Magnetic Detection Device Bridge Circuit Failure Analysis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing magnetic detection devices using TMR elements face challenges in detecting failures due to oxide film breakdown and complex configurations, leading to difficulties in identifying resistance changes caused by foreign substances or physical factors, especially when multiple TMR elements fail, resulting in undetectable output waveforms.
Innovation Solution
A magnetic detection device is configured with a bridge circuit formed by connecting magnetoresistance elements in series, one end grounded, and an amplifier with a switching mechanism to detect failures by measuring voltage changes at the output terminal, allowing for simpler configuration and failure detection without the need for multiple switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Wheatstone bridge circuit with multiple TMR elements is used to detect magnetic field changes, then measurement precision is improved, but device complexity increases and failure detection becomes difficult
Solution Approach 1:
The patent extracts the failure detection function from the main measurement circuit by introducing a separate test signal path. A test signal input terminal and test signal output terminal are added to apply test signals directly to TMR elements without interfering with the normal magnetic field detection operation. This separation allows independent testing of each TMR element's resistance while maintaining the bridge circuit's measurement precision.
Solution Approach 2:
The patent introduces test signals as an intermediary mechanism to detect TMR element failures. By applying small test signals through dedicated test signal terminals and measuring the resulting currents or voltages, the system can identify resistance changes in individual TMR elements without disrupting the primary magnetic field detection function. This intermediary testing approach simplifies failure detection while preserving measurement precision.
2Reliability
If multiple TMR elements are connected in a bridge circuit to improve reliability, then measurement precision improves, but failure detection capability deteriorates when multiple elements fail simultaneously
Solution Approach 1:
The patent segments the failure detection process by providing individual test signal paths to each TMR element in the bridge circuit. By applying test signals separately to each element and measuring their responses independently through the test signal output terminal, the system can identify which specific element has failed even when multiple elements are compromised. This segmentation transforms a collective failure detection problem into individual element testing.
Solution Approach 2:
The patent implements preliminary failure detection by periodically applying test signals to TMR elements before they cause system failure. The test signal mechanism allows proactive identification of resistance changes in individual elements, enabling early replacement or adjustment before the failures accumulate to affect overall system reliability. This preliminary testing prevents catastrophic failures while maintaining bridge circuit reliability.
3Reliability
If switching means are added to detect TMR element failures, then reliability improves, but device complexity increases
Solution Approach 1:
The patent makes the test signal input terminal and test signal output terminal multi-functional components. These terminals serve dual purposes: they are part of the normal bridge circuit operation during magnetic field detection and simultaneously serve as test signal application and measurement points for failure detection. This universality eliminates the need for separate dedicated test terminals or switching mechanisms, maintaining reliability improvement while minimizing added complexity.
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 configuration enables reliable detection of TMR element failures by converting current changes into voltage, ensuring that even multiple failed units can be identified through voltage measurements, simplifying the detection process and reducing circuit complexity.
Implementation Method 1
magnetoresistance element that is an electromagnetic conversion element so as to form a Wheatstone bridge circuit, a constant-voltage power supply is connected between two opposing electrodes of this Wheatstone bridge circuit, and change in the resistance value of the magnetoresistance element is converted into voltage change, thereby detecting change in the magnetic field
Implementation Method 2
tunnel magnetoresistance (hereinafter referred to as TMR) element whose non-magnetic intermediate layer 112 is made of an insulator. The electric characteristics of the TMR element are generally known to be expressed in the form of a conductance G. Letting a relative angle of the magnetization direction of the magnetization free layer 113 with respect to that of the magnetization fixed layer 111 be θ, the conductance G can be expressed as below: G=G0+G1 cos θ
Data Source
AI summary
A magnetic detection in which a first element (3) and a second element (4) that are a magnetoresistance element whose resistance value changes in response to an external magnetic field are connected in series with each other so as to form a bridge circuit, one end of the bridge circuit is connected to a power supply (5), the other end thereof is grounded, a connecting point (6) between the first element (3) and the second element (4) is connected to an amplifier means (9), at least one switching means (1) is connected in series with the bridge circuit, and an output terminal (11) of the amplifier means (9) is connected to a failure detection means (12).