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The presence of extremely high concentrations of gases other than the working gas (accompanying gases)
may prevent the measurement of the working gas concentration – due to the high absorption of the IR
radiation by the accompanying gas (e. g. CO
2
in the CH
4
detector).
3.1.2 Effect of oxygen concentration value
Concentration of oxygen in the atmosphere doesn't affect the detector indication.
3.2 Influence of temperature
Within the scope of the sensor's environmental parameters, the influence of slow temperature changes is
compensated electronically. However, rapid temperature changes can cause false indications.
3.3 Influence of pressure
When there is no reaction gas in the atmosphere surrounding the sensor, pressure changes do not
cause a change in the sensor's indications (no effect on the sensor's "zero").
A change in the absolute pressure can cause changes in the sensor's indications during the
presence of the reaction gas in the atmosphere, due to the fact that the sensor sensitivity is
dependent on the partial pressure.
An appropriately high pressure impulse can damage the sensor.
An appropriately high pressure impulse can damage the sensor.
3.4 Influence of moisture
Within the environmental parameters of the sensor the influence of moisture on the measurement is
negligible.
3.5 Influence of vibrations, impacts
Vibrations can trigger the so-called microphone effect in the sensor – manifested by the change in the read
concentration.
It should be ensured that the detector is not exposed to shock and vibration in excess of the amplitude of
vibrations amounting to 0.15 mm of the frequencies of over 10 Hz. Under no circumstances should the peak
acceleration exceed the value of 19.6 m/s 2 .
3.6 Influence of physicochemical phenomena
In the case of chemical compounds with high flash point (approx. 50°C and above) it is necessary to
remember that in typical environmental conditions (ambient temperature below 40°C), it is unlikely that
they will be able to produce atmospheres close to 100% LEL. Particularly in the case of ambient
temperatures below 0°C it may occur that achieving measurable concentrations by the catalytic sensor (of
10% LEL) is impossible. Another measurement method is required in this case.
4 Factors shortening the lifetime of the sensor
Liquid or solid contaminants present in the atmosphere may cause erroneous indications of the sensor,
and over time, a damage to the sensor by the contamination of its gas path (e.g. water vapor condensed on
the optical elements of the sensor will leave the contaminants present in it before the evaporation).
Corrosive gases (mainly NH
3
, H
2
S, SO
2
, HCl), especially in the presence of water vapor, can lead to a physical
destruction of the sensor's gas path.
Atest-Gaz A. M. Pachole sp. j.
ul. Spokojna 3, 44-109 Gliwice, Poland
VAT No.: PL 9691433231
tel.: +48 32 238 87 94
fax: +48 32 234 92 71
e-mail: contact@atestgaz.pl
p. 3/3 Appendix: PU-Z-064-ENG R01
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