T
arget
value determination
•
In hard
vacuum test
mode,
l
possible case:
- The
target value is the value of an external calibrated leak connected
to the installation to
test
or at the inlet port of the leak detector.
—>
Case A
•
In sniffing
test
mode, 2 possible cases:
-
the target value is the value of an external calibrated leak.
—>
Case A
-
If a container or installation is filled with a known gas mixture
including Helium, it is possible to enter helium
concentration
as
a
target value.—>
Case
B
Case A
When an external calibrated leak is used, it is
recommended
to take
into account date of calibration and
temperature
effect for calculating
the target value from the calibrated leak value as shown on its
identification label.
HELIUM CALIBRATED LEAK
Helium leak rate : 1.0x10
-8
mbar.l/s at 20 °C
Date of calibration : 10
Dec
2001
%
loss
per year : 2
%
%
increase
per °C : 3
%
Example
of calibrated leak label indications (as listed here):
If the date is
l
st
Dec 2003 (about 2 years after calibration) and
calibrated leak
(ambient) temperature
is 25 °C:
T
arget
value =
l
.0x
l
0
-8
x[
l
+0.0
3
x(25-20)]x[
l
-(0.02x2)]
=
l
.
l
x
l
0
-8
mbar
.l/s
Case
B
Checking
function
with
an external calibrated
Reminder:
l
PPM
=
l
.0x
l
0
-6
(concentration)
Example
: container with
l
00
PPM
helium mixture.
2
possibilities
:
➥enter target value = 0 E+02 to display the
test
result
in PPM
➥enter target value =
l
.0
E-04 to display the
test result
in helium
concentration
(
l
00
PPM
=
l
00
x
l
0
-6
=
l
x
l
0
-4
)
leak
C
302
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