Electromagnetic flowmeter, as a kind of precision of flow measuring instrument, is through a set of system for each phase of work, should not only consider the hardware factors, also want to evaluate the software part of the work effect and analysis, this article through to the actual needs of users and electromagnetic flowmeter excitation technology at home and abroad, on the basis of analyzing the proposed and implemented with ac excitation as excitation method of electromagnetic flowmeter, HART communication interface, etc.
Especially for the anti-interference performance of the proposed a more ideal solution.
By analyzing the various hardware and software anti-interference measures, the needs of users, using microprocessor (
手臂)
With the digital signal processor (
DSP)
With the combination of high performance and generalization of the cell, with software anti-interference and hardware anti-jamming collaborative method, better to overcome the traditional power frequency ac excitation mode in all kinds of interference, more in humanization, intelligent, ease operation and maintenance convenience features such as the infrared remote control, the WEB server interface, realized the optimization of the design scheme of electromagnetic flowmeter.
1.
Electromagnetic flowmeter scheme selection considering the high-end settlement, accumulated electromagnetic flowmeter in addition to meet the traffic flow, the general function such as atc testing needs, but also have a HART communication, WEB server, and other functions, and meet the needs of the digital filter algorithm, so the core of this system in the electromagnetic
flow meter transducer using ARM + DSP structure, composed of a high performance computing platform.
And as a result of the limitation of communication between dual processor board wiring and general requirements, then select the programmable logic devices, to realize the ARM and DSP serial to parallel communication.
Using ARM + DSP structure can complete a number of parallel tasks and complex algorithm both high-end electromagnetic flowmeter core processing capacity requirements;
Is generally selected on the communication, the traditional general logic devices, such big power consumption, wiring trouble, poor anti-interference, which can realize the combination of logic and temporal logic function is simple, and the complex programmable logic devices (
CPLD)
Can realize complex temporal logic, and function of complex in the pulse of claims, the device itself also has online debugging, the characteristics of strong anti-interference, so on the two ARM and DSP core processor on the communication of complex programmable logic devices become * *.
2.
Electromagnetic flowmeter based on hardware structure design scheme selection of electromagnetic flowmeter, and integrated intelligent electromagnetic flowmeter products at home and abroad, the development trend of integration, networking, hardware system structure as shown.
Hardware system block diagram of the electromagnetic flowmeter hardware subsystem is mainly composed of double CPU module, a programmable logic device module, signal input module, excitation output module, signal output module, HART interface module, the WEB server interface module, display module, debugging interface module, power supply module, etc.
The function of each module is described as follows: the dual core processor module: by ARM processor, DSP processor, Flash, an SRAM, FRAM and related circuit constitute a small system, the hardware platform of software system at the same time.
Programmable logic devices module: using the complex programmable logic devices (
CPLD)
Realize the ARM and DSP serial to parallel communication, and generate 4 -
20 ma output pulse electric current, flow integrating pulse.
Electrode weak signal input module, the sensor output signal and reference signal and the feedback of the excitation signal is amplified and converted to digital quantity, so that into the digital signal processor (
DSP)
Software filtering processing.
Excitation output module: by D/A converter output low-rising values produce excitation signal, and through the power amplifier output to the sensor, the way of excitation signal generated by the DSP control.
Signal output module: 4 - controlled by the program
20 ma current, flow integrating pulse output, analog output circuit is simplified.
HART interface module: ARM UART1 interface as a plate with the HART output interface, in order to achieve and interface of the control system.
WEB server interface module: consists of 10 m Ethernet control chip, in order to implement the remote online user software changes instrument parameters, and other functions.
Display module: by 51 microcontroller, infrared remote control receiver, OLED display screen and buttons, easy operation, observe the flow of information.
Users can through the keys or infrared remote control system parameter setting, and OLED display shows the instantaneous flow and cumulative flow, in order to meet the requirements of different languages at the same time, this system can also display the English interface.
Debugging interface module: is composed of the JTAG interface and ISP interface.
Power supply module: for the entire system to provide a variety of grades of stable and reliable power supply.
3.
Electromagnetic flowmeter software function design software system mainly includes the following modules: signal sampling module, monitoring module, algorithm module, interpersonal interaction module, communication module between the chip and digital filter modules.
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