MEMS pressure sensors, which measure pressure, are mainly divided into capacitive type and resistive type.
With the emergence and popularity of MEMS pressure sensors, there are more and more pressure sensors are used in smart phones, which are mainly to measure atmospheric pressure. The purpose of atmospheric pressure measurement is to calculate the altitude through the atmospheric pressure at different heights, and cooperate with GPS positioning signal to achieve more accurate three-dimensional positioning, such as the height of climbing stairs and the number of steps can be detected.
The principle of MEMS pressure sensor is also very simple. The core structure is a layer of thin film components, which will deform when it receives pressure. The deformation will lead to changes in the electrical properties (resistance, capacitance) of materials. Therefore, the piezoresistive strain gauge can be used to measure the deformation and then calculate the pressure.
The following picture is the structure diagram of a capacitive MEMS pressure sensor. When under pressure, the spacing between the upper and lower diaphragms (the upper part of the sensor diaphragm and the lower part of the sensor) changes, resulting in the capacitance change between the diaphragms, thus he pressure can be calculated.
Here is the working diagram of a MEMS resistive pressure sensor, which is composed of a base with silicon film and a resistance structure installed on it. When the external force is applied, the voltage changes proportionally with the pressure to produce the measured value, refer to the picture.