Capacitance Diaphragm Gauge Vibration Damping via Electrostatic Feedback
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Solution Overview
Problem
Capacitance diaphragm gauges (CDGs) face measurement errors due to external vibrations causing diaphragm deflections at its natural frequency, which are indistinguishable from actual pressure changes, leading to inaccurate pressure readings.
Innovation Solution
A system and method that senses diaphragm motion at its natural frequency, filters the signal to isolate vibration-induced effects, and uses a feedback circuit to apply electrostatic forces opposing these vibrations, thereby suppressing their impact on pressure measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the CDG measures pressure by sensing capacitance change from diaphragm deflection, then pressure measurement is achieved, but external vibrations cause false deflections that are indistinguishable from real pressure changes, reducing measurement accuracy
Solution Approach 1:
The patent applies feedback control by sensing diaphragm motion at its natural frequency, filtering this signal, and applying electrostatic forces through the fixed electrode to counteract the detected vibrations. This closed-loop feedback system continuously monitors and compensates for vibration-induced deflections, thereby maintaining measurement accuracy despite external vibrational disturbances.
Solution Approach 2:
The patent replaces mechanical vibration damping approaches with an electrostatic field-based solution. Instead of using mechanical dampers or isolators, the system uses electrostatic forces generated by applying voltages to the fixed electrode to counteract the mechanical vibrations of the diaphragm, thus substituting a mechanical problem with an electrical control solution.
2Adaptability or versatility
If the diaphragm is exposed to pressure differential to enable measurement, then pressure sensing function is achieved, but the diaphragm becomes susceptible to resonant vibrations at its natural frequency, causing measurement errors
Solution Approach 1:
The system maintains reliable pressure sensing under vibration by implementing a feedback control mechanism that detects resonant vibrations through capacitance changes, filters these signals, and applies counteracting electrostatic forces to suppress the vibrations, thereby ensuring measurement reliability across varying operational conditions.
Solution Approach 2:
The patent changes the electrical parameters (voltage applied to fixed electrode) dynamically in response to detected vibration conditions. By adjusting the electrostatic field strength based on the sensed diaphragm motion, the system adapts to vibrational disturbances while maintaining accurate pressure sensing capability.
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 approach effectively reduces or eliminates the errors caused by diaphragm vibrations, enhancing the accuracy of pressure measurements by counteracting vibration-induced deflections with targeted electrostatic forces.
Implementation Method 1
The feedback signal is applied to the diaphragm and the fixed electrode to cause the diaphragm to be deflected counter to the deflection caused by vibration to thereby suppress the deflection caused by vibration
Implementation Method 2
The presence of the natural frequency signals superimposed on the pressure signal is determined by sensing variations in the output of a sensor at or near the known natural frequency of the diaphragm
Data Source
AI summary
A system and method mitigate the effects of these external vibrations on a capacitance diaphragm gauge by sensing the motion of the diaphragm at the first natural frequency of the diaphragm of the CDG. The presence of the natural frequency signals superimposed on the pressure signal is determined by sensing variations in the output of a sensor at or near the known natural frequency of the diaphragm and filtering that known low frequency from the output. The filtered signal is used in a feedback circuit to impose electrostatic forces on the diaphragm. The imposed electrostatic forces oppose the motion created by the external vibration to suppress the effects of the vibration on the pressure measured by the CDG.