Humidity meters, also known as hygrometers, determine the current moisture content in the surrounding air. The amount of water vapor contained in the air not only affects human well-being and performance, but also the durability and functionality of many products. Since many materials absorb moisture from the ambient air and can release it to it, the air humidity also influences the material moisture. Therefore, when it goes about materials and devices, there are exact values for the air temperature and for the air humidity that are specified for storage and application.
Too much moisture can cause chipping, mold or bacteria, and corrosion. Too low moisture values can make processing more difficult and cause drying cracks in some materials. The humidity can be determined quickly and easily with an air humidity measuring device. If there are deviations from the desired values, it is possible to take targeted measures to change the air humidity.
Humidity meters show the humidity as an absolute or relative value. The maximum amount of water vapor that can be absorbed from one cubic meter of air increases with the temperature. Therefore, the relative air humidity always depends on the current temperature. It specifies the ratio of the available water vapor content to the maximum possible water vapor content saturation amount under the current temperature and pressure conditions in percent.
The relative humidity is often abbreviated as rH or RH. To prevent any damage to the moisture-sensitive materials, the formation of condensation on these materials must be avoided.
Since the warm air can absorb more water vapor than the cold one, condensation occurs on cold surfaces when warm air cools down. This effect can be often seen on mirrors after a long hot shower and on glasses when someone enters a warm humid room after being in a cold environment outside.
Even in tents and pavilions, where warm air rises to the cold tent roof, condensation often forms on cool evenings. From which surface temperature there is a risk of condensation formation depends on the current air temperature and humidity.
Many humidity meters can indicate the corresponding dew point for the measured temperature and humidity. The dew point is the temperature below which the water vapor becomes dew or fog. Humidity meter in living rooms Humidity meters are often used for living rooms, in which the measured values are read directly by the people present in the room. If the measured humidity values are too low or too high, the humidity can be increased or removed by airing or ventilation. If there are moisture problems on the exterior components of the apartments, the heating and ventilation behavior of the residents is often checked with the help of the humidity measuring device that can record the data.
These humidity meters store the measurement time, temperature and humidity at fixed intervals. The data show when which fluctuations occurred. To evaluate the measurement data, the statements of the residents regarding the use of the space and the outside climate should also be taken into account when the problem arises.
As a rule, moisturizing caused by the condensation failures can first be identified on the geometric or material-related thermal bridges. To avoid this, the component temperature must be kept above the dew point.
The dew point can be determined in the humidity measuring device from the values for temperature and humidity. In addition, some devices have an additional sensor for measuring the surface temperatures, with which the wall or ceiling temperature and the dew point temperature can be compared directly. Humidity meter in rooms with high water vapor The ventilation of the rooms with high water vapor such as bathrooms, shower rooms, kitchens can also be controlled depending on the existing air humidity.
For example, there are fans with the integrated air humidity sensors for venting the indoor bathrooms, which extract the air from the room only when the selected limit value is exceeded. Humidity meter in transport containers Goods are often transported over long distances and under fluctuating climatic conditions.
A thermo-hygrometer with storage function placed next to the goods to be transported records the climatic conditions during the transportation. The changes in temperature and humidity values during the transportation can be detected and evaluated.
If the goods show damage at the destination, the data stored in the humidity measuring device can be used to check whether the climatic conditions during the transport were the cause for the damage. If necessary, the goods can be protected by a more suitable packaging during the next transport. Humidity meter in greenhouses The optimal air humidity in greenhouses has a major impact on the healthy growth and yield of the crops.
Pest infestation may occur if the moisture content is too high or too low. The growth stops when the humidity is too low and if the humidity is too high, no fruit can be formed because the pollen clumps, and no fertilization takes place. The values can be easily monitored with an air humidity measuring device.
If you choose the humidity measuring device with a signal output, it is possible to control ventilation and irrigation systems depending on the measured humidity values.
Humidity meter in museums and archives Irreplaceable cultural assets and files are endangered if stored incorrectly.
To avoid the damage caused by moisture and to ensure the desired indoor climate conditions, museums and archives are continuously monitored by means of the humidity meters. The air humidity measuring device either records the measurement data, which can be checked by the responsible for the task persons, or it passes the data on further directly to the devices for climate control.
Measuring range and accuracy Many of the available humidity meters cover the range from 0 to percent relative humidity. Just a few also specify the humidity as an absolute value in grams per cubic meter. The accuracy when it goes about the relative air humidity in the peripheral areas is often worse than in the central area.
Depending on the application, the attention much be paid, that the humidity measuring device provides the desired accuracy in the climatic area to be monitored and that it can be adjusted to the correct value in the event of deviations. Data storage and data transmission options in a humidity measuring device The continuous recording of the values for temperature and humidity with the air humidity meter is important for the proof of compliance with storage and operating conditions.
The heating and ventilation behavior in the apartments and in the workplace can also be verified with the stored measurement data from a humidity measuring device. There are data loggers with built-in internal memory that are read out via a USB interface or devices with storage on an SD card. Also humidity meters with data output via analog interfaces with 4 to 20 milliamps or 0 to 10 volts are available. Some humidity meters offer connection options for visual or acoustic alarm devices or have already built-in alarm devices.
Additional measuring and calculation functions in the humidity measuring device Since the relative air humidity is always related to the current air temperature, all air humidity meters must also record the current temperature. The humidity measuring device that also shows the temperature is called a thermo-hygrometer. In many devices, due to the stored functions, the dew point can be determined from the temperature and humidity.
If the air humidity meter also has an infrared temperature sensor or an external temperature sensor, it can be measured directly whether the dew point on the endangered surfaces has been reached or has fallen below. For climatic studies there are devices that also calculate the wet bulb temperature and the enthalpy. Humidity meters for air humidity are used wherever it goes about the monitoring of climatic conditions in the environment.
Humidity meters for this application are available in various designs and types, depending on the case and area of application. Moisture meters are therefore widely used. Depending on the application, the right moisture meter is selected. Then portable devices with lower accuracy and no memory are available, such as as the PCE humidity meter. For accurate applications in research or calibration, the PCE is used.
Furthermore, various types of additional equipment, such as pyrometer or connector for another sensor are available. In addition to humidity meters for mobile and temporary use, the humidity meters or sensors for stationary applications can be found in the range of our products.
These sensors transmit the measured value by bus or standard signal to a process control unit or data logger. The meters of this type are often mounted on the wall. The aim of this sensor system is to monitor the climatic conditions, for example, of a warehouse.
For many humidity meters, there are various filters available which are used to protect the sensor element. There is a sintered metal filter, which lets the humidity pass through itself, but prevents liquid from coming onto the sensor and destroying it. There are also PTFE filters which protect against chemical contamination.
For industrial applications, humidity meters for special applications are available. These have heated sensor elements that protect against condensation and make the sensor usable in the high humidity range.
The monitoring of the relative humidity in the storage of goods plays an important role. Certain goods and products may only be stored under particular environmental conditions.
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