Domestic unsolved problems of the intelligent meter instrument: flowmeter are susceptible to interference, external vibration and the vibration of the industrial field is widespread;
Limited range lower limit, cannot be accurately measure low flow rate, small flow rate.
When traffic hours, the sensor output signal is weak, easy to submerged by noise.
So adopt the method of digital signal processing (DSP) to solve these problems appeared in the low velocity signal from strong noise, thus expand smart meters range limit.
In order to achieve the accurate measurement of low flow velocity signal, using more powerful FPGA chip to play better effect of digital processing method to improve detection precision.
1.
Digital
vortex flowmeter hardware structure design of hardware mainly is: the vortex signal processing circuit, liquid crystal display circuit, keyboard control circuit and the FPGA algorithm processing module.
The block diagram as shown in figure 1.
1.
1 choose TI microprocessor MSP430 series MCU, is a kind of with ultra-low power consumption of the powerful microcontroller.
Working current depending on working mode is 0.
1μ
A -
280μ
A, the voltage of 1.
8 v to 3.
6V。
MSP430F149 has rich on-chip outside moulding piece, the precision of built-in 12 AD conversion module, precision analog comparator, multiplier, etc of the more important interface to the hardware module, this can save the outside of the CPU module, ask when improving the efficiency of code execution.
In the digital occupies a very important position in the
vortex flow meter.
1.
2 analog signal processing module is coming from the vortex street sensor alternating voltage signal, and ten contains A lot of noise and vibration, so be through specific circuit into A microprocessor to identify the voltage signal, then the results by the A/D conversion circuit into the CPU.
Vortex signal processing circuit including signal amplifying circuit and filter circuit.
Coming from the vortex street sensor is relatively weak alternating voltage signal, this signal is not easy to obtain and microprocessor processing, so it should pass before entering the CPU signal conditioning circuit to form A certain rule, must have the strength of the signal, and then by the A/D conversion circuit analog voltage into A signal into A digital signal to digital signal processing.
As shown in figure 2, the Vi is an alternating voltage signal, which range from 0 to 1 v.
2 v, phase signals from 0 to 180 degrees.
In view of the A/D conversion circuit of MSP430 cannot be negative voltage conversion, when making signal amplification and A reference voltage, Vref to do so after the signal amplification in V, suitable for the requirements of the AD conversion circuit.
Amplifier A1 is mainly for signal amplification, magnification of 100, and A2 in the second-level amplification and low-pass filtering, including the role of C3 and C4 is to filter, filter the part of the high frequency interference signals.
Through the signal amplification and filtering processing, Vo becomes relatively good signal, can be used for analysis of microprocessor.
Vo of the quality of the signal and velocity signal frequency is proportional to the signal frequency is higher, the quality of the Vo, the better.
1.
3 keyboard display the function of the keyboard module mainly through the keyboard monitor complete display, environmental impact and initialization parameter Settings, etc.
The keyboard USES the noncoding keyboard.
Keyboard employs four keys: set the national health, incremental, shift and environmental interference detection ten keys.
Before a key in the form of a key multi-purpose complete display content selection, parameter setting function, keys are used to determine the environmental interference in real-time interference caused by external vibration frequency.
Keyboard circuit adopts resistance on the falling edge, the interrupt way to connect and CPU, achieve response keyboard control procedures.
However, due to adopt non coding keyboard and dragon hardware & other;
Eliminate shake & throughout;
Circuit, so that need in the software & other;
To shake & throughout;
。
The effect of liquid crystal display module mainly display of measured data, the parameter of the measured medium state of displaying and parameter Settings.
LCD display content of JianShi is determined by the state of the keyboard, the display, LCD display frequency, flow, medium temperature, pressure, etc. ;
In the parameter setting state, display and parameter about content, setting, etc.
2.
The FPGA algorithm processing module adopts ACEX1K device EPIK50TC144 series of Altera company as the FPGA realization of cross-correlation algorithm.
EPIK50TC144 device has the following features: 1.
High performance.
Can be on a single chip to implement low power design, device integration within the enhanced embedded array blocks (
EAB)
, such as high speed memory can be realized and Mega functions of specific logic.
2.
High density.
Series ACEX1K device contains logical unit (
莱斯)
From 576 to 4992.
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mass flow meter, please feel free to contact us.
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