Comparator-Regulated Wheatstone Bridge for Precise Impedance Sensing
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Solution Overview
Problem
Existing analog to digital converters (ADCs) face challenges such as high power consumption, low resolution, and inadequate performance in applications with limited power budgets or high resolution requirements.
Innovation Solution
The development of advanced ADC designs and architectures that include innovative components like non-linear N-bit digital to analog converters (DACs), transistors, and metal-oxide-semiconductor field-effect transistors (MOSFETs) to enhance resolution, bandwidth, and power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ADC designs are used, then device simplicity is maintained, but resolution and measurement precision are insufficient
Solution Approach 1:
The ADC is divided into multiple independent modules: a first ADC for sensing impedance magnitude, a second ADC for sensing impedance phase, and a controller that processes both signals. This segmentation allows each module to be optimized for its specific function, achieving high resolution without excessive overall complexity.
Solution Approach 2:
A controller acts as an intermediary between the two ADCs and the processing system. It receives the magnitude signal from the first ADC and the phase signal from the second ADC, then processes these intermediate signals to generate the final impedance measurement, coordinating the complex multi-ADC system.
2Measurement precision
If high resolution ADCs are implemented, then measurement precision improves, but power consumption increases
Solution Approach 1:
The high-resolution measurement function is segmented across two separate ADCs rather than using one ultra-high-resolution ADC. This allows each ADC to operate at moderate resolution levels while collectively achieving high measurement precision, reducing the power consumption associated with single high-resolution conversion.
Solution Approach 2:
The system uses periodic switching between the first ADC (sensing magnitude) and the second ADC (sensing phase) under controller coordination. This time-division multiplexing approach allows high-resolution measurements to be achieved through sequential sampling rather than continuous high-power operation.
3Measurement precision
If impedance sensing accuracy is improved, then measurement precision increases, but signal to noise ratio decreases
Solution Approach 1:
The controller serves as an intermediary that processes the magnitude signal from the first ADC and the phase signal from the second ADC. It combines these two measurements to calculate impedance, using the phase information as an additional dimension that improves accuracy while the coordinated processing minimizes noise accumulation.
Solution Approach 2:
The impedance measurement is formed as a composite of two separate measurements: magnitude from the first ADC and phase from the second ADC. By combining these two independent measurement channels, the system achieves higher overall accuracy while the diversity of measurement methods helps average out noise components.
Data Source
AI summary
An impedance sensing circuit includes first and second current sources and first and second bias current sources that are appropriately coupled to first and second resistors. The impedance sensing circuit also includes a comparator that compares a first voltage based on the first terminal of the first resistor to a second voltage based on the first terminal of the second resistor to generate a comparator output signal. Either the comparator output signal or a digital signal based on the comparator output signal operates to regulate the current signals output from the first and second current sources so that the first voltage is same as the second voltage. The comparator output signal and the digital signal is representative of a difference between the first voltage and the second voltage that is based on an impedance difference between the first resistor and the second resistor.