Designing and building a multi-channel temperature measurement system with the capabilities of storage, processing, display and sending through the network

Master of Electrical Engineering, Electronics Orientation

Abstract

Precise temperature measurement and control in industrial and research systems is of particular importance, and the correct operation of some industrial and laboratory instruments is possible only in a specific location with a small number of channels (maximum 8 channels). Therefore, we decided to build a 64-channel temperature measurement system with the goals of measuring with a maximum accuracy of 0.25 degrees Celsius, scattering in a space of up to 900 meters (depending on the type of cable), measuring 64 channels in a maximum time of 1 second, accurately displaying the temperature on the computer and the possibility of uploading data.

It uses TCP/IP and RS485 and uses an AVR microcontroller to measure the temperature and package it. Each AVR microcontroller on the side boards measures the temperature of 4 thermocouples and packages them in a special format and sends them to a computer program at the same time. Also, a powerful computer software has been written for this system that performs display, storage, loading and various processing tasks. To evaluate the accuracy and performance, we tested the system for a long period of time (2 to 3 days) and the desired results were obtained. This system has a suitable temperature range and accuracy, so it can be used in industrial buildings, greenhouses, poultry breeding centers and research works.

This system is currently designed to measure the temperature of the K-type thermocouple, but with a slight change in the side boards, you can read the value of any type of sensor (convert its data to digital) and send them to the program in a special package intended for data. Posted under computer. This system can also be converted into a control system with minor changes in peripheral boards and computer program.

Key words

Temperature Datalogger, Displaying Temperature, Processing on Temperature Signal, Ethernet, Digital Filter Filter

Foreword

Instruments for measuring and recording physical quantities are widely used in the laboratory industry and for general use. Nowadays, the advancement of technology and the use of electronic components, in addition to the ease of use of the tools, have also brought with them very high accuracy and greater economic efficiency.

As can be seen from the topic of this master's degree project, systems for measuring temperature are designed and built with a special method. There are many different methods for measuring this physical quantity, and we have chosen the thermocouple measurement method, which is widely used in the industry. This project consists of two parts, hardware and software, in the hardware part, it has been tried to use common chips in the market, and standard methods of communication between electronic chips have been used to connect different parts of the hardware with each other. For analyzing, displaying, recording information, uploading and also controlling the performance of the hardware part, a complex software has been designed in the LabVIEW environment.

Since this system undoubtedly has its faults and shortcomings, all of you professors, enthusiasts and students are requested to help me improve the next versions of this system with your criticisms and suggestions regarding possible software and hardware defects and deficiencies. Say.

The rise of the liquid level was not only due to the heat or coldness of the air. Rather, other factors such as changes in atmospheric pressure also contributed to this work, which revealed the inaccuracy of Galileo's thermometer.

In 1631, Ray proposed changes to Galileo's thermometer. His proposal was Galileo's inverted bottle, in which only cooling and heating were recorded due to the contraction and expansion of water.

In 1635 Duke Ferdinand of Tuscany, who was interested in science, made a thermometer in which he used alcohol (which freezes at a temperature much lower than that of water) and closed the tube so tightly that the alcohol could not evaporate. Finally, in 1640, scientists at the Lynchian Academy in Italy made a prototype of a new thermometer that used mercury and removed at least some of the air from the top of the closed tube. It is interesting to note that it took about half a century for the thermometer to fully evolve.

Following the discovery of the thermometer by Gabriel Daniel Fahrenheit, the Dutch scientist in the 17th century made a type of gas and alcohol thermometer that can measure air temperature with greater accuracy. In 1714, he designed a mercury thermometer and calibrated it with a high accuracy factor in a special way. Fahrenheit published the results of his research in 1724. He also defined a special scale for heat, which later and even to this day has been named after him. He was inspired by the cold winter of 1709 and used a mixture of ice, solid ammonium chloride, and water to determine the zero degree. By choosing this zero, he hoped that there would be no more negative temperatures.

In 1742, the Swedish Celsius announced that he had discovered a simpler and more practical scale instead of the Fahrenheit thermal scale. He used two specific points that could be produced anywhere in the world as a reference for his work. One was the melting point of ice at zero degrees Celsius and the other was the boiling point of water at 100 degrees Celsius. He divided the distance between them into one hundred equal parts, and this made it possible for any thermometer to be easily adjusted and calibrated at these two points (0 and 100 degrees Celsius). Zero degrees is the freezing point of water and one hundred degrees is the boiling point of water at a pressure of one atmosphere. Fahrenheit degree: The origin of this scale is not exactly clear, but it has been reported that zero Fahrenheit was obtained by placing the thermometer bubble in a mixture of ice and chloroammonium, and the highest point of this scale is the temperature at which mercury begins to boil; Between these two temperatures, it is divided into 600 degrees, where the freezing point of water is 32 degrees and the boiling point of water is 212 degrees Fahrenheit.

Kelvin: In the SI system, absolute temperature is measured in degrees Kelvin. In fact, absolute zero on the Kelvin scale is -273 degrees Celsius, considered by its inventor, Lord Kelvin, this temperature is the lowest possible temperature and at this temperature the kinetic energy of molecules reaches zero. The following relationships can be used to convert temperature units:                                                                                                 (1-1)

(°C × 1.8) + 32 = °F.                                                                                           (1-2)

1-4- Types of temperature measurement methods

There are two main methods for temperature measurement:

1-4-1- Temperature measurement using non-electric transducers

1-4-1-1- Thermometers (fluid content thermometers)

1-4-1-1-1- Liquid content thermometers: the basis of the work of this type of thermometers is the relationship between temperature and liquid volume.

VT = V0 (1+ ?T + ?T2 +...).                                                                                   (1-3)

The liquid used in this type of device is generally alcohol, hydrocarbons and mercury.