RTD Variable Excitation Current for Accurate High-Temperature Measurement
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Solution Overview
Problem
RTD measurements in industrial process control systems suffer from inaccuracies due to noise and systematic errors, particularly at high temperatures, which affect the measurement of process variables like temperature.
Innovation Solution
Implementing a variable excitation current method that adapts to temperature ranges, using recursive least square estimation and adaptive excitation current to minimize noise and systematic errors, enhancing measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed excitation current is used in RTD measurement, then the measurement system is simple, but measurement accuracy deteriorates due to noise and systematic errors
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed excitation current to a variable excitation current that adapts to different temperature ranges. The system dynamically adjusts the excitation current based on the measured temperature, optimizing the balance between signal strength and noise reduction at each temperature point, thereby improving measurement accuracy without excessive complexity
Solution Approach 2:
The patent changes the excitation current parameter from a constant value to a variable value that depends on temperature. By adjusting the excitation current as a function of temperature, the system compensates for noise and systematic errors, improving measurement precision while maintaining manageable system complexity through parameter adaptation
2Measurement precision
If variable excitation current with multiple values is applied, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent segments the temperature measurement range into multiple intervals, with each interval having an optimized excitation current value. This segmentation allows the system to use multiple current values for improved accuracy while managing complexity by organizing the measurement process into discrete, manageable temperature ranges rather than requiring continuous complex adjustment
Solution Approach 2:
The patent implements periodic action by systematically cycling through different excitation current values corresponding to different temperature ranges. The measurement process periodically switches between discrete current levels based on the temperature interval, providing improved accuracy through multiple measurements while maintaining systematic and manageable complexity
3Measurement precision
If least square estimation is used to account for random effects, then measurement accuracy improves, but computational complexity increases
Solution Approach 1:
The patent applies feedback by using least square estimation to process measurement data and adjust the temperature calculation based on the relationship between excitation current and voltage measurements. The feedback mechanism systematically accounts for random effects by analyzing the statistical relationship between measurements, improving accuracy while the computational complexity is managed through efficient estimation algorithms
4Measurement precision
If recursive least square estimation is used, then measurement accuracy improves, but computational complexity increases
Solution Approach 1:
The patent applies continuity of useful action through recursive least square estimation, which continuously updates the temperature measurement as new data becomes available. This continuous refinement process improves measurement accuracy by constantly accounting for random effects and systematic variations, while the recursive nature of the algorithm manages computational complexity by building upon previous calculations rather than requiring complete re-computation
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
Improves RTD measurement accuracy by 2 to 5 times, providing better estimation of resistance and temperature with reduced errors, especially at high temperatures.
Implementation Method 1
The resistance of the RTD varies as a function of temperature. RTD sensors are thus temperature-sensing devices in which the resistance of an RTD sensor increases with temperature.
Implementation Method 2
measuring a voltage with a resistance temperature detector using a variable excitation current
Data Source
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AI summary
A method, apparatus and system for measuring a temperature can involve measuring a voltage with a resistance temperature detector using a variable excitation current, and deriving a process temperature from the voltage measured by the resistance temperature detector. The process temperature can be further derived by applying a plurality of values of the variable excitation current, measuring corresponding values of voltage, and estimating a resistance by applying a least square estimation. The process temperature can also be derived by applying a different value of the variable excitation current at every iteration, using a recursive least square estimation to measure a resistance, and using confidence intervals for instrument diagnostics.