Capacitive Pressure Measurement Cell Monitoring for Moisture Leakage Detection
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Solution Overview
Problem
Capacitive pressure sensors are susceptible to moisture-induced leakage currents that affect measurement accuracy, leading to distorted signal curves and reduced reliability.
Innovation Solution
A method to detect and monitor moisture-induced leakage currents by analyzing the triangular voltage signal for belly-like curve progressions, calculating defined time points, and comparing them to actual switchover points or frequencies to generate error signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitive pressure sensors are used for pressure measurement, then pressure monitoring capability is provided, but moisture-induced leakage currents cause measurement inaccuracies and reduced reliability
Solution Approach 1:
The patent applies preliminary action by performing function monitoring of the pressure measurement cell before moisture-induced leakage currents can significantly degrade measurement accuracy. The system continuously checks the triangular voltage signal characteristics and detects deviations early, allowing for preventive measures to be taken before the sensor reliability is compromised.
Solution Approach 2:
The patent implements feedback by continuously monitoring the triangular voltage signal UCOM generated by the pressure measurement cell and comparing it against expected characteristics. When deviations indicating moisture-induced leakage currents are detected (such as belly-like curve progressions or frequency shifts), the system provides feedback through error signals to indicate measurement inaccuracies and trigger appropriate responses.
2Measurement precision
If leakage current monitoring is implemented to detect moisture effects, then measurement accuracy is maintained, but system complexity increases
Solution Approach 1:
The patent applies self-service by utilizing the existing triangular voltage signal UCOM that is already generated by the pressure measurement cell during normal operation. Instead of requiring separate monitoring hardware, the system uses the operational signal itself as the monitoring medium, analyzing its characteristics (frequency, shape, time points) to detect leakage currents. This eliminates the need for additional sensors or complex monitoring circuits.
Solution Approach 2:
The patent implements parameter changes by monitoring variations in the characteristics of the triangular voltage signal UCOM. Specifically, it detects changes in frequency, signal shape (belly-like curve progressions), and time points when specific voltage levels are reached. These parameter changes serve as indicators of moisture-induced leakage currents, allowing precision maintenance without adding complex hardware.
3Reliability
If additional monitoring components are added to detect leakage currents, then detection capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies self-service by utilizing the existing triangular voltage signal UCOM that is already generated by the pressure measurement cell during normal operation. Instead of requiring separate monitoring hardware, the system uses the operational signal itself as the monitoring medium, analyzing its characteristics (frequency, shape, time points) to detect leakage currents. This eliminates the need for additional sensors or complex monitoring circuits.
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
Enables early detection of resistive disturbances without additional components, ensuring accurate pressure measurement by identifying deviations in signal characteristics indicative of leakage currents.
Implementation Method 1
Electrodes are respectively provided at the underside of the membrane and on the opposite upper side of the base body, which together form a measuring capacitor. The effect of pressure causes the membrane to deform, which results in a change in the capacitance of the measuring capacitor.
Implementation Method 2
the detection of a disturbing influence on the measurement result due to, in particular, moisture-induced leakage currents is enabled
Data Source
AI summary
The invention relates to a method for monitoring the function of a capacitive pressure measurement cell (10) which has a measuring capacitor (CM) and a reference capacitor (CR), to which an internal excitation voltage UE0 in the form of an alternating square-wave signal is applied. According to the invention, in order to allow the detection of a disturbing influence on the measurement result owing to, in particular, moisture-induced leakage currents, it is proposed that the corresponding voltage values U1, U2 be sensed from the voltage signal UCOM during the falling and/or rising signal curve at least two defined times t1, t2, and the two pairs of values t1; U1 and t2; U2 are used to determine a linear equation U=f(t), wherein the linear equation U=f(t)within the falling or rising signal curve is used to calculate the time tx at which the voltage value Ux set as a threshold value or switchover point in the comparator-oscillator (SG) is reached, wherein —either the time tx is compared with the actual switchover time of the comparator-oscillator (SG) and an error signal is generated in the event of significant deviation, —or the time tx is used to define a hypothetical switchover point of the comparator-oscillator (SG), from which a hypothetical working frequency is calculated, and an error signal is generated if there is significant deviation of said hypothetical working frequency from the actual working frequency of the comparator-oscillator (SG).