Tank Level Measurement Using Correlated Reference Echo Signals

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Solution Overview

Problem

Conventional level measurement systems face challenges in accurately determining the travel time between a reference echo signal and an echo pulse due to significant amplitude offsets at the interface, leading to measurement errors.

Innovation Solution

The method employs a correlation measure between secondary reference signals (FSR and SSR) generated during tank operation, calculating a plurality of correlation function values to identify the maximum match, thereby eliminating the need for amplitude offset measurements and providing an accurate time interval (Tm) for level calculation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional amplitude offset measurement methods are used to determine travel time, then the measurement process is straightforward, but significant amplitude offsets between echo signal and reference echo signal lead to measurement errors

Engineering Contradiction:

Improvelevel measurement accuracyVSAvoidmeasurement reliability under amplitude offset conditions

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent transforms the measurement approach by changing from amplitude-domain comparison to time-domain correlation. Instead of measuring amplitude offsets directly, the system correlates the echo signal with the reference echo signal to find the time delay that maximizes correlation, thereby eliminating sensitivity to amplitude variations at the interface

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces correlation function calculation as an intermediary process between signal acquisition and travel time determination. The correlation function acts as a mediator that is insensitive to amplitude offsets, allowing accurate time delay measurement even when signal amplitudes differ significantly

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If reference echo signal subtraction is performed to determine time position, then the process is simple, but amplitude deviations at interface pulse points make comparison difficult and error-prone

Engineering Contradiction:

Improvesignal comparison simplicityVSAvoidtime position determination accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical subtraction operation with a correlation-based time delay estimation. Instead of subtracting amplitude values at corresponding time positions, the system uses cross-correlation to find the time shift that aligns the signals, which is more robust to amplitude variations

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If conventional methods are used to handle interface pulses, then the system works for empty tanks, but significant amplitude offsets are present when product material is in the tank

Engineering Contradiction:

Improvesystem functionality across tank conditionsVSAvoidlevel measurement precision with product material

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent makes the measurement system adaptive to changing tank conditions by using correlation-based time delay estimation. The correlation method dynamically adjusts to different signal amplitudes and interface conditions, maintaining measurement precision whether the tank is empty or contains product material

Inventive Principle:

Principle #15Dynamics

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 enhances the accuracy of level measurement by directly deriving Tm from correlation function properties, reducing noise errors and ensuring precise level determination.

Implementation Method 1

measuring signals reflected (echo signals) including signals from that surface or interface... determine the time position of the echo pulse in the echo signal to determine travel time T

Methodology Applied

Scientific EffectTime of Flight: Time of Flight

Implementation Method 2

measuring signals reflected (echo signals) including signals from that surface or interface... the echo pulse has an associated echo amplitude

Methodology Applied

Scientific EffectEcho: Echo

Data Source

PatentEP3271691B1Level measurement using correlation between a pair of secondary reference signals

Publication Date: 2025.12.03 HONEYWELL INTERNATIONAL INC

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AI summary

A method (200) of measuring a level of a material (112) in a tank (105). A first secondary reference (FSR) signal (131) is generated (201) when a reference pulse (301) is transmitted into the tank (105) and a second secondary reference signal (SSR) signal (132) is generated when an echo signal (310) responsive to the reference pulse is received. A plurality of FSR signals and a plurality of SSR signals are stored (202). The plurality of FSR signals and plurality of SSR signals are transferred (203) to a correlator block (140) which calculates (204) a plurality of correlation function values (CFVs) that have magnitudes reflecting a degree of matching between pairs of the SSR signals with their associated FSR signals. Using a maximum CFV result a time interval (Tm) is calculated (205) between the FSR signal and SSR signal associated with the maximum CFV result, and the level of material in the tank is determined from Tm (206).