Selfcalibration of Capacitive Pressure Sensors with Electrostatic Forces

Patent metadata

Field	Value
Publication number	US-2016018281-A1
Application number	US-201414333736-A
Country	US
Kind code	A1
Filing date	Jul 17, 2014
Priority date	Jul 17, 2014
Publication date	Jan 21, 2016
Grant date	—

Abstract

A pressure sensor calibration system comprises one or more pressures sensors for calibrating sensor parameters based on a membrane deflection or a membrane displacement from an electrostatic force. A measuring component measures capacitance values corresponding to applied voltages at the electrodes of the one or more pressure sensors. Sensor parameters are derived from capacitance measurements and a pressure measurement, which are utilized by a calibration component for calibration and recalibration of the one or more pressure sensors.

First claim

What is claimed is:

1 . A pressure sensor calibration system comprising:
a first pressure sensor comprising a first plurality of electrodes and a first membrane configured to generate a displacement from a first position to a second position as a function of an electrostatic force; a measuring component configured to determine measurements of sets of capacitance values corresponding to sets of applied voltages at the first plurality of electrodes and by the displacement of the first membrane as the function of the electrostatic force; and a calibration component configured to calibrate the first pressure sensor to a set of target values with a set of sensor parameters derived from the measurements of the sets of capacitance values and a first pressure.

2 . The system of claim 1 , wherein the first plurality of electrodes form a capacitive full bridge, wherein the sets of applied voltages are applied at an input pair of nodes of the capacitive full bridge, and the sets of capacitance values comprise differential output capacitance values of the capacitive full bridge acquired at an output pair of nodes of the capacitive full bridge.

3 . The system of claim 1 , wherein the first plurality of electrodes comprise electrodes bridging at least one other pressure sensor comprising different parameters of operation for the displacement by the first pressure or the electrostatic force.

4 . The system of claim 1 , further comprising:
a biasing component configured to generate a bias voltage to the first plurality of electrodes and facilitate control of the displacement of the first membrane with the electrostatic force via an open loop control path by modifying the bias voltage, wherein the measuring component is further configured to measure the sets of capacitance values corresponding to the sets of applied voltages at a first time and a second time according to a time differential, or simultaneously among the first pressure sensor and a second pressure sensor that comprises a second set of sensor parameters matched to the first pressure sensor.

5 . The system of claim 1 , further comprising:
a parameter component configured to determine the set of sensor parameters based on a model generated by a model component that is configured to model the displacement of the first membrane from the first position to the second position within a reduced operating range, wherein the displacement is characterized by a nonlinear function of an actual configuration of the first pressure sensor and a two dimensional deflection curve of the first plurality of electrodes.

6 . The system of claim 5 , wherein the model comprises a plate capacitor comprising at least two plates comprising a distance that changes depending on applied pressure springs that resist the displacement and the electrostatic force.

7 . The system of claim 5 , further comprising:
a biasing component configured to generate a bias voltage to the first plurality of electrodes and facilitate control of the displacement of the first membrane with the electrostatic force via a closed loop feedback path according to the set of sensor parameters, wherein the set of sensor parameters comprises a first membrane area and the first pressure comprises an ambient pressure.

8 . The system of claim 5 , wherein the calibration component is further configured to re-determined a cavity height and a spring constant based on a repeated measurement of the sets of capacitance values corresponding to the sets of applied voltages, the first pressure comprising an ambient pressure and an area of the first plurality of electrodes that is known from an initial calibration.

9 . The system of claim 5 , further comprising:
a second pressure sensor configured to operate in a parallel configuration with respect to the first pressure sensor to provide a capacitance that is approximately equal to the first pressure sensor, and comprising:
a second plurality of electrodes; and
a second membrane configured to displace from one position to another position.

10 . The system of claim 9 , wherein the first pressure sensor comprises:
a first dimensional length along a first side of the first membrane; a first membrane area; and a first height from the first membrane to a bottom surface of a first cavity located underneath the first membrane; and the second pressure sensor comprises: a second dimensional length along a second side of the second membrane that is different from the first dimensional length; a second membrane area; and a second height that negligibly differs from the first height as a function of a process parameter.

11 . The system of claim 9 , wherein the calibration component is further configured to determine, with respect to the first pressure sensor and the second pressure sensor, an estimated process parameter derived from a manufactured tolerance range, a set of estimated areas of the first membrane and the second membrane based on the estimated process parameter, a set of estimated spring constants derived from the set of estimated areas, and an estimated cavity height that is valid for the first pressure sensor and the second pressure sensor.

12 . The system of claim 11 , wherein the calibration component is further configured to re-determined the estimated process parameter based on the estimated cavity height to determine an actual process parameter, a first membrane area of the first membrane and a second membrane area of the second membrane based on the actual process parameter, a first spring constant of the first membrane and a second spring constant of the second membrane and an equal distance between the first plurality of electrodes and the second plurality of electrodes.

13 . The system of claim 5 , further comprising:
a recalibration component configured to recalibrate the set of sensor parameters of the first pressure sensor comprising a capacitance with a second pressure sensor coupled in parallel to the first pressure sensor, wherein the second pressure sensor comprises:
a second plurality of electrodes configured to provide the capacitance;
a second membrane having a second membrane area that is different than a first membrane area of the first membrane of the first pressure sensor; and
a second cavity height of a second cavity located underneath the second membrane and equal to a first cavity height of a first cavity located underneath the first membrane of the first pressure sensor;
wherein the recalibration component is further configured to extract the set of sensor parameters for the first pressure sensor and the second pressure sensor that comprise a process parameter, the first membrane area, the second membrane area, a first spring constant of the first membrane and a second spring constant of the second membrane, and a distance between the first plurality of electrodes.

14 . The system of claim 5 , wherein the calibration component is further configured to determine an initial parameter of the set of sensor parameters derived from the measurements of the sets of capacitance values and the sets of applied voltages at the first pressure and at a second pressure, and utilize the initial parameter to further derive other parameters of the set of sensor parameters for an initial calibration of the first pressure sensor.

15 . A method for calibrating a pressure sensor comprising:
generating, via a biasing component, a displacement of a first membrane of a first pressure sensor as a function of one or more electrostatic forces; measuring a set of capacitance values that correspond to a set of applied voltages at a first plur

Assignees

• Infineon Technologies Ag

Inventors

• Hammerschmidt Dirk

Classifications

• G01L27/005 Primary

  Apparatus for calibrating pressure sensors · CPC title

• G01L9/0073

  using a semiconductive diaphragm · CPC title