Resistive Sensor Interface With Switched Single-ADC Ratio Readout
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Solution Overview
Problem
Existing technologies for measuring unknown resistances in sensor electronic interfaces, particularly in automotive applications, face inefficiencies and inaccuracies due to the need for multiple analog-to-digital conversions and lack of precision when comparing voltages across reference and unknown resistances.
Innovation Solution
A device comprising a reference resistance in series with the unknown resistance, utilizing changeover-switch modules and a single analog-to-digital converter with negative feedback loops, specifically first-order continuous-time sigma-delta converters, to efficiently calculate the digital representation of the unknown resistance as a ratio of voltages across the resistances, optimizing operations for both RX < RREF and RX > RREF scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two separate analog-to-digital converters are used to measure voltages across reference and unknown resistances, then measurement capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines two separate analog-to-digital conversion functions into a single converter by time-multiplexing the input signals. The converter alternates between measuring the voltage across the reference resistance and the voltage across the unknown resistance, effectively performing the work of two converters with one device.
Solution Approach 2:
The measurement process uses periodic switching between the two voltage measurement channels. The single converter operates in periodic intervals, first converting the reference voltage signal, then converting the unknown resistance voltage signal, repeating this cycle continuously to achieve both measurements.
2Measurement precision
If multiple analog-to-digital conversion operations are performed, then measurement completeness is improved, but processing time and operational overhead increase
Solution Approach 1:
The measurement system maintains continuous operation by immediately transitioning from one voltage measurement to the next without idle periods. The single converter continuously alternates between measuring the reference voltage and the unknown resistance voltage, ensuring no measurement opportunity is lost while minimizing total conversion time through efficient sequential processing.
Data Source
AI summary
A device to read a variable resistor has an analog to digital converter (ADC), a first switch and a second switch. The ADC has a first ADC input, a second ADC input and an ADC output. The first switch selectively couples a first voltage indicative of a voltage across a first resistance to the first ADC input. The second switch selectively couples a second voltage indicative of a voltage across a second resistance to the second ADC input. The ADC outputs a signal indicative of a value of the second resistance.