GX-2009 Operator’s Manual
Operation • 23
Operation
This section describes the operation of the GX-2009 in Measuring Mode. It explains how
enter Display Mode to view the peak gas readings of the four target gasses, the STEL and
TWA readings for H
2
S and CO, and the full scale detection range value for each target gas. It
covers important issues regarding combustible gas detection. It also covers alarm indications
and use of the aspirator adapter accessory.
Normal Operation
When the GX-2009 comes out of its startup sequence, see “Start Up” on page 18, it enters
Measuring Mode and is in normal operation if no alarm indications are taking place. It is
advisable to perform a fresh air adjustment when the GX-2009 comes out of its startup
sequence as described in “Start Up”. If
Auto Zero Adjustment
is set to
On
, be sure to follow
the guidelines in Step 9 in “Start-up Procedure” on page 18.
In the Normal Operation Screen of Measuring Mode, the battery level, time, and gas
concentrations for each channel are displayed on the LCD. The time is in the lower right
corner and the battery level is in the lower left corner. Combustible gas is displayed as a
percentage of the lower explosive limit (%LEL), oxygen is displayed as a volume percentage
(vol%), H
2
S and CO as parts per million (ppm). The combustible channel gas name is CH
4
if
it is calibrated to methane (CH
4
) or HC if it is calibrated to a another combustible gas. See
“Combustible Gas Detection” on page 25 for a discussion of the combustible channel gas
name and calibration.
Display Mode
You can access Display Mode while in Measuring Mode by using the POWER MODE button.
In Display Mode you can view and reset the peak readings for each target gas, view the TWA
and STEL values for CO and H
2
S, and view the detection range full scale for each target gas.
STEL is an acronym for short-term exposure limit, and it is the average reading of the target
gas during the last 15 minutes. TWA is an acronym for time-weighted average, and it is the
average reading for the target gas during the last eight (8) hours. If eight (8) hours has not
elapsed since the unit was turned on, the TWA is still calculated over eight hours, with the
missing time assigned a zero (0) value for the readings. Similarly, if the unit has not been on
for 15 minutes, the missing time is assigned a 0 value and the STEL is calculated over 15
minutes. The peak readings, STEL values, and TWA values are cleared when the unit is turned
off.
To enter Display Mode and view items or reset the peak readings, do the following:
1. Make sure the GX-2009 is in the Measuring Mode Normal Operation screen. The GX-
2009 must be in the Normal Operation Screen for you to access Display Mode.
0 20.9
5:15
CO ppm H2S ppm
CH4 %LEL OXY vol%
0 0.0
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