METER GROUP AquaLab 4TE - AQUALAB Service, Maintenance, and Troubleshooting; AQUALAB Verification and Calibration Procedures

45
AQUALAB
The water activity readings should be within ±0.003 a
w
of the given value for the dew
point or ±0.015 for capacitance when testing the verication standard. The standards
will read at 25 °C. If other temperatures are required, refer to Table 5.
Table 5 Temperature correction of verication standards
Temperature
(°C)
Water
0.50 mol/kg
KCL
2.33 mol/kg
NaCl
6.00 mol/kg
NaCl
8.57 mol/kg
LiCl
13.41 mol/kg
LiCl
17.18 mol/kg
LiCl
15 1.000 0.984 0.923 0.761 0.492 0.238 0.140
20 1.000 0.984 0.922 0.760 0.496 0.245 0.145
25 1.000 0.984 0.920 0.760 0.500 0.250 0.150
30 1.000 0.984 0.920 0.760 0.504 0.255 0.155
35 1.000 0.984 0.920 0.760 0.508 0.261 0.160
40 1.000 0.984 0.921 0.760 0.512 0.266 0.165
50 1.000 0.984 0.894 0.740 0.517 0.275 0.172
NOTE The AQUALAB measures these verification standards to ±0.003 a
w
with the dew point sensor and ±0.015 a
w
with
the capacitance sensor.
6. The readings may lead to one of three outcomes.
a. If the AQUALAB reads within ±0.003 a
w
of the rst verication standard for dew point
and ±0.015 for capacitance, take two readings of the second verication standard.
The second water activity reading for the second verication standard should be
within ±0.003 a
w
for the dew point and ±0.015 for the capacitance sensors.
b. If either verification standard is not correct, it is probably due to contamination of the
sensor chamber. Clean and air out the chamber (Section4.2) and repeat verification
from step2.
c. If readings are consistently outside the water activity of the first verification standard
by more than ±0.003 a
w
for dew point and ±0.015 for capacitance, a linear offset
can be applied. Adjust the reading to match the correct verification standard value
(Section4.1.2).