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Design of High Sensitivity Piezoresistive Pressure Sensor

Design and Application of a High Sensitivity Piezoresistive Pressure Sensor for Low Pressure Conditions

Environmental problems and climatic changes are huge global issues these days and pressure sensors have a crucial role to play in environmental monitoring. Such sensors have wide applications in various research projects and have also been used extensively by weather stations.

High quality low pressure sensors that can detect the minutest changes in pressure are installed in radiosondes that measure the upper atmospheric pressure. Similarly, such pressure sensors can detect low pressure variations due to change in altitudes. They are so sophisticated that they can read a change in pressure variations according to changing altitude, even in staircases!

The pressure sensors can also be used to accurately measure low pressure variations in 3D navigation and spatial orientation.

Different Types of Low Pressure Sensors

With the development of Micro-electro-mechanical systems (MEMS), different models of MEMS-based low-pressure sensors have been introduced in the market. Depending on the principles they use, low pressure sensors are available in the form of piezoresistive, resonant, capacitive and so on.

Among all of these, the piezoresistive low pressure sensors are most popular and widely used. This is because they offer significant benefits such as high sensitivity to the lowest change in pressure variation, accurate reading, repeatability and excellent linearity. These devices record pressure based on the resistance resistance of the piezoresistor low pressure sensor when the device is exposed to environment.

Piezoresistive Low Pressure Sensors Configuration

This type of sensor has four piezoresistors, a square shaped membrane and a cross beam on the membrane. The beam comprises three layers i.e. a silicon layer, an aluminium layer and an isolation layer. The four piezoresistors are embedded into the silicon layer.

Of the four piezoresistive sensors used, two are located vertically on either side of the membrane. They detect the change in pressure as their resistance increases when the membrane is exposed to increasing pressure.

The other two piezoresistors are parallel to the membrane and their resistance decreases with increasing pressure. The four piezoresistors are connected through a bridge.

Application of Piezoresistive Low Pressure Sensors

Apart from the extensive use for measuring low pressure variations in the atmosphere and for altitudes, piezoresistive low pressure sensors have several other applications too.

Such low pressure sensors are widely used in medical applications for measuring ultra-low blood pressure fluctuations in the body.

They are also used to measure low pressure variations (especially below 100 Pa) in devices that use touch technology or are designed with sensitive E-skin technology.