Environnement
S.A
MP101M
Duplication prohibited
SEPTEMBER 2013
2–4
The measurement method is governed by the following relations:
a) Blank filter at start of cycle
N
1
= N
0
e -k (m
0
+ m
1
)
N
0
Count without absorbent (see Remark)
N
1
Corrected count, in counts per second, on blank filter (air + filter) (see NOTE)
m
0
Density of blank filter (mg/cm
2
)
m
1
Density of air (mg/cm
2
) at temperature T1
NOTE :
As concerns N
1
and N
2
(see below): the corrected value N displayed by the unit is
deduced from the non-corrected value N' as a function of the dead time
of the counter
tube (G.M.) by the formula:
N =
N'
1 - N'
1
1
1
The density of the air (m
1
) contained in the volume V between the source and the detector is deduced
from the temperature of the air knife (T
1
) measured at the start of the cycle, using the following
relation:
m =
V
S
=
T
T
.
V
S
1
0
0
1
T
0
= 273.15 K
V = 2.46 10
-3
l
0
= 1.293 g/l
S = 2.4 cm
2
a) Charged filter at end of period or cycle
N = N e
2
0
-k (m + m + m 2
0
)
N
2
Corrected count, in counts per second, through matter ( collected dust + air).
Remark:
The activity of the source does not affect the measurement of the density deposited
since the magnitude N
0
characterizing it disappears when N
1
/N
2
is resolved. The time
interval separating the blank filter measurement is negligible with respect to the period
of the radio element used (5730 years).
Summary of Contents for MP101M
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