1、附录 A Research on pulse output model digital vortex flow meters The vortex flow meter is widely used in different fields due to its flexibility to various media, non-mobile parts, simple structure and long life etc. However, it has poor performance when operating at low flow rate where the Signal-to-
2、Noise ratio is very small or even the signal is submerged by the noise. The traditional analog vortex flow meter has benefits of steady signal, high accuracy and good real time in the regular flow range, while it also has a disadvantage of weak signal difficult to detect at low flow rate, which lead
3、s to unsatisfying lower limit and a smaller range ratio of 10:1. Based on the previous efforts a pulse output model digital vortex flow meter is developed successfully, which inherits the advantages of the analog one and make up its shortage mentioned above. The digital vortex flow meter with its do
4、uble-core structure that means a couple of CPUs made up of DSP and MSP430 identifies the vortex signals from noises by the frequency spectrum analyzing algorithm in DSP at low flow rate where the analog one is not accurate, or even cant work. Meanwhile it works out by its microcontroller MSP430 the
5、frequency of the vortex signal that is square waves output from pre-amplifier for the vortex signals in the regular flow range where the Signal-to-Noise ratio isnt too much small and the analog one is accurate and real time. This dissertation consists of theory, hardware/software design and experime
6、nt. The main point includes: 1.The scheme called double-channel work model of the pulse output model digital vortex flow meter is designed. The principle is a switch of two different methods to detect the vortex signal. That is using spectrum analysis of digital signal at low flow rate and frequency
7、 counting like analog vortex flow meters in the regular flow range. The critical criterion of the switch point is the uncertainty of the frequency. 2.A pulse output model digital vortex flow meter is developed successfully. The flow meter is studied respectively at DN25 and DN50 pipelines of the wat
8、er flow experiment facility and DN50 and DN100 pipelines of the gas flow experiment facility that locate at Process Detect & Control Laboratory in Tianjin University. And the data shows that the digital flow meter has the property of a better lower limit than the analog one and a bigger range ratio
9、of 1:28.5 41.3. Masses of experiments on the digital vortex flow meter have been carried out at the water flow experiment facility and the gas flow experiment facility of Tianjin University respectively. The result shows that the pulse output model digital vortex flow meter has a satisfying lower li
10、mit that increases the range ratio effectively, strong ability and good real time and thus it is of great practicability. The 21st century is the century information, information and materials and new technology as the main pillar of society from the human revolution is industrialization era to info
11、rmation era, as the perception, acquisition, conversion, processing and transmission of information technology and the indispensable testing instrument, has become an important technology and computer equivalent and daily life and production of all fields. Along with the rapid development of science
12、 and technology, industrial production get continuous development, the detection technology and puts forward many new requirements, and new technology and instrument appearance and further promote the development of science and technology, the development degree of detecting technology has decided t
13、o science and technology level, in other words detection techniques and instruments is the measure of modern science and technology level of a mark. This one, as testing technology is an important part of flow metering with national economic and national defense, science and technology, the close re
14、lationship in economic development plays an important position. After continuous efforts, and technical workers have developed pyretic and various characteristics of flow meter. According to the measuring method and the structure of the classification method, will be divided into differential pressu
15、re meter flowmeter, volumetric flowmeter, fluid flow, ultrasonic vibration flowmeter, mass flowmeter, insert flowmeter open-channel flow and other flowmeter, 11 kinds . The research of the vortex flowmeter belongs to the hydrodynamic vibration flowmeter are widely used . Vortex flowmeter is accordin
16、g to the fluid velocity of vibration frequency and the corresponding principle of work. As early as in 1878 straw Strophe published about fluid velocity relationship with the vibration frequency, straw, vortex frequency is said to stop features of similar size and the velocity of the relationship. P
17、eople in the early vortex research mainly is the purpose of prevention. Vortex flow vibration phenomenon for measuring the study began in the 1950s, such as wind meter and ship speed gauge etc, at the end of the 1960s began to develop close pipeline flow - vortex flowmeter. 1970s and 1980s vortex fl
18、owmeter unusually quick development, development outstanding type resistance fluid and detection methods of vortex flowmeter, and mass production, such as the market in just a few short years time to arrive from laboratory batch production process of the sample flow is unique. Vortex flowmeter is a
19、fluid vibration flowmeter, set in the fluid flow vortex happened (resistance from vortex happen) alternately on both sides of the body produces regular vortex, the spiral called Carmen vortex, swirling in spiral happen asymmetrical body downstream, vortex flowmeter is arranged by measuring the vorte
20、x frequency and realization of flow measurement. Vortex flowmeter by sensors and switches two parts. Sensors (including vortex flow resistance occurs, components, instrument) such as table, converter including pre-amplifier, filtering plastic circuit, D/A transformation circuit, output interface cir
21、cuit, terminals, bracket and shields, etc. In recent years, intelligent flowmeter is the microprocessor, communications and other functions that are installed in converter module. According to the detection means, vortex flowmeter stress can be divided, capacitive and thermal type, type of ultrasoni
22、c vibration, strain, and photoelectric and fiber, etc. Among them, stress (also called the piezoelectric) vortex flowmeter with its fast response and strong signal, working temperature range wide, strong adaptability and high reliability etc, has become the main products vortex flowmeter type. This
23、vortex flowmeter, it is to test the lift in form stress testing devices, piezoelectric conversion variable charge signal, clinch a deal the charge amplifier, filtering, plastic after vortex signal. Piezoelectric sensor signals, fast response and low cost, manufacturing process, but is more sensitive
24、 to vibration. As mentioned, vortex flowmeter has many advantages, and there are many problems to be solved, especially in the measurement of small flow, vortex useful signal is very weak, yi was drowned, low noise signal under the velocity measurement caused great difficulties. In order to solve th
25、is problem, the domestic and overseas scholars and scientific research institutions in research and application of various solutions, namely of digital signal processing method to solve, but most just stay in the research on the method of high efficiency, and not be applied algorithm support for pro
26、duction. At present, the domestic production of the vortex flowmeter is limited to the analog circuit application method of vortex signal processing (called simulation vortex flowmeter), this can not solve the low SNR, leading to lower the problem than only achieve high, range 1:1 scale theory, far
27、below zero. Foreign company, Yokogawa only Rosemount and ABB has developed the application of digital signal processing methods of signal processing vortex, namely digital vortex flowmeter, but specific technology is not open. In recent years, the vortex signal processing methods about the study man
28、y (such as wavelet method of adaptive LMS changes, etc), the algorithm of tianjin university professor zhang tao presided over the research of vortex sensor output signal for exploration of digital signal processing won great progress. Ling Qing master according to the signal features and vortex of
29、signal processing method, the requirements for maximum likelihood estimation results in cycle chart are put forward on the basis of more suitable for relaxation of the vortex frequency estimation method of graph, commit cycle and the simulation experiments. This method with high resolution and high
30、frequency characteristics of the calculation efficiency, strong resistance to complex noise interference ability. WuPeng master based on wavelet transform, deposing principle of flow measurement specific requirements, and puts forward a suitable vortex flow sensor signal processing methods of single
31、 reconstruction filter is given, and the method of selecting, filter series of this method can effectively expand vortex flow sensor range. However, due to the above two methods, the complexity of algorithm, real-time computation is not guaranteed, and applied in practice. Along with the Digital Sig
32、nal Processor Digital Signal processing (DSP) technology, referred to the rapid development and wide application, make complex Signal processing algorithm can achieve in hardware. DuanRuiFeng master a set of DSP and MSP430 microcontroller combination of the vortex digital signal processing system, using slack trapped cycle graph method for calculating the vortex flowmeter signal frequency. Experimental results show that the vortex flow dual-core digital
