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concentrations over 100% LEL, even temporarily persistent ones, can lead to a physical wear of the
sensor. For these reasons, detectors operating in places where such conditions may occur
are / should be equipped with mechanisms to prevent the negative effects of high concentrations,
a very high concentration of combustible gas (well above 100% LEL) leads to a decrease in oxygen
concentration – thereby lowering the sensor's indication. Volumetric concentrations close to 100%
can result in a zero sensor response, as shown in the figure (example: a small room and a large
amount of flammable gas released into the atmosphere). See section 3.1.2.
Figure 3: Sample characteristic of catalytic sensor
3.1.2
Effect of oxygen concentration value
Oxygen is required for a proper operation of the catalytic sensor. If the monitored atmosphere contains gas
or gases that dilute or replace air (thereby reducing the oxygen concentration), for example, nitrogen or
carbon dioxide, then the catalytic detector can give a low or even zero response.
A similar effect can occur when large amounts of reaction gas are released to the atmosphere(creating a
concentration over the measurement range) – due to a too low amount of oxygen, the concentration
indication of the detector will be lower than it actually is, and it may even be zero.
3.2 Influence of temperature
The temperature can have an influence on the sensor's characteristics. Within the scope of the detector's
environmental parameters, its influence is compensated electronically.
3.3 Influence of pressure
Within the environmental parameters of the sensor, the influence of pressure on the measurement is
negligible.
3.4 Influence of moisture
Within the environmental parameters of the sensor the influence of moisture on the measurement is
negligible.
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. 4/5 Appendix: PU-Z-054-ENG R02
•
Ur – output voltage of the sensor
LEL – lower explosive limit
UEL – upper explosive limit
0,88 %
(20% LEL)
U
EL
LE
L