Construction Of Simple Thermocouples And Determination Of Their Temperature Responses Capabilities

ABSTRACT

This project is construction of a simple thermocouple and determination of their temperature responses capabilities. Thermocouple is a temperature sensor that are made from two metal alloys whose when the two metals are brought together to form a junction, a voltage is generated when there are temperature differences between them.

CHAPTER ONE

1.0                                                        INTRODUCTION

Thermocouples are the most widely used temperature measuring devices. They are more user-friendly, cost-effective, and durable temperature sensors. They provide results very quickly and have several benefits over other devices used in temperature measurement. They contain two dissimilar conductors contacting each other at one or more points. Thermocouples work on the principle of the Peltier-Seebeck effect. A voltage is produced when there is a difference in the temperature of one of the spots from the reference temperature at other areas of the circuit. Besides measuring and controlling temperature, a thermocouple is capable of converting a temperature gradient into electricity.

A wide choice of thermocouples are available to address the requirements of every possible industrial application, including Micro Thermoplastic, Standard and Mini Plug Thermocouples, Washer Style Thermocouples, Transition Thermocouples, and Bayonet Thermocouples. Many different aspects need to be considered in the selection of an appropriate thermocouple for a specific application. Some of the factors include chemical resistance, temperature range, vibration and abrasion resistance, and installation requirements.

Different alloys are employed to measure different temperature ranges. Properties such as corrosion resistance are also a selection factor for thermocouples. Standardization of thermocouples is typically done against a reference temperature of 0°C. Electronic methods of cold-junction compensation are normally used by practical instruments to adjust for changing temperature at the instrument terminals. The varying characteristics of the thermocouple can also be compensated for by electronic instruments in order to optimize the accuracy and precision of measurements.

Ceramic tubes and insulators offered by Precision Ceramics are commonly used in combination with thermocouples across a myriad of industries to facilitate monitoring the performance and consistency of production processes, particularly in adverse and aggressive chemical environments at elevated temperatures of up to1700°C.

Commercial thermoplastic are interchangeable, economical, and supplied with standard connectors. Unlike most other temperature measurement devices, external form of excitation is not required for thermoplastic because they are self-powered. They are capable of measuring a broad range of temperatures. Nevertheless, accuracy is the major drawback of thermoplastic. It is hard to achieve system errors of below 1°C.

An electric potential is generated at any junction of dissimilar metals with respect to temperature. Thermoplastic for practical temperature measurement are junctions of specific alloys exhibiting predictable and repeatable relationship between voltage and temperature. When the distance between the measuring device and the measurement point is large, extension wires may be used for intermediate connection. These wires are relatively inexpensive when compared to the thermonuclear making materials.

Knowing the significance of thermoplastic for industrial applications, Precision Ceramics has produced a host of high-tech ceramic tubes and insulators from two specific types of material. One material is Dimulit, which is a compound of silicon oxide and aluminum oxide. This low-cost material is suitable for applications involving high temperatures of up to1500°C. Rubalit is another material, which is almost pure aluminum oxide. This material exhibits very high chemical resistance and temperature stability at temperatures of up to1700°C. It also has superior electrical resistivity and mechanical strength.

1.1                                             OBJECTIVE OF THE PROJECT

The main objective of this work is to construct a simple thermonuclear and determination of their temperature responses when using copper, aluminum, iron, zinc and  combination of copper and zinc, copper and iron, zinc and iron, copper and aluminum, iron and aluminum, zinc and aluminum.

1.2                                         SIGNIFICANCE OF THE PROJECT

Thermoplastic are valuable in science and engineering, due to features such as their fast reaction time and small size. They have the ability to accurately measure extreme temperatures, with ranges from 270 to 2,500 degrees Celsius, and errors within 0.5 to 2 degrees Celsius.

1.3                                           LIMITATION OF THE PROJECT

The only limitation of thermoplastic is that the signals produced may be non-linear, and thus they need to be calibrated carefully.

1.4                                              TYPES OF THERMOCOUPLE

There are several different types. They are classified according to the maximum temperature they can measure, where they can operate, and their ruggedness. The most common ones are J, K, T, and E. For example, Type J thermocouples can be used without a covering called a sheath, although one is recommended in order to prolong their life. Type J thermocouples can function in environments where there is not enough free oxygen, and can measure up to 760 degrees Celsius.

1.5                                          APPLICATION OF THE PROJECT

Thermocouples are the most popular type of temperature sensors. They are used as hospital thermometers, and in diagnostics testing for vehicle engines. Some gas appliances such as boilers, water heaters, and ovens use them as safety features; if the pilot light is out, the thermocouple stops the gas valve from operating. They are also used as an aid in milk pasteurization, and as food thermometers. In industry, they are valuable as probes and sensors.