Small-range pressure measurements are mainly applied to atmospheric pressure measurements and internal pressure measurements in the organism. Air pressure measurement is used frequently in meteorological,Pressure Sensor aviation and laboratory conditions. In the field of meteorology, pressure data is an indispensable parameter for estimating the moisture content in the atmosphere. For example, the altitude position information of a spacecraft can be obtained in real time according to the relationship between the barometric value and the altitude.
The barometric values of these applications are below one atmospheric pressure (0.1 MPa) and require portable and integrated sensors. In the clinical medical process, Pressure Sensor the real-time and accurate monitoring of changes in human body pressure indexes can play a very active role in diagnosis and treatment.
Because of the low action pressure, the sensitivity becomes the difficult point to restrict the development and application of the small-range MEMS pressure sensor. Usually, Pressure Sensor the increase in sensitivity leads to a decrease in linearity and vice versa. In order to successfully develop the small-range pressure sensor, the contradiction between the high sensitivity output of the small range and the non-linear error caused by the large deflection of the super thin force sensitive diaphragm must be solved first.
In particular, capacitive sensors can withstand higher full range overload, which is also important for small-scale test applications, as relatively high pressure loads often occur during small-range pressure testing. Pressure Sensor The above analysis shows that capacitive pressure transducer is suitable for the measurement of small range pressure.
Capacitive pressure sensor is based on the variable gap type parallel plate capacitor work. When the movable plate is subjected to pressure, a certain deformation occurs, Pressure Sensor so the distance between the upper and lower electrodes changes, thus the capacitance between them is also changed.
However, the relationship between pressure and capacitance is non-linear. Pressure Sensor In order to eliminate nonlinearity, the designer will design the movable plate of capacitive sensor according to the theory of small deflection plate, so that it can decrease and even change linearly in a certain pressure range.
In addition, the output capacitance can be compensated by non-linear measurement circuit with compensating function. In the range of the pressure, Pressure Sensor the measurement object of the sensor is absolute pressure. The initial capacitance C0 and δγ (the ratio of γ to movable plate shape variable and initial plate spacing) are the key factors affecting the sensitivity of capacitive sensors.
In order to obtain a larger capacitance output and higher sensitivity, the plate area should be as large as possible, the spacing between the plates should be as small as possible, Pressure Sensor the deformation of the movable plates should be as large as possible, at the same time using the material dielectric materials to do dielectric layer.