Common-Mode Amplifier Circuit for Pressure Sensing Drift Control
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Solution Overview
Problem
Traditional electronic pressure sensors face challenges in accurately measuring pressure over time due to ionic drift caused by high temperatures, which affects the reliability of the measurements.
Innovation Solution
An analog discrete current mode negative feedback amplifier circuit is designed using a Wheatstone bridge configuration with alternating power supplies to prevent ionic drift, coupled with differential and common mode amplifiers to separate pressure and temperature signals, and a low-pass filter to enhance signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional electronic pressure sensors are used to measure pressure over time, then pressure measurement is achieved, but ionic drift caused by high temperatures reduces measurement reliability
Solution Approach 1:
The patent applies periodic action by alternating the polarity of the excitation voltage applied to the strain gauge bridge between positive and negative cycles. This periodic polarity reversal prevents ionic drift by periodically resetting any accumulated ionic charges in the piezoresistive material, thereby maintaining measurement reliability over time without being affected by temperature-induced ionic drift
Solution Approach 2:
The patent implements feedback through a dual-channel measurement system that continuously monitors both the strain gauge output and a reference channel. The system compares signals from both channels and uses feedback mechanisms to compensate for common-mode errors including ionic drift effects, thereby improving measurement reliability through active error correction
2Measurement precision
If high temperature is present in pressure sensing, then pressure measurement capability is maintained, but temperature causes ionic drift that degrades measurement accuracy
Solution Approach 1:
The patent uses feedback through a differential measurement architecture that continuously compares the strain gauge signal with a reference signal. The feedback mechanism detects temperature-induced common-mode changes and actively compensates for them, maintaining pressure measurement precision even under high temperature conditions by subtracting the temperature effect from the total signal
Solution Approach 2:
The patent applies parameter changes by utilizing the temperature dependence of electrical parameters to advantage. The system measures both the differential signal (pressure) and common-mode signal (temperature) and uses the known relationship between temperature and electrical parameters to calculate and compensate for temperature effects, thereby maintaining measurement precision across varying temperatures
3Reliability
If alternating power supplies are used to prevent ionic drift, then measurement reliability improves, but circuit complexity increases
Solution Approach 1:
The patent merges the excitation function and measurement function into a single integrated circuit architecture. The alternating power supply for preventing ionic drift is combined with the differential amplifier and reference channel into one unified system, reducing overall circuit complexity while maintaining measurement reliability through the synergistic operation of these combined functions
Solution Approach 2:
The patent implements multi-functionality by designing a circuit that simultaneously performs excitation of the strain gauge bridge, differential amplification, common-mode rejection, and temperature compensation. This universal circuit design achieves multiple objectives including ionic drift prevention and reliability improvement without proportionally increasing complexity, as each component serves multiple purposes
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 effectively reduces ionic drift, allowing for precise pressure measurements while also enabling the detection of temperature changes, thereby improving the accuracy and reliability of pressure sensing applications.
Implementation Method 1
Traditional electronic pressure sensors face challenges in accurately measuring pressure over time due to ionic drift caused by high temperatures
Implementation Method 2
An analog discrete current mode negative feedback amplifier circuit is designed using a Wheatstone bridge configuration
Implementation Method 3
coupled with differential and common mode amplifiers to separate pressure and temperature signals
Implementation Method 4
each coupled to a common mode amplifier. Each of the amplifiers with the negative feedback configuration can have a low-pass filter configured on the negative feedback loop
Implementation Method 5
Each of the amplifiers with the negative feedback configuration can have a low-pass filter configured on the negative feedback loop
Data Source
AI summary
An analog discrete current mode negative feedback amplifier circuit for use with a micro-fused strain gauge is disclosed. The amplifier circuit includes a Wheatstone bridge coupled to a first power supply and a second power supply. The first power supply and the second power supply can be configured such that the periodically alternate between two voltage levels. The Wheatstone bridge can be coupled to a negative feedback amplifier circuit with common mode detection. The amplifier circuit can comprise a differential amplifier with a negative feedback configuration coupled to a common mode amplifier. In addition, the output of each of the amplifiers can be coupled to a common-mode amplifier. In a pressure sensing application, the output of the common mode amplifier serves to output the temperature while the differential amplifiers serve to output the pressure.