Magnetoresistive Cross-Point Array for Low-Power Liquid-Level Sensing
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Solution Overview
Problem
Existing liquid level sensors using reed switches or magnetoresistive sensors face issues such as fragility, high manufacturing costs, limited resolution, high power consumption, and sensitivity to noise and temperature, making them inefficient and costly.
Innovation Solution
A digital liquid level sensor utilizing a magnetoresistive sensor cross-point array with passive MTJ elements, diodes, and a microcontroller to minimize power consumption and enhance resolution, using a flexible PCB board and chip-on-board technology for assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reed switches are used in a linear array to detect liquid level, then the sensor can detect digital states of switches, but the resolution is limited by the large size of reed switches and manufacturing cost is high
Solution Approach 1:
The sensor array is divided into multiple independent sensor elements (reed switches or magnetoresistive sensors) arranged in a linear array, each capable of detecting liquid level at different positions. This segmentation allows for higher resolution through multiple measurement points while maintaining ease of manufacture by using standardized, modular sensor elements that can be individually produced and then assembled into the array configuration.
Solution Approach 2:
Multiple identical or similar sensor elements are replicated across the linear array to create multiple detection points. By copying the same sensor design (whether reed switch or magnetoresistive sensor) across multiple positions, the system achieves higher resolution without increasing manufacturing complexity, as each element can be produced using the same standardized process.
2Ease of operation
If all digital switches are powered simultaneously in a magnetoresistive switch design, then digital output can be obtained, but power consumption is high
Solution Approach 1:
Instead of powering all magnetoresistive switches simultaneously, the system employs periodic scanning where only a subset of switches is powered at any given moment. The microcontroller sequentially activates different groups of switches in time-multiplexed fashion, obtaining digital output readings from each group in turn. This periodic activation maintains full digital measurement capability while dramatically reducing average power consumption, as each switch is powered only briefly during its scanning interval rather than continuously.
Solution Approach 2:
The system dynamically controls the power state of magnetoresistive switches based on operational requirements. Rather than maintaining a static powered state for all switches, the system dynamically activates and deactivates specific switches or groups of switches according to the scanning sequence, optimizing the balance between digital output capability and power consumption in real-time.
3Measurement precision
If impedance design is used to measure liquid level with resistor array, then liquid level can be measured, but the readout is sensitive to noise and temperature requiring calibration
Solution Approach 1:
The system replaces the impedance-based measurement approach (which is sensitive to noise and temperature) with a digital switching approach. Instead of measuring continuous resistance values that require calibration, the magnetoresistive switches provide discrete digital output states (on/off or high/low) that are inherently more robust against environmental interference. This substitution of measurement paradigm eliminates the need for temperature calibration and reduces sensitivity to electrical noise.
Solution Approach 2:
The system changes the measurement parameter from continuous impedance (resistance) to discrete digital states. By transitioning from measuring analog resistance values that vary continuously with liquid level to detecting digital on/off states of magnetoresistive switches, the system achieves measurement that is less sensitive to temperature and noise, as digital thresholds provide natural hysteresis and immunity to small signal variations.
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 sensor achieves reliable, rapid, and cost-effective digital liquid level measurement with reduced power consumption and improved resolution by using a magnetoresistive sensor cross-point array with passive MTJ elements and diodes.
Implementation Method 1
a magnetoresistive sensor cross-point array with passive MTJ elements
Implementation Method 2
Adding diodes in series with MTJ (magnetic tunnel junction) elements allows arranging multiple small passive MTJ element strings in a cross-point array architecture
Data Source
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AI summary
Disclosed is a digital liquid level sensor based on a magnetoresistive sensor cross-point array, including: a plurality of TMR magnetic sensor chips; a microcontroller, a row decoder, and a column decoder, wherein the microcontroller is electrically connected to the row decoder and the column decoder, the TMR magnetic sensor chips include a plurality of MTJ elements, diodes are connected between each row of MTJ elements and a row lead or a column lead, the TMR magnetic sensor chips are addressed by means of data decoded by the row decoder and the column decoder and on the basis of the equation Address = m + [M x (n - 1)], Address representing an address value, and m representing the value of a current row, and the microcontroller is used for scanning addresses of the TMR magnetic sensor chips for the address of an MTJ element in the highest active state, converting the address value into a liquid level value in a linear proportional relationship therewith, and transmitting the liquid level value to an output interface; and a permanent magnet and a protective tube. The power consumption of a sensor element is greatly minimized by powering only one sensor chip element each time.