Resistance Measurement Circuit With Direct Temperature Compensation
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Solution Overview
Problem
Conventional circuits for temperature-compensated resistance measurement in electronic systems are complex and require additional components, such as temperature sensors and numerical processors, which increase complexity and reduce measurement speed and accuracy.
Innovation Solution
A circuit comprising a sensor circuit with diode elements, a reference circuit with current sources, and a sigma-delta converter that generates a digital output directly compensating for temperature by logarithmically compressing voltage differences, eliminating the need for temperature sensors and numerical processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional temperature compensation circuits are used, then temperature dependence is compensated, but device complexity increases due to additional temperature sensors and numerical processors
Solution Approach 1:
The patent combines the temperature compensation function with the resistance measurement function into a single integrated circuit. The measurement circuit simultaneously measures both the unknown resistance and the temperature-dependent reference voltage, eliminating the need for separate temperature sensors and numerical processors. This merging approach maintains temperature compensation accuracy while significantly reducing device complexity.
Solution Approach 2:
The reference circuit is designed to serve multiple functions: it provides a temperature-dependent reference voltage for compensation, acts as a temperature sensor itself, and enables both resistance measurement and temperature compensation through a single measurement path. This multi-functionality eliminates the need for dedicated temperature sensing components and processing units.
2Reliability
If conventional temperature compensation with numerical processing is used, then temperature effects are corrected, but measurement speed decreases due to processing requirements
Solution Approach 1:
The patent replaces the mechanical/computational approach of numerical processing with an electrical/analog approach. The sigma-delta modulator directly converts the voltage ratio (which already contains temperature compensation) into a digital output signal without requiring separate temperature reading, calculation, and correction steps. This substitution dramatically increases measurement speed while maintaining compensation accuracy.
Solution Approach 2:
The measurement circuit automatically performs temperature compensation through its inherent design. The ratio of the unknown resistance voltage to the reference voltage automatically cancels out temperature effects, and the sigma-delta modulator directly outputs the compensated result. No external temperature sensing or computational correction is needed - the system self-compensates in real-time.
3Productivity
If conventional resistance measurement is used, then resistance value is obtained, but measurement accuracy is reduced due to temperature dependence
Solution Approach 1:
The patent changes the measurement parameter from absolute voltage to voltage ratio. By measuring the ratio of the unknown resistance voltage to the temperature-dependent reference voltage, the temperature parameter effectively cancels out. This parameter transformation enables simultaneous high-speed measurement and high-precision temperature compensation without requiring separate processing steps.
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 provides a fast, accurate, and simplified measurement of resistance by removing temperature dependence, reducing current consumption, and enhancing dynamic range, making it suitable for applications like gas concentration measurement systems.
Implementation Method 1
the voltage VBE across the pn-junction of a bipolar diode that may be a transistor of which base and collector are short-circuited is (equation 1): VBE = V0 + (KT/q)·ln(IE/IS). The voltage VBE depends from the emitter current IE and is logarithmic so that the dynamic range of the measurement is enlarged by the logarithmic compression. The term KT/q represents the temperature dependency.
Implementation Method 2
a sigma-delta converter circuit comprising a first stage and a downstream connected second stage, the first stage comprising: a first and a second capacitor and an integration element, the first capacitor selectively coupled to one of the output terminals of the sensor circuit and the second capacitor coupled to one of the first and second output terminals of the reference circuit; and the second stage comprising an output terminal configured to provide a bitstream dependent on the resistance to be measured.
Data Source
AI summary
A circuit for measuring an unknown resistance of a resistive element comprises a sensor circuit to generate a differential voltage dependent on the resistance of the resistive element and a reference circuit to generate a differential reference voltage and a sigma-delta converter comprising a first stage, wherein a first capacitor is selectively coupled to one of the output terminals of the sensor circuit and a second capacitor is coupled to one of the output terminals of the reference circuit. The circuit generates logarithmically compressed values.