Research And Development, Based On The Hart Bus Intelligent Vortex Flow Meter

Field bus, make relationships between the process control devices and even the high control management network, as a communication network among intelligent instruments in the field of process control automation, manufacturing automation. As HART field bus proposals a solution superimposing the digital signal at the present field control system without risk, the intelligent instruments based on HART technique are widely used.With the development and appliance of the Digital Signal Processing, its high speed and powerful faculty of processing of data are recognized by people. It is a trend to use Digital Signal Processing for a real-time supervisory control and data analysis. The Digital Signal Processing has unexampled predominance in improving reliability, and realizing more complex and more exact control.The intelligent Vortex Flowmeter based on HART field bus, which is introduced in the paper measures the Vortex frequency made from flow signal, combining with the project of ChangSha mining research institute.The intelligent Vortex Flowmeter makes use of powerful processor faculty and abundant module of the newly Ultralow-power consumption Mixed Signal Microcontroller(MSP430fl49) in accord with the technological criterion of HART communication protocol, solving the most difficult technological problem only with device in hardware.The traditional Vortex Flowmeter counts the pulse signals produced by Schmitt trigger that is proportional to Vortex frequency, but the door Voltage that can give rise to trigger not only restrains the noise but also limits the low limitation of the Flowmeter. The intelligent Vortex Flowmeter introduced in this paper expands the low limitation through hardware combining with software.It is proved by the theory of Vortex signal that Vortex frequency is proportional to liquid speed and the amplitude of signal is proportional to the square of liquid speed. The signal amplitude is quite different in the different period.The project of the Vortex Flowmeter adds Transconductance amplifier in the input circuit,and adjusts Transconductance amplifier's amplifier coefficients realizing the automatic gain control function through PWM signal with feedback.hi addition, the software method traces the frequency of Vortex signal through the adaptive notch filter algorithm, the character of the adaptive notch filter algorithm can be described as below: it is of recursive prediction error(RPE)form and uses a special constrained model(etc. constrained poles and zeros) of infinite impulse response(IIR) with anumber of parameters; The convergent filter is characterized by highly narrow bandwidth and uniform notches of desired shape ;The filter has a transfer function that is 1 almost everywhere but at the site of notch frequency.Through emulation it has a good character of anti-intrusion, and it not only improves the precision but also expends the limitation of Flowmeter. It is applicable to gas,vapor and liquid and it has more performance than cost.