Improved low power consumption two-wire system vortex shedding flowmeter

Improved low power consumption two-wire system vortex shedding flowmeter

  • CN 101,451,864 B
  • Filed: 12/22/2008
  • Issued: 12/26/2012
  • Est. Priority Date: 12/22/2008
  • Status: Active Grant
First Claim
Patent Images

1. improved low-power and two-wire vortex shedding flowmeter comprises piezoelectric sensor, differential charge amplifier, voltage amplifier, programmable amplifier, low-pass filter, voltage follower, BPF. group, the logical selected on-off circuit of band, peak detection circuit, shaping circuit, single-chip microcomputer, man-machine interface circuit, 4~

  • 20mA output and electric power management circuit, constant current source, temperature sensor, pressure transducer, differential amplifier, 16 analog to digital converters;

    It is characterized in that;

    The charge signal of piezoelectric sensor output changes voltage signal into through the differential charge amplifier, because amplitude is very little, so, again through one-level fixing voltage amplifier and one-level programmable amplifier;

    Signal after the amplification is through low-pass filter, and the high frequency interference in the filtered signal is divided into 2 the tunnel then;

    The 1 road signal is exported by voltage follower, and ADC sampling and conversion by single-chip microcomputer carries become digital quantity;

    The FFT that single-chip microcomputer is counted to signal less;

    Through the mode that adopts assembly language programming, uniform data to use that the Q13 fixed-point number is represented, fixed-point number calculates and determine whether according to every grade of operation result size being shifted;

    Guarantee the requirement of the interior amount of precision, real-time and internal memory of algorithm;

    Do power spectrum analysis, obtain the frequency values of signal, come the passage of select tape bandpass filter group;

    The 2 road signal is delivered to the BPF. group, carries out filtering;

    Spectrum analysis result by single-chip microcomputer decides the filtered signal in certain road of output;

    Output signal through the BPF. group is divided into 2 the tunnel;

    The 1 the road delivers to peak detection circuit;

    Peak detection circuit is delivered to the peak value of signal the input end of Chip Microcomputer A C;

    Single-chip microcomputer is sampled to the peak value of signal and is changed, and adjusts the enlargement factor of programmable amplifier according to peak value, makes the amplitude of signal reach optimum range;

    The 2 the road delivers to the shaping circuit of being made up of comparer carries out shaping, and shaping circuit is made up of comparer, has added a threshold, and waveform will surpass threshold value ability trigger pulse, after signal carries out shaping, is output as the square wave of rule, sends into single-chip microcomputer again, counts;

    Signal after the shaping is delivered to the timer input end of single-chip microcomputer, adopts acquisition mode, utilizes multicycle equal precision measurement method;

    Paired pulses is counted;

    It is vortex signal impulse meter TA that timer A promptly is set, and it is filler pulse counter TB that timer B is set, and lets the PWM module TA1 of TA regularly send out the triggering lock-on signal;

    Timing is decided by the lower limit of survey frequency;

    TA and TB catch the number and the filler pulse number of vortex signal pulse respectively according to the time interval of triggering between the lock-on signal for adjacent twice, and the working clock frequency of catching the umber of pulse that obtains and TB according to TA and TB calculates the frequency of vortex signal;

    Single-chip microcomputer is presented at flow information on the LCD according to count results, and passes through the DAC conversion of self, delivers to 4~

    20mA output and electric power management circuit, converts the output of 4~

    20mA current signal to through V/I;

    Said BPF. group is made up of 1 low-pass filter and 7 BPF.s;

    Wherein, low-pass filter is made up of amplifier U6A, capacitor C 17, C22, resistance R 18, R21, R22, R25, decoupling capacitance C24;

    The 1st BPF. is by amplifier U6D, capacitor C 32, C33, C30, resistance R 31, R37, R41, and amplifier U6B, capacitor C 28, C36, resistance R 29, R33, R34, R38 form;

    The 2nd BPF. be by amplifier U7A, capacitor C 42, C43, C40, resistance R 45, R51, R55, decoupling capacitance C26, and amplifier U7B, capacitor C 38, C46, resistance R 43, R47, R48, R52 form;

    The 3rd BPF. is by amplifier U7D, capacitor C 50, C52, C53, resistance R 59, R65, R69, and amplifier U7C, capacitor C 48, C56, resistance R 57, R61, R62, R66 form;

    The 4th BPF. is by amplifier U9A, capacitor C 51, C54, C55, resistance R 60, R68, R70, decoupling capacitance C27, and amplifier U9B, capacitor C 49, C57, resistance R 58, R63, R64, R67 form;

    The 5th BPF. is by amplifier U9D, capacitor C 41, C45, C44, resistance R 46, R54, R56, and amplifier U9C, capacitor C 39, C47, resistance R 44, R49, R50, R53 form;

    The 6th BPF. is by amplifier U8C, capacitor C 31, C34, C35, resistance R 32, R40, R42, and amplifier U8D, capacitor C 29, C37, resistance R 30, R35, R36, R39 form;

    The 7th BPF. is amplifier U8B, capacitor C 19, C20, C21, resistance R 20, R27, R28, and amplifier U8A, capacitor C 18, C23, resistance R 19, R23, R24, R26, decoupling capacitance C25 form;

    The circuit structure of these 7 BPF.s is identical, all is to become with 1 low-pass filter cascaded series with 1 Hi-pass filter, still;

    Parameter is different, thereby passband is different, interconnects again;

    Cover the frequency band range of vortex shedding flow meter, and have certain overlapping between adjacent passband.

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