CN100427894C - Differential pressure type measurement signal processor for flow mass of vortex street - Google Patents
Differential pressure type measurement signal processor for flow mass of vortex street Download PDFInfo
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- CN100427894C CN100427894C CNB2006101546314A CN200610154631A CN100427894C CN 100427894 C CN100427894 C CN 100427894C CN B2006101546314 A CNB2006101546314 A CN B2006101546314A CN 200610154631 A CN200610154631 A CN 200610154631A CN 100427894 C CN100427894 C CN 100427894C
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Abstract
A signal processing system for differential pressure vortex shedding quality flow determination is disclosed. The differential pressure between upstream and downstream of vortex shedding flowmeter generator is tested by differential pressure sensor, the differential pressure is connected with the signal processing apparatus of the differential pressure vortex shedding quality flow determination, in the apparatus, the output signal of the differential pressure sensor via the gain-programmed amplifier, average value separation, frequency resolution, adaptive filtering to generate the vortex shedding frequency signal and the differential pressure average value signal, then two signals which via the analogue/digital conversion (add) are sent to the SCM for the related arithmetic, the quality flow of the measured liquid in measuring channel is gained. The apparatus designed in the invention realizes the direct measurement for the quality flow of liquid in measuring channel, and characterized in simple structure, high accuracy of measurement, low cost, strong interference immunity and wide applicability.
Description
Technical field
The present invention relates to a kind of differential pressure type measurement signal processor for flow mass of vortex street.
Background technology
The measurement of mass rate is the emphasis and the difficult point problem of procedure parameter detection range.Utilizing existing traditional volumetric displacement meter, through improving, improve and improving, develop into mass flowmeter, is an important trend of mass flow measurement technical development, and vortex shedding flow meter is exactly important representative wherein.At present more representational is lift formula mass flowmeter for vortex street, it adopts piezoelectric sensor to measure vortex street frequency and vortex lift simultaneously, but the signal amplitude of vortex lift correspondence is relevant with multiple factors such as piezoelectric element stability, amplifier stability, on-the-spot mounting condition, measured medium temperature, and accuracy of measurement is difficult to improve.
A kind of new mass flow measurement methods that patent inventor of the present invention proposes has been applied for patent of invention " vortex mass flow measuring method " and has been obtained mandate.The present invention is on the basis of above patent of invention, by design to vortex mass flow signal processing circuit and related hardware, and the vortex mass flow measurement mechanism that develops.
Summary of the invention
The purpose of this invention is to provide a kind of differential pressure type measurement signal processor for flow mass of vortex street.
Differential pressure type vortex mass flow measuring-signal treating apparatus: single-chip microcomputer joins with programmable amplifier, A/D converter, sef-adapting filter respectively, programmable amplifier and signal averaging separation circuit, A/D converter join, programmable amplifier and signal frequency separation circuit, sef-adapting filter, A/D converter join, and programmable amplifier and differential pressure pick-up, constant-current supply join.
Described programmable amplifier circuit is that amplifier A1 the 8th pin joins through digital regulation resistance U1 and amplifier A1 first pin.
The signal frequency separation circuit is that the positive input of amplifier A2 is joined with capacitor C 1, capacitor C 2, the positive input terminal of amplifier A2 is through resistance R 6 ground connection, the negative input end of amplifier A2 is through resistance R 9 ground connection, the output terminal of amplifier A2 joins through resistance R 1 and capacitor C 1, capacitor C 2, and the output terminal of amplifier A2 is through resistance R 8, resistance R 9 ground connection.
The signal averaging separation circuit is that the positive input terminal of amplifier A3 joins with resistance R 2, resistance R 3, the positive input terminal of amplifier A3 is through capacitor C 4 ground connection, the negative input end of amplifier A3 is through resistance R 4 ground connection, the output terminal of amplifier A3 joins with capacitor C 3, resistance R 2, and the output terminal of amplifier A3 is through resistance R 4, resistance R 5 ground connection.
Sef-adapting filter is that the positive input terminal of amplifier A4 is through resistance R 7 and power supply V
DDJoin, the positive input terminal of amplifier A4 is through resistance R 10 ground connection, the output terminal of the negative input end of amplifier A4 and amplifier A4 joins, the positive input terminal of amplifier A5 and resistance R 12 are joined, the positive input terminal of amplifier A5 joins through the output terminal of resistance R 11 with amplifier A4, the negative input end of amplifier A5 is through resistance R 13 ground connection, and the output terminal of amplifier A5 joins through the negative input end of resistance R 14 with amplifier A5, and the output terminal of the input end of wave filter U2 and amplifier A5 joins.
The device of the present invention design has been realized the direct measurement to pipeline inner fluid mass rate, have simple in structure, accuracy of measurement is high, cost is low, strong interference immunity, characteristics such as applied widely.
Description of drawings
Fig. 1 is signal measurement apparatus of the present invention and signal processing apparatus synoptic diagram;
Fig. 2 is a signal processing apparatus The general frame of the present invention;
Fig. 3 is a programmable amplifier circuit diagram of the present invention;
Fig. 4 is signal frequency separation circuit figure of the present invention;
Fig. 5 is signal averaging separation circuit figure of the present invention;
Fig. 6 is that voltage of the present invention promotes and the sef-adapting filter circuit diagram;
Fig. 7 is the graph of a relation of vortex street frequency of the present invention and volumetric flow rate;
Fig. 8 is the relative error figure of measurement volumes flow of the present invention;
Fig. 9 is the graph of a relation of differential pressure mean of the present invention and volumetric flow rate;
Figure 10 is the ratio of differential pressure mean of the present invention and vortex street frequency and the graph of a relation of mass rate;
Figure 11 is the relative error figure that the present invention measures mass rate.
Embodiment
Signal measurement apparatus of the present invention and signal processing apparatus are as shown in Figure 1.In measuring tube 1, be provided with the vortex generation body 2 of vortex shedding flow meter, in the vortex generation body upstream 0.5D～D of vortex shedding flow meter (D is the measuring tube interior diameter), have a pressure port 3, in the vortex generation body downstream 0.5D of vortex shedding flow meter, have another pressure port 4, between two pressure ports, be connected to differential pressure pick-up 5, be connected to signal processing circuit 6 after the differential pressure pick-up 5, be connected to single-chip microcomputer 7 after the signal processing circuit 6.
The The general frame of differential pressure type measurement signal processor for flow mass of vortex street such as Fig. 2.Single-chip microcomputer joins with programmable amplifier, A/D converter, sef-adapting filter respectively, programmable amplifier and signal averaging separation circuit, A/D converter join, programmable amplifier and signal frequency separation circuit, sef-adapting filter, A/D converter join, and programmable amplifier and differential pressure pick-up, constant-current supply join.Power to differential pressure pick-up with constant-current supply, convert differential pressure signal to a millivolt magnitude voltage signals, after program control amplification and auto adapted filtering are handled, obtain frequency signal and differential pressure mean value, again after the A/D conversion by the single-chip microcomputer collection, single-chip microcomputer carries out just having obtained mass rate after the computing.The low-power consumption type MSP430 series microprocessor that Single Chip Microcomputer (SCM) system has adopted TI company to produce.
The millivolt magnitude voltage signals that differential pressure pick-up produces comprises two signal values: the one, and the frequency signal of vortex street is used for measuring the volumetric flow rate of fluid; The 2nd, the average value signal of differential pressure and frequency signal are used for measuring the mass rate of fluid together.Traditional vortex street volumetric displacement meter, adopt analogue filter circuit that signal of sensor is carried out filtering mostly, the method by shaping, counting obtains the vortex street frequency then, and this method exists range ratio limited in application, a little less than the antijamming capability, shortcomings such as circuit versatility difference.For antijamming capability and the versatility of improving circuit, improve measuring accuracy and range ratio, adopted programmable amplifier and programmable filter to replace traditional circuit, make circuit under different operating modes, can have adaptive ability, and the online regulating circuit parameter of energy, therefore the effective filtering interference signals of energy improves frequency measurement accuracy and measurement range.The specific implementation Method and circuits is as follows:
(1) programmable amplifier
As shown in Figure 3, the programmable amplifier circuit method design programmable amplifier that adopts instrumentation amplifier to add digital potentiometer replaces traditional amplifier.Instrumentation amplifier is selected AD620 for use, and it has characteristics such as low maladjustment voltage drift, low noise, and the size that only need change outer meeting resistance can be provided with 1～1000 gain amplifier.Outer meeting resistance adopts digital regulation resistance MAX5402, and its end resistance is 10K, and tap number is 256, and has characteristics such as low temperature floats.Single-chip microcomputer can change the enlargement factor of instrumentation amplifier by changing the resistance of data potentiometer, has realized the online adjusting of enlargement factor.
The concrete annexation of circuit is: amplifier A1 the 8th pin joins through digital regulation resistance U1 and amplifier A1 first pin, the 3rd, two pins of amplifier A1 meet positive-negative output end Vin+, the Vin-of differential pressure pick-up respectively, and the 7th, the 4th pin of amplifier A1 meets positive and negative film V
CCAnd V
EE.The 5th pin ground connection of amplifier A1, the 6th pin of amplifier A1 connects signal frequency separation circuit and mean value separation circuit.
(2) frequency separation, mean value separation circuit
As shown in Figure 4, the signal frequency separation circuit is that the positive input of amplifier A2 is joined with capacitor C 1, capacitor C 2, the positive input terminal of amplifier A2 is through resistance R 6 ground connection, the negative input end of amplifier A2 is through resistance R 9 ground connection, the output terminal of amplifier A2 joins through resistance R 1 and capacitor C 1, capacitor C 2, and the output terminal of amplifier A2 is through resistance R 8, resistance R 9 ground connection.
As shown in Figure 5, the signal averaging separation circuit is that the positive input terminal of amplifier A3 joins with resistance R 2, resistance R 3, the positive input terminal of amplifier A3 is through capacitor C 4 ground connection, the negative input end of amplifier A3 is through resistance R 4 ground connection, the output terminal of amplifier A3 joins with capacitor C 3, resistance R 2, and the output terminal of amplifier A2 is through resistance R 4, resistance R 5 ground connection.
Comprise vortex street frequency signal and differential pressure average value signal through the signal after the programmable amplifier amplification, in order to obtain this two paths of signals simultaneously, the bivalent high-pass filter that to have designed a cutoff frequency be 0.5Hz comes the isolated DC component, obtains AC signal, i.e. the vortex street frequency signal.The second-order low-pass filter that to have designed a cutoff frequency simultaneously be 0.5Hz is isolated AC compounent, obtains direct current signal, i.e. the differential pressure average value signal.Amplifier all adopts CA3240.
(3) auto-adaptive filter circuit
As shown in Figure 6, sef-adapting filter is that the positive input terminal of amplifier A4 is through resistance R 7 and power supply V
DDJoin, the positive input terminal of amplifier A4 is through resistance R 10 ground connection, the output terminal of the negative input end of amplifier A4 and amplifier A4 joins, the positive input terminal of amplifier A5 and resistance R 12 are joined, the positive input terminal of amplifier A5 joins through the output terminal of resistance R 11 with amplifier A4, the negative input end of amplifier A5 is through resistance R 13 ground connection, and the output terminal of amplifier A5 joins through the negative input end of resistance R 14 with amplifier A5, and the output terminal of the input end of wave filter U2 and amplifier A5 joins.
Wave filter U2 circuit connecting relation is: wave filter U2 first pin and wave filter U2 the 6th pin join, and the output terminal of wave filter U2 second pin and amplifier A5 joins, wave filter U2 the 3rd pin ground connection, and wave filter U2 the 4th, the 7th pin meets power supply V
DD, wave filter U2 the 5th pin connects A/D converter, and wave filter U2 the 8th pin connects single-chip microcomputer.
The vortex street frequency signal changes with fluctuations in discharge, and under different calibers and medium, it is worth between 1～2000Hz, and the undesired signal frequency also can change along with the variation of vortex street frequency, and when flow velocity is more little, when signal was weak more, suffered interference was just obvious more.The filtering parameter of conventional filtering circuit can not onlinely be adjusted, and therefore is difficult to effective filtering interference signals, and the utility model has designed auto-adaptive filter circuit for this reason.The programmable switch capacitor filter MAX7404 that wave filter adopts MAXIM company to produce, it is a low pass, 8 rank, elliptic function filter can be set the corner frequency of 1Hz～10kHz, and the stopband rejection ratio is 60dB.The vortex street frequency signal converts unipolar signal to behind the voltage lifting circuit that two CA3240 amplifiers are formed, adjust output frequency by single-chip microcomputer again, then can be according to the suitable low-pass filter corner frequency of current demand signal frequency setting, so just can adapt to filtering requirements under different tube diameters, different medium, the different in flow rate, improve the versatility of circuit.
In order to improve the interference free performance of vortex shedding flow meter, better adapt to the request for utilization of industry spot, fft algorithm is used and vortex shedding flow meter, so that from the vortex signal that contains noise, accurately extract the vortex street frequency signal.The fft algorithm calculated amount is very big, and the arithmetic speed of general single-chip microcomputer can't satisfy the requirement of real-time, has proposed a kind of improved fft algorithm for this reason.
If the real sequence that x (n) is 2N orders is divided into even number set x with x (n)
1(n) and odd number group x
2(n), promptly
x
1(n)＝x(2n)，n＝0，1，...，N-1 (1)
x
2(n)＝x(2n+1)，n＝0，1，...，N-1 (2)
Then with x
1(n), x
2(n) form a sequence of complex numbers:
y(n)＝x
1(n)+jx
2(n) (3)
Obtain by N point FFT computing:
Y(k)＝DFT[x
1(n)]+jDFT[x
2(n)]＝X
1(n)+jX
2(n) (4)
K=0 in the formula, 1 ..., N-1.
And actual that require is the pairing X of real sequence x (n) (n) that 2N is ordered, its same X
1(n), X
2(n) relation is as follows:
In the formula
In single-chip microcomputer, storing a floating number needs 4 bytes, only needs 2 bytes and store an integer, and the operand of floating number will be much larger than the operand of integer, therefore if can replace floating point arithmetic, not only can save storer, and can reduce operand in a large number with integer arithmetic.((value of k π/N) adopts the method for look-up table to obtain coefficient then when calculating, and can save the computing time of asking trigonometric function, has further reduced the operand of fft algorithm for k π/N) and sin to ask for coefficient cos in advance.By some above improvement, on the MSP430 processor, realized this algorithm at last.Through test, the FFT that calculates 2048 sampled points only needs 56ms, satisfies the time requirement of measuring in real time fully.
Flow media is to test under the situation of water in measuring tube.The water buffer tank makes stability of flow when testing for pipeline provides constant hydraulic pressure, and the size of discharge is regulated by variable valve, and flow range is 2～20m
3/ h.Electromagnetic flowmeter provides the normal stream value of the water that enters experimental section as the normal stream scale, and precision is 0.5%.The volumetric flow rate density with water on duty that records by electromagnetic flowmeter promptly gets the standard quality flow value.
The vortex street frequency that obtains from differential pressure signal and the relation of volumetric flow rate are as shown in Figure 7.As seen from the figure, signal frequency has the fine linear relationship that gets with the fluid volumetric flow rate.By linear fit, can obtain the volumetric flow rate instrument coefficient is 2.542Hz/ (m
3/ h), to demarcate the back instrument and show volumetric flow rate as shown in Figure 8 with the relative error between the standard scale volumetric flow rate, maximum relative error is less than 2.0%.Fig. 9 is the relation between differential pressure mean value and the flow, as seen from the figure, is to be approximate quadratic relation between differential pressure mean value and the flow.Figure 10 has provided the relation between the ratio of mass rate and differential pressure mean and vortex street frequency, and data among the figure are carried out linear fit, and obtaining the mass rate instrument coefficient is 78.344 (kg/h)/(Pa/Hz).Figure 11 has provided with the mass rate of mass rate instrument coefficient (78.344 (kg/h)/(the Pa/Hz)) calculating of demarcating and the relative error of standard quality flow, and in the scope of experiment of flow greater than 6000kg/h, relative error is all less than 2.0%.
Above result shows that the differential pressure type vortex mass flow measuring-signal treating apparatus that utilizes the present invention to propose can record the mass rate of flow media in the pipeline accurately and conveniently.
Claims (4)
1, a kind of differential pressure type measurement signal processor for flow mass of vortex street, it is characterized in that: single-chip microcomputer respectively with programmable amplifier, A/D converter, sef-adapting filter joins, programmable amplifier and signal averaging separation circuit, A/D converter joins, programmable amplifier and signal frequency separation circuit, sef-adapting filter, A/D converter joins, programmable amplifier and differential pressure pick-up, constant-current supply joins, described signal frequency separation circuit is: the positive input of amplifier A2 and capacitor C 1, capacitor C 2 is joined, the positive input terminal of amplifier A2 is through resistance R 6 ground connection, the negative input end of amplifier A2 is through resistance R 9 ground connection, the output terminal of amplifier A2 is through resistance R 1 and capacitor C 1, capacitor C 2 is joined, and the output terminal of amplifier A2 is through resistance R 8, resistance R 9 ground connection.
2, a kind of differential pressure type measurement signal processor for flow mass of vortex street according to claim 1 is characterized in that: described programmable amplifier circuit is that amplifier A1 the 8th pin joins through digital regulation resistance U1 and amplifier A1 first pin.
3, a kind of differential pressure type measurement signal processor for flow mass of vortex street according to claim 1, it is characterized in that: the positive input terminal that described signal averaging separation circuit is amplifier A3 joins with resistance R 2, resistance R 3, the positive input terminal of amplifier A3 is through capacitor C 4 ground connection, the negative input end of amplifier A3 is through resistance R 4 ground connection, the output terminal of amplifier A3 joins with capacitor C 3, resistance R 2, and the output terminal of amplifier A3 is through resistance R 4, resistance R 5 ground connection.
4, a kind of differential pressure type measurement signal processor for flow mass of vortex street according to claim 1, it is characterized in that: described sef-adapting filter is that the positive input terminal of amplifier A4 joins with power vd D through resistance R 7, the positive input terminal of amplifier A4 is through resistance R 10 ground connection, the output terminal of the negative input end of amplifier A4 and amplifier A4 joins, the positive input terminal of amplifier A5 and resistance R 12 are joined, the positive input terminal of amplifier A5 joins through the output terminal of resistance R 11 with amplifier A4, the negative input end of amplifier A5 is through resistance R 13 ground connection, the output terminal of amplifier A5 joins through the negative input end of resistance R 14 with amplifier A5, and the output terminal of the input end of wave filter U2 and amplifier A5 joins.
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| CN100427894C true CN100427894C (en) | 2008-10-22 |
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| CN105698881A (en) * | 2016-03-15 | 2016-06-22 | 江苏华海测控技术有限公司 | High-precision electromagnetic flowmeter based on fast Fourier transform |
| CN107907169A (en) * | 2017-12-22 | 2018-04-13 | 苏州捷研芯纳米科技有限公司 | Flow-measuring method and flow measurement device for differential pressure flow sensor |
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2006
- 2006-11-13 CN CNB2006101546314A patent/CN100427894C/en not_active Expired - Fee Related
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4545258A (en) * | 1983-07-05 | 1985-10-08 | Rosemount Inc. | Circuit with adjustable amplitude and rolloff frequency characteristics |
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| CN2224401Y (en) * | 1994-08-29 | 1996-04-10 | 宁夏回族自治区银河仪表厂 | Signal processor for flow-metering instrument |
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