Bridge Voltage Inversion Circuit for Low-Pressure 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 firmware handling, especially at pressures below 1 Torr.
Innovation Solution
A bridge voltage inversion circuit that inverts the capacitance difference at vacuum pressure, eliminating the need for additional amplification and gain/phase adjustments by maximizing bridge voltage amplitude at vacuum and minimizing it at full-scale pressure, using a transformer with a primary and secondary winding, a reference capacitor, and a sensor capacitor that senses pressure, with the reference capacitor having a greater capacitance than the sensor capacitor at full scale.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal amplification is applied at low pressures, then signal amplitude is increased for ADC digitization, 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, which reverses the phase relationship behavior. This inversion eliminates the need for complex gain/phase adjustment circuits while maintaining reliable phase relationships across the pressure range, directly resolving the contradiction between signal amplitude and phase relationship reliability.
2Measurement precision
If high signal amplification is applied at vacuum pressure, then signal amplitude is sufficient for digitization, but amplifier nonlinearity is introduced
Solution Approach 1:
The patent changes the capacitance parameter relationship between reference and sensor capacitors, making the sensor capacitor larger. This parameter change fundamentally alters the signal generation mechanism, allowing sufficient signal amplitude at vacuum pressure without requiring high-gain amplification that would introduce nonlinearity, thus resolving the contradiction between signal amplitude and linearity.
3Reliability
If multiple gain/phase adjust blocks are added, then phase relationship uncertainty is cancelled and reference capacitor matching is achieved, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts and eliminates the need for complex gain/phase adjustment blocks by fundamentally changing the capacitor sizing relationship. This extraction of unnecessary components directly reduces device complexity and power consumption while maintaining reliable phase relationships through the inverted capacitor configuration.
4Measurement precision
If signal averaging is increased in digital domain, then signal quality is improved, but pressure transient response is slowed
Solution Approach 1:
The patent performs preliminary action by optimizing the signal generation at the analog front end through inverted capacitor sizing. This ensures high signal quality is achieved at the source before digitization, eliminating the need for extensive digital signal averaging and thereby preserving fast pressure transient response while maintaining measurement precision.
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 enhances signal quality at vacuum pressures, reduces noise, simplifies firmware design, and eliminates the need for additional amplification stages and precise capacitance matching, resulting in improved manufacturability and performance for low-pressure gauges without the need for complex circuitry.
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
Data Source
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.