Impedance Measurement Front-End Circuit with Mode Switching
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Solution Overview
Problem
Existing impedance measurement devices are limited by size, power consumption, and production costs due to the need for separate components and modes for voltage source and current source measurements.
Innovation Solution
A front-end circuit that uses a single operational amplifier and mode selection-switch units to switch between voltage source and current source modes, sharing input and output terminals and excitation signals, allowing for reduced component count and power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate readout units for voltage source and current source modes are integrated on a single circuit board, then both measurement modes are supported, but the circuit board size is limited by the components needed for both readout units
Solution Approach 1:
The patent merges the voltage source readout unit and current source readout unit into a single integrated circuit board. The voltage source readout unit includes a voltage-to-current converter and the current source readout unit includes a current-to-voltage converter, both sharing common operational amplifiers, resistors, and other components on the same circuit board, enabling dual measurement mode capability without requiring separate boards
Solution Approach 2:
The circuit board is designed with universal components that can serve multiple functions. Operational amplifiers are configured to operate in different modes (voltage-to-current conversion and current-to-voltage conversion) depending on the measurement mode selected. This multi-functionality allows a single circuit board to support both voltage source and current source impedance measurements without requiring dedicated separate units
2Adaptability or versatility
If separate readout units for voltage source and current source modes are used, then both measurement modes are supported, but power consumption increases
Solution Approach 1:
The patent combines the power consumption burden of two separate readout units into a single shared infrastructure. Common components such as operational amplifiers, resistors, and supporting circuitry are shared between the voltage source and current source modes, reducing the total power consumption compared to having completely separate units for each measurement mode
3Adaptability or versatility
If separate readout units for voltage source and current source modes are used, then both measurement modes are supported, but production costs increase
Solution Approach 1:
The patent merges the voltage source readout unit and current source readout unit into a single integrated circuit board, reducing the total component count and assembly complexity. This consolidation lowers production costs by eliminating the need to manufacture, test, and assemble two separate readout units, while still providing both measurement mode capabilities
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
Enables compact, low-power impedance measurement in both voltage source and current source modes, reducing production costs and size while maintaining measurement accuracy.
Implementation Method 1
the operational amplifier is operated as closed-loop amplifier, whereby a feedback-loop is formed between the inverting input and the Op-Amp output
Implementation Method 2
The operational amplifier comprises an inverting input and an Op-Amp output... the excitation signal controls... either a current flowing through the electrodes and the sample or a voltage across the electrodes and the sample
Data Source
Figure 1~3
Figure 4a~4b
AI summary
The front-end circuit (1) for an impedance measurement comprises an excitation-terminal (12), intended to receive an excitation signal relative to a common ground (11), a first and a second input-terminal (13a,b), intended to be connected to two electrodes (3a,b), a first and a second output-terminal (14a,b), whereby each one of the two output-terminals (14a,b) is intended to provide a measurement signal during a use of the front-end circuit (1) in a measurement, preferably to an analogue to digital converter device (4); a first and a second mode selection-switch-unit (15a,b), each with two mode switch-inputs, an operational amplifier (16) and a reference resistor (17). During a measurement and depending on the state of the mode selection-switch-units (15a,b), a feedback-loop of the operational amplifier (16) comprises either a sample (130) arranged between the two input-terminals (13a,b) or the reference resistor (17).