Novasina LabTouch-aw Operating Instructions Manual
Also see for LabTouch-aw: Operating instructions
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Contents
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5Englishwww.novasina.com2. General Product Description2.1 System OverviewThe LabTouch-aw system has been specifically developed for determining thewater activity in a test sample like food, cosmetics or pharmaceuticals. Wateractivity is defined as the current volume and availability of “free” water in asample and should not be directly compared with the water content (g water/g sample). The water activity is given as the aw – value and ranges between0 (absolute dryness) and 1 (100% relative humidity) and is a relative, sample-mass independent measurement. Only this free water takes an active part inthe exchange of moisture with the ambient air and can possibly form the idealmedium for microbiological growth on the surface and influences the biologicalfunctions of microorganisms which has an impact on the microbiological stabilityplus chemical and physical properties of a product.Special laboratory equipment is required for water activity (aw -value)determination which quantifies the air humidity directly over a sample in aclosed chamber after reaching the humidity equilibrium between free water inthe sample and water in the surrounding air.The measured air humidity is directly proportional to the aw -value. An accurateand reproducible measurement is thereby only possible if the sample temperatureis kept constant (i.e. 25°C) and if the measurement is taken after reachingthe humidity equilibrium. Thus it is obvious that the measurement of wateractivity always take some time, means is not finished within a few seconds.The establishment of the equilibrium is sample-independent and can not beshortened anyhow due to the fact that it is physics and chemistry.An inevitable pre-requisite for determining water activity with extreme precisionis the use of an excellent moisture sensor that provides exact, reproducibleresponse over a very wide range (moisture from 0....100% rH), no hysteresisand a good chemical robustness. Novasina has been developing specialelectrolytic moisture sensors that stand out for such unique properties for morethan 50 years.The integrated, resistive electrolytic LabTouch-aw sensor is based on the newchemical substance of the Novasina „Novalyte Technology“, which achievesthe required accuracy and reproducibility for the daily sample measurementin the lab.The complete LabTouch-aw system comprises two software options and canbe optimally adapted to customer's needs. |
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