RKI Instruments GX-8000(PT0-098) - Manual (Page 22)

4 How to Use 4-5. How to detect
GX-8000 - 22 -
NOTE
• If the combustible gas reading exceeds 100% LEL, the CO reading rises temporarily but this is not
abnormal.
• In a low-temperature environment, the operating time is shortened due to the battery performance
property.
• At a low temperature, the response of the LCD display may get slow down.
• If a combustible gas with a higher concentration than %LEL is drawn, some gas may remain in the gas
sampling hose due to adsorption in the hose, gas sampling probe, etc. After drawing a
high-concentration combustible gas, clean the gas monitor to remove the adsorbed gas (draw fresh air
and check that the reading becomes zero).
Performing fresh air adjustment before cleaning it completely will result in inaccurate adjustment,
giving adverse influence on measurement. In such a case, remove the gas sampling hose before
performing fresh air adjustment to avoid inaccurate adjustment.
• Perform gas detection in the vol% range (Type-A and E only) in a place where the presence of a
high-concentration combustible gas is known.
NOTE
<Influence of Coexisting Gases on High-Concentration Combustible Gas Sensor> (TYPES-A and E Only)
A thermal-conductivity sensor that detects high-concentration combustible gases, based on the principle
of detection using a difference in thermal conductivities of gases, may display a reading that is disturbed
by a considerable change in the concentration of gases other than the combustible gases that coexist in
the atmosphere.
However, the influence of oxygen on readings can be automatically corrected by the sensor, which
detects oxygen at the same time, by feeding back a change in the oxygen concentration to the detection
result of high-concentration combustible gases.
If coexisting gases other than oxygen undergo a high concentration change, the influence from the
change cannot be automatically corrected. This sensor is adjusted to be able to detect high-concentration
combustible gases in the air as well as in an nitrogen atmosphere. If the composition of the atmosphere
other than nitrogen is known in advance, adjusting the sensor in accordance with the atmosphere can
alleviate influences on readings. For information on the adjustment procedure, see the separate
"Maintenance Manual."
CAUTION
• Before performing gas detection, attach the gas sampling probe provided with the gas monitor to
prevent disturbances by air dust.
• When you measure concentrations of oxygen in inert gases for a long time, the carbon dioxide
concentration in the air must be 15% or less. When you use the gas monitor in the air with a
carbon dioxide concentration of 15% or higher, perform measurement in as short time as
possible. Using the gas monitor under high concentrations for a long time may shorten the life of
the oxygen sensor.
• An oxygen concentration higher than a certain level is required for the combustible gas %LEL
sensor of the gas monitor to correctly detect gases and display concentrations.
• During combustible gas detection (%LEL range), long-time detection of a high-concentration
combustible gas may adversely influence the sensor.
• Use the gas monitor with the LCD display facing upward. The gas monitor, when used with the
LCD display in a tilted or flat status, may not display correct values.