Operation
Range Menu
Thermo Fisher Scientific
Model 42
i
Trace Level Instruction Manual
3-13
The Gas Units screen defines how the NO, NO
2
, and NO
x
concentration
readings are expressed. Gas units of parts per billion (ppb) and micrograms
per cubic meter (μg/m
3
) are available. The μg/m
3
gas concentration mode is
calculated using a standard pressure of 760 mmHg and a standard
temperature of 20 °C.
When switching from ppb to μg/m
3
, the analog ranges all default to the
highest range in that mode. For example, when switching from μg/m
3
to
ppb, all the ranges default to 200 ppb. Therefore, whenever you change
units, you should also check the range settings.
●
In the Main Menu, choose Range >
Gas Units
.
Note
If the units change from ppb to μg/m
3
or vice versa, the instrument
should be re-calibrated, particularly if the user’s standard temperature is
different from 20 °C. A display warning will appear that ranges will be
defaulted and calibration parameters reset.
▲
GAS UNITS:
CURRENTLY: PPB
SET TO: UG/M3 ?
AND SET RANGES AND CAL TO
X
DEFAULT SETTINGS
XXXXXXXXXX
©ª
CHANGE VALUE
SAVE
RANGE AVG DIAGS ALARM
The NO, NO
2
, and NO
x
Ranges screen defines the concentration range of
the analog outputs. For example, a NO
2
range of 0–50 ppb restricts the
NO
2
analog output to concentrations between 0 and 50 ppb.
The display shows the current NO, NO
2
, or NO
x
range. The next line of
the display is used to change the range. The range screen is similar for the
single, dual, and auto range modes. The only difference between the
screens are the words “High” or “Low” displayed to indicate which range is
displayed. The example below shows the NO range screen in single mode.
For more information about the dual and auto range modes, see “
Single
Range Mode
”, “
Dual Range Mode
”, and “
Auto Range Mode
” earlier in
this chapter.
Gas Units
NO, NO
2
, and NO
x
Ranges