humimeter RH2 aW value measuring chamber user manual
Page 32
EMC wood
Shows the wood equilibrium moisture content (for wood stored under these condi-
tions) in % wood moisture and the temperature in the selected unit (°C or °F).
EMC POM
Shows the POM granulate equilibrium moisture content (for granulate stored under
these conditions) in % moisture content and the temperature in the selected unit
(°C or °F).
Water activity
Water activity is also described as free, non-cellularly bound water in products such as
food. The water activity is described in chapter "7.2 Definition water activity".
Free calibration curves
There are free calibration curves in the measuring device. These can be used for special
products.
On request Schaller Messtechnik GmbH can develop customer-specific calibration
curves for your product.
7.2 Definition water activity
Water activity is the ratio of the partial water vapour pressure in food (p) to the satura-
tion vapour pressure of pure water (p0). It is an important indicator for the product
quality in the food, tobacco and pharmaceutical industry and is represented in an aw
value from 0 to 1.
The water activity is synonymous with the equilibrium moisture content – the relative
humidity at which the material to be measured is in equilibrium with the ambient air.
The relative humidity of air however is expressed in %.
The water activity is temperature-dependent. For the determination of the water acti-
vity at a desired temperature, the measuring device and the material being measured
should be stored at the same temperature before starting the measurement.
The humimeter RH2 water activity measuring chamber is suited for the measurement
of materials such as cereal products, coffee, cocoa, muesli, butter, mixtures of dried
fruit, spices, granulates, mushrooms, sugar, xylitol, biscuits or dried sausage as well as
many other types of food where a check of the water activity is necessary.
The humimeter RH2 water activity measuring chamber is generally not suited for liquids
as well as juices (syrup), acidic food such as onions, fruits and tropical fruits or food
and beverages containing alcohol, such as filled chocolates. Vinegar and acids destroy
the calibration and the sensor.
To Next Page
Loading...
