Vibratory Meter Frequency Spacing to Prevent Intermodulation Distortion

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Solution Overview

Problem

Intermodulation distortion signals interfere with the characterization of frequency responses in vibratory meters, leading to inaccurate detection of changes in sensor assemblies due to coating, erosion, corrosion, or damage, as these signals can have frequencies within the demodulation window and corrupt the measurement.

Innovation Solution

A system and method that determine frequency spacings for a first and second signal applied to a sensor assembly, ensuring that intermodulation distortion signals generated are outside the demodulation window, thereby preventing interference and allowing for accurate characterization of the sensor's frequency response.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple test tones are applied to characterize frequency response, then measurement completeness is improved, but intermodulation distortion signals are generated that interfere with measurement accuracy

Engineering Contradiction:

Improvefrequency response characterization accuracyVSAvoidintermodulation distortion signal interference

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent changes the frequency spacing parameter between test tones to specifically prevent intermodulation distortion signals from falling within the demodulation window. By carefully selecting frequency spacings, the system maintains measurement completeness while avoiding the harmful interference caused by intermodulation distortion.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent acknowledges that intermodulation distortion signals are inevitably generated by non-linearities, but converts this harmful effect into a manageable issue by predicting distortion signal frequencies and ensuring they fall outside the demodulation window. This approach uses the predictable nature of intermodulation distortion to maintain measurement accuracy.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Adaptability or versatility

If test tones are spaced closer together, then frequency response coverage is improved, but intermodulation distortion signals are more likely to fall within the demodulation window

Engineering Contradiction:

Improvefrequency response coverageVSAvoidmeasurement reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent optimizes the frequency spacing parameter to achieve a balance between coverage and reliability. By calculating appropriate frequency spacings based on the demodulation window characteristics, the system ensures test tones are close enough for comprehensive coverage while maintaining sufficient spacing to prevent distortion signals from interfering with measurements.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If sequential cycling of test tones is used, then intermodulation distortion interference is reduced, but measurement time increases and time-variance effects corrupt results

Engineering Contradiction:

Improvefrequency response characterization accuracyVSAvoidmeasurement time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent uses periodic multi-tone drive signals applied simultaneously to the sensor assembly, rather than sequential cycling. This approach reduces measurement time significantly while the carefully selected frequency spacings prevent intermodulation distortion from corrupting the simultaneous measurements.

Inventive Principle:

Principle #19Periodic action

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 ensures accurate detection of physical changes in sensor assemblies by excluding intermodulation distortion signals from the characterization, thus reliably identifying corrosion, erosion, and other issues, and maintaining the accuracy of frequency response characterization.

Implementation Method 1

Each type of sensor may have unique characteristics, which a meter must account for in order to achieve optimum performance. For example, some sensors may require a tube apparatus to vibrate at particular displacement levels.

Methodology Applied

Scientific EffectVibration: Vibration

Implementation Method 2

A multi-tone drive signal is typically comprised of a resonant component, or drive tone, that is at the resonance frequency of a sensor assembly

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 3

non-linearities in the sensor assembly can form intermodulation distortion signals from the multi-tone drive signal

Methodology Applied

Scientific EffectIntermodulation distortion:

Data Source

PatentUS11169013B2Frequency spacings to prevent intermodulation distortion signal interference

Publication Date: 2021.11.09 MICRO MOTION INC

AI summary

A system (800) for determining frequency spacings to prevent intermodulation distortion signal interference is provided. The system (800) includes a sensor assembly (810) and a meter verification module (820) communicatively coupled to the sensor assembly (810). The meter verification module (820) is configured to determine a frequency of a first signal to be applied to a sensor assembly (810) of a vibratory meter and set a demodulation window about the frequency of the first signal. The meter verification module (800) is also configured to determine a frequency of the second signal to be applied to the sensor assembly such that a frequency of an intermodulation distortion signal generated by the first signal and the second signal is outside the demodulation window.