In a no helium polluted
environment,
do
a
measure
of the helium in the air with
the sniffer probe to adjust.
Depending on the
measurement result,
cut the neddle according to the precautions
indicated below.
Put
back correctly the needle in the nozzle.
Repeat these
operations until the
flowmeter displays the value of the
maximum
flow taken by the sniffer probe
(60 ± 2 sccm).
Repeat these
operations until the display
corresponds
to the display with the
standard sniffer probe in the helium of
the
air
.
If the
message
“sniffer probe clogged” appears in the control panel display during
these adjustments,
please refer to ””Sniffer probe clogged”
message”
§.
Needle replacement
(continued)
Precautions
to cut the needle.
It is
necessary
to cut small
amounts
of the needle, especially when we
are near the target value: refer to the figure below
.
Needle
length
cut at one
time
10
mm
0.39
inch
5
mm
0.19
inch
1
mm
0.04
inch
Example
:
4 mm for 80
%
Be
careful in
this zone
T
arget
value
seeked
0 % 50 % 70 % 80 % 100 %
Example:
•
target value = 60 sccm
•
value displayed on the flowmeter : 48
sccm
(= 80 % of
the target value)
remove
the needle from the nozzle and cut 4 mm from
the straight
end.
3
Use
of the old
needle
as a reference
With this method, the uncertainty about the maximum flow taken by
the sniffer probe is more important
:
•
Maximum flow taken: 60 ± 10 SCCM
•
Leak
flow (Q): 4x10
-6
mbar.l/s < Q < 6x10
-6
mba
r
.l/s.
Take
out the filter
(see
“Filter exchange” §).
6
/8
To Next Page
Loading...
