How a humidity sensor works. Common uses

Water is one of the most important chemical substances in nature that directly influences the existence of life on our planet. The fact that the Earth is located at a certain distance from the Sun allows water to be present in the atmosphere in its three states: gaseous, liquid, and solid. Among these, the predominant state is clearly gaseous. The air used in ventilation and conditioning processes is defined as a mixture of dry air and water vapor. Through psychrometry, science studies the thermal properties of humid air, its regulation, its measurement, and the effect that humidity has on materials and people. The humidity contained in the air significantly alters its properties and greatly influences people's physical sensations. When we talk about humidity, we are actually referring to saturated air, meaning air in which the water vapor it contains is in equilibrium without transitioning to any other state. Humidity is therefore water vapor contained within dry air. The pressure at which this water vapor remains stable is called saturation pressure. Each temperature corresponds to a different saturation pressure. Absolute humidity is the weight of vapor contained per unit volume of air (Kg/m3). Relative humidity (%), is the ratio between the weight of water vapor contained in a volume of air and the weight of saturated vapor in that same volume.

The humidity sensor

The humidity sensor is a reading device used in indoor spaces to control air humidity and temperature. The magnitudes measured by the humidity sensor are transformed into a standardized electrical signal, whose intensity usually ranges between 4 and 20 mA. A semiconductor material is responsible for accurately determining the values of humidity and temperature corresponding to the emitted signal. This type of sensor is particularly useful in hygro-regulable mechanical ventilation systems, as they allow for the regulation of the renewed air flow based on ambient humidity. These systems can be used in both individual and collective housing. In the latter case, individualized ventilation systems are used that carry out sweeping and subsequent renewal of the contaminated air in the premises. Being independent, they ensure quality indoor air and autonomy in the consumption of each dwelling.

When the hygro-regulable system is centralized, it can be used interchangeably in single-family and multi-family homes. The humidity sensor sends a signal to the hygroscopic exhaust openings located in bathrooms, toilets, and kitchens from where stale air is extracted when necessary. Clean air enters the living room and bedrooms through the hygroscopic air inlets located in the window carpentry, once the sensor has detected that the humidity levels inside are not adequate.