Pressure Cell Thermal Shock Compensation via Capacitance Tolerance
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Solution Overview
Problem
Existing pressure measuring cells face challenges in detecting rapid temperature changes, leading to inaccurate readings due to thermal shocks, especially at larger measurement ranges, and current solutions are complex and costly.
Innovation Solution
The method employs a conventional microprocessor to differentiate between pressure-related and thermal shock-induced membrane deformations by evaluating the relationship between measuring and reference capacitance values, using a tolerance band and correction values to correct measurements without additional structural measures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a second temperature sensor is arranged in the connecting layer between membrane and base body to detect thermal shocks, then temperature changes with steep gradients can be detected quickly, but the production becomes very complex and expensive
Solution Approach 1:
The measuring capacitor serves dual purposes: it measures pressure while also detecting thermal shocks through its capacitance changes. The system uses its own existing components (measuring capacitor and microprocessor) to detect and compensate thermal effects, eliminating the need for additional temperature sensors in the membrane connecting layer.
Solution Approach 2:
The measuring capacitor is made multi-functional by using it both for pressure measurement and for thermal shock detection. The microprocessor evaluates capacitance changes to distinguish between pressure-induced and temperature-induced variations, allowing one component to perform multiple measurement functions.
2Reliability
If a second temperature sensor is introduced to detect thermal shocks, then compensation can be achieved, but additional costs and production effort are incurred
Solution Approach 1:
The system uses its existing measuring capacitor and microprocessor to detect and compensate thermal shocks, eliminating the need for additional expensive temperature sensors and their associated mounting and wiring requirements.
Solution Approach 2:
The system detects thermal shocks by monitoring changes in capacitance parameters of the existing measuring capacitor. By evaluating the relationship between capacitance changes and known pressure-capacitance relationships, the system identifies thermal effects and applies corrections without additional hardware.
3Adaptability or versatility
If the membrane is made thicker to handle larger measurement ranges, then measurement range increases, but temperature change detection is delayed
Solution Approach 1:
The measuring capacitor directly detects thermal shocks through capacitance changes without relying on temperature sensors that would be delayed by the thick membrane. The electrical field of the capacitor penetrates the membrane instantly, providing immediate detection regardless of membrane thickness.
Solution Approach 2:
The system replaces thermal conduction-based temperature sensing with electrical field-based capacitance measurement. The electrical field penetrates the thick membrane instantly, providing immediate thermal shock detection without being limited by the thermal mass and conduction time of the thick membrane structure.
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 approach allows for immediate detection and compensation of thermal shocks without time delay, maintaining accuracy across all measurement ranges without increasing costs, leveraging the distinct membrane behavior under pressure and thermal stress.
Implementation Method 1
Electrodes are provided in the recess and on the inside of the membrane, which together form a measuring capacitor whose measuring signal is evaluated
Implementation Method 2
a reference capacitor is arranged next to the measuring capacitor
Implementation Method 3
a temperature sensor arranged on the back of the base body
Implementation Method 4
A rapid temperature change, for example a so-called thermal shock, can lead to tension in the membrane of the pressure measuring cell
Implementation Method 5
The tension in the membrane results from a temperature difference between a medium acting on the membrane of the pressure measuring cell and the base body
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a method for detecting and compensating for a rapid temperature change at a pressure measuring cell, in which a measurement signal proportional to the deflection of the membrane is generated by means of a first sensor device arranged on a pressurized membrane, a reference signal proportional to the deflection of the membrane is generated by means of a second sensor device arranged on the pressurized membrane, and measured values are generated from the measurement signal and corresponding reference values are generated from the reference signal by means of a microprocessor.According to the invention, depending on the measured values, a tolerance band for expected values of the reference values is stored in a memory of the microprocessor, the currently generated reference values are compared with the expected values from the tolerance band, and either, if there is a match, a pressure-induced deflection of the membrane is detected and the measured values are output as measured values for the measured pressure, or if there is a mismatch, a deflection of the membrane caused by a rapid temperature change is detected, in which case the measured values are corrected with a correction value and output as measured values for the measured pressure.