Vaisala MMT162 User Manual
Page 48
User's Guide ______________________________________________________________________
46 __________________________________________________________________ M210934EN-C
3.
Define the correlation between aw, T and PPM (w/w) from the
measured values. Calculate A and B according to the following
example.
[ ]
[ ]
( ) ( )
1
/
1
-
2
/
1
1
(
-
2
(
T
T
T
PPM
LOG
T
PPM
LOG
A
sat
sat
)
)
=
[ ]
)
(
A/T1
-
1
T
PPM
LOG
B
sat
=
Example (measured water content 213 ppm):
T (°C)
aw
ppm
saturation
24.1
0.478
213/0.478 = 445.6067
57.6
0.188
213/0.188 = 1132.979
A = (LOG(1132.98)-LOG(445.607))/(1/(57.6+273.16)-
1/(24.1+273.16)) = -1189.4581
B= LOG(445.607)-(-1189.4581)/(24.1 + 273.16) = 6.6503583
Assumptions:
The isoterm of water activity versus water concentration is linear and the
solubility curve has the form of the given equation.