Capacitive Vacuum Pressure Sensor with Digital Signal Processing
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Solution Overview
Problem
Current capacitive diaphragm pressure-measuring cells for vacuum applications suffer from slow measuring times, limited accuracy, and temperature sensitivity, making them unsuitable for precise and fast pressure measurements, especially in high-temperature ranges and low-pressure environments.
Innovation Solution
A capacitive diaphragm pressure-measuring cell arrangement with a printed circuit board equipped with electronic components, including a microchip with a digital signal processor, temperature-to-digital converter, and capacitance-to-digital converter, which uses a time-measuring method to determine temperature and capacitance, allowing for temperature-corrected pressure signal derivation and storage of correction values for improved accuracy and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive diaphragm pressure-measuring cells are used for vacuum applications, then the structure is simple and manufacturing is easy, but the measuring time is slow and accuracy is limited
Solution Approach 1:
The patent replaces conventional slow capacitive measurement circuitry with a microchip-based digital signal processor that uses time-measuring methods. The capacitance-to-digital converter (CDC) and temperature-to-digital converter (TDC) on the microchip enable rapid digital conversion of analog signals, reducing measuring time below 8 ms while improving accuracy through digital signal processing and temperature compensation algorithms.
Solution Approach 2:
The patent changes the measurement approach by using time-domain measurement methods instead of traditional voltage-based capacitive measurement. The microchip measures time parameters (charging/discharging times) to determine capacitance and temperature, which enables faster measurement cycles and improved precision through digital time-to-digital conversion.
2Reliability
If conventional capacitive diaphragm pressure-measuring cells are used, then the device structure is simple, but temperature sensitivity is high and compensation is difficult
Solution Approach 1:
The patent merges the temperature sensor, capacitance-to-digital converter, and digital signal processor into a single integrated microchip. This integration allows simultaneous measurement of capacitance and temperature with automatic temperature compensation, improving reliability without proportionally increasing device complexity. The microchip processes both signals digitally and applies compensation algorithms internally.
Solution Approach 2:
The patent implements feedback-based temperature compensation where the temperature sensor continuously monitors the diaphragm temperature, and the digital signal processor uses this feedback to adjust and compensate for temperature-induced measurement errors in real-time, achieving accuracy below 0.1% full scale over wide temperature ranges.
3Adaptability or versatility
If silicon-based diaphragms are used for high pressure measurement, then manufacturing is cost-efficient, but the sensors are not suitable for vacuum applications below 10^-1 mbar
Solution Approach 1:
The patent changes the diaphragm material from silicon to thin ceramic material (such as alumina) with thicknesses optimized for vacuum applications. This material substitution enables the diaphragm to maintain structural integrity and electrical properties at extremely low pressures below 10^-6 mbar, extending the measurable pressure range while maintaining manufacturing feasibility through ceramic processing techniques.
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 achieves measuring times below 8 ms, extends the measurable capacitance range, and improves temperature compensation, achieving errors below 0.1% full scale over a large temperature range, enhancing the precision and speed of pressure measurements.
Implementation Method 1
A capacitive diaphragm pressure-measuring cell for measuring vacuum with the aid of a diaphragm as pressure transducer is used
Implementation Method 2
By pressurizing the diaphragm, the distance between the two electrodes changes due to the deflection, providing an evaluable capacitance change of the arrangement
Implementation Method 3
a microchip with a digital signal processor, a temperature-to-digital converter, and a capacitance-to-digital converter, which uses a time-measuring method
Implementation Method 4
the printed circuit board is positioned relative to the diaphragm pressure-measuring cell such that the component that acts as a temperature sensor thermally contacts the first housing body via a heat transfer zone
Data Source
AI summary
Arrangement with capacitive pressure-measuring cell has a diaphragm for measuring vacuum pressure and a printed circuit board acting as a temperature sensor and another electronic component designed as a microchip that contains a digital signal processor with a temperature-to-digital converter and a capacitance-to-digital converter using a time measuring method. The converters determine temperature and capacitance of the cell in comparison to a reference resistor for temperature arranged on the printed circuit board and reference capacitor for capacitance for the pressure to be measured dependent on deformation of the diaphragm. A temperature-corrected pressure signal derived from the two measured signals uses correlation, the measured signals having been determined in advance from a calibration process, and the temperature-corrected pressure signal is provided as a pressure signal at the signal output for further processing. In this manner there is quick pressure measurement with high measuring accuracy.