what is water activity?

water activity (aw) is the relative humidity which is reached at equilibrium in a sealed container in which a hygroscopic product has been placed, but expressed on a scale of 0…1. water activity measurement is most commonly used in the food industry, where it is used to determine shelf life and quality.

what is equilibrium relative humidity?

equilibrium relative humidity (erh) is the value of relative humidity into which a hygroscopic product can be placed where no net exchange of moisture between the product and the surrounding environment can take place. it is expressed on a scale of 0…100%. erh is typically used in the paper and pharmaceutical industries, but can be applied to almost any product that is sensitive to moisture, or where the presence of moisture can effect product handling.

water activity or erh?

both aw and erh are an expression of the amount of free water vapour present on a product, both at its surface and within its structure, and are practically the same measurement expressed in a slightly different way. throughout this document we will refer to water activity,but this can be interchanged with erh. where specified, rotronic products offer the user the possibility to se-lect display units of aw or %rh.

what is moisture content?

moisture content, when referring to a solid material, is an expression of the percentage of the material’s weight which is water (both in liquid or gaseous phase); usually referred to as ‘percent moisture content’. this term is widely used in many areas of industry.

correlation between water activity and moisture content

why is water activity measured?

water activity is an important parameter in the food and pharmaceutical industries. it represents the mass of free water within a product, which is of fundamental importance for many enzymatic reactions and especially for the growth of micro-organisms.the water within a product such as food is bound by various ingredients such as proteins, salt or sugar. this chemically bound water is not available for the micro organisms, and hence they cannot replicate. the higher the amount of water-binding ingredients in a product is, the less water can evaporate. therefore, the water vapour pressure over the product is in direct correlation to the amount of water that

is available for the micro organisms. water activity has an important influence on product stability (e.g. microbiological stability, flavour retention), handling properties such as the agglomeration of powders, chemical stability and physical properties such as dimensions of paper.

water activity measurement offers a non-destructive, easy-to-use measurement in a wide range of convenient configurations for both laboratory and on-site use.

hygropalm aw1 portable water activity inductor

specifications：

accuracy: ±0.015 aw,  ±0.3℃ （ 23℃±2℃）

probe: one exchangeable water activity probe.

probe temperature:  5...+50℃

measuring range: 0...1 aw

display: simultaneously display water activity, temperature or humidity.

resolution: 0.001aw,0.1%rh, 0.1℃/°f, 0.01

calibration: two point temperature，4 point humidity

surface environment: 0-100%rh none dewing, -10...+60℃

overall dimension: 295mm×70mm×35mm, ip50,abs

applications: food industry、medicine、chemistry warehouse,etc.

features: awquick model obtain result in 4 – 6 minutes. batter supply, convenient for locale manufacturing procedure.

collocation：hygropalm aw1-set/40 kit  

hygrolab aw bench-top water activity instrument

specifications：

accuracy: ±0.015 aw,  ±0.3℃ （ 23℃±2℃）   

probe: max four exchangeable water activity probes.

probe temperature:  5...+50℃

measuring range: 0...1 aw

display: simultaneously display water activity, temperature or humidity.

power supply: 220v/9v adapter

resolution: 0.001aw,0.1%rh, 0.1°c/°f, 0.01

calibration: two point temperature，4 point humidity

surface environment: 0-100%rh none dewing, -10...+60℃

overall dimensions: aluminum鋁220mm×170mm×55mm,

applications: food industry、medicine、chemistry warehouse, etc.

feature：communicate with computer.

configuration ：