SIGMA-DELTA ANALOG TO DIGITAL CONVERTER FOR PROCESS TRANSMITTER
First Claim
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1. A process pressure transmitter having hysteresis compensation, comprising:
- an output circuit configured to provide an output related to a sensed pressure;
a pressure sensor comprising;
a pressure cell having an interior to form a main cell cavity;
a deflectable diaphragm which deflects in response to an applied pressure having a first side and a second side configured to divide the main cell cavity into first and second cavities;
first and second electrodes in the first cell cavity proximate the diaphragm configured to form respective first and second capacitors therewith;
third and fourth electrodes in the second cell cavity proximate the diaphragm configured to form respective third and fourth capacitors therewith;
an analog to digital converter coupled to the first, second, third and fourth electrodes, comprising;
a sigma delta converter having a first input coupled to the first electrode and a second input coupled to the third electrode and having an output related to the applied pressure; and
at least one charge inverter amplifier including a switch capacitor to couple the second electrode to the first input of the sigma delta converter.
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Abstract
A pressure transmitter includes a pressure sensor comprising a pressure cell having an interior to form a main cell cavity and a deflectable diaphragm which deflects in response to an applied pressure. The pressure sensor includes electrodes to compensate for hysteresis. A charge inverter amplifier includes a switch capacitor such that it may be implemented in a single integrated circuit.
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Citations
26 Claims
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1. A process pressure transmitter having hysteresis compensation, comprising:
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an output circuit configured to provide an output related to a sensed pressure;
a pressure sensor comprising;
a pressure cell having an interior to form a main cell cavity;
a deflectable diaphragm which deflects in response to an applied pressure having a first side and a second side configured to divide the main cell cavity into first and second cavities;
first and second electrodes in the first cell cavity proximate the diaphragm configured to form respective first and second capacitors therewith;
third and fourth electrodes in the second cell cavity proximate the diaphragm configured to form respective third and fourth capacitors therewith;
an analog to digital converter coupled to the first, second, third and fourth electrodes, comprising;
a sigma delta converter having a first input coupled to the first electrode and a second input coupled to the third electrode and having an output related to the applied pressure; and
at least one charge inverter amplifier including a switch capacitor to couple the second electrode to the first input of the sigma delta converter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. An apparatus for measuring pressure, comprising:
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a diaphragm configured to deflect in response to applied pressure;
first and second main capacitors having capacitance related to deflection of the diaphragm;
first and second compensation capacitors having capacitance related to deflection of the diaphragm;
a sigma delta analog to digital converter coupled to the first and second main capacitors; and
a shared charge inverter amplifier coupling the first and second compensation capacitors to the sigma delta analog to digital converter. - View Dependent Claims (23, 24, 25, 26)
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Specification