Multi-zone Pressure Mat Using Two Electrodes and Voltage Division
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Solution Overview
Problem
Existing multi-zone pressure sensitive sensor mats with multiple electrodes are costly and have a short lifespan due to oxidation and mechanical wear, leading to increased resistance and invalid logic signals, which complicates detection of patient presence and movement, especially in healthcare settings where timely alerts are crucial.
Innovation Solution
A multi-zone pressure sensitive mat with only two electrodes connected to a central processing unit, utilizing a relative variable resistance circuit to measure voltage levels and AC signal amplitudes, allowing for extended lifespan and reduced power consumption, while using lower cost conductive carbon ink and implementing a calibration routine to maintain sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple electrodes are used in multi-zone pressure sensitive sensor mat, then the number of sensor zones increases, but the cost and power consumption increase proportionally
Solution Approach 1:
The patent combines multiple sensor zone detections into a single electrode system. The first electrode detects pressure across multiple zones by measuring voltage divisions created by conductive ink patterns, eliminating the need for separate electrodes for each zone. This merging approach maintains multi-zone functionality while reducing electrode count to just two electrodes total.
Solution Approach 2:
The single first electrode serves multiple functions by detecting pressure in different zones through voltage division. The conductive ink patterns create variable resistance regions that allow one electrode to indirectly sense multiple zones, making the electrode universal for all zone detections rather than requiring dedicated electrodes for each zone.
2Reliability
If conductive carbon ink of low resistance value is used, then the sensor circuit resistance decreases, but the cost increases
Solution Approach 1:
The patent changes the measurement parameter from absolute resistance to voltage division ratio. Instead of measuring resistance directly (which requires low resistance ink), the system measures voltage divisions created by relative resistance changes in conductive ink patterns. This parameter change allows use of lower cost conductive ink while maintaining detection accuracy through differential measurement.
Solution Approach 2:
The patent replaces direct electrical resistance measurement with voltage division measurement. By using voltage measurements across conductive ink patterns rather than direct resistance measurement, the system can use higher resistance (lower cost) conductive ink while maintaining sensor functionality through the voltage division principle.
3Reliability
If pressure sensitive sensor mat is used to detect patient presence, then the detection capability is provided, but the lifespan decreases due to oxidation and ageing effects
Solution Approach 1:
The patent implements calibration routines that periodically adjust detection thresholds based on measured baseline conditions. This feedback mechanism compensates for resistance changes due to oxidation and ageing by dynamically adapting the detection criteria, maintaining accurate patient presence detection throughout the extended lifespan of the sensor mat.
Solution Approach 2:
The patent performs calibration during manufacturing and initialization to establish baseline resistance values before the sensor is deployed. This preliminary action pre-compensates for expected resistance changes due to oxidation, extending the functional lifespan by establishing reference points that account for future degradation.
4Duration of action of stationary object
If voltage level measurement with relative variable resistance circuit is used, then the lifespan is extended, but the measurement precision requirements increase
Solution Approach 1:
The system uses feedback through calibration routines that establish baseline voltage levels and adjust detection thresholds based on measured conditions. This feedback compensates for drift and aging effects, maintaining measurement precision over extended periods without requiring higher initial precision components.
Solution Approach 2:
The patent uses conductive ink patterns with specific geometric arrangements that create voltage division ratios less sensitive to absolute resistance changes. The composite structure of conductive ink on flexible substrate creates a measurement system where geometric ratios dominate over material property variations, reducing precision requirements.
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 extends the lifespan of the sensor mat, reduces hardware costs, and effectively detects patient presence and movement with enhanced sensitivity, enabling timely alerts for safety and health monitoring, such as detecting seizures and immobility, with up to 36 individual sensor zones using only two electrodes.
Implementation Method 1
the AC signal is bypassed through a capacitor from the input port
Implementation Method 2
filtered through a low pass filter (LPF)
Implementation Method 3
amplified through an amplifying circuit
Implementation Method 4
the DC signal is fed into the first ADC unit from the input port
Data Source
AI summary
The present invention discloses a multi-zone pressure sensitive mat comprises a first electrode and a second electrode, wherein: the first electrode connects to an input port of a central processing unit and the second electrode connects to the digital ground return port of the central processing unit; the central processing unit comprises at least one MCU, the MCU comprises a first ADC unit and a second ADC unit, wherein electrical signal form the input port is split into original DC signal and its AC signal, wherein the DC signal is fed into the first ADC unit from the input port, the AC signal is bypassed through a capacitor from the input port, filtered through a LPF, amplified through an amplifying circuit and fed into the second ADC unit; wherein a preset threshold voltage level and a preset interval of time are stored in the MCU; the MCU detects the presence, the absence and the movement of human on bed by measuring voltage value from output port of the first ADC unit and amplitude of the AC signal from output port of the second ADC unit.