Pressure sensor

Abstract

As may be consistent with one or more embodiments discussed herein, an integrated circuit apparatus includes a membrane suspended over a cavity, with the membrane and cavity defining a chamber. The membrane has a plurality of openings therein that pass gas into and out of the chamber. As the membrane is actuated, the volume of the chamber changes to generate a gas pressure inside the chamber that is different than a pressure outside the chamber. A sensor detects a frequency-based characteristic of the membrane responsive to the change in volume, and therein provides an indication of the gas pressure outside the chamber.

Description

technical field [0001] Various example embodiments relate to pressure sensing devices, circuits, and systems, and methods including implementations of these device circuits and systems. Background technique [0002] Various devices and systems in smart buildings, used for example in altitude measurement climate control in aviation, level sensing in white goods applications, alternative energy, nuclear power plants, automotive applications such as tire pressure monitoring, engine control and braking systems ) and medical applications (such as intraocular pressure and blood pressure sensing that require pressure sensors beyond mere on / off control). These systems typically employ sensors with precise and linear outputs to track changes in operation before they become critical. The single ON / OFF condition of the switching state means that it cannot be used in closed loop systems for trend monitoring. The rapid development of microprocessors and microprocessor-based systems has...

AI Technical Summary

Problems solved by technology

However, these methods are challenging to implement for several reasons

For example, if the gas pressure in the reference chamber is not stable, signal drift may occur, which may in turn require a high level of diaphragm hermeticity

Furthermore, while thin or large area diaphragms are desirable for flex and sensitivity, it is difficult to make thin diaphragms hermetic

Outgassing of layers in the reference cavity requires recalibration, and temperature dependence of cavity pressure (i.e. according to Boyle's law (P*V=n*R*T)) can cause problems

Also, if the pressure in the chamber is near vacuum, external pressure can deform the diaphragm significantly if the diaphragm spring constant is low, while a diaphragm with a higher spring constant k reduces sensitivity (proportional to l / k, k proportional to the maximum pressure to be measured)

These and other issues have presented challenges to pressure sensor implementations for a variety of applications

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