Resistance Measurement Using Time-Division Multiplexing
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Solution Overview
Problem
Traditional resistive temperature measurement systems require multiple dedicated wires for each resistive temperature device (RTD), leading to increased system weight and wiring complexity.
Innovation Solution
A resistance measurement system that uses a single line to connect multiple resistors in series, with each resistor having a parallel capacitor forming an RC pair, allowing for the determination of each resistor's resistance by sampling the total voltage at specific times after other RC pairs have reached steady state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple dedicated wires are used to measure each RTD separately, then measurement precision is improved, but device complexity and weight increase
Solution Approach 1:
Multiple RTD measurements are merged into a single wire communication channel. The patent combines multiple resistance measurement functions into one shared wire by using time-division multiplexing with RC circuits, where each RTD's measurement is sequentially performed at different time intervals, allowing all measurements to share the same physical medium.
Solution Approach 2:
The system dynamically switches between different measurement modes by controlling the RC circuit time constants. By adjusting the resistance values in the RC circuits, the system can selectively measure different RTDs at different times, creating a dynamic time-division multiplexing scheme that adapts to different measurement requirements.
2Reliability
If multiple dedicated wires are used for each RTD, then reliability is improved, but weight of moving object increases
Solution Approach 1:
The patent merges multiple dedicated measurement channels into a single shared wire by using time-division multiplexing. Each RTD measurement is performed sequentially in time, with RC circuits providing the necessary isolation and timing control, thereby reducing the total wire count from N+1 to just 2 wires while maintaining measurement reliability through proper signal conditioning.
Solution Approach 2:
RC circuits serve as intermediary elements between the RTDs and the measurement system. These RC circuits act as buffers and timing control mechanisms that enable reliable sequential measurement of multiple RTDs over a single wire, preventing signal interference and ensuring accurate measurements despite the shared medium.
3Device complexity
If a single line is used to connect multiple resistors, then device complexity is reduced, but difficulty of detecting and measuring increases
Solution Approach 1:
The system uses dynamic time-division multiplexing controlled by RC circuits to sequentially isolate each RTD for measurement. By dynamically adjusting the time constants and switching between different measurement intervals, the system can extract individual resistance values from the combined single-wire signal, making the measurement process manageable despite the shared medium.
Solution Approach 2:
The measurement system employs periodic excitation signals and sampling at specific time intervals determined by RC time constants. Each RTD is measured periodically at its designated time slot, with the RC circuits ensuring proper signal conditioning and timing, thereby converting a complex simultaneous measurement problem into a series of simpler periodic measurements.
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 approach reduces the number of wires required from N+1 to 2, decreasing system weight and complexity while enabling accurate measurement of multiple resistive elements.
Implementation Method 1
each resistor having a parallel capacitor forming an RC pair
Implementation Method 2
determination of each resistor's resistance by sampling the total voltage
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A resistance measurement system can include a plurality of resistors connected in series along a single line. The plurality of resistors can include N resistors. The system can include a plurality of capacitors for at least N-1 of the resistors. Each capacitor can be connected in parallel to the single line with a respective resistor to form a respective resistor-capacitor (RC) pair. Each RC pair can include a different time constant such that each RC pair reaches a steady state voltage at a different time. The system can include a current supply connected to the single line to supply a current to the line. The system can include a control module configured to sense a total voltage across the single line and to successively determine resistance of each resistor from the total voltage based on the current, a known total steady state voltage, and known time-to-steady-state-voltages of each RC pair and/or resistors.