CN101619992A - Weak signal extraction system for fluidic flowmeter based on related amplification technology and method - Google Patents
Weak signal extraction system for fluidic flowmeter based on related amplification technology and method Download PDFInfo
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Abstract
The invention discloses a weak signal extraction system for a fluidic flowmeter based on a related amplification technology and a method. The system adopts the related amplification technology as a signal processing mode of the fluidic flowmeter. A flow choking part is installed in a measuring tube; a first electrode, a third electrode and a second electrode are respectively installed at the front side and the back side of the flow choking part; a U-shaped excitation structure is installed on the measuring tube and can carry out excitation control by being connected with an excitation drive circuit; the second electrode is connected with the ground end of a related amplification circuit through a wire; the first electrode and the third electrode are connected to a differential amplification input end of the related amplification circuit; the output end of the related amplification circuit is respectively connected with an AD conversion circuit and a singlechip circuit, and the AD conversion circuit is connected to the singlechip circuit; and the singlechip circuit also fulfills the functions of LCD display and the like. By adopting the method, the fluidic flowmeter has the advantages of lower limit, wide measurement range, high accuracy, and the like.
Description
Technical field
The present invention relates to the input field of fluidic flowmeter, relate in particular to a kind of Weak signal extraction system for fluidic flowmeter and method based on related amplification technology
Background technology
Current global scarcity along with the energy and water resource, the startup of priority projects such as national project of South-to-North water diversion, the whole society is more and more higher to the requirement of water metering.Mechanical water meter has at home and abroad obtained using widely with advantages such as its price simple in structure are low, and mechanical water meter exists transmission resistance, mechanical movable part to cause its precision higher than less trouble.And fluidic flowmeter does not almost have crushing, non mechanical movable, and the reliability height, the fluidic flowmeter measurement lower limit is low simultaneously, but signal is easy to be subjected to external interference when hanging down flow velocity.
Existing fluidic flowmeter generally adopts the difference amplifying technique to extract signal, and the advantage that adopts this method is that the feeble signal amplifying power is strong; Shortcoming is easily power frequency component to be amplified out in air the time, causes the metering of flow mistake easily.And adopting the jet flow of related amplification technology to divide amplifying technique better signal amplification performance in respect of ratio, the lower limit performance is better, also can suppress the industrial frequency noise interference when being placed in the air and prevent the mistake metering.
Summary of the invention
The present invention is directed to the deficiency of existing flow detection technology, a kind of Weak signal extraction system for fluidic flowmeter and method based on related amplification technology is provided, make fluidic flowmeter have characteristics such as lower limit is low, accurate measurement, broad quantum.
The objective of the invention is to be achieved through the following technical solutions:
A kind of Weak signal extraction system for fluidic flowmeter based on related amplification technology, it comprises jet base table, flow detection circuit and U type excitation structure.Described jet base table comprises first electrode, second electrode, third electrode, choked flow piece, feedback channel and measuring tube; First electrode, second electrode, third electrode and choked flow piece are installed in the measuring tube, and first electrode and third electrode are in choked flow piece one side, and second electrode is at the choked flow piece opposite side.The flow detection circuit comprises single-chip microcomputer, relevant amplifying circuit, A/D convertor circuit, excitation driving circuit and LCD display, single-chip microcomputer links to each other with LCD display with relevant amplifying circuit, A/D convertor circuit, excitation driving circuit respectively, the excitation driving circuit links to each other with U type excitation structure, first electrode of jet base table, second electrode, third electrode link to each other with relevant amplifying circuit, and relevant amplifying circuit links to each other with A/D convertor circuit.
A kind of fluidic flowmeter feeble signal extracting method of using above-mentioned Weak signal extraction system for fluidic flowmeter is characterized in that, may further comprise the steps:
(1) Single-chip Controlling excitation driving circuit produces required excitation field.
(2) electrode acquired signal is with the relevant amplifying circuit of signal input.
(3) relevant amplifying circuit amplifies back input A/D convertor circuit with electrode signal.
(4) A/D convertor circuit carries out analog to digital conversion to the electrode signal that amplifies, and sends into single-chip microcomputer, and single-chip microcomputer obtains flow signal according to the numerical value that analog to digital conversion obtains, and carries out LCD simultaneously and shows.
The invention has the beneficial effects as follows:
1. the present invention is applied in related amplification technology on the fluidic flowmeter flow detection, has characteristics such as measurement lower limit is low, accurate measurement, broad quantum;
2. adopt electromechanical detection method to have characteristics such as the pipe vibration of preventing, fluid oscillation, electromagnetic radiation;
3. adopt related amplification technology can effectively suppress industrial frequency noise and disturb, when water hangs down flow velocity, can bigger gain amplify, good measuring water flow lower limit performance is arranged.
Description of drawings
Fig. 1 is the synoptic diagram of jet base table and U type excitation structure;
Fig. 2 is an electrical block diagram of the present invention;
Fig. 3 is an interface microcontroller circuit diagram of the present invention;
Fig. 4 is a relevant amplification circuit structure synoptic diagram of the present invention;
Fig. 5 is excitation driving circuit figure of the present invention;
Fig. 6 is A/D convertor circuit figure of the present invention;
Among the figure, 1, first electrode, 2, second electrode, 3, third electrode, 4, choked flow piece, 5, feedback channel, 6, measuring tube, 7, U type excitation structure.
Embodiment
Describe the present invention below with reference to the accompanying drawings in detail, it is more obvious that purpose of the present invention and effect will become.
The Weak signal extraction system for fluidic flowmeter that the present invention is based on related amplification technology comprises jet base table, flow detection circuit and U type excitation structure.
As shown in Figure 1, jet base table structure and U type excitation structure synoptic diagram have been provided among the figure.The jet base table comprises first electrode 1, second electrode 2, third electrode 3, choked flow piece 4, feedback channel 5 and measuring tube 6.First electrode 1, second electrode 2, third electrode 3 and choked flow piece 4 are installed in the measuring tube 6, first electrode 1, second electrode 2 and third electrode 3 all with the insulation of the tube wall of measuring tube 6, first electrode 1 and third electrode 3 are installed in choked flow piece 4 one sides, and second electrode 2 is installed in choked flow piece 4 opposite sides.U type excitation structure 7 constitutes by coiling outside magnetic core, is installed in the by-pass port of jet base table side, produces AC magnetic field near three electrodes.
As shown in Figure 2, provided the one-piece construction synoptic diagram of exciting part and flow detection circuit among the figure.The flow detection circuit comprises single-chip microcomputer, relevant amplifying circuit, A/D convertor circuit, excitation driving circuit and LCD display, single-chip microcomputer links to each other with LCD display with relevant amplifying circuit, A/D convertor circuit, excitation driving circuit respectively, and the excitation driving circuit links to each other with U type excitation structure in order to produce alternating magnetic fields.First electrode 1 of jet base table, second electrode 2, third electrode 3 link to each other with relevant amplifying circuit, and relevant amplifying circuit links to each other with A/D convertor circuit.
As shown in Figure 3, single-chip microcomputer of the present invention can adopt the MSP430F4XX series monolithic of American TI Company, but is not limited thereto.Be example with MSP430F436 below, the realization of micropower circuit is described.In cmos device, power consumption P is directly proportional with system clock frequency f, P ∝ V
2F, wherein V is a supply voltage.The operating voltage of general single-chip microcomputer is constant, so will reduce system clock frequency f as much as possible.Therefore, MSP430F436 only meets low frequency crystal oscillator LFXT1=32.768KHz, does not meet high frequency crystal oscillator XT2.When MSP430F436 needed high-speed cruising, the FLL+ by MSP430F436 provided the radio frequency system clock.The BP0 of MSP430F436, BP1, BP2, BP3, S0, S1, S2 ..., the S25 power consumption that links to each other with segment code type liquid crystal LCD display only needs several uA, the OPEN of MSP430F436, CLOSE link to each other with the excitation driving circuit, REF2, REF1 pin link to each other with relevant amplifying circuit, and DIN, DOUT, DRDY, SCLK, CS, RESET pin link to each other with A/D convertor circuit.
As shown in Figure 4, provided the structural representation block diagram of relevant amplifying circuit among the figure.The relevant amplifying circuit that uses among the present invention comprises differential amplifier circuit, bandwidth-limited circuit, in-phase amplification circuit, first multiplier circuit, second multiplier circuit, first low-pass filter circuit, second low-pass filter circuit, differential amplifier circuit, bandwidth-limited circuit, in-phase amplification circuit link to each other successively, in-phase amplification circuit links to each other with second multiplier circuit with first multiplier circuit respectively, first low-pass filter circuit links to each other with first multiplier circuit, and second low-pass filter circuit links to each other with second multiplier circuit.
Differential amplifier circuit can select the ICL7650 chip to build, bandwidth-limited circuit can select the MAX268 chip to build, in-phase amplification circuit can select the ICL7650 chip to build, multiplier circuit can select the AD630 chip to build, low-pass filter circuit can select the MAX291 chip to build, but is not limited thereto.Single-chip microcomputer provides two-way reference signal REF1, REF2 respectively for first multiplier circuit, second multiplier circuit, and this two-way reference signal all adopts the square-wave signal with the excitation signal same frequency, and two paths of signals REF1, REF2 differ 90 ° on phase place.The output signal AN1 of low-pass filter, AN2 links to each other with A/D convertor circuit.
The signal that electrode obtains is: when water flows through jet stream water meter, produce the current of cyclical variation (frequency is f) near the water meter electrode, simultaneously owing to produce the magnetic field of cyclical variation (frequency is F) by field circuit.By conductive fluid kinetic property E=BLV in magnetic field, excitation field frequency F comparative electrode ambient water change frequency f is a high frequency, the useful signal that electrode obtains promptly be equivalent to frequency just be the signal of f through ovennodulation, and this useful signal is faint, is submerged in the big noise.
The principle of relevant amplifying circuit is: the signal that differential amplifier circuit can obtain electrode carries out difference and amplifies, first electrode of cancellation simultaneously, the common noise signal of third electrode.Bandwidth-limited circuit can carry out further filtering to noise signal and strengthen signal to noise ratio (S/N ratio).Carrying out in-phase amplification circuit again can further amplify signal, further carries out multiplier and low-pass filter and can obtain useful signal and can carry out filtering to greatest extent to noise signal.The benefit of taking two-way multiplier and low-pass filter is the integrality that can guarantee one of them road signal, prevents that reference signal and useful signal phase differential from bringing the situation that might detect less than signal for 90 °.
As shown in Figure 5, the excitation driving circuit comprises 2 PNP triode Q4, Q5,4 NPN triode Q6, Q7, Q8, Q9,6 resistance R 35, R36, R37, R38, R39, R40, two capacitor C 12, C13.The annexation of excitation driving circuit is: an end of resistance R 38 and resistance R 39 is connected to two pin OPEN, CLOSE of single-chip microcomputer, the other end of R39 links to each other with the base stage of capacitor C 12, triode Q7, the other end of R38 links to each other with the base stage of capacitor C 13, triode Q4, the other end ground connection of capacitor C 12 and capacitor C 13.The collector of triode Q7 links to each other with base stage, the resistance R 35 of triode Q5, the collector of triode Q6 links to each other with base stage, the resistance R 36 of triode Q4, the emission collection of the other end, Q4 and the Q5 of resistance R 35 and resistance R 36 links to each other with power supply VCC, the collector of triode Q4 links to each other with the collector of triode Q9, the collector of triode Q5 links to each other with the collector of triode Q8, the collector of triode Q5 links to each other with the MOTER+ pin, the collector of triode Q4 links to each other with the MOTER-pin, and MOTER+, MOTER-pin link to each other with field coil and be used for controlling magnetic field.The base stage of triode Q8 links to each other with emitter, the resistance R 41 of triode Q6, and the base stage of triode Q9 links to each other the other end ground connection of the emitter of the emitter of triode Q9 and triode Q8, resistance R 40 and resistance R 41 with emitter, the resistance R 40 of triode Q7.
As shown in Figure 6, A/D convertor circuit comprises an AD conversion chip U10, a datum chip U11,7 capacitor C 1, C2, C3, C4, C5, C6, C7, a crystal oscillator OSC, the AD conversion chip can be selected the MAX7705 chip of MAXIM company, and the datum chip can be selected the MAX6002 chip of MAXIM company.The annexation of A/D convertor circuit is: pin DIN, DOUT, DRDY, RESET, CS and the SCLK of AD conversion chip U10 link to each other with single-chip microcomputer, and AN1 links to each other with relevant amplifying circuit with AN2.C1, C2, C3, C4, C5, C6, C7 are filter capacitor, power supply VCC gives AD conversion chip U10 and reference voltage chip U11 power supply, the datum output terminal OUT of U11 links to each other with AD conversion chip REF end, at AD conversion chip CLKI and CLKO termination crystal oscillator OSC, the OSC two ends connect an end of capacitor C 1 and capacitor C 4 respectively, the other end ground connection of capacitor C 1 and capacitor C 4.
Fluidic flowmeter feeble signal extracting method based on related amplification technology of the present invention comprises the steps:
1. Single-chip Controlling excitation driving circuit produces required excitation field
As shown in Figure 5, single-chip microcomputer links to each other with the excitation driving circuit by OPEN, CLOSE pin, and the output pin MOTOR+ of excitation driving circuit, MOTOR-pin link to each other with U type excitation structure as shown in Figure 1.OPEN, CLOSE pin by control single chip computer produce square-wave signal, can obtain the excitation field with the square-wave signal same frequency.
2. the electrode acquired signal is imported relevant amplifying circuit with signal
By three electrodes are installed on the jet base table, wherein first electrode, third electrode are the signals collecting end, and second electrode is with reference to the ground end.As shown in Figure 4, first electrode, third electrode are wired to the difference of relevant amplifying circuit prime differential amplifier circuit and amplify input end, and second electrode is connected to the ground end of relevant amplifying circuit.
3. relevant amplifying circuit magnifying electrode signal
Relevant amplifying circuit amplifies electrode signal earlier through difference, difference is amplified the signal that obtains carry out bandpass filtering, and bandpass filtering can improve signal to noise ratio (S/N ratio).The signal that bandpass filtering is obtained carries out the homophase amplification then, the homophase amplifying signal is sent into multiplier 1, multiplier 2, wherein multiplier 1 amplifies the signal multiplication that obtains with single-chip microcomputer reference signal REF1 and homophase, multiplier 2 amplifies the signal multiplication that obtains with single-chip microcomputer reference signal REF2 and homophase, the signal of two-way multiplier output links to each other with the two-way low-pass filter respectively, and the circuit of process multiplier and low-pass filter is equivalent to carry out secondary filtering and can further improve signal to noise ratio (S/N ratio).Relevant at last amplifying circuit obtains two-way amplifying signal AN1, AN2.
4.AD change-over circuit carries out analog to digital conversion to the electrode signal that amplifies, and sends into single-chip microcomputer, single-chip microcomputer obtains flow signal according to the numerical value that analog to digital conversion obtains, and carries out LCD simultaneously and shows.
As shown in Figure 6, two-way amplifying signal AN1, the AN2 of relevant amplifying circuit link to each other with AN1, the AN2 port of A/D convertor circuit respectively, carry out analog to digital conversion, convert analog voltage signal to digital signal.The digital signal that is converted to is sent into single-chip microcomputer, and the numerical value that single-chip microcomputer is converted to according to AD is judged the frequency of AN1 and AN2 signal, thereby can be obtained calculating flow signal, can carry out LCD simultaneously and show.
Like this, as follows: as when water flows through measuring tube, to produce vibration based on the working flow of the fluidic flowmeter system of related amplification technology.Produce periodically variable water-flow signal around the electrode, be proportional to the oscillation frequency f of water according to the mean flow rate of the principle current of jetting type water meter, i.e. V=Kf, wherein K is an instrument coefficient.Producing frequency by single-chip microcomputer simultaneously is that the excitation signal drive coil of F makes it to produce alternating magnetic field B and acts on the jetting type water meter, and the field frequency F of general excitation is much larger than the oscillation frequency f of water.Because glassware for drinking water has weak inductive, thereby the generation induction electromotive force on the cutting magnetic line electrode, electromotive force computing formula are E=BLV, because B is that frequency is the periodically variable signal of F, and V is a frequency is the periodically variable signal of f, and L is that constant is relevant with meter performance.It is that the baseband signal of f is modulated that the induction electromotive force E that obtains is equivalent to frequency, through the demodulation amplification of relevant amplifying circuit, can effectively suppress noise and amplify useful signal, and the oscillation frequency f of the water of measuring, thus can calculate the mean flow rate V of water.But, there is LCD display can carry out the demonstration of integrated flow, instantaneous delivery on the water meter simultaneously according to single-chip microcomputer corresponding calculated integrated flux.
Adopt related amplification technology to come the benefit of metered flow to be: relevant with reference signal according to useful signal, and noise signal is with uncorrelated this characteristic of reference signal, inhibition noise signal that can very big limit improves signal to noise ratio (S/N ratio), thereby makes instrument that good lower limit flow measurement performance be arranged.As when entering the industrial frequency noise signal of 50HZ, we select excitation frequency is 420HZ, the frequency that water vibrates in the fluidic flowmeter cavity is 0.1～60HZ, the frequency spectrum that can know the effective discharge signal that electrode obtains is at 360HZ～480HZ, can select difference to amplify the logical 350HZ～500HZ of being of bandpass filter band of back level, the effective discharge signal can pass through bandpass filter smoothly, and the industrial frequency noise signal is then by the bandpass filtering filtering.Can further amplify signal behind the bandpass filtering, the demodulation effect by multiplier and low-pass filter obtains effective flow signal again.The hydrodynamic noise that adopts relevant amplification method can effectively resist power frequency interference and high frequency is disturbed, and with the effective discharge signal on the bigger gain magnifying electrode, lower flow signal detects and is achieved.
Claims (4)
1, a kind of Weak signal extraction system for fluidic flowmeter based on related amplification technology is characterized in that, it comprises jet base table, flow detection circuit and U type excitation structure.Described jet base table comprises first electrode (1), second electrode (2), third electrode (3), choked flow piece (4), feedback channel (5) and measuring tube (6).First electrode (1), second electrode (2), third electrode (3) and choked flow piece (4) are installed in the measuring tube (6), and first electrode (1) and third electrode (3) are in choked flow piece (4) one sides, and second electrode (2) is at choked flow piece (4) opposite side.The flow detection circuit comprises single-chip microcomputer, relevant amplifying circuit, A/D convertor circuit, excitation driving circuit and LCD display, single-chip microcomputer links to each other with LCD display with relevant amplifying circuit, A/D convertor circuit, excitation driving circuit respectively, the excitation driving circuit links to each other with U type excitation structure, first electrode (1) of jet base table, second electrode (2), third electrode (3) link to each other with relevant amplifying circuit, and relevant amplifying circuit links to each other with A/D convertor circuit.
2, according to the described Weak signal extraction system for fluidic flowmeter of claim 1 based on related amplification technology, it is characterized in that described relevant amplifying circuit comprises differential amplifier circuit, bandwidth-limited circuit, in-phase amplification circuit, first multiplier circuit, second multiplier circuit, first low-pass filter circuit and second low-pass filter circuit.Differential amplifier circuit, bandwidth-limited circuit, in-phase amplification circuit link to each other successively, in-phase amplification circuit links to each other with second multiplier circuit with first multiplier circuit respectively, first low-pass filter circuit links to each other with first multiplier circuit, and second low-pass filter circuit links to each other with second multiplier circuit.First electrode (1) of jet base table, second electrode (2), third electrode (3) link to each other with differential amplifier circuit.
3, according to the described Weak signal extraction system for fluidic flowmeter of claim 1 based on related amplification technology, it is characterized in that, described excitation driving circuit comprises two PNP triode Q4, Q5, four NPN triode Q6, Q7, Q8, Q9, six resistance R 35, R36, R37, R38, R39, R40 and two capacitor C 12, C13.Wherein, an end of resistance R 38 and resistance R 39 is connected single-chip microcomputer, and the other end of R39 links to each other with the base stage of capacitor C 12, triode Q7, and the other end of R38 links to each other with the base stage of capacitor C 13, triode Q4, the other end ground connection of capacitor C 12 and capacitor C 13.The collector of triode Q7 links to each other with base stage, the resistance R 35 of triode Q5, the collector of triode Q6 links to each other with base stage, the resistance R 36 of triode Q4, the emission collection of the other end, Q4 and the Q5 of resistance R 35 and resistance R 36 links to each other with power supply VCC, the collector of triode Q4 links to each other with the collector of triode Q9, the collector of triode Q5 links to each other with the collector of triode Q8, the collector of triode Q5 links to each other with the MOTER+ pin, the collector of triode Q4 links to each other with the MOTER-pin, and MOTER+, MOTER-pin link to each other with field coil and be used for controlling magnetic field.The base stage of triode Q8 links to each other with emitter, the resistance R 41 of triode Q6, and the base stage of triode Q9 links to each other the other end ground connection of the emitter of the emitter of triode Q9 and triode Q8, resistance R 40 and resistance R 41 with emitter, the resistance R 40 of triode Q7.
4, a kind of application rights requires the fluidic flowmeter feeble signal extracting method of 1 described Weak signal extraction system for fluidic flowmeter, it is characterized in that, may further comprise the steps:
(1) Single-chip Controlling excitation driving circuit produces required excitation field.
(2) electrode acquired signal is with the relevant amplifying circuit of signal input.
(3) relevant amplifying circuit amplifies back input A/D convertor circuit with electrode signal.
(4) A/D convertor circuit carries out analog to digital conversion to the electrode signal that amplifies, and sends into single-chip microcomputer, and single-chip microcomputer obtains flow signal according to the numerical value that analog to digital conversion obtains, and carries out LCD simultaneously and shows.
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| CN200910100932A CN101619992A (en) | 2009-08-10 | 2009-08-10 | Weak signal extraction system for fluidic flowmeter based on related amplification technology and method |
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| CN200910100932A CN101619992A (en) | 2009-08-10 | 2009-08-10 | Weak signal extraction system for fluidic flowmeter based on related amplification technology and method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104655201A (en) * | 2014-12-19 | 2015-05-27 | 重庆川仪自动化股份有限公司 | Exciting circuit |
| CN107478279A (en) * | 2016-06-08 | 2017-12-15 | 西尼尔(南京)过程控制有限公司 | Electromagnetic flowmeter and its excitation voltage regulation method |
-
2009
- 2009-08-10 CN CN200910100932A patent/CN101619992A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104655201A (en) * | 2014-12-19 | 2015-05-27 | 重庆川仪自动化股份有限公司 | Exciting circuit |
| CN104655201B (en) * | 2014-12-19 | 2017-08-11 | 重庆川仪自动化股份有限公司 | A kind of field circuit |
| CN107478279A (en) * | 2016-06-08 | 2017-12-15 | 西尼尔(南京)过程控制有限公司 | Electromagnetic flowmeter and its excitation voltage regulation method |
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Open date: 20100106 |