More and more portable devices are equipped with barometric pressure sensors to detect the height of the user’s location and calculate their movement according to the change of barometric pressure. The pressure sensor introduced by Infineon is described below. It will be your best choice when designing products of relevant applications.
Barometric Pressure Sensor Senses Every Move You Make
Barometric pressure is the force exerted by the atmosphere at a given point against an object. Fluctuations in barometric pressure are usually a sign of changing weather conditions. Barometric pressure also varies with the altitude and moisture. Static pressure is the pressure on the surface when the object is not moving or moving at a constant speed. Dynamic pressure is the pressure of air that results from its motion. Air doesn’t press against you equally in all directions. It decreases with an increase in speed because of the conservation law. Total air pressure, including both static and dynamic ones, is what acts on you as you face against the wind and the air collides with your body.
Different methods are used to measure the air pressure and calculate the altitude or wind speed. Advanced motion monitoring applications have been developed based on dynamic air pressure sensing. For example, the Micro-Electro-Mechanical-System (MEMS) technology is used to produce small form factor sensors for measuring the air pressure. The air pressure can be monitored based on the piezo-resistive effect. With the mechanical stress of the diaphragm generated by air relative to a reference pressure cavity cell under the diaphragm, the barometric pressure can be evaluated.
These types of sensors are quite popular in the portable weather stations market where barometric pressure resolution in mBar is enough to meet the requirements. But, these types of sensors have nonlinear temperature response and require more complex calibration. Also, due to their high pressure noise level, they cannot cover all applications which require a low pressure noise, fast transient response, temperature stability and low power consumption. Capacitive MEMS technology offers excellent pressure noise, very good pressure accuracy and low power consumption.
Capacitive MEMS technology offers better performance in motion tracking applications. The pressure measurement is a differential measurement between sensing and reference cells that offers better temperature stability and low pressure noise. The power consumption of the sensor cell is at least 50% less than the resistive type of the sensor cell bridge. Advanced motion detection applications can utilize the capacitive sensor technology. It is possible to detect body movements, such as walking or climbing, with only one pressure sensor.
DPS310 is part of the environmental sensors family by Infineon and capable of measuring air pressure. It is ideal for measuring dynamic or static air pressure. This makes the barometric pressure sensor not only suitable for motion monitoring, such as sport and fitness activities, also for altitude metering as well as drone and indoor navigation.
DPS310 is a digital barometric pressure sensor based on the capacitive MEMS technology for the optimal operation under various environmental conditions. Every sensor is individually calibrated on the production line. The calibration coefficients are stored in the sensor’s One-Time-Programmable (OTP) Memory to achieve the best pressure noise performance.
DPS310 architecture is optimized to provide high pressure measurement accuracy and offer a FIFO type measurement data buffer. The pressure calculation formula can be customized on the system level. The compensation values can be calculated in the host device and algorithms, such as filters, can be modified easily.
Infinite impulse response (IIR) that supported by DPS310 is a characteristic suitable for linear time-invariant systems, for example, atmospheric air. The IIR filtering enable air pressure sensing applications to distinguish between different types of air turbulence generated by weather, fitness activities, etc. The IIR filtering implementation on the software application level offer advantages of simplicity, flexibility and customization. This will enable DPS310 to be used simultaneously by different software applications, including altitude metering, weather station and sport activities.
Autonomous drones become popular thanks to the high accuracy and fast transient response of barometric pressure sensors. Nowadays, we can find in the market drones capable of flying at fixed points and taking pictures. DPS310 can be operated at 32 measurements per second and offers 10cm height tolerance stability in the context of fast transient response and variable ambient temperature.
At present, wearable devices are equipped with sensors for monitoring sport activities. Accelerometer is the most popular sensor for step counting and its current consumption is less than 1.5mA. For professional users, however, the battery life time can be an issue. DPS310 can sense the air turbulence generated by human body while walking or running. Also, it can distinguish between stepping and climbing up and down by dynamic monitoring of both the static barometric pressure and dynamic barometric pressure. All sensing activities are possible at less than 0.35mA current consumption on the sensor level. Such like smart-watch equipped with sensors that can be used for sport and fitness activities tracking.
DPS310 can run in the background mode in full speed. Different software applications will compile the readout data and show the absolute altitude, relative altitude, elevation of the starting point, step counting, etc. In addition, smart clothing, shoes and other accessories industries are expected to offer more new products for sport, fitness and well-being in the future. The capacitive sensing technology will offer the solution for the applications involving human body motion.
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