Thermocouple Cold-Junction Compensation for Fast Accurate Measurement
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Solution Overview
Problem
Existing thermocouple temperature measurement methods suffer from slow stabilization times, leading to inaccurate results when quick measurements are required.
Innovation Solution
A thermocouple arrangement and method using two digital temperature sensors to measure the temperatures of both connector terminals, calculating a weighted average based on the Seebeck coefficients of the conductors, and applying correction coefficients for accurate hot end temperature determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single temperature sensor is used to measure the cold end temperature, then the device complexity is reduced, but the measurement precision deteriorates due to temperature differences between connector terminals
Solution Approach 1:
The patent divides the cold end temperature measurement into two separate measurement points (first connector terminal and second connector terminal), each measured by dedicated temperature sensors. This segmentation allows independent measurement of temperature differences at the cold end, enabling more precise compensation calculations without requiring a single averaged measurement point.
2Measurement precision
If temperature stabilization is waited for before measurement, then the measurement precision improves, but the measurement time increases
Solution Approach 1:
The patent performs preliminary measurement of temperature differences at the two cold end connectors and calculates compensation values before the actual temperature measurement is needed. By pre-calculating the weighted average temperature and applying compensation to the thermal voltage, the system eliminates the need to wait for thermal stabilization, providing accurate measurements immediately.
3Device complexity
If the Seebeck coefficient is treated as constant, then the calculation complexity is reduced, but the measurement precision deteriorates due to temperature dependence
Solution Approach 1:
The patent changes the Seebeck coefficient from a constant value to a temperature-dependent parameter. The system obtains Seebeck coefficient values corresponding to different temperatures (including the calculated cold end temperature and hot end temperature) and uses these variable values in the compensation calculations, significantly improving measurement accuracy while managing complexity through systematic data tables or formulas.
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
Enables rapid and accurate temperature measurements by compensating for temperature differences at the cold end, significantly reducing stabilization time and improving measurement accuracy.
Implementation Method 1
The thermocouple produces a temperature-dependent voltage as a result of the Seebeck effect, and this voltage can be interpreted to measure temperature.
Implementation Method 2
A thermal voltage is created when the ends of a metal wire locate in different temperatures when free electrons of atoms within the metal wire will move from a hot end to a cold end.
Data Source
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AI summary
The present invention relates to measuring temperature (t) using a thermocouple (30), with a first measurement point (33) along a positive conductor (31), and a second measurement point (34) along a negative conductor (32). The arrangement is configured to obtain a Seebeck coefficient (S) for the material pair; and to measure a first temperature (t1) in the cold end of the thermocouple (30) at a first measurement point (33); and to measure a second temperature (t2) at a second measurement point (34). Thermal voltages (U1, U2) are measured. The arrangement further calculates a weighted average of the temperature (Tave) by dividing a temperature difference of the first (t1) and second (t2) temperatures with a ratio N = U1/U2; and calculates temperature (t) in the hot end of the thermocouple (30) based on the obtained Seebeck coefficient (S) for the material pair and the calculated weighted average of the temperature (Tave).