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вул. Інститутська 11, м. Хмельницький, 29016

МЕТОД ЗМЕНШЕННЯ ТРУДОМІСТКОСТІ ПЕРЕХОДУ ДО ІНДИВІДУАЛЬНОЇ ФУНКЦІЇ ПЕРЕТВОРЕННЯ ВИМІРЮВАЛЬНОГО КАНАЛУ
З НЕЛІНІЙНИМИ БЛОКАМИ

THE METHOD OF REDUCING THE LABOR OF THE TRANSITION TO THE INDIVIDUAL FUNCTION OF CONVERSION OF THE MEASURING CHANNEL WITH NONLINEAR BLOCKS

Сторінки: 92-98. Номер: №3, 2020 (285)
Автори:
В.В. Кочан
Науково-дослідний інститут Інтелектуальних комп’ютерних систем
Західноукраїнського національного університету
V. KOCHAN
Research Institute of Intelligent Computer Systems
Western Ukrainian National University
DOI: https://www.doi.org/10.31891/2307-5732-2020-285-3-15
Рецензія/Peer review : 07.04.2020 р.
Надрукована/Printed : 04.06.2020 р.

Анотація мовою оригіналу

У статті запропоновано метод переходу до індивідуальної функції перетворення вимірювального каналу з декількома нелінійними блоками, який має суттєво нижчу трудомісткість порівняно із традиційним підходом. Пропонований метод подано на прикладі перетворювача температура-частота на базі термістора та мультивібратора на базі операційного підсилювача і мостового перетворювача. Проведений аналіз похибок вимірювального каналу показав, що вони не перевищують ±1°С у діапазоні вимірювання від мінус 20°С до +100°С при чутливості 0,003°С.
Ключові слова: вимірювання температури, термістор, похибка вимірювання, функція перетворення, калібрування, нелінійні блоки.

Розширена анотація англійською мовою

In scientific research and in the praxis of the engineer often appear spontaneous problems of temperature measurements. However, as a rule of thumb, cheap sensors and simple measuring circuits have large errors and nonlinear conversion characteristics. Therefore, the task of determining an individual conversion characteristic of such Ad-hoc measurement systems is complex and time consuming. In the range from – (20… 0) ºС to + (100 (120))С, it is reasonable to use the thermistor as a temperature sensor due to its low price, high sensitivity and wide range of nominal resistance. However, the thermistor are characterized by a large variation of its parameters. The permissible deviation of the resistance from the nominal one at 20ºC can reach ± 20%, and the permissible deviation of the temperature coefficient from the nominal one can reach ± 5%. It is reasonable to determine the individual thermistor conversion function in two reference fixed points. The first point is the melting point of ice. As the second point for calibrating the thermistor, it is reasonable to use the axillary temperature of a healthy person. In the vast majority of cases, this temperature is 36.6°C. The method for a significant simplification of obtaining the individual conversion characteristic for a measuring system with nonlinear blocks is considered in this article. For this purpose, there is developed a technique of considerably lower complexity. The proposed method is illustrated on the case study of the temperature-to-frequency converter. The temperature-to-frequency converter is based on the thermistor as a temperature sensor and the multivibrator. The latter is based on the operational amplifier and the bridge circuit. The error analysis carried out for the whole measuring system revealed that the total measurement error does not exceed ± 1 ° C within the measurement range from –20 ° C to + 120 ° C with the sensitivity of 0.003 ° C. The total error of measurements can be further reduced in approximately 2-4 times when using the mercury thermometer with the error of ± 0.1 ° C to determine individual conversion characteristic of the considered measuring system .. The proposed solution combines knowledge from the many fields of knowledge such as electronics, instrumentation, and metrology. Thus, the proposed solution can be used as a base for student training.
Key words: temperature change, thermistor, change of temperature, changeover function, calibration, non-linear blocks.

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