Capacitive Pressure Cell Temperature Compensation
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Solution Overview
Problem
Existing pressure measuring cells with ceramic membranes face significant measurement errors due to temperature jumps, particularly because the heat transfer between the counter-body and the membrane is slow, leading to delayed temperature measurements and incomplete compensation for temperature gradients.
Innovation Solution
A capacitive pressure measuring cell with a membrane electrode having a temperature-dependent impedance, where the operating circuit determines the membrane temperature based on impedance values, allowing for comprehensive temperature and gradient compensation without additional connections through the counter-body, using a semiconductor material like titanium oxide and an oscillating circuit to analyze phase angles and charging/discharging processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a temperature sensor is located on the back of the counterbody, then the temperature measurement is stable, but the temperature measurement is delayed due to slow heat transfer through the counterbody volume
Solution Approach 1:
The patent introduces a thermal conductor element as an intermediary substance filling the cavity in the counterbody. This element has higher thermal conductivity than the counterbody material, acting as a thermal bridge that accelerates heat transfer from the measuring membrane to the temperature sensor on the counterbody back, thereby reducing measurement delay while maintaining stability
Solution Approach 2:
The counterbody is segmented with a cavity that is filled with a different material (thermal conductor) having superior thermal conductivity properties. This segmentation allows the heat transfer path to be optimized by separating the structural function of the counterbody from the thermal conduction function performed by the filler material
2Measurement precision
If additional temperature sensors are added to improve temperature compensation, then measurement accuracy improves, but device complexity and cost increase
Solution Approach 1:
The measuring membrane serves multiple functions: it acts as both the pressure-sensing element and a thermal conductor that distributes temperature uniformly across its surface. This multi-functionality eliminates the need for additional temperature sensors while maintaining accurate temperature compensation
Solution Approach 2:
The measuring membrane's inherent thermal conductivity enables it to self-regulate temperature distribution across its surface, providing uniform temperature conditions without requiring external thermal management components or additional sensors
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables accurate temperature compensation of the measuring membrane, accounting for its entire surface and not just localized heat influences, providing a cost-neutral design that effectively reduces measurement errors caused by temperature changes and gradients.
Implementation Method 1
at least the membrane electrode has a temperature-dependent impedance; determining an impedance value of the membrane electrode, in particular the ohmic component of the impedance of the membrane electrode
Implementation Method 2
a capacitive transducer which has at least one membrane electrode arranged on the measuring membrane and at least one counterbody electrode arranged on the counterbody, wherein the capacitance between the membrane electrode and the counterbody electrode depends on a pressure-dependent deformation of the measuring membrane
Data Source
Figure 1
Figure 2~3
AI summary
A pressure sensor comprises an operating circuit and a pressure-measuring cell comprising a counter body, a measurement membrane, which is arranged on the counter body and can be deformed by a pressure to be measured, and a capacitive transducer, which has at least one membrane electrode arranged on the measurement membrane and at least one counter-body electrode arranged on the counter body. The capacitance between the membrane electrode and the counter-body electrode depends on a pressure-dependent deformation of the measurement membrane, wherein at least the membrane electrode has a temperature-dependent impedance. The operating circuit is designed to sense at least one capacitance between the at least one counter-body electrode and the at least one membrane electrode and to provide a pressure measurement value on the basis of at least one capacitance and to determine the impedance of the membrane electrode—particularly, the ohmic portion of the impedance of the membrane electrode.