RKI Instruments GX-2009 Manual - Manual (Page 23)

GX-2009 Operator’s Manual Operation • 18
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 13, 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 13.
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 20 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,
0 20.9
5:15
CO ppm H2S ppm
CH4 %LEL OXY vol%
0 0.0