Automatic Verification System Of Industrial Thermocouple, The Labview Platform

Thermocouple is a kind of temperature sensor commonly used at the industrial scene. Thermoelectric characteristic of these thermocouples will be changed when they are influenced by environment, medium atmosphere, temperature and so on. It is more serious especially under some special operating modes such as high temperature, corrosivity atmosphere etc. When thermoelectric characteristic of these thermocouples is out of range, the temperature that the thermocouples point out will be distorted and their measurement error will be greater. So thermocouples should be calibrated.In the early period, the thermocouple is calibrated by man. In this way, it is the operator's experience that controls the temperature to its calibrated point, and then tries his best to make it stable for calibrating. While calibrating, the operator notes down the data of the thermocouple, and at the same time, switches over the thermocouple. But it cannot assure the accuracy in stable condition, and also there exists the time-delay error in this method. What's more, there are too many human elements in it. Therefore, this method cannot assure the strict technological requirements in the calibration of the thermocouple.In recent decades, along with the popularization of the computers and the development of the digital instruments, there are many researches at home and abroad on the auto calibration for thermocouple. These researches have achieved great progress and developed auto-calibrating system for industrial thermocouple, which solves the auto calibration of the field instrument. But these systems have adopted the traditional programming language on computer programming. In addition, once the system is formed, the corresponding parameter cannot be changed freely and the system cannot be amended or updated by the temperature measurement engineer. The things we hope are these: the temperature measurement engineer can change the auto-calibrating system for industrial thermocouple freely, and he can become the designer, user, maintainer, and regenerator of the auto-calibrating system.As the result of the openness and graphical way of programming of LabVIEW,only if the temperature measurement engineer knows the basic knowledge of programming, he can design the computer measure and control system. Therefore, this paper starts from the present research state of the temperature auto calibration system both at home and abroad, and puts forward the auto calibration system for industrial thermocouple based on LabVIEW flatform. The specific content involves in the following aspects:1. It analyses the operating principle, calibration, scale mark of the thermocouple and the necessary data handling in the process of the calibration. This offers the theory proof for the auto calibration of the thermocouple for the following part of this paper.2. Through the large-tonnage investigation and research of the producing and developing factories of auto calibration system for the industrial thermocouple, it concludes the most frequently used electrical measuring instruments, and makes the corresponding drivers for them under the LabVIEW flatform so that the users can choose the electrical instrument according to their own situation.3. According to the related requirement of the calibration regulation, design the software of auto calibration system for the industrial thermocouple , including the data acquisition, temperature control, data handling, and the maintaining and printing of the result of calibration.4. During the process of the furnace temperature control, it applies the traditional PID control scheme, fuzzy control and the single nerve unit self-adapting compound control scheme. The paper expounds in detail the rudimentary algorithm of these two control schemes, and programs these two algorithms under the LabVIEW flatform. And eventually put them into use in the calibration, and compare their temperature control effects.5. Use this system to calibrate the K-type thermocouple, then through the analysis of the experiment results to prove the data handling of this software.At the end of paper,the results of the research are summarized for further improvement.