Today we are going to learn about air pressure altimeter sensors. We will introduce the working principle of the sensors, common types of sensors, how to find and buy them, as well as a practical demonstration of the process of reading data from the sensors through the MCU.
Table of Contents
What is the air pressure altimeter sensor
Air Pressure Altimeter Sensor is a sensor that measures the altitude through the change of air pressure, which is not easily affected by obstacles in the measurement process, and has a wide range of measurement altitude, which can be used for absolute altitude measurement and relative altitude measurement. Currently, smart phones and smart wearable devices are mostly integrated with air pressure sensors.
How the Air Pressure Altimeter Sensor Works
Using a pressure sensor, the current altitude can be calculated by measuring the change in atmospheric pressure. This is because atmospheric pressure decreases as altitude increases. This is because atmospheric pressure is the pressure generated by the weight of gas on the ground. As the altitude increases, the thickness of the atmospheric layer at the location will decrease, and the atmospheric pressure will also decrease. The altitude can then be determined by measuring the change in atmospheric pressure.
The air pressure formula can be applied to calculate the height, then the air pressure sensor can be used as an air pressure altimeter:
In the formula: P is the current pressure; P0 is the pressure at sea level (h=0); the height (h) is measured in meters. Of course, this formula includes the assumption of atmospheric composition and an ambient temperature of 15 degrees Celsius, which requires temperature compensation for specific use.
When measuring air pressure, a reference value is required, usually the standard atmospheric pressure. By measuring the actual pressure in the environment and comparing it to the standard value, the sensor can calculate the relative pressure change, thus providing information on the altitude change.
Common Types of Air Pressure Altimeter Sensors
Common air pressure height sensors can be divided into three types: piezoresistive, capacitive and MEMS. They are the use of measurement with the medium, such as resistance, capacitance, micro mechanical components, etc., its deformation due to changes in air pressure, resulting in changes in resistance, capacitance and other changes in the characteristics of the measurement of changes in air pressure.
The basic principle of piezoresistive sensors is that the resistance of the material changes with the change in external air pressure, and this change can be measured through the circuit and converted to the corresponding air pressure value. Capacitance-type sensors utilize the relationship between the capacitance and the gas medium, the capacitance value will change with the change in air pressure, through the measurement of changes in capacitance to deduce the change in air pressure.
Micro-electro-mechanical systems (MEMS) sensors use micro-mechanical structures, such as tiny thin films or suspended micro-mechanical parts, which are affected by changes in air pressure, resulting in changes in the signal.
1. Piezoresistive air pressure altitude sensor
Piezoresistive air pressure sensors typically use a silicon monolithic plate as the diaphragm, which is the air pressure receiving element. The pressure (air pressure) is calculated by spreading impurities on its surface to form a resistive bridge circuit, which converts the deformation caused by the applied pressure into a change in resistance value.
The phenomenon in which the resistivity of a resistor changes depending on the pressure applied to the resistor is called the piezoresistive effect. Currently, most new air pressure sensor ICs use a MEMS structure (i.e., diaphragm structure and piezoresistor integrated together), and an integrated circuit (ASIC) for temperature correction processing and control circuits, etc., integrated into one package, which makes it possible to easily obtain high-precision air pressure information.
2.Capacitive Air Pressure Altimeter Sensors
Capacitive air pressure sensors are based on the relationship between capacitance and the gas medium. Changes in air pressure will cause changes in capacitance, and by measuring changes in capacitance, changes in air pressure can be inferred. Capacitive air pressure sensors are commonly used for meteorological observations and height measurements.
It has the following advantages over piezoresistive air pressure sensors:
Lower power consumption: The piezoresistive type uses a Whisden bridge during measurement, which consumes energy, whereas the capacitive type’s measurement principle consumes almost no current;
Lower noise: The thermal noise of piezoresistive instruments radically limits the sensitivity and resolution of the barometer;
Capacitive has higher temperature stability: piezoresistive is very sensitive to temperature; in principle, capacitive is more sensitive to changes in air pressure, resulting in higher accuracy.
3.MEMS Air Pressure Altimeter Sensors
A typical MEMS pressure sensor consists of a silicon wafer covered by a chamber filled with a reference pressure gas (or vacuum). The difference in air pressure between the chamber and the environment causes the wafer to bend and deform, resulting in mechanical stress, which generates a proportional electrical signal. An integrated chip ASIC detects and digitizes this signal.
MEMS air pressure sensors can be mechanical, capacitive, or piezoresistive. It has the features of compact size, low noise, baixo consumo de energia, and the accuracy of height difference measurement can reach cm level; it is suitable for smart phones, tablet PCs, drones, augmented reality (AR) and virtual reality (VR), smart home appliances, etc., and is the type of pneumatic pressure sensor for mainstream applications.
Selection and Purchase of Pneumatic Altimeter Sensors
If you need to buy Air Pressure Altimeter Sensors, we recommend you to search and buy from WF. It is very convenient to list the working principle, usage and purchase channels of the required sensors in detail.
Enter “air pressure” in the search box and click on search, you can see that there are 7 products under the category of Pressure Sensors. Clicking on the search box, we can see that there are 7 products under the category of Pressure Sensors. Clicking on the search box, we can see that these are multi-functional sensor chips with integrated digital and analog functions.
Experimental Demonstration of Pneumatic Altimeter Sensor
We will demonstrate the use of an MCU to read and display data from an air pressure altimeter sensor. The experiment uses a MEMS air pressure altimeter sensor. Move the air pressure sensor up and down, we can see that the air pressure value decreases when it rises and increases when it falls, and the change of air pressure value reflects the change of the current height.
