Rotronic AwTherm Water Activity Meter

The Rotronic AwTherm water activity meter is temperature-controlled to determine the water activity of a sample maintained at a known temperature. Water activity, which is used as a measure of product consistency, is strongly dependent on temperature. Stabilizing the temperature prevents imprecise results due to external temperature influences. The AwTherm's wide control range permits measurements to be obtained directly in the tempered manufacturing or storage process. The meter's measuring head is removable, which allows for greater precision, since the probe can be calibrated or adjusted for both temperature and humidity.

The measurement of water activity is a key parameter in the quality control of moisture-sensitive products or materials. Water activity is a measure of the water vapor pressure generated by the free or non-chemically bound water in foods and other products. The bound water and moisture content cannot be measured with this method. The free water in a product influences its microbiological, chemical and enzymatic stability. This is especially important in the case of perishable products such as foodstuffs, grain, and seeds as well as in many products in the pharmaceutical and cosmetic industries. If there is too much free water available, the products spoil, and if there is too little water available, other product properties can be negatively influenced. The measurement of water activity also provides useful information on properties such as the cohesion, storage life, agglomeration or pour-ability of powders, tablet stability, and the adherence of coatings.

The AwTherm meter is based on the same technology as the Rotronic HygroGen2 temperature and humidity calibration suite of instruments which manipulate forced air to create highly stable thermal conditions with minimal gradients within the measurement environment. The meter uses a Rotronic HygroClip2 series probe to control and measure conditions. The AwTherm has a measuring head that can be removed entirely for calibration of both Aw and temperature parameters against references traceable to National Standards.