In-e-hylab-v4_11 – ROTRONIC HygroLab User Manual
Page 42
IN-E-HyLab-V4_11
Rotronic AG
Bassersdorf, Switzerland
Document code
Unit
Instruction Manual
Document Type
HygroLab bench top indicator version 4:
instruction manual
Document title
Page 42 of 51
© 2006; Rotronic AG IN-E-HyLab-V4_11
in the pharmaceutical industry where it provides useful information regarding the cohesion of
tablets and pills, or the adherence of coatings. Water activity can be directly compared with the
relative humidity of the ambient air to prevent dimensional changes in a product (paper,
photographic film), to prevent hygroscopic powders (powdered sugar, salt) from caking or turning
into a solid block, etc
Water activity can be used with some products (mostly synthetic products) as a means of indirectly
measuring the total moisture content. This requires developing sorption isotherms to this purpose.
Sorption isotherms are graphs that provide the relationship between water activity and moisture
content at constant temperature. For most natural products, repeatable sorption isotherms cannot
be reliably developed and water activity should be regarded as separate from moisture content.
17.2 Using the HygroLab 2 or 3 to measure water activity
Both the HygroLab 2 and 3 can be used to measure the water activity of foods, pharmaceuticals
and cosmetics. Both models can be configured to display humidity as water activity
(1.00 aw = 100 %RH).
HygroLab 2:
When used as a stand alone unit, the HygroLab 2 can be used for conventional water activity
measurements with up to 4 probes simultaneously.
Productivity in the laboratory can be greatly increased by using the HygroLab 2 together with a PC
on which the HW4 software has been installed (version 2.0.0 or higher). With this combination, the
following functions are available (see note below):
Accelerated water activity measurement (AwQuick mode): allows the measurement of most
products in typically 5 minutes.
Full equilibration measurement (AwE mode) with automatic detection of equilibrium conditions
with optional recording of the entire equilibration process.
Automatic capture to a text file of the measurements, including probe and product identification
(both in the AwQuick and standard mode).
The HW4 water activity function can run simultaneously on all 4 probes, using the same mode for
all probes.
Note: Access to the water activity functions of HW4 requires a product key. A product key can be
purchased at the same time as the HygroLab or it can be purchased later.
HygroLab 3:
Both the AwQuick and AwE measuring modes are already built into the HygroLab 3 and up to 4
probes can be used simultaneously.
When the HygroLab 3 is used together with a PC on which the HW4 software has been installed,
the following additional functions are available:
Recording of the entire equilibration process of a product sample (standard mode only).
Capture of measurements to text file (both in the AwQuick and standard mode).
Note: Access to the water activity functions of HW4 requires a product key. A product key can be
purchased at the same time as the HygroLab or it can be purchased later.