Alarm Enclosure Tamper Detection Using Inductive Frequency Shift

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Solution Overview

Problem

Existing tamper detecting devices for alarm systems rely on mechanical switches, which require precise dimensional tolerances and can introduce mechanical stresses and higher costs, and are not effective in detecting tampering when the enclosure and wall bracket are removed together from a mounting surface.

Innovation Solution

A tamper detecting device using a frequency setting inductor on a printed circuit board, which detects changes in inductive properties due to relative movement between a metal element and the detector, eliminating the need for precise mechanical alignment and reducing costs by up to 30% compared to traditional mechanical switches.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a mechanical switch is used for tamper detection, then the alarm system can detect enclosure separation, but the device requires precise dimensional tolerances and generates mechanical stresses

Engineering Contradiction:

Improvetamper detection reliabilityVSAvoiddimensional tolerances

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent replaces the mechanical switch system with an inductive detection system using a frequency setting inductor and detector. This substitution eliminates the need for mechanical contact and precise dimensional tolerances, as the inductive field can detect relative movement without physical contact between components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the detection parameter from mechanical position (switch contact) to inductive properties (frequency change). By monitoring changes in the inductive properties of the frequency setting inductor caused by relative movement between the metal element and detector, the system achieves tamper detection without mechanical constraints.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a mechanical switch is used for tamper detection, then the alarm system can detect enclosure separation, but the device incurs higher costs and compression stresses

Engineering Contradiction:

Improvetamper detection reliabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses a frequency setting inductor made as a metal trace winding on a printed circuit board, which is a low-cost component compared to mechanical switches. This approach reduces manufacturing costs while maintaining reliable tamper detection functionality.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If a mechanical switch is used for tamper detection, then the alarm system can detect enclosure separation, but it cannot detect tampering when enclosure and wall bracket are removed together

Engineering Contradiction:

Improvetamper detection coverageVSAvoiddetection scenario coverage

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent introduces a metal element as an intermediary between the wall bracket and the detection system. The inductive detector monitors the relative position of this metal element, enabling detection of tampering scenarios where the enclosure and wall bracket are removed together, as the metal element's position relative to the detector changes in these scenarios.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution provides reliable tamper detection with reduced mechanical design challenges and costs, enabling effective alarm triggering even when the enclosure and wall bracket are removed together from a mounting surface, enhancing the security of wireless communication systems and home alarm installations.

Implementation Method 1

the detector is configured to trigger an alarm event in response to a measured change in inductive properties of the frequency setting inductor, wherein the relative movement between the metal element and the detector changes the inductive properties of the frequency setting inductor

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP3582197B1An enclosure for an alarm node

Publication Date: 2021.07.21 VERISURE SARL

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AI summary

An enclosure (60) for an alarm node (12; 12'; 14; 14'; 16; 21; 23; 30), comprising a tamper detecting device (46) configured to detect relative movement between a metal element (50; 51) and an inductive detector (48), wherein the inductive detector (48) comprises an oscillator (52) with a frequency setting inductor (54) and wherein a frequency detecting unit (56) is operatively connected to the inductive detector (48) and configured to trigger an alarm event when a change of the oscillator frequency larger than a predetermined value has been detected.