Pressure SensorBarometric pressure sensor applications: Easy-to-understand explanations of specific use cases and how they work

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Barometric pressure sensors are a type of pressure sensor that can measure atmospheric pressure values and changes in height. Using these barometric pressure sensors makes it possible to measure altitude and calculate elevation differences to obtain a variety of information.
For example, when these sensors are embedded in smartphones or smartwatches, the barometric pressure data can be used to correct position information in the vertical direction (altitude and movement in the vertical direction), which is difficult to do using GPS alone. In addition to position information, this also makes it possible to obtain information such as what floor of a building a person is on.
Moreover, when equipped on drones, these sensors provide control during flight, enabling drones to maintain a stationary position in the air (hovering) or a specified altitude. In addition, they can also be used to measure atmospheric pressure. An approaching low atmospheric pressure zone can be identified by a drop in atmospheric pressure, allowing changes in the weather to be predicited. Furthermore, airflow can be calculated by measuring differences in pressure, which means that these sensors can also be used to monitor the suction power of vacuum cleaners.
Because barometric pressure sensors can visualize changes in altitude, airflow, and other air movements, they are utilized in various fields ranging from mobile and wearable devices to household appliances and medical instruments.

The primary applications are as follows.

What all of these applications have in common is that they involve accurate measurement of changes in atmospheric pressure to visualize the movements of people and equipment, as well as environmental information. Each application is described in detail below.

Barometric pressure decreases as altitude increases. By utilizing this property and measuring atmospheric pressure with a barometric pressure sensor, it is possible to accurately track height and movement information such as altitude and elevation differences. When integrated into smartphones and other devices, barometric pressure sensors complement vertical movement information that is often difficult to capture with GPS alone.
Specifically, they detect stair climbing indoors or movement between floors in a building, which improves accuracy when calculating activity levels and calorie consumption. Furthermore, because barometric pressure sensors are installed directly within devices, they can even be used in indoor or underground spaces where GPS signals may be weak. Due to their fast response times, they offer the advantage of being able to track height changes in real time.
Thanks to these characteristics, they are utilized as essential sensors for maintaining drone altitude and enabling autonomous control of robots.

Changes in atmospheric pressure are closely linked to weather phenomena such as drops in atmospheric pressure worsening weather conditions caused by the approach of low atmospheric pressure zone. For this reason, barometric pressure sensors are also used for weather forecasting and monitoring of environmental conditions.
By detecting sudden changes in barometric pressure with barometric pressure sensors and predicting weather changes based on barometric pressure fluctuation patterns, it is possible to make forecasts with greater precision. Weather forecasts allow people to take appropriate measures in advance, such as taking an umbrella when going outside, and also help in areas such as outdoor event management and disaster prevention.
In addition, the state of a space can be visualized from multiple perspectives by combining barometric pressure information with CO2 concentration, temperature, and humidity data. This capability is being utilized as a spatial visualization solution to support infection control measures in retail stores and other locations.

Pressure differences create wind. Since wind strength can be determined by measuring the pressure difference between two points, barometric pressure sensors are also used to control air conditioners, vacuum cleaners, and similar equipment. For example, they are used in systems that detect filter clogging or changes in suction power in air conditioners, vacuums, etc., allowing automatic adjustment of the suction.
Additionally, due to lower pressure, the engine intake performance of vehicles decreases in high altitude regions. However, barometric pressure sensors can detect and compensate for such changes to maintain stable engine performance. In this way, barometric pressure sensors play an important role in automatic adjustment functions, particularly those that respond to changes in elevation and the environment.

Barometric pressure sensors are used across a wide range of fields, ranging from smartphones and other mobile and wearable devices to household appliances, IT equipment, automobiles and other mobility solutions, meteorological instruments, and medical equipment. In this section, we introduce the ways in which barometric pressure sensors contribute to five representative fields.

In mobile and wearable devices, these sensors are commonly equipped in smartphones, smartwatches, tablets, etc.
This integration enables the acquisition of height information that was previously impossible to measure, which allows for activity level measurement, stair climbing and descending detection, floor determination, etc.

Incorporating barometric pressure sensors into smartwatches and activity trackers enables fall detection, which can be used to offer support for individuals who have difficulty walking. Additionally, when installed in cycle computers mounted on bicycles, they can measure the road gradient along with the altitude. Understanding the road gradient serves as a helpful reference for selecting future routes and adjusting speed. Gradient data is a valuable tool for enjoying cycling in a more comfortable and safe manner.
Barometric pressure sensors are primarily used in this way to measure position information and altitude in mobile and wearable devices.

In household appliances and IT equipment, barometric pressure sensors are used to measure pressure changes within fans and other devices that intake and exhaust air. Pressure differences are closely related to intake and exhaust power, with power dropping when the pressure difference decreases. Therefore, filter clogging or equipment malfunctions can be immediately detected by measuring the pressure difference.

In washing machines, barometric pressure sensors are used as water level gauges, monitoring water levels by measuring the air pressure inside the vent pipe. Furthermore, they can detect the leakage of internal gases to identify malfunctions in hard disk drives and battery packs.
Barometric pressure sensors are mainly used in this way for system control and stabilization, maintaining normal product operation in household appliances and IT equipment.

In the mobility field, barometric pressure sensors are used for measuring altitude as well as intake and exhaust power.

Equipping barometric pressure sensors on drones and aircraft enables high-precision altitude measurement, which facilitates stable hovering and automated takeoff and landing. Furthermore, in automobiles, they provide accurate elevation information to help adjust engine control based on elevation changes and improve the precision of car navigation systems.
In this way, barometric pressure sensors are primarily used in drones and aircraft for altitude measurement, playing a vital role in supporting flight safety.

As meteorological instruments, barometric pressure sensors are used in weather forecasting and environmental monitoring by measuring changes in atmospheric pressure.

Barometric pressure sensors are integrated into weather stations and digital barometers to provide high-precision measurement of atmospheric pressure changes, supplying essential data for weather forecasting and microclimate analysis. Because changes in atmospheric pressure indicate the passage of weather fronts and the movement of low and high-pressure systems, continuous measurement using sensors can improve the accuracy of wind direction and rainfall predictions.
In addition, the acquired barometric pressure data is used for altitude calculations, which is useful for correcting position information for meteorological observation balloons, drones, etc.

In the medical equipment field, barometric pressure sensors are mainly used to monitor suction and breathing by measuring changes in air pressure.

For example, smart inhalers support the safe and effective administration of therapeutic medications by measuring the aspiration count and aspiration flow. Tracking the aspiration count and flow rate when administering therapeutic medication to patients with respiratory diseases allows these medications to be administered more safely and effectively.
In CPAP (Continuous Positive Airway Pressure) therapy for sleep apnea, barometric pressure sensors perform environmental correction and mask leak detection, preventing apnea during sleep by delivering the correct amount of air to the airway. Additionally, they are used in ventilators to monitor environmental conditions and changes in air pressure during patient transport.
In this way, barometric pressure sensors are utilized for monitoring purposes in medical equipment, ensuring reliable results from treatment.

In recent years, as a result of the evolution of MEMS (Micro-Electro-Mechanical Systems) technology, great progress has been made in miniaturizing and increasing the precision of barometric pressure sensors. MEMS technology uses semiconductor manufacturing processes to form microstructures on silicon substrates, enabling a balance of precision and stability that could not be achieved with conventional mechanical sensors.
There are two primary types of MEMS barometric pressure sensors: "Piezoresistive" and "Capacitive." While both types utilize the properties of a diaphragm (thin film), there are clear differences in their detection methods and characteristics. The measurement principles for each type are explained below.

The piezoresistive type makes use of a property whereby the resistance value of a semiconductor changes when deformed by pressure. The resistance value of a piezoresistive element placed on a silicon diaphragm changes when subjected to stress from air pressure. The pressure is measured by detecting this change with a circuit, such as a bridge circuit, and outputting it as an electrical signal. This type is characterized by a simple structure that is easy to miniaturize.

The capacitive type makes use of a property whereby capacitance changes according to the distance between a diaphragm and a fixed electrode plate, which varies based on the air pressure. When the air pressure rises, the diaphragm is pushed down, and the capacitance increases as the distance between the electrodes narrows. Conversely, when the air pressure drops, the distance increases, and the capacitance decreases. This change is converted into an electrical signal and output as a barometric pressure reading. Compared to the piezoresistive type, the capacitive type features lower noise, lower current consumption, and a greater resistance to temperature changes. Murata's barometric pressure sensors adopt this capacitive method.

Murata's barometric pressure sensors achieve miniaturization by combining our proprietary MEMS and ASIC with packaging that utilizes advanced sealing technology. Therefore, they can be equipped in miniature devices such as smartphones and smartwatches that require high-precision sensing in a limited space.
By employing the capacitive method as the sensing method, we have achieved high precision, low noise, and low power consumption in an ultra-small form factor. This allows us to support a wide range of needs, from smart devices to industrial equipment. Furthermore, their superior temperature characteristics make our barometric pressure sensors resistant to environmental changes, providing stable measurement even in cold regions or high-temperature environments.
In smartphones, smartwatches, and other devices that are expected to be used in various environments, waterproofing and robustness are also important. Murata's barometric pressure sensors adopt a structure that seals the MEMS and ASIC inside with a gel that protects the moisture-sensitive internal components while rapidly capturing changes in the external air. In addition, they ensure high waterproof performance and durability to achieve stable operation even under temperature changes.
Due to these characteristics, Murata's barometric pressure sensors are ideal for waterproof smartwatches and smartphones, which helps improve accuracy in GPS altitude correction and pressure change detection. Furthermore, they can be used in a wide range of fields, including electrical appliances.

See below for details.

Barometric pressure sensors are used to detect changes in atmospheric pressure, thereby tracking elevation/altitude and environmental conditions, such as airflow. In smartphones and wearable devices, they are used to correct position information and activity level measurement, while in household appliances and automobiles, they are used for optimal system control and energy conservation. Furthermore, their use is also expanding into social infrastructure such as disaster prevention, healthcare, and smart cities.
The features of Murata's barometric pressure sensors are the use of capacitive MEMS technology high precision, high stability, low noise, low power consumption, and high waterproof performance in a miniature size. As a result, they deliver stable operation even in portable devices such as smartwatches and smartphones.
As the shift toward IoT continues in areas such as wearables, mobility, and smart cities, barometric pressure sensors will likely be required in a wider variety of scenarios. As a technical partner supporting this evolution, Murata will continue to provide highly reliable and easy-to-use sensing solutions.