GX-3R Pro Operator’s Manual Chapter 4: Display Mode • 48
TWA Screen (TWA)
The TWA Screen displays the time weighted average (TWA) readings for H
2
S, CO, CO
2
, and
super toxic only.
The TWA reading is the average reading over the last 8 hours. If 8 hours have not elapsed since
the last time the TWA reading was cleared, the average is still calculated over 8 hours. The
missing readings are assigned a 0 value. If LUNCH BREAK is set to OFF (factory setting), the
TWA is cleared when the GX-3R Pro is turned off.
If LUNCH BREAK is set to ON, the GX-3R Pro will remember TWA readings when it is turned
off so it can continue them when it is turned on again. See page 106 for instructions to turn the
lunch break feature on (default is off).
Combustible Sensor Target Gas Conversion (HC
GAS LIST)
This screen only appears if D MODE SETTING in User Mode is set to ON (factory setting) and
if the instrument’s calibrated target gas is CH4 or iC4H10 (select target gas in Gas Select Mode’s
GAS COMBO item, calibrate with target gas in User Mode’s GAS CAL item).
The HC GAS LIST screen allows you to select a converted target gas based on a CH4 or iC4H10
calibration. It does not change the calibrated target gas. You must go to Gas Select Mode’s GAS
COMB item to change the calibrated target gas.
Selecting a converted target gas in HC GAS LIST (based on a CH4 or iC4H10 calibration) does
not provide the same reading accuracy as selecting a calibrated target gas in Gas Select Mode’s
GAS COMBO item and calibrating with that target gas in User Mode.
Selecting a converted target gas in HC GAS LIST does not
mean that the combustible gas sensor
will respond only to that gas. The combustible gas sensor responds to a number of gases
regardless of the target gas selection.
However, if H2 is selected as the target gas in HC GAS LIST, the sensor will not respond to the
gases listed with an “x” in the “Available Target Gas Conversions During LIMITED HC GAS
LIST Status” column of the table below.
TWA
7:49
0.75
CO2 vol%
6 5.5
CO ppm H2S ppm
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