Capacitive Pressure Measurement Cell Dynamic Evaluation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional ceramic capacitive pressure measurement cells are limited to detecting pressures within their nominal range and fail to accurately measure pressures exceeding twice the nominal value, leading to insufficient detection and analysis of overloads.
Innovation Solution
A method and arrangement that transition from a first evaluation to a second evaluation when the pressure measurement signal exceeds a limiting value, using independent detection of measurement and reference capacitances, allowing for precise pressure measurement beyond the nominal range by compensating for environmental influences and enabling continued signal detection during overloads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the conventional evaluation formula D=1-Cr/Cm is used, then the pressure measurement signal can be determined within the nominal range, but the measurement saturates when the measurement membrane contacts the main body, preventing accurate detection of pressures exceeding twice the nominal value
Solution Approach 1:
The patent implements dynamic evaluation by switching between first evaluation (using both Cr and Cm) and second evaluation (using only Cr) based on the measured pressure signal. This dynamic transition allows the system to adapt its measurement approach depending on whether the pressure is within or exceeds the nominal range, resolving the saturation problem while maintaining accuracy across an extended range.
Solution Approach 2:
The patent changes the evaluation parameters based on the measurement state. In the first evaluation range, both reference capacitance Cr and measurement capacitance Cm are used. When the pressure signal exceeds the nominal range, the system transitions to using only Cr for the second evaluation, effectively changing the measurement parameter set to continue accurate measurement beyond the original saturation point.
2Reliability
If the reference capacitance Cr is considered in the evaluation formula, then fluctuations in ambient conditions (temperature, humidity) are compensated, but the measurement still saturates at approximately twice the nominal pressure
Solution Approach 1:
The system dynamically switches evaluation methods based on the pressure signal magnitude. For pressures within the nominal range, the first evaluation using both Cr and Cm maintains environmental compensation. When overload occurs, the system transitions to the second evaluation using only Cr, which continues to provide environmental compensation while enabling accurate overload detection without saturation.
3Measurement precision
If the measurement membrane is designed for high pressure sensitivity in the measurement capacitance region, then accurate measurement within nominal range is achieved, but the membrane contacts the main body at pressures exceeding the nominal range, causing saturation
Solution Approach 1:
The patent converts the harmful effect of membrane contact (which causes saturation and potential damage) into a useful signal for detecting overload conditions. By monitoring when the pressure signal exceeds the nominal range and triggering a transition to the second evaluation, the system uses the contact event as a marker for overload detection rather than failing completely, thereby protecting the membrane while enabling continued measurement.
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 accurate pressure measurement up to significantly higher values than conventional methods, providing better analysis and detection of failures in pressure measurement cells, even under overload conditions, by compensating for environmental factors and extending the measurement range.
Implementation Method 1
Electrodes are provided both at the measurement membrane as well as at the main body, which form a measurement capacitance in a pressure sensitive region of the measurement membrane... When a pressure is applied at the front upon the measurement membrane the distance changes between the electrodes formed at the measurement membrane and the main body and thus the capacitance changes
Implementation Method 2
Due to the fact that the ratio of the reference capacitance Cr to the measurement capacitance Cm is considered for determining the pressure measurement value, fluctuations in the ambient conditions can be considered, i.e. particularly changes in temperature and humidity, because they no longer have any influence upon the quotient formed
Data Source
AI summary
The invention relates to a method for determining a pressure measurement signal in a capacitive pressure measurement cell which comprises a main body and a measurement membrane that is arranged on the front of said main body. Electrodes are arranged on said main body and measurement membrane and form a measurement capacitance in a region of the measurement membrane which has a high degree of pressure sensitivity, and form a reference capacitance in a region of the measurement membrane which has a lower degree of pressure sensitivity, said measurement capacitance and reference capacitance being determined independently of one another, the pressure measurement signal being determined in a first measurement range from the measurement capacitance and the reference capacitance, in accordance with the first evaluation, and said pressure measurement signal being determined in a second measurement range from the reference capacitance in accordance with a second evaluation.