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滨 州 学 院毕业设计(论文)开题报告题 目基于单片机的粮库温湿度智能检测系统的研究 系 (院)物理与电子科学系 年级 2009级 专 业 电子信息科学与技术 班级 1班 学生姓名 董乃旭 学号 指导教师 李 洁 职称 讲师 滨州学院教务处二一三年三月An Automatic Measuring System Based on Atmospherical Measurement Used for Temperature RelayFor temperature relay, it is very important to measure its temperatures for action and reversion. In this paper, anautomatic measuring system based on atmospherical measurement is discussed, which is very simple andprecise in practical application. In atmospherical measurement, it is crucial to design a favorable temperaturefield. The resistance stove is designed for simulating temperature field. The even temperature is improved bylong-time warm-up and placing orifice-board in testing room. According to the enactment controlling temperature curve, the algorithm of fuzzy control is used to control the temperature in temperature field. The regulating voltage mode of double-direction Bi-directional thyristors is used for controlling temperature. The system consists of the console and the resistance stove,and the console includes software platform and hardware platform. In this system, The method of grouping the resistance wire of resistance stove according to the power is put forward, and the performance of resistance stove is improved based on this method. The measuring precision is improved by using the minimum two-multiplication to calibrate the error. At present, the system has been practically applied in manufacture, which has gained obvious economy benefit and will be widely applied in the future.1. IntroductionThe temperature relay is one of common relays, which takes action when the outside temperature arrives at the given temperature. The temperature relay performs lots of functions, such as temperature control, fire alarm, automatic ignition, wiring heat-protection, so it is widely used in scientific research, industry and defense industry etc. For temperature relay, it is very important to measure its temperatures for action and reversion. But in the current manufacture, the manual measuring methods, such as spot-check method, mercuric thermometer method etc, dominate the measuring methods. However there are some inescapable short comings in these methods, such as low efficiency, large labor intensity and bad precision etc. Thus measurement has become the bottleneck of the quality of temperature relay. With the perpetual progress in the technology, the need for product quality gets more and more strict and the degree in manufacture automatization gets more and more deep. For temperature relay, today the manual measuring methods have become unfitted for the need for manufacture and will be necessarily replaced by the automatic measuring methods. In this paper, an automatic measuring system based on atmospherical measurement is discussed, which is very simple and precise in practical application.2. Measuring principieTwo kinds of metals whose inflated coefficient make a great deal of difference are hard composed together, and then the dishing twin-sheet metal comes into being.When the temperature relay arrives at a certain given value, one upward curving force will come into being in twin-sheet metal as a result of big expanding for nether metal and small expanding for upper metal. When the twin-sheet metal bends at a certain extent, it will drive the electric contact and switch on or switch off the circuit. When the temperature relay reduces at a certain given value, the twin-sheet metal gradually involutes. When the twin-sheet metal resumes at a certain extent, it will 3rd International Symposium on Instrumentation Science and Technology Aug. 1822, 2004, Xian. China drive the electric contact in inverse direction and switch on or switch off the circuit. The working principle of dishing twin-sheet metal is described as Fig1:1-the initiatory state(room temperature), 2-the state after heated or cooled, 3-displacement.The temperature relay takes action due to the rising of ambience temperature or the heating of passing current.The resistance of relay is very small. So compared with the temperature rising caused by ambience temperature, the temperature rising caused by current heating also is very small and can be ignored. Thus measuring temperatures for action and reversion is implemented by controlling the environment temperature. There are three methods for measuring temperatures for action and reversion, which are liquid measurement, atmospherical measurement and testing-block measurement in GJB1517-92.1 Liquid MeasurementIn the constant temperature trough whose temperature can be intercalated, the medium that is water or oil is equably churned up. The measuring method is that the product is placed in the constant temperature trough heated or cooled. Because the liquid is equably churned up, the even temperature, good and the temperature precision is fairly high in which the temperature error is the temperature fluctuating degree is 0.3. Thus the heating coherence of the products that are placed in different position in the constant temperature trough is very good, the measuring precision is very high and the parameter-repeating quality is all right. But this method is just applied in sealed temperature relay and the oil can stain the product. So few manufacturer adopts the method. Only the disputed appears and precise measurement is needed, the method is adopted.2 Atmospherical MeasurementThe electrical oven whose temperature can be intercalated equably churns up the atmosphere. The measuring method is that the product is placed in the electrical oven heated or cooled. In the temperature field, the even temperature that is 2and the temperature precision in which the temperature error is 2 and the temperature fluctuating degree is 1.5are both not good. The heating coherence of the products that are placed in different position in the electrical oven, the measuring precision and the parameter-repeating quality apparently are not as much as liquid measurement. But the method is widely adopted because of simpleness,few pollution and batch.3 Testing-block MeasurementA coppery block with a thermometer whose diameter is6090mm and whose thickness is 2030mm and a set of heating or cooling device make up of the measuring system.The measuring method is that in the room temperature the product is tightly placed on the surface of testing-block that is placed on the heating or cooling device whose temperature can be adjusted, and the temperature characteristic of the product is determined by measuring the temperature of the testing-block. Adjusting temperature of the testing-block is very hard because of measured in the room temperature, thus only a few product can be measured each time and the method unfitsfor volume-produce. But because of its simpleness, it fits for a small quantity of produce.Generally speaking, if the product is sealed and isnt stained by oil, liquid measurement is adopted; if the product is placed in the heating or sealed body, atmospherical measurement is adopted; if the product is placed on the surface of the controlled object in room temperature, testing-block measurement is adopted. In this system, atmospherical measurement is adopted.In atmospherical measurement, the electrical oven is used for simulating the environmental temperature around the temperature relay. So for accomplishing measurement and enhancing precision, it is crucial to design a favorable temperature field. In this system, the resistance stove is designed for simulating temperature field. The performance of the temperature field is greatly improved by the even temperature and by the algorithm for controlling temperature.Because the temperature field takes atmosphere as the diathermanous medium, heat convection has a great effect on the distribution of the temperature field. In course of measuring, the fan is used for strengthening heat convection. But because of heat radiation in the testing room and obstruction from the diathermanous board onthe clamp that doesnt make heated atmosphere swimmingly cycle, the temperature field degressively distributes by height in the vertical, and the temperature grads field comes into being. Thus the temperature asymmetry is inevitable. In this system, two methods are used for improving the even temperature. One is that by long-time warm-up atmosphere in testing room is adequately heated and the temperature grads is reduced.The other is that the orifice-board for making airflow equably flow is placed in testing room, thereby the temperature stability in the section of the measuring point is effectively ensured.In the light of academic analysis and repeating experimentation, the perfect controlling temperature curve of the temperature field is described as Fig 2:TB-the demarcated temperature for action , the parameter which express the decentralization of the temperature for action. Firstly the temperature high-rate rises. When the temperature arrives at the range of the temperature for action, the temperature rises by the slower rate K2 and the temperature for action is measured. When the temperature arrives at the upper limit of the temperature for action, the temperature falls by the slower rate K3 and the temperature is measured. For the resistance stove, lag, inertia and nonlinear are bad and the parameter changes with time. Thus according to the enactment controlling temperature curve, the algorithm of fuzzy control is used to control the temperature in temperature field. So the model of the controlled object can be avoided identifying and Robust is excellent. The regulating voltage mode of double-direction Bi-directional thyristors is used for controlling temperature. Firstly the value and error of the temperature are fuzzied, and then the fuzzy rule from repeating experimentation does fuzzy illation, then through the barycenter method fuzzy estimate calculates the accurate value, at last after D/A transform the accurate value controls the Bi-directional thyristors by regulating voltage, so temperature risingOr falling of the resistance stove can be controlled.3. Automatic measuring systemAutomatically controlled by the computer, the temperature of the resistance stove reposefully rises from the lower limit of the temperature for action. When the relay takes action, the temperature for action is displayed and the arraignment appears, then the computer automatically controls the temperature reposefully falling. When the relay reverts, the temperature for reversion is also displayed and the arraignment appears, thereby an integrated measuring process ends.Based on Windows2000 operating system, the software developed by Microsoft Visual Basic 6.0 makes up of measuring module, user interface and database of measuring result. As control core of the measuring system, the measuring module automatically controls temperature rising or falling of the resistance stove, real-time acquires the temperature signal and the switch signal of the temperature relay, measures and records temperatures for action and reversion, alarms beyond the temperature range etc. The user interface consists of command button and menu, real-time temperature curve and the windows that real-time display measuring state and real-time modify parameters, which offers the user a friendly man-machine interface. forms for the future analysis and estimate. Thus the database of measuring result is created, which effectively performs the functions of data backup and printing recordation. Furthermore, some accessorial programs are designed, such as hardware exception handles, real-time modify parameters program, upgrade program etc, which effectively enhance reliability and maintainability of the system.In this system, two methods are adopted aiming at some technical difficulty in measuring process, which obviously enhance the holistic quality.1 The method of grouping the resistance wire of resistance stove according to the powerThe three-phase SSR electric power regulator indirectly regulates heating power through regulating switching on and off time of the resistance wire, thereby controls temperature rising or falling of the resistance stove. But the regulative extent of high-power stove wire is so wide that it is very difficult to accurately control the rate of rising or falling. For enhancing regulative sensitivity, lower-power stove wire should be adopted. However because the system comes down to more than twenty products and the measuring upper limit arrives at 600, the low-power stove wire cannot heat to such a high temperature. Facing to this problem, the method ofgrouping the resistance wire of resistance stove according to the power is put forward, which is that the low-power stove wire is applied in low temperature and the high-power stove wire is applied in high temperature. It is practically proved that the method effectively solves above problem and improves the quality of resistance stove.2 The holistic minimum two-mu

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