Skin Moisture Sensor Standby Power Reduction via Electrode Switching
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Solution Overview
Problem
Conventional skin moisture content measuring apparatuses consume excessive power in measurement standby mode due to the characteristics of operational amplifiers, leading to infinite current flow and high power consumption when electrodes are not in contact with the skin.
Innovation Solution
The apparatus connects a reference (R) electrode and a current (C) electrode via a switch or resistor, and includes a microcontroller to control the connection between them, forming a loop only when the electrodes contact the skin, thereby reducing power consumption by minimizing current flow during standby mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the operational amplifier is kept in open loop state during standby mode, then the circuit is simple to operate, but infinite current flows and power consumption becomes huge
Solution Approach 1:
A switch is introduced as an intermediary component between the operational amplifier output and the C electrode. This switch mediates the connection state, allowing the circuit to be in standby mode without direct connection, thereby preventing infinite current flow while maintaining operational simplicity through controlled connection/disconnection.
Solution Approach 2:
The circuit transitions from a static open-loop state to a dynamic state where the connection between the operational amplifier and C electrode can be changed. The switch enables the circuit to adapt its connection state based on operational requirements, reducing power consumption during standby while maintaining measurement capability during operation.
2Use of energy by moving object
If the R electrode and C electrode are disconnected during standby mode, then power consumption is reduced, but the circuit cannot be ready for immediate measurement
Solution Approach 1:
The switch is pre-configured and controlled to be in the closed position during standby mode, establishing the connection between R and C electrodes in advance. This preliminary action ensures the circuit is ready for immediate measurement without requiring additional setup time, while still allowing power consumption reduction through controlled disconnection when measurement is not needed.
Solution Approach 2:
The microcontroller monitors the operational state and automatically controls the switch to maintain appropriate connection states. This feedback mechanism ensures the circuit remains ready for measurement by detecting when measurement conditions are met and automatically establishing the necessary electrode connections.
3Use of energy by moving object
If the switch connects R and C electrodes during standby mode, then power consumption is reduced, but the connection must be reliably broken during measurement
Solution Approach 1:
The manual or mechanical switch operation is replaced with electronic control through a microcontroller that drives the switch based on detected measurement conditions. This substitution ensures reliable and consistent connection/breakage timing, eliminating mechanical wear and improving connection reliability while maintaining power consumption reduction benefits.
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 significantly reduces power consumption during standby mode by controlling the electrical connection between the R and C electrodes, ensuring only a minute current flows, thereby stabilizing the circuit and conserving energy.
Implementation Method 1
an operational amplifier, having an inverting input terminal connect with the R electrode, and having an output terminal connect with the C electrode
Data Source
AI summary
An apparatus to measure skin moisture content, the apparatus including: an electrode unit comprising a reference (R) electrode, a current (C) electrode, and a measuring (M) electrode; an operational amplifier having an inverting input terminal connect with the R electrode, and having an output terminal connect with the C electrode; a first switch connecting the R electrode and the C electrode, and releasing a connection between the R electrode and the C electrode when the electrode unit contacts with the skin of a user; and a microcontroller controlling the connection between the R electrode and the C electrode via the first switch is provided.