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Advisor(s)
Abstract(s)
Este documento tem como objetivo testar a efetividade prática de um circuito de condicionamento de sinal de um sensor de temperatura, nomeadamente um termopar. Antes de adquirir o sinal de um sensor para digitalização, um dos requisitos no condicionamento de sinal, consiste na implementação de um circuito de compensação de junção fria, para a obtenção mais precisa do valor de tensão obtido. O termopar permite medir a temperatura através da diferença de potencial entre dois metais distintos. Com base neste contexto, outra tensão é gerada na conexão entre o termopar e o terminal do dispositivo de aquisição de sinal. O circuito de compensação de junção fria melhora a medição ao providenciar a temperatura nesta junção e aplica a correção necessária. Inicialmente procedeu-se ao estudo de circuitos de compensação de junção fria para dispositivos de aquisição de sinais. O circuito de compensação de junção fria do termopar depende do tipo de termopar que se pretende utilizar. A calibração do circuito, graças à utilização de potenciómetros, permite ajustar a tensão de referência do circuito de compensação de junção fria e assim obter valores muito próximos aos valores de referência da tabela do termopar. A diminuição e o aumento significativo de temperatura no sensor, permitiu analisar o comportamento do circuito de compensação de junção fria e verificar que os valores obtidos eram consistentes e coerentes com os valores de referência da tabela do termopar. Além disso, permitiu saber aproximadamente qual a temperatura da fonte de calor utilizada.
This document aims to test the practical effectiveness of a signal conditioning circuit for a temperature sensor, namely a thermocouple. Before acquiring the signal from the sensor for digitization, one of the signal conditioning requirements consists of implementing a cold junction compensation circuit, to obtain a more accurate voltage value. The thermocouple allows temperature to be measured through the potential difference between two different metals. Based on this context, another voltage is generated in the connection between the thermocouple and the signal acquisition device terminal. The cold junction compensation circuit improves the measurement by taking the temperature at this junction and applying the necessary correction. Initially, the study of cold junction compensation circuits for signal acquisition devices was carried out. The thermocouple cold junction compensation circuit depends on the type of thermocouple to be used. Calibrating the circuit, thanks to the use of potentiometers, allows adjusting the reference voltage of the cold junction compensation circuit and thus obtaining values very close to the reference values in the thermocouple table. The significant decrease and increase in temperature in the sensor made it possible to analyze the behavior of the cold junction compensation circuit and verify that the values obtained were consistent and coherent with the reference values in the thermocouple table. Furthermore, it allowed us to know approximately the temperature of the heat source used.
This document aims to test the practical effectiveness of a signal conditioning circuit for a temperature sensor, namely a thermocouple. Before acquiring the signal from the sensor for digitization, one of the signal conditioning requirements consists of implementing a cold junction compensation circuit, to obtain a more accurate voltage value. The thermocouple allows temperature to be measured through the potential difference between two different metals. Based on this context, another voltage is generated in the connection between the thermocouple and the signal acquisition device terminal. The cold junction compensation circuit improves the measurement by taking the temperature at this junction and applying the necessary correction. Initially, the study of cold junction compensation circuits for signal acquisition devices was carried out. The thermocouple cold junction compensation circuit depends on the type of thermocouple to be used. Calibrating the circuit, thanks to the use of potentiometers, allows adjusting the reference voltage of the cold junction compensation circuit and thus obtaining values very close to the reference values in the thermocouple table. The significant decrease and increase in temperature in the sensor made it possible to analyze the behavior of the cold junction compensation circuit and verify that the values obtained were consistent and coherent with the reference values in the thermocouple table. Furthermore, it allowed us to know approximately the temperature of the heat source used.
Description
Keywords
Termopar Aquisição de Sinais Circuito de Compensação de Junção Fria
Citation
Fábio Brito, Rui Barata, Fernando J. Velez and Antonio Reis, “Circuito de Compensação de Junção Fria para Termopar,” Actas do ICEUBI – International Congress on Engineering 2024, Covilhã, Portugal, nov. 2024.
Publisher
Faculdade de Engenharia