Air humidity measurement: key terms explained

Measuring air humidity correctly plays a crucial role in many areas of our lives and industry. From the preservation of our health and the protection of our apartments from mold to ensuring product quality in production and storage - the air humidity measurement is indispensable.

But why is the humidity measurement so important? Moisture influences the materials and products that we use every day, as well as the environmental conditions in which we live and work. Too high moisture content can lead to mold, rust formation and a shortening of the durability of food. On the other hand, too low moisture can lead to drying out materials and products as well as health problems such as dry mucous membranes and skin.

In this guide contribution we explain the most important terms related to the topic of air humidity measurement.

1. Relative humidity (RH, relative humidity): The relative humidity refers to the ratio of the current water vapor content of the air to the maximum water vapor capacity at a certain temperature, expressed in percent. If the relative humidity in the air humidity measurement is 50 %, this means that the air contains 50 % of the maximum amount of water that can hold it at the current temperature. In air conditioning and building automation, the relative humidity is crucial to control comfort and material properties. In warehouses for food, the control of the RH is important to prevent spoilage. The normal air humidity outdoors is between 30 and 50 %. However, these values ​​can vary depending on the climate and weather. Values ​​above and below this area can be perceived as uncomfortable. In addition to the air humidity measurement, the Air quality measurement indoors Crucial for a healthy work environment.

2. Measure absolute humidity: The absolute humidity indicates the actual amount of water vapor in the air, expressed in grams per cubic meter (g/m³). This unit of measurement is independent of the temperature and gives a precise idea of ​​the amount of water in the air. In industrial drying processes, such as B. in paper production, exact absolute moisture controls must be carried out as part of the humidity measurement in order to ensure the quality of the end product. Air humidity measurement also plays a central role in the Design indoor climate. You can find more about why temperature and humidity are decisive for well -being counselor.

Water vapor content of the air (in g/m³) depending on the temperature

3. Dew point: The dew point is the temperature in which the air is saturated and the water vapor condenses into water. This value is important for avoiding condensation problems in air conditioning systems and the storage of industrial goods, since condensation can cause rust and mold. In the oil and gas industry, the dew point is crucial for the drainage of natural gas.

4. Wet ball temperature: The wet ball temperature is measured by holding a thermometer with a damp cloth around the sensor in an air flow. The evaporation of water from the cloth cools down the sensor and the difference to the dry temperature shows the moisture content of the air. This technology is often used in meteorological stations and in cold stores. For precise humidity measurement, the Selection criteria for temperature sensors Crucial to achieve precise results.

5. Hygrometer: A hygrometer is a measurement device for air humidity. There are different types of hygrometers, including mechanical, electrical and digital versions. Hygrometers are used in museums to ensure stable air humidity conditions and to protect works of art from moisture damage.
   
   
   1. Capacitive hygrometer: With a capacitive hygrometer, a hygroscopic layer is used between two electrodes. The moisture changes the capacity of the layer, which is measurable. This type of hygrometer is widespread in HLK technology (heating, ventilation, air conditioning) and in electronic production to measure humidity and thus avoid damage to sensitive components.
   
   
   2. Resistive hygrometer: A resistant hygrometer measures the resistance of a hygroscopic material. This resistance changes with the moisture. A typical area of ​​application are industrial quality controls, such as: B. in food production, where the exact humidity measurement is crucial for durability and quality.
   
   
   3. Electrolytic hygrometer: An electrolytic hygrometer serves the air humidity measurement by measuring the current flow by a hygroscopic salt. This process is often used in industrial processes to monitor moisture in drying chambers or in the production of hygroscopic materials.
   
   
   4. DEW Point Hygrometer: A DEW Point Hygrometer determines the dew point by cooling a mirror until condensation occurs. This method for air humidity measurement is used in gas processing and transport to ensure that no condensation occurs in pipelines, which could lead to constipation and corrosion.
   
   
6. Hydrometer: A hydrometer measures the specific weight of liquids and can indirectly also determine moisture, especially in cooling systems and for battery tests. In the food industry, it is often used to check the concentrated liquids such as syrup or juice.


7. Saturation: Seating describes the state in which the air contains the maximum amount of water vapor at a certain temperature. This state is critical of industrial drying processes in which the humidity must be controlled precisely to ensure effective drying, for example in the textile industry.


8. Sorption -isotherm: A sorption -isotherm shows the relationship between the moisture of a material and the relative humidity of the ambient gas. These curves are important for the storage and packaging of hygroscopic materials, such as: B. pharmaceuticals and grain.


9. Water activity (AW): Water activity is the measure of the availability of water for microbiological activities in a material, expressed as a fraction of the water vapor pressure. In the food industry, water activity is monitored to prevent the growth of microorganisms and increase durability.


10. Moisture penetration: Moisture penetration describes the process through which moisture penetrates into a material and spreads in it. This is crucial in the construction industry to prevent mold formation, and in the packaging industry to ensure the integrity of moisture barriers.