Resistance Thermometer Circuit Temperature Drift Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing resistance thermometer systems in process automation face challenges in accurately measuring temperature-dependent process variables due to drift and temperature behavior variations within the measurement circuit, which can be influenced by ambient temperature changes and component aging, affecting the precision of measurements for variables like pH and conductivity.
Innovation Solution
A method and electrical circuit that utilize precision resistors and a resistance thermometer to determine temperature coefficients, allowing for precise temperature measurement and compensation of temperature dependence across the entire system, using a constant electrical current and data processing to solve for temperature coefficients and calculate the temperature of the circuit, thereby accounting for temperature variations in process variables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resistance thermometer is used to measure temperature-dependent process variables, then temperature measurement capability is provided, but drift and temperature behavior variations in the measurement circuit affect measurement precision
Solution Approach 1:
The patent applies feedback by continuously monitoring the actual temperature behavior of the measurement circuit using precision resistors as reference elements. The measured voltage values from these reference resistors are fed back to calculate actual temperature coefficients, which are then used to compensate the process variable measurements in real-time, eliminating drift effects
Solution Approach 2:
The patent changes the parameter approach by not assuming fixed temperature coefficients, but rather dynamically determining them through measurements. By measuring voltages across precision resistors at different temperatures and calculating actual temperature coefficients from these measurements, the system adapts to changing circuit characteristics over time and temperature ranges
2Device complexity
If the measurement circuit is simplified, then device complexity is reduced, but temperature behavior variations cannot be accurately compensated
Solution Approach 1:
The patent introduces intermediary reference elements (precision resistors R1, R2, R3) that mediate between the measurement circuit and the evaluation unit. These intermediaries provide temperature-dependent voltage signals that enable the calculation of actual temperature coefficients without requiring complex direct measurements of the entire circuit behavior
3Device complexity
If temperature coefficients are assumed fixed, then calculation complexity is reduced, but temperature drift cannot be compensated
Solution Approach 1:
The patent performs preliminary action by pre-establishing the relationship between voltage measurements and temperature coefficients through a linear system of equations. By solving this system in advance or in real-time, the actual temperature coefficients are determined before they are needed for compensation, enabling the system to adapt to changing conditions without complex real-time calculations during measurement
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 enables accurate determination of temperature-dependent process variables by compensating for temperature drift and variations within the measurement circuit, ensuring precise measurements over time and dynamically adjusting for component tolerances, thus improving the reliability of temperature measurements in process automation.
Implementation Method 1
Pure metals exhibit greater resistance changes than alloys and have a relatively constant temperature coefficient of electrical resistance. For precise measurements of temperature by means of a resistance thermometer, one uses noble metals, most often, platinum or nickel
Implementation Method 2
For resistance measurement, a constant electrical current must flow through the resistor. The applied voltage is an easily measurable signal proportional to the resistance
Implementation Method 3
The applied voltage is an easily measurable signal proportional to the resistance—and therewith to the temperature to be measured
Data Source
AI summary
A method for determining a physical and/or chemical, temperature dependent, process variable of process automation technology utilizing a resistance thermometer (RPt1000), wherein the resistance thermometer (RPt1000) is installed in an electrical circuit, comprising the steps of: measuring a first voltage (U1) across at least a first precision resistor (R1); measuring a second voltage (U2) across at least a second precision resistor (R2); measuring a third voltage (U3) across at least a third precision resistor (R3), wherein cyclically or continuously a constant electrical current (I) is sent through the at least first precision resistor (R1), the at least second precision resistor (R2) or the at least third precision resistor (R3); determining temperature coefficients (a, b, c) characteristic for the electrical circuit by means of the first voltage (U1), the second voltage (U2) and the third voltage (U3); sending the constant electrical current (I) through the resistance thermometer (RPt1000) and measuring a voltage (U) across the resistance thermometer (RPt1000); and determining the temperature (T) by means of the temperature coefficients (a, b, c) and the measured voltage (U). An electrical circuit and a sensor of process automation technology, especially a conductivity sensor, comprising such an electrical circuit are also discussed.