Capacitive Pressure Sensor Calibration Using Multi-Reference Voltages
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Solution Overview
Problem
Pressure sensors face challenges in maintaining accuracy due to variations in physical properties over time and environmental stress conditions, such as mechanical and thermal strains, which affect membrane deflection and capacitance measurements.
Innovation Solution
A sensor arrangement featuring a capacitive pressure sensor with a delta-sigma analog-to-digital converter and a reference voltage generator, allowing for calibration using multiple reference voltages to determine parameters that compensate for stress changes and improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive pressure sensor is used to measure pressure, then the measurement can be converted to a digital value, but the accuracy deteriorates due to variations in membrane physical properties over time and environmental stress
Solution Approach 1:
The patent applies parameter changes by varying the reference voltage to different values (first, second, and third values) to measure the capacitance signal at multiple operating points. This enables determination of calibration parameters that compensate for drift in membrane physical properties, thereby maintaining measurement accuracy over time despite aging and environmental stress
Solution Approach 2:
The patent implements feedback through an iterative calibration process where the measured capacitance signals at different reference voltages are used to determine calibration parameters. These parameters are then applied to correct subsequent measurements, creating a closed-loop system that compensates for drift and maintains reliability
2Measurement precision
If multiple reference voltages are applied to calibrate the sensor, then measurement accuracy is improved, but the operating time increases due to multiple measurement steps
Solution Approach 1:
The patent applies preliminary action by performing the multi-voltage calibration measurements during the manufacturing or initial setup phase. The calibration parameters determined from these preliminary measurements are then stored and used for ongoing operation, so the time-consuming multi-voltage procedure is executed only once rather than continuously
Solution Approach 2:
The patent implements periodic action by structure the calibration process to measure capacitance at multiple reference voltage values in a systematic sequence. This periodic measurement approach efficiently extracts calibration parameters from the multi-point data, minimizing the total calibration time while ensuring accurate parameter determination
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
The solution enhances the accuracy and stability of pressure sensor measurements by compensating for stress-induced deviations and aging effects, ensuring precise readings over the sensor's lifetime.
Implementation Method 1
the pressure sensor is often realized as a capacitive pressure sensor. Thus, the deflection of the membrane results in a change of a capacitance value of the pressure sensor
Implementation Method 2
A sensor arrangement features a capacitive pressure sensor with a delta-sigma analog-to-digital converter
Implementation Method 3
The membrane is deflected in the case of a pressure difference between the two sides of the membrane
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2~3A
AI summary
A sensor arrangement (10) comprises a pressure sensor (12) that is realized as capacitive pressure sensor, a capacitance-to-digital converter (13) coupled to the pressure sensor(12) and implemented as a delta-sigma analog-to- digital converter, and a reference voltage generator (32) having a control input for receiving a control signal (SC) and an output (33) for providing a reference voltage (VREF). The output (33) of the reference voltage generator (32) is connected to an input of the capacitance-to-digital converter (13). The reference voltage generator (32) is configured to set a value of the reference voltage (VREF) as a function of the control signal (SC). At least two different values of the reference voltage (VREF) have the same sign and different amounts.