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Sensors 2013, 13(12), 17084-17097; doi:10.3390/s131217084

Evaluation of Piecewise Polynomial Equations for Two Types of Thermocouples

1 Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan 2 Department of Bio-Industrial Mechantronics Engineering, National ChungHsing University, Taichung 40227, Taiwan
* Author to whom correspondence should be addressed.
Received: 24 November 2013 / Revised: 9 December 2013 / Accepted: 10 December 2013 / Published: 12 December 2013
(This article belongs to the Section Physical Sensors)
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Thermocouples are the most frequently used sensors for temperature measurement because of their wide applicability, long-term stability and high reliability. However, one of the major utilization problems is the linearization of the transfer relation between temperature and output voltage of thermocouples. The linear calibration equation and its modules could be improved by using regression analysis to help solve this problem. In this study, two types of thermocouple and five temperature ranges were selected to evaluate the fitting agreement of different-order polynomial equations. Two quantitative criteria, the average of the absolute error values |e|ave and the standard deviation of calibration equation estd, were used to evaluate the accuracy and precision of these calibrations equations. The optimal order of polynomial equations differed with the temperature range. The accuracy and precision of the calibration equation could be improved significantly with an adequate higher degree polynomial equation. The technique could be applied with hardware modules to serve as an intelligent sensor for temperature measurement.
Keywords: piecewise polynomial equation; regression analysis; thermocouples piecewise polynomial equation; regression analysis; thermocouples
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Chen, A.; Chen, C. Evaluation of Piecewise Polynomial Equations for Two Types of Thermocouples. Sensors 2013, 13, 17084-17097.

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