The Research On The Non-Magnetic Calorimeter Based On Wireless Sensor Networks

With the development of Chinese economic and the improvement of people's living standards, the demand for heat supply have been changed from a single family units in the past to the whole community today, and the concept of central heating, no matter from strengthening social harmony or from the perspective of environmental protection and energy conservation has the value of promoting. In fact, the energy is a kind of commodity. The traditional method to share the heating costs in collective should be improved. Therefore implementing the reform of heat metering system is of practical significance. It will greatly improve the utilization of energy resources and reduce waste.Currently, the development of Calorimeter technology is slow relatively, and the quality of water is not satisfactory in our country. These objective circumstances and specific conditions restrict the market expansion of Calorimeter. Based on the technique of Wireless Sensor Network, a no-magnetic-calorimeter's remote wireless communication is researched deeply in this paper. And a complete solution of reducing power consumption and wireless transmission is provided. The paper details in the establishment of the mathematical model, the hardware circuit design, and the realization of software. This design of the calorimeter in the paper used a inductive non-magnetic flow sensor can be applied to the areas with poor water quality. This design applies an ultra-low power consumption MCU and ultra-low power consumption wireless transceiver modules to achieve the low power design target. Using of wireless sensor network technology considering every calorimeter in a district as a node to form wireless sensor network for data transmission, remote wireless meter reading has be achieved. The design of non-magnetic calorimeter and the application of wireless sensor network technology to achieve the wireless meter-reading in this paper have some reference value to the products development of the related fields, such as the Home Networking.Firstly, Calorimeter signal acquisition circuit completes to get the temperature signal and the flow signal of water in the pipeline. And the temperature acquisition circuit uses the PT1000 as the temperature sensor. By the analog multiplexer 74HC4052 and the precision resistors, we can ensure the relative accuracy of data collection. For the power, I use a transistor to control to"put on"the temperature acquisition circuit. The circuit's structure is very simple, but it can reach the corresponding measurement requirements quite well. The flow acquisition circuit is based on non-magnetic flow sensor, in the absence of magnetic. The base meter can avoid issues such as degaussing, attracting scale magnetic substances which may bring to be plugged. The circuit design needs precise parameters. The main idea is that when the inductance in the non-magnetic sensor and the capacitance in the circuit begin to vibrate, the pulse oscillation circuit begins to charge for the capacitance. Because the metal which occupy half of the impeller need to cost a part of energy consumption, its attenuation wave will be changed with the impeller rotating and the two different waves correspond to two states, which can calibrate the impeller different locations. So this method completes the flow's pulse counting function. Therefore, the whole process is that when there are water flowing through the base meter, the impeller will rotate and its speed is proportional to the average flow speed in the pipeline, then the metal on the impeller will be driven to rotate, and its rotation makes the metal sheet and the non-metal sheet on the impeller close to the oscillating coil periodically, this will influence the coil's oscillation frequency because of the role of eddy current. Then through the flow detection interface circuit, two different frequency waveforms will be sent to the MCU.Secondly, the Calorimeter's core information processing unit is based on the ultra-low power MCU MSP430F149,this set of MCU have ultra-low power consumption, variety of on-chip peripheral modules, so they have been widely applied. The MCU mainly complete temperature and flow's information collection, data processing and data storage correction. Taking power requirements into consideration, I need to design the signal acquisition circuit's timing strobe. In consideration of the sub-Table of PT1000 is too large, it will take up too much system storage resource if I take this approach directly. To meet the basic accuracy requirements, I use the Lagrangian interpolation methods to deal with the numerical information to finish the temperature's software calibration. This makes the data collected in the processing speed and data accuracy are both balanced. Because the impeller flow meter counts the flow of water through the impeller rotation, whereas the impeller itself will have certain mechanical error, according to the calorimeter industry standard, when the flow speed is different, the impeller's flow value is different. Thus I need to calibrate the flow value, to make sure the accuracy of flow measurement. In the paper we can use different points of the flow to finish the appropriate calibration. Then we can store the data in Flash corresponding regional for prepare for the follow-up comparison and the transmission processing.Thirdly, Calorimeter's wireless module uses the chip CC2420 which is based on the WSN. The main design idea is that a large number of wireless sensor nodes through wireless communication become a multi-hop and self-organizing network. In the paper, I image the individual household heat meters in a district as a wireless transceiver node. Through experiments prove, Two nodes are near maximum communication rate 250kb/s, the communications distance in the maximum power is about 100 m, it can pass through two walls at most. After the installation, the node locations have been fixed, and two adjacent nodes can not pass through many layers wall. So we can consider the location-based routing GEM. In the paper I mainly focus on the two nodes'communication and have completed the MSP430F149 and CC2420's transmission between the SPI Bus. Through four lines of communication and control of the four lines, I can complete the operation of the CC2420's internal registers and the control of wireless data transceiver. At the same time, I design the specific data frame format about the Calorimeter value which need to transmit to ensure all information send accurately and effectively. As the wireless sensor network has low rates, low power, low cost, flexible self-configuration, network topology, and other notable feature. Therefore the calorimeter transfer through WSN should have some practical value.Finally, in the paper, there are many problems inevitably, for example, the"put on"time of each circuit is based on their respective power consumption, only in this way can allow battery to maximize the use of life. Flow sensor is the core of the calorimeter; it may have to choose according to the actual occasion, water quality, cost, technical aspects for consideration. Due to the advancement of technology, perhaps there will be more effective and economic flow sensor. On the CC2420 operation, paper only mentions the simple communication of two nodes, not specific to the senior operations on ZigBee protocol stack layers, such as the Routing Protocol, encryption and decryption in the net layer. Future, I could start corresponding researches in these fields. In addition, I might transplant the operating system TinyOS to the CC2420, it could play the real value in areas such as power consumption and network. Of course, all the above there are large space and design value, So we will wait for further products'R & D work.