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Assessment of the accuracy of a virtual multi-channel temperature measuring instrument

Maśnicki Romuald, Pałczyńska Beata

Scientific Journal of Gdynia Maritime University

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2023

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nr 127

57--70

EN

The multi-channel temperature measurement system developed works with NTC thermistors. The article presents the results of theoretical and empirical evaluation of accuracy obtained in measurement channels. The basis for the theoretical assessment is the mathematical model for each of the measurement channels and the characteristics of the system elements included in the circuits of the measurement channel. Two different methods were used to theoretically estimate the accuracy: the Gauss Formula and the Monte Carlo method. The empirical assessment of accuracy is supported by measurement data collected during the calibration procedures for the device developed and the results of verification measurements performed on a working device. The exemplary results presented of the accuracy assessment, obtained in the selected channel, are representative of the properties of all other measurement channels. The results of both methods of assessing accuracy in measurement channels are very similar, which confirms the assumptions regarding the implementation of the instrument developed and its good metrological properties.

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NTC thermistor nonlinearity compensation using Wheatstone bridge and novel dual-stage single-flash piecewise-linear ADC

Jovanović Jelena, Denić Dragan

Metrology and Measurement Systems

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2021

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Vol. 28, nr 3

523--537

EN

NTC thermistors are frequently used low in cost temperature sensors which provide some of the most desirable sensing features. However, due to the nonlinear static transfer function their sensitivity decreases with temperature increase, causing lower measurement accuracy in some regions of the measurement range. This paper proposes a method for NTC thermistor nonlinearity compensation using a Wheatstone bridge and a novel dual-stage single-flash piecewise-linear ADC. Both conversion stages are performed using the same flash ADC of a novel design based on a reduced number of comparators employed. In this manner, simpler design, lower production costs, higher compactness and lower power consumption of the linearizing ADC, are achieved. The proposed linearizing method is tested on the Vishay NTCLE413E2103F520L thermistor, in the range from 0°C to 100°C, and the obtained results confirmed the effectiveness of the method in measurement accuracy improvement: when the flash ADC of 10-bit resolution is employed the accuracy obtained is 7.4747 ·10-5°C.

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A Novel Design Of An NTC Thermistor Linearization Circuit

Lukić J., Denić D.

Metrology and Measurement Systems

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2015

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Vol. 22, nr 3

351--362

EN

A novel design of a circuit used for NTC thermistor linearization is proposed. The novelty of the proposed design consists in a specific combination of two linearization circuits, a serial-parallel resistive voltage divider and a two-stage piecewise linear analog-to-digital converter. At the output of the first linearization circuit the quasi-linear voltage is obtained. To remove the residual voltage nonlinearity, the second linearization circuit, i.e., a two-stage piecewise linear analog-to-digital converter is employed. This circuit is composed of two flash analog-to-digital converters. The first analog-to-digital converter is piecewise linear and it is actually performing the linearization, while the second analog-to-digital converter is linear and it is performing the reduction of the quantization error introduced by the first converter. After the linearization is performed, the maximal absolute value of a difference between the measured and real temperatures is 0.014°C for the temperature range between - 25 and 75°C, and 0.001°C for the temperature range between 10 and 40°C.