Ionization Pressure Gauge Bias Voltage Control
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Solution Overview
Problem
Hot cathode ionization vacuum pressure gauges face issues with servo control complexity and cost, coupled electron emission current and cathode bias voltage, leading to inaccurate and unreliable pressure measurements due to dead times and contamination-induced leakage currents.
Innovation Solution
A transistor circuit with low input impedance is used to independently control cathode bias voltage and electron emission current, along with a microcontroller for calibration and leakage current mitigation, allowing for continuous adjustability and accurate pressure measurement without dead times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If servo control is used to maintain cathode bias voltage, then pressure measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the cathode bias voltage control function from the traditional servo circuit and implements it through a dedicated voltage source circuit. This separation eliminates the need for complex servo control mechanisms while maintaining accurate voltage control, directly resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent segments the control system into independent functional modules: a voltage source circuit for cathode bias voltage control, a current source circuit for electron emission current control, and a microcontroller for coordination. This modular segmentation simplifies the overall device complexity while preserving measurement accuracy through dedicated control circuits
2Measurement precision
If servo control is used to maintain cathode bias voltage, then pressure measurement accuracy is improved, but response time decreases due to dead time
Solution Approach 1:
The patent implements preliminary action by pre-establishing stable cathode bias voltage through the dedicated voltage source circuit before measurement begins. This eliminates the settling time required by traditional servo systems, as the voltage is already stabilized and ready for immediate accurate measurement, thus resolving the contradiction between precision and response time
Solution Approach 2:
The patent ensures continuous useful action by maintaining constant cathode bias voltage through the dedicated voltage source circuit throughout the measurement process. This eliminates the intermittent dead time periods in servo-controlled systems, allowing continuous accurate pressure measurements without interruption, thereby resolving the contradiction between measurement precision and response time
3Reliability
If electron emission current is increased to compensate for leakage currents, then measurement reliability is improved, but cathode lifetime decreases
Solution Approach 1:
The patent introduces an intermediary leakage current compensation mechanism that measures and subtracts leakage current from the total measured current. This allows the system to maintain accurate pressure measurements using lower electron emission currents, thus preserving cathode lifetime while ensuring measurement reliability through mathematical compensation rather than increasing physical current
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the electron emission current to optimal low levels while using software-based leakage current compensation algorithms. This changes the measurement approach from high-current physical compensation to low-current computational compensation, maintaining reliability while extending cathode lifetime
4Device complexity
If electron emission current and cathode bias voltage are coupled in traditional design, then circuit simplicity is maintained, but measurement accuracy deteriorates during transient conditions
Solution Approach 1:
The patent segments the coupled voltage and current control into independent circuits: a voltage source circuit for cathode bias voltage and a current source circuit for electron emission current. This segmentation allows each parameter to be controlled independently without affecting the other, eliminating measurement inaccuracies during transients while maintaining overall circuit simplicity through modular design
Solution Approach 2:
The patent extracts the voltage control function from the current control circuit, creating a separate dedicated voltage source circuit. This separation eliminates the coupling that causes measurement errors during transient conditions, as voltage changes no longer affect current settings and vice versa, while maintaining simplicity through independent dedicated circuits
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 reliable, accurate, and continuous pressure measurements, extending gauge service life and reducing manufacturing costs by decoupling electron emission current and cathode bias voltage, while effectively mitigating leakage currents.
Implementation Method 1
The cathode is heated by current flow initiated by a voltage source to cause the electron emission
Implementation Method 2
the electrons impact molecules and atoms of gas, constituting the atmosphere whose pressure is to be measured, and create ions
Data Source
Figure 1A~1B
Figure 1C~2A
Figure 2B
AI summary
Devices and corresponding methods are provided to operate a hot cathode ionization pressure gauge (HCIG). A transistor circuit can be configured to pass the electron emission current with low input impedance and to control cathode bias voltage. Emission current and cathode bias voltage can be controlled independently of each other, without a servo settling time. HCIGs can be calibrated with respect to leakage current.