Process Variable Transmitter Noise Detection and Avoidance
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Solution Overview
Problem
Process variable transmitters in control systems face errors due to noise frequencies from sources like piston pumps, pulsating pressure, vibration, and external interference, which interfere with accurate measurement of process variables.
Innovation Solution
A method is implemented in process variable transmitters to detect noise frequencies and adjust the sensor control signal frequency to avoid interference by using a processor to identify noise characteristics, phase shift the coil drive frequency, and change it to a non-interfering range, ensuring accurate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the sensor control signal frequency is kept at a fixed value for stable operation, then the ease of operation is improved, but measurement precision deteriorates due to interference from process noise at specific frequencies
Solution Approach 1:
The patent implements dynamic frequency adjustment by continuously monitoring the process spectrum and adapting the sensor control signal frequency in real-time. The microprocessor detects noise frequencies and automatically shifts the control signal frequency away from interfering frequencies, transforming the static frequency system into a dynamic one that adapts to changing process conditions.
Solution Approach 2:
The patent changes the frequency parameter of the sensor control signal based on detected process noise characteristics. By modifying the frequency parameter dynamically rather than keeping it fixed, the system avoids measurement errors caused by resonance or interference at specific frequencies while maintaining operational simplicity through automated adjustment.
2Measurement precision
If the sensor control signal frequency is continuously adjusted to avoid noise, then measurement precision is improved, but device complexity increases due to additional processing requirements
Solution Approach 1:
The patent integrates multiple functions into the existing microprocessor: noise spectrum analysis, frequency detection, and control signal frequency adjustment. The same microprocessor that controls the sensor also performs spectral analysis and automatic frequency adaptation, eliminating the need for separate dedicated hardware components and reducing overall system complexity despite the advanced functionality.
Solution Approach 2:
The system performs self-diagnosis and self-adjustment by automatically detecting noise frequencies and correcting its own operating parameters. The microprocessor monitors the process spectrum and autonomously adjusts the sensor control signal frequency without external intervention, making the system self-sufficient and reducing the need for additional control hardware or manual calibration.
3Measurement precision
If spectral analysis is performed continuously to detect noise frequencies, then measurement precision is improved, but use of energy increases due to constant processing
Solution Approach 1:
The patent implements periodic spectral analysis rather than continuous analysis, updating the frequency adjustment at intervals based on process changes. The microprocessor performs spectrum analysis at strategic moments to detect significant noise frequency shifts, reducing computational load and energy consumption while maintaining measurement precision by adjusting frequency only when necessary.
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 significantly reduces measurement errors by effectively filtering out noise frequencies, improving the accuracy of process variable measurements by ensuring the sensor control signal operates away from noise-inducing frequencies.
Implementation Method 1
performing a spectral transform on the measured output signal to identify a frequency of the process noise
Implementation Method 2
This can result in a beat frequency to appear on the measured output signal that measures the process flow
Data Source
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AI summary
A process variable transmitter includes a sensor drive controller that outputs a sensor drive signal that is used to drive a sensor that senses a process variable. The sensor drive controller changes the frequency of the sensor drive signal to avoid frequencies and associated harmonics at which noise occurs and which could interfere with the sensor signal.