
* Some compounds may reduce the sensitivity of the combustible gas sensor by poiso-
ning or inhibiting the catalytic action or by polymerizing on the catalytic surface.
For an instrument calibrated on Pentane, multiply the displayed %LEL value by the con-
version factor above to get the true %LEL.
These conversion factors should be used only if the combustible gas is known.
These conversion factors are typical for a SIRIUS Multigas Detector. Individual units may
vary by ±25% from these values.
Table 9. OXYGEN – Typical Performance Specifications
RANGE
RESOLUTION
REPRODUCIBILITY** 0.7% O
RESPONSE TIME
* See Table 5. Instrument specification, NOTE
** See Table 14. PID Typical Performance Specifications. NOTE
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
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 atmos-
phere 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 envi-
ronment 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 in-
creases. 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 oxy-
gen 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 at a temperature
within 30 °C of the temperature-of use for the least effect.
0 to 25% O
2
0.1% O
2
for 0 to 25% O
2
90% of final reading
Performance Specifications
2
30 seconds with sample line and
probe (normal temperature range*)
3 minutes with sample line and
probe (extended temperature range*)
8
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