2 ABOUT AQUALAB AquaLab
At equilibrium, the relative humidity of the air in the chamber is the
same as the water activity of the sample.
2.5 AquaLab and Temperature
Samples not read at room temperature during the read cycle will
equilibrate with the AquaLab temperature before the water activity
is displayed. Large temperature differences will cause longer reading
times, since a complete and accurate reading will not be made until
the sample and the instrument are within 2
◦
C of each other. There
are several advantages in having a temperature-controlled water ac-
tivity meter. A few major reasons are:
1. Research purposes. Researchers can use temperature con-
trol to study the effects of temperature on the water activity of
a sample, make a comparison of the water activity of different
samples independent of temperature, and conduct accelerated
shelf-life studies or other water activity studies where temper-
ature control is critical. There are many shelf-life, packaging,
and isotherm studies in which temperature control would be
very beneficial. (See Section 14. Further Reading for more
information)
2. Compliance with government or internal regulations for
specific products. Though the water activity of most products
varies by less than ±0.002 per
◦
C, some regulations require
measurement at a specific temperature. The most common
specification is 25
◦
C, though 20
◦
C is sometimes indicated.
3. Minimization of extreme ambient temperature fluctu-
ations. If the environmental and AquaLab temperatures fluc-
tuate by as much as ±5
◦
C daily, water activity readings will
vary by ±0.01 a
w
. Temperature control eliminates variations
due to changes in ambient conditions.
Series 4TE/4TEV/4TE-DUO
The AquaLab Series 4TE models have thermoelectric components
installed to allow the instrument to maintain a set chamber temper-
6
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