Magnet Drop-Out Encoder for Fuel Meter Tamper Detection
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Solution Overview
Problem
Fluid distribution systems face challenges in accurately measuring fluid quantities due to tampering, such as mechanical disconnection of encoders or interference from strong magnetic fields, which can lead to theft and are limited by the combustible environment, requiring tamper-resistant designs that avoid electrical and mechanical hazards.
Innovation Solution
An encoder with a slidably mounted magnet holder and magnetic sensor that detects changes in magnetic field flux density and direction, triggering an error signal if the encoder is removed or tampered with, and is designed to operate safely in combustible environments by minimizing electrical and mechanical interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional magnetic encoders are used in fuel distribution systems, then fluid quantity measurement is achieved, but the system becomes vulnerable to mechanical disconnection and magnetic field interference
Solution Approach 1:
The patent replaces traditional mechanical encoder connections with a magnetic field-based detection system. The magnet attached to the piston shaft generates magnetic field signals detected by sensors, eliminating mechanical linkages that can be disconnected. This substitution maintains measurement precision while significantly improving tamper resistance, as magnetic field interference can be detected and flagged as tampering attempts.
Solution Approach 2:
The patent introduces a magnet as an intermediary element between the piston shaft and the encoder sensors. This magnet serves as a mediator that transmits rotational position information through magnetic field signals rather than direct mechanical contact. The intermediary magnet enables non-contact measurement while providing detectable signals for tamper detection, resolving the contradiction between measurement capability and security.
2Object-affected harmful factors
If switches and mechanical interactions are avoided in the encoder, then safety in combustible environments is improved, but tamper detection capability is reduced
Solution Approach 1:
The patent replaces mechanical switches and contacts with magnetic field sensing and electronic signal processing. The magnet attached to the piston shaft generates magnetic field signals that are detected by magnetic sensors, eliminating the need for mechanical switches that could create sparks. Tamper detection is achieved by monitoring changes in magnetic field signal characteristics, maintaining security without mechanical interactions.
Solution Approach 2:
The patent detects tampering by monitoring changes in magnetic field parameters (strength, frequency, pattern) rather than relying on mechanical switch positions. When the magnet is displaced or interfered with, the magnetic field signal parameters change in detectable ways, enabling tamper detection through parameter analysis instead of mechanical means.
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
The encoder effectively prevents tampering by shutting down the fuel pump upon detection of encoder removal or magnetic interference, ensuring accurate fuel measurement and payment, while maintaining safety through reduced risk of sparks and electrical arcs.
Implementation Method 1
a magnetic sensor positioned relative to the magnet-shaft for measuring a change in the magnetic field (e.g. a change in the direction of the magnetic field) caused during rotation
Implementation Method 2
a magnet affixed to the shaft via a slidably arranged magnet holder... allowing for axial movement of the magnet relative to the magnetic sensor in response to removal of the encoder from the piston meter
Data Source
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Figure 3
Figure 4~5
AI summary
An encoder to be mounted to a shaft extending from a piston meter configured to compute a volume of distributed fluid includes a magnet affixed to the shaft via a floating magnet holder, a magnetic sensor configured to sense the flux density and direction of a magnetic field created by the magnet and to output a signal indicating the flux density and direction of the magnetic field to a printed circuit board, and the printed circuit board configured to output a signal indicating the volume of distributed fluid if the encoder has not been tampered with and configured to output an error signal if the encoder has been tampered with.