7 VERIFICATION AND CALIBRATION AquaLab
7 Verification and Calibration
It is important to verify AquaLab water activity calibration against
known standards to guarantee optimal performance and accuracy.
Decagon recommends verification daily, once per shift or before each
use. Decagon also recommends annual factory calibration to main-
tain optimal performance.
7.1 Water Activity Verification
AquaLab uses the chilled-mirror dew point technique to determine
water activity. Because this is a primary measurement of relative
humidity, no calibration is necessary; but we recommend periodic
calibration to verify for linear offset. The components used by the
instrument to measure water activity are subject to contamination
which may affect the AquaLab performance. When this occurs, it
changes the accuracy of the instrument. This is what is called a “lin-
ear offset.” Therefore, frequent verification assures you that your
AquaLab is performing correctly. Linear offset is checked by using
two different verification standards.
Verification Standards
Verification standards are specially prepared unsaturated salt solu-
tions having a specific molality and water activity value which are
accurately measurable. The verification standards that were sent
with your initial shipment are very accurate and readily available
from Decagon. Using verification standards to verify accuracy can
greatly reduce preparation errors. For these reasons, we recommend
using standards available through Decagon for the most accurate
verification of your AquaLab performance. Performance Verifica-
tion Standards come in six water activity levels: 1.000, 0.984, 0.920,
0.760, 0.500, and 0.250 a
w
. The standards are produced under a
strict quality assurance regime. Please contact Decagon Devices to
order additional standards via sales@aqualab.com or 509-332-5601.
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