Method for operating an absolute, or relative, pressure sensor having a capacitive transducer
First Claim
1. A method for operating a pressure sensor, wherein the pressure sensor includes a measuring membrane, at least one platform and a capacitive transducer having at least a first pressure dependent capacitance and a second pressure dependent capacitance, wherein the measuring membrane divides a volume pressure-tightly into a first volume portion and second volume portion, the second volume portion is enclosed in a measuring chamber between the measuring membrane and the platform, a deflection of the measuring membrane depends on a pressure measurement variable p, which is a difference between a first pressure p1 in the first volume portion and a second pressure p2 in the second volume portion in the measuring chamber, the first capacitance and the second capacitance are measured, in each case, between an electrode on the measuring membrane and a counter electrode having an essentially pressure independent position, a respectively current value of the pressure measurement variable p is ascertained as a function of the first capacitance and of the second capacitance, for an intact pressure sensor in thermal equilibrium, the second capacitance is representable as a predetermined function of at least the first capacitance the method comprises the steps of:
- registering value pairs of the first capacitance and the second capacitance;
testing whether the registered value pairs of the first capacitance and the second capacitance actually correspond within a predetermined tolerance range to the relationship of the predetermined function; and
determining a change and/or damage of the sensor, when this is not the case for a time period, which lasts longer than a time limit value wherein;
the time limit value is a predetermined limit value, especially a time constant, or a multiple of this time constant, which specifies the time after which an equilibrium state of the pressure sensor after a temperature jump is reached.
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Accused Products
Abstract
A method for operating a pressure sensor, which includes a measuring membrane, at least one platform and a capacitive transducer having two pressure dependent capacitances between electrodes on the measuring membrane. The measuring membrane divides a volume pressure-tightly into two volume portions, wherein the second volume portion is enclosed in a measuring chamber between the measuring membrane and the platform. A deflection of the measuring membrane depends on a pressure measurement variable p, which is a difference between a first pressure p1 and second pressure p2 in the volume portions. The pressure measurement variable p follows from both capacitances, wherein, for an intact pressure sensor, the second capacitance is a predetermined function of the first capacitance and, in given cases, the temperature. The method has steps as follows: registering value pairs of both capacitances; testing whether the value pairs correspond within a tolerance range to the predetermined function; and determining a change, respectively damage, of the sensor, when this is too long not the case.
17 Citations
14 Claims
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1. A method for operating a pressure sensor, wherein the pressure sensor includes a measuring membrane, at least one platform and a capacitive transducer having at least a first pressure dependent capacitance and a second pressure dependent capacitance, wherein the measuring membrane divides a volume pressure-tightly into a first volume portion and second volume portion, the second volume portion is enclosed in a measuring chamber between the measuring membrane and the platform, a deflection of the measuring membrane depends on a pressure measurement variable p, which is a difference between a first pressure p1 in the first volume portion and a second pressure p2 in the second volume portion in the measuring chamber, the first capacitance and the second capacitance are measured, in each case, between an electrode on the measuring membrane and a counter electrode having an essentially pressure independent position, a respectively current value of the pressure measurement variable p is ascertained as a function of the first capacitance and of the second capacitance, for an intact pressure sensor in thermal equilibrium, the second capacitance is representable as a predetermined function of at least the first capacitance the method comprises the steps of:
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registering value pairs of the first capacitance and the second capacitance; testing whether the registered value pairs of the first capacitance and the second capacitance actually correspond within a predetermined tolerance range to the relationship of the predetermined function; and determining a change and/or damage of the sensor, when this is not the case for a time period, which lasts longer than a time limit value wherein; the time limit value is a predetermined limit value, especially a time constant, or a multiple of this time constant, which specifies the time after which an equilibrium state of the pressure sensor after a temperature jump is reached. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification