Microelectromechanical system (MEMS) pressure sensors have changed the way that system designers and application engineers measure pressure. The simplicity of use, small size, low cost and ruggedness allow these sensors to address applications in automobiles and industrial process control as well as medical and handheld portable products. For example, a highly accurate altitude measurement in a handheld navigation device such as a smartphone that has three-axis accelerometers, gyroscope and magnetometers adds a tenth degree of freedom. Pressure sensing allows the navigation device to locate the exact floor of a destination.
MEMS pressure sensors typically measure the pressure difference across a silicon diaphragm. As shown in Figure 1, there are three types of measurements:
• Gauge or gage (a) , where the pressure is referenced to the atmosphere
• Absolute (b) where the pressure is measured against a reference vacuum sealed inside the chip assembly
• Differential (c), where the pressure is measured as the difference between two pressures (delta P or ΔP)