RKI Instruments GX-8000(PT0-098) - Manual (Page 24)

4 How to Use 4-5. How to detect
GX-8000 - 24 -
(TYPES-A and E Only)
If Auto Range is set on a type with the vol% range for combustible gases, the display is automatically
switched to the vol% range when the concentration of a detected combustible gas exceeds 100%LEL.
When the concentration drops, the display returns to the %LEL range again. The following shows an
example of switching timing.
Diagram of gas concentrations and range switching timing under Auto Range setting
5 vol%
(100%LEL)
3 vol%
(60%LEL)
%LEL range %LEL range vol% range
Switching point Switching point
CH
4
concentration
CAUTION
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. For the sake of more
accurate gas detection and concentration display, therefore, this gas sensor may perform detection
using the vol% sensor if the built-in oxygen sensor of this unit detects an oxygen concentration
lower than a certain level in the atmosphere.
In other words, the display changes at the timing shown above when the oxygen concentration is
equal to or higher than a certain level. If it is lower than a certain level, however, the vol% sensor is
used for detection even if the combustible gas concentration is lower than the switching point.