Bridge Voltage Inversion Circuit for Low-Pressure Vacuum Gauge Signals
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Solution Overview
Problem
Existing vacuum gauge analog front end circuits face challenges with signal amplification at low pressures, leading to unpredictable phase relationships, noise injection, and nonlinearity, which compromise signal quality and require complex gain/phase adjust blocks and additional circuitry, especially at pressures below 1 Torr.
Innovation Solution
A bridge voltage inversion circuit is introduced, where the capacitance of the sensor capacitor is minimized at vacuum pressure, and the reference capacitor is selected to be 10% greater, inverting the amplitude relationship, eliminating the need for additional amplification and gain/phase adjustments, and enhancing signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal amplification is applied at low pressures, then signal quality for digitization is improved, but phase relationship becomes unpredictable and noise is injected
Solution Approach 1:
The patent inverts the traditional approach by making the sensor capacitor larger than the reference capacitor, reversing the polarity of the bridge voltage signal. This inversion allows the use of a fixed gain amplifier instead of variable gain, eliminating the noise injection and phase relationship problems associated with high-level signal amplification at vacuum pressures.
Solution Approach 2:
The patent changes the capacitance parameter relationship between reference and sensor capacitors (making Cs > Cref instead of Cref > Cs), which fundamentally alters the bridge voltage characteristics. This parameter change enables the system to achieve better signal quality without requiring high amplification factors, thereby avoiding noise injection.
2Adaptability or versatility
If variable gain amplification is used in discrete steps, then signal amplification at different pressure levels is achieved, but discontinuity occurs between gain stages
Solution Approach 1:
The patent extracts the variable gain block from the signal path entirely, replacing it with a fixed gain amplifier. This elimination of the variable gain mechanism removes the source of discontinuity between gain stages while still achieving the necessary signal amplification through the inverted bridge configuration.
Solution Approach 2:
By inverting the bridge voltage polarity through capacitor selection (Cs > Cref), the patent eliminates the need for variable gain amplification across different pressure levels. The fixed gain amplifier provides consistent amplification without the discontinuities that occur when switching between discrete gain stages.
3Measurement precision
If multiple gain/phase adjust blocks are added, then phase relationship uncertainty is cancelled and reference capacitor matching is achieved, but device complexity increases
Solution Approach 1:
The patent removes the need for multiple gain/phase adjust blocks and reference capacitor matching circuitry by fundamentally changing the bridge configuration. The inverted bridge voltage approach (Cs > Cref) inherently provides stable phase relationships and eliminates the complexity of additional adjustment blocks.
Solution Approach 2:
The patent enables the bridge circuit to self-regulate the phase relationship and signal amplitude through the fixed capacitor ratio (Cs > Cref). This self-service mechanism eliminates the need for external gain/phase adjust blocks and complex matching procedures, reducing overall device complexity.
4Measurement precision
If signal averaging is increased in digital domain, then signal-to-noise ratio is improved, but pressure transient response slows down
Solution Approach 1:
The patent performs signal quality enhancement at the analog front end through the inverted bridge configuration and fixed gain amplification, before the signal reaches the digital domain. This preliminary action improves the signal-to-noise ratio early in the signal chain, eliminating the need for extensive signal averaging that would slow down pressure transient response.
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 provides improved signal quality at vacuum pressures, reduces circuit complexity and power consumption, and simplifies manufacturability by eliminating the need for additional amplification stages and precise capacitance matching, while maintaining performance across the full scale range.
Implementation Method 1
a transformer including a primary winding and a secondary winding that outputs a bridge voltage
Implementation Method 2
a sensor capacitor connected to a second side of the secondary winding of the transformer. The sensor capacitor senses and responds to a pressure. A capacitance of the sensor capacitor is at a minimum when the pressure is at vacuum
Data Source
Figure 1~2
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AI summary
The disclosed invention provides a bridge voltage inversion circuit for vacuum gauge and a pressure gauge sensor that includes the bridge voltage inversion circuit. The bridge voltage inversion circuit for a pressure gauge includes a reference capacitance, a sensor capacitance, and a transformer including a primary winding and a secondary winding that outputs a bridge voltage. The reference capacitor is connected to a first side of the secondary winding of the transformer, and the sensor capacitor is connected to a second side of the secondary winding of the transformer. The sensor capacitor senses and responds to a pressure, and a capacitance of the sensor capacitor is at a minimum when the pressure is at vacuum. The capacitance of the sensor capacitor at vacuum is less than a capacitance of the reference capacitor.