Water Activity Meters

A water activity meter is an instrument used to measure the water content and water activity of a substance. It is commonly used in quality control and research in industries such as food, cosmetics, and pharmaceuticals. Water content usually refers to the weight percentage of water contained in a substance, usually expressed as "%". Water activity refers to the ratio of the number of free water molecules in a substance to the number of free water molecules in pure water, usually expressed as "aw". The larger the aw value, the more free water in the substance is available for microbial growth and chemical reactions.

Working Principle of Water Activity Meter

1. Drying method

The drying method is a common method for determining the moisture content of a substance. The sample is heated to a certain temperature in a hot air or vacuum environment to evaporate all the free water in it, and then the change in sample weight is measured to calculate its moisture content.

2. Capacitance method

The capacitance method is a method that uses capacitance changes to determine the moisture content and humidity of a substance. The sample is placed between two electrodes, an AC electric field is applied at a constant temperature, and the moisture content of the sample is calculated by measuring the change in capacitance.

3. Infrared method

The infrared method is a method of measuring the water content of a substance by using the property of water in the substance to absorb infrared rays. The sample is placed between the infrared radiation source and the detector, the intensity change of the infrared rays absorbed by the sample is measured, and the water content of the sample is calculated by comparing it with the standard curve.

4. Resistance method

The resistance method is a method that uses the effect of moisture in a substance on its resistance value to determine the moisture content and activity of a substance. The sample is placed between two electrodes, and a DC electric field is applied at a constant temperature to calculate the moisture content and activity of the sample by measuring the change in resistance value.

Application of Water Activity Meter

1. Food industry: The water content and activity of food have a significant impact on its taste, nutritional value, shelf life, etc. By using a water activity meter, the water content and activity of food can be controlled to ensure its quality stability and safety.
2. Cosmetics industry : The water content and activity in cosmetics have an important impact on their stability, moisturizing properties, etc. By using a water activity meter, the water content and activity in cosmetics can be controlled to ensure their quality stability and safety.
3. Pharmaceutical industry : The water content and activity of drugs have an important impact on their efficacy, stability, shelf life, etc. By using a water activity meter, the water content and activity of drugs can be controlled to ensure their quality stability and safety.

Advantages of Water Activity Meter

1. Non-destructive testing: The water activity meter can measure without destroying the sample to ensure the integrity of the sample.
2. Fast and accurate: The water activity meter can quickly and accurately determine the water content and activity in the sample, improving production efficiency and product quality.
3. Easy to operate: The water activity meter is easy to operate, does not require professional skills, and is suitable for use in various industries.
4. Multifunctional: The water activity meter can simultaneously determine the moisture content and humidity in a substance, and has a variety of measurement modes to choose from.

The water activity meter is an instrument used to measure the moisture content and humidity in a substance. It is widely used in the food, cosmetics, pharmaceutical and other industries. Its working principle includes drying method, capacitance method, infrared method and resistance method. The water activity meter has the advantages of non-destructive detection, fast and accurate, easy operation and multi-function. It is an indispensable and important tool in modern production.