Verifi Cation And Calibration; Water Activity Verifi Cation - Decagon Devices AquaLab 4TE Operator's Manual

AquaLab

7. Verifi cation and Calibration

7. Verifi cation and Calibration
It is important to verify AquaLab's water activity calibration against
known standards to guarantee optimal performance and accuracy.
Decagon recommends verifi cation daily, once per shift or before
each use.

Water Activity Verifi cation

AquaLab uses the chilled-mirror dewpoint technique to determine
water activity. Because this is a primary measurement of relative hu-
midity, no calibration is necessary; however, it is important to verify
for linear off set periodically. Th e components used by the instru-
ment to measure water activity are subject to contamination which
may aff ect the AquaLab's performance. When this occurs, it changes
the accuracy of the instrument. Th is is what is called a "linear off set."
Th erefore, frequent verifi cation assures you that your AquaLab is
performing correctly. Linear off set is checked by using two diff erent
verifi cation standards.
Verifi cation Standards
Verifi cation standards are specially prepared unsatuarated salt solu-
tions having a specifi c molality and water activity value which are
accurately measurable. Th e verifi cation standards that were sent with
your initial shipment are very accurate and readily available from
Decagon. Using verifi cation standards to verify accuracy can greatly
reduce preparation errors. For these reasons, we recommend using
standards available through Decagon for the most accurate verifi ca-
tion of your AquaLab's performance.
Performance Verifi cation Standards come in fi ve water activity lev-
els: 1.000, 0.984, 0.760, 0.500, and 0.250 a . Th e standards are
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