Magnetic Encoder Tamper Detection for Fluid Dispensing
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Solution Overview
Problem
Traditional encoders in fluid distribution systems are vulnerable to mechanical disconnection and tampering, particularly in combustible environments, which can lead to inaccurate measurement and theft, and existing designs face limitations due to ventilation requirements and the risk of sparks.
Innovation Solution
The use of two magnetoresistive sensing elements to detect the absolute strength of the magnetic field and presence of stray fields, allowing for detection of lost connections and tampering attempts, with a controller comparing output signals to predetermined threshold values to generate error signals and prevent fluid dispensing in case of tampering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional encoders are used in fluid distribution systems, then the system can measure fluid quantity, but the encoder is vulnerable to mechanical disconnection and tampering
Solution Approach 1:
The patent replaces the traditional mechanical encoder system with a magnetic field-based sensing system. Instead of using mechanical components that can be physically disconnected, the invention uses a magnet attached to the rotating member and magnetic sensors that detect changes in the magnetic field. This substitution eliminates the vulnerability to mechanical tampering while maintaining measurement accuracy through magnetic field detection.
Solution Approach 2:
The patent introduces a magnetic field as an intermediary between the rotating member and the sensing system. The magnet attached to the rotating member creates a magnetic field that mediates the transmission of rotational information to the magnetic sensors. This intermediary approach allows for contactless measurement, preventing mechanical disconnection while ensuring accurate fluid quantity measurement.
2Measurement precision
If magnet-based encoders are used to improve measurement capability, then the encoder can detect rotational position, but the system becomes vulnerable to magnetic interference and tampering
Solution Approach 1:
The patent applies local quality by positioning multiple magnetic sensors at specific locations around the magnet's rotation path. Each sensor is strategically placed to detect the magnetic field at a particular angular position. This localized sensing approach enables precise rotational position detection while the distributed sensor arrangement provides redundancy against magnetic interference, as the system can identify and compensate for localized magnetic disturbances.
3Object-affected harmful factors
If encoders are located within the ventilated cabinet to allow fuel vapor evacuation, then the system can prevent vapor accumulation, but the encoder becomes susceptible to electrical arcs and sparks
Solution Approach 1:
The patent replaces traditional electrical switches and mechanical contact-based encoders with a magnetic field-based sensing system. The magnetic sensors detect changes in the magnetic field caused by the rotating magnet without requiring electrical contacts or mechanical switching actions. This eliminates the source of electrical arcs and sparks while maintaining the ability to measure rotational position for fluid quantity determination.
Solution Approach 2:
The patent uses the magnetic field as a non-contact intermediary to transmit rotational information from the rotating member to the sensing system. This intermediary approach eliminates the need for electrical contacts or mechanical switches that could generate sparks, making the encoder inherently safe for use in ventilated cabinets where fuel vapors are present.
4Object-generated harmful factors
If mechanical interactions are avoided to prevent sparks, then the system can operate safely in combustible environments, but the encoder cannot mechanically detect tampering
Solution Approach 1:
The patent replaces mechanical tamper detection mechanisms with a magnetic field-based detection system. The magnet is attached to the rotating member in a manner that its magnetic field signature is unique to the authentic configuration. Magnetic sensors detect this magnetic field, and any attempt to tamper with the system (such as replacing the magnet with a counterfeit one) would alter the magnetic field characteristics, triggering tamper detection without requiring mechanical interactions that could generate sparks.
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 solution provides a tamper-resistant and accurate measurement system that can operate in combustible environments, effectively preventing theft and ensuring accurate fluid volume measurement while maintaining a compact design.
Implementation Method 1
The sensors make use of the magnetoresistive effect, which is the tendency of a material (e. g. ferromagnetic) to change the value of its electrical resistance in an externally applied magnetic field.
Data Source
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AI summary
The present invention relates to an encoder for a fluid dispensing system comprising a magnetic sensor (200) for detecting a rotational angle (ω) of a rotary member (300) around an axis of rotation; a magnet (310) for generating a magnetic field (Ho), the magnet (310) being arranged on the rotary member (300) so that the magnetic poles (312, 314) generate a magnetic field perpendicular to the axis at the magnetic sensor about which the rotary member (300) rotates; wherein the magnetic sensor (200) comprises at least a first and a second magnetic sensing element (210, 220), the first magnetic sensing element (210) configured to generate at least a first output signal, and the second magnetic sensing element (220) configured to generate at least one second output signal, wherein the output signals are indicative of a sensed magnetic field associated at least in part with the magnet, wherein the magnetic sensing elements (210, 220) and the magnet (310) are arranged at predetermined distances from one another centered on the axis of rotation (322); a controller which is configured to compare at least one of the first and second output signals to a first and second predetermined threshold value (limit1, limit2) associated with the predetermined distance, and to calculate field angles of the first signals, to calculate a difference of the field angles, and to compare the difference with a third predetermined threshold value (limits). The controller generates an error signal if a result of at least one of the comparisons to the first and second predetermined threshold values indicates a tamper attempt.