CHAPTER 3 - OPERATING INSTRUCTIONS
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87-900-045-01
(D)
In the "automatic zero" mode of operation, the zero
value is continuously updated.
If the effective concentration is lower than the zero
value, the display shows some "<" characters, each
corresponding to about 2 ppm below zero (negative!!)
and "0" flashes.
The "automatic zero" (AZ) mode of operation may be
used to set the instrument to zero.
If there is no Helium, switch the instrument to
"automatic zero" and wait till the display shows no "<"
characters and the "0" blinks no longer. In this
condition, the instrument is cleared to less than 1 ppm
and it is then possible to operate it in "fixed zero" by
pressing the ZERO pushbutton again.
3.3.6 SET POINT mode
This mode can be activated or disactivated by using
the MODE pushbutton.
When the MODE pushbutton is pressed for the first
time, the set point is activated and the selected set
point level is displayed (fig. 3-31).
I . . . . . . . . . I 0
S
P Y
Y
Y Y *
Figure 3-31
Subsequently the selected measurement unit is shown
(fig. 3-32).
I . . . . . . . . . I 0
S P X X X X X X X *
Figure 3-32
When a leak lower than the set point selected level is
sensed, its value is regularly displayed. When the set
point level is overtaken, then the indicated leak value
stops at the set point level and the LEAK signal
appears (fig. 3-33).
❙❙❙❙
. . . . . . . . .
❙❙❙❙
L E A K
S P X X X X X X X *
Figure 3-33
If the leak value decreases below the set point, then
the actual leak value is shown again and the leak
signal disappears.
NOTE
When the set point is activated the intermittent audio
signal with frequency proportional to helium
concentation is always disabled, and a continuous
audio signal (which indicates the overtaking of the
selected set point level) is enabled.
3.3.7 CLEANUP operation
NOTE
Before starting the CLEANUP sequence, move the
HeliTest away from helium sources.
If after exposing the probe at high Helium
concentrations (higher that 10
4
ppm), the concentration
inside the instrument remains high even after moving
the probe away from the source of Helium. The
instrument can be “cleaned” by activating the
CLEANUP function.
By simultaneously pressing the ZERO and PROBE
pushbuttons for 2 seconds, the function of quick zero
setting is activated, and the display will be as shown in
fig. 3-34:
- - - C L E A N U P - - -
❙❙❙❙
. . . . . . . . . . .
❙❙❙❙
*
Figure 3-34
If the CLEANUP is successful (minimum 30 seconds),
the display shows (fig. 3-35):
- - - C L E A N U P - - -
O K
*
Figure 3-35
and then, automatically, the HeliTest returns to the
operative mode of operation in which the CLEANUP
was started.
If the zero setting has not been reached 5 minutes after
starting, the display will show as in fig. 3-36.
- - - C L E A N U P - - -
N O T
C O M P L E T E D
Figure 3-36
NOTE
When this message is displayed the HeliTest is
automatically switched off after 1 minute. Repeat the
self test procedure (paragraph 3.2.1) if the CLEANUP
function is not successfully completed.