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CHAPTER 3 - OPERATING INSTRUCTIONS
19
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3.3.1 PROBE operation
The PROBE pushbutton enables or disables the
sampling line and on the display we can read P.ON
(refer to fig. 3-22) or P.OFF (refer to fig. 3-26).
R E A D Y
H S M S P . O F F A Z
*
Figure 3-26
NOTE
The sampling line operates only when the probe is
extracted from its socket.
3.3.2 LIGHT operation
By pressing the AUDIO and SENS pushbuttons
simultaneously for 1 second, the display lights up for 20
seconds. If they are kept pressed for 2 seconds, the
display will remain lit until the two above pushbuttons
will be pressed again.
3.3.3 AUDIO operation
The AUDIO pushbutton enables or disables the audio
signal, with a frequency proportional to the Helium
concentration; it operates only in the measurement
mode.
3.3.4 Sensitivity changes
If a change in sensitivity is desired, press the
pushbutton SENS: it switches between HS mode (high
sensitivity 2 ppm) and LS mode (low sensitivity, 100
ppm).
During the transition (about 20 seconds), the display
will appear as in fig. 3-27 when switched HS to LS, and
as in fig. 3-28 when switched from LS to HS.
H S
- - > L
S
P L E A S E W A I T
*
Figure 3-27
L S
- - > H
S
P L E A S E W A I T
*
Figure 3-28
During operation in low sensitivity mode, the display will
show LS in the bottom left corner (see
fig. 3-29).
❙❙❙❙
. . . . . . . . .
❙❙❙❙
X X
10
X
L S
p p m
*
Figure 3-29
3.3.5 ZERO operation
By pressing the ZERO pushbutton, the mode of
operation changes from "automatic zero" (default
condition, fig. 3-22) to "fixed zero".
In the measurement mode, an FZ indication appears
on the display (see fig. 3-30) when the fixed zero is
selected.
❙❙❙❙
. . . . . . . . .
❙❙❙❙
X X
10
X
p p m
F Z
*
Figure 3-30
The zero value is calculated by integrating the Helium
concentration value for about 10 seconds.
In the "fixed zero" mode of operation, the zero value is
not updated, even if the Helium background
concentration changes.