CN201795819U - Static drift rejection model of time difference method ultrasonic flowmeter - Google Patents
Static drift rejection model of time difference method ultrasonic flowmeter Download PDFInfo
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- CN201795819U CN201795819U CN2010202242515U CN201020224251U CN201795819U CN 201795819 U CN201795819 U CN 201795819U CN 2010202242515 U CN2010202242515 U CN 2010202242515U CN 201020224251 U CN201020224251 U CN 201020224251U CN 201795819 U CN201795819 U CN 201795819U
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Abstract
The utility model discloses a static drift rejection model of a time difference method ultrasonic flowmeter, which comprises an amplifying and filtering circuit, a first comparator, a second comparator with a latching function, a third comparator, a counter, a phase inverter and a logic and arithmetic unit. The model has the advantages that the first comparator and the second comparator with the latching function are utilized to perform hardware threshold comparison, the third comparator is utilized to perform zero-cross comparison, and the problem that the reach time of ultrasonic signals is misjudged because the voltage magnitude of the ultrasonic signals is changed can be properly solved through the method of the combination of hardware threshold comparison and zero-cross comparison, and the reach time of the ultrasonic signals can be accurately obtained, so that the downstream time and the counterstream time can be accurately measured, the static drift is greatly reduced, and simultaneously the model can eliminate measured error data through a pulse counting method, and greatly improve the measuring accuracy of the time difference method ultrasonic flowmeter.
Description
Technical field
The utility model relates to a kind of time difference ultrasonic flowmeter measuring technique, especially relates to a kind of static drift of time difference ultrasonic flowmeter and suppresses model.
Background technology
Ultrasonic flowmeter can be realized noncontact, high-acruracy survey, has broad quantum, no crushing, forms advantage such as simple, sensitivity height, has a wide range of applications in fields such as petrochemical complex, wastewater treatment, industry and domestic waters.
The ultrasonic flowmeter development has had multiple metering system so far, can be divided into propagation speed differential method, doppler effect method, wave beam deflection method etc. by measuring principle.Time difference method is a kind of metering system in the ultrasonic flowmeter propagation speed differential method, compares with other metering systems, and it has the simple and measuring accuracy advantages of higher of metering system, so it receives much concern always.
To be called time difference ultrasonic flowmeter with the ultrasonic flowmeter that the time difference method metering system is measured, Fig. 1 has provided the metering circuit block diagram of time difference ultrasonic flowmeter, this metering circuit comprises microcontroller, the timing chip, drive circuit module, receiving circuit module, change-over switch, memory circuit, first ultrasonic transducer and second ultrasonic transducer, drive circuit module is mainly by pulse signal generating circuit, signal conditioning circuit and transducer driving circuit are formed, receiving circuit module mainly is made up of signal receiving circuit and signal transformation circuit, change-over switch has first port, second port, the 3rd port and four ports of the 4th port, microcontroller respectively with memory circuit, the timing chip, change-over switch and pulse signal generating circuit are connected, the timing chip is connected with signal transformation circuit, transducer driving circuit is connected with first port of change-over switch, signal receiving circuit is connected with the 3rd port of change-over switch, first ultrasonic transducer is connected with second port of change-over switch, and second ultrasonic transducer is connected with the 4th port of change-over switch.First ultrasonic transducer and second ultrasonic transducer both can be launched ultrasonic signal, again can received ultrasonic signal, first ultrasonic transducer and second ultrasonic transducer are controlled by change-over switch the emission or the reception of ultrasonic signal, change-over switch is controlled by microprocessor, but first ultrasonic transducer is in two kinds of different states with second ultrasonic transducer in the same time period, promptly when first ultrasonic transducer is in emission state, second ultrasonic transducer then should be in accepting state, this moment, first port of change-over switch linked to each other with second port, be that transducer driving circuit links to each other with first ultrasonic transducer, the 3rd port links to each other with the 4th port, and promptly signal receiving circuit is connected with second ultrasonic transducer; When second ultrasonic transducer is in emission state, first ultrasonic transducer then should be in accepting state, this moment, first port of change-over switch linked to each other with the 4th port, be that transducer driving circuit is connected with second ultrasonic transducer, second port of change-over switch links to each other with the 3rd port, and promptly signal receiving circuit links to each other with first ultrasonic transducer; Microcontroller is used for connection, control wave between each port of control its switch and produces circuit output drive pulse signal, reads the count value in the timing chip and finish the calculating of numerical value and this count value is stored to memory circuit.Suppose between metering circuit shown in Figure 1 at a time in the section that first ultrasonic transducer is in emission state and second ultrasonic transducer is in accepting state, first port of microprocessor controls change-over switch is connected with first ultrasonic transducer, the 3rd port of control its switch is connected with second ultrasonic transducer simultaneously, this moment microcontroller, pulse signal generating circuit, signal conditioning circuit, transducer driving circuit, first port of change-over switch and second port, first ultrasonic transducer, second ultrasonic transducer, the 3rd port of change-over switch and the 4th port, signal receiving circuit, signal transformation circuit constitutes a path, microprocessor controls pulse signal generating circuit output drive pulse signal, pulse signal generating circuit is transferred to signal conditioning circuit with drive pulse signal, microprocessor controls timing chip picks up counting simultaneously, signal conditioning circuit carries out filter shape to the drive pulse signal that produces to be handled and obtains amplitude and frequency and the transducer drive signal that is complementary and be transferred to transducer driving circuit, the microprocessor control its switch will be mated first port and second port transmission of drive signal by change-over switch and be given first ultrasonic transducer, first ultrasonic transducer produces ultrasonic signal, ultrasonic signal is propagated in pipeline, the ultrasonic signal that the second super wave transducer receives is fainter, be mingled with more undesired signal in this ultrasonic signal, second ultrasonic transducer will be mingled with the ultrasonic signal of undesired signal and give signal receiving circuit by the 3rd port and the 4th port transmission of change-over switch, signal receiving circuit is amplified the ultrasonic signal that contains undesired signal, Filtering Processing, signal transformation circuit carries out the shaping processing to ultrasonic signal and obtains pulse signal, the timing of microprocessor controls timing chip finishes, microcontroller reads suitable from the timing chip, the adverse current time and the mistiming of calculating, finally obtain instantaneous delivery, carry out smothing filtering to obtaining the instantaneous delivery sequence at last, finally obtain instantaneous delivery accurately, and by memory circuitry stores in storer.
S1 and s2 represent first ultrasonic transducer and second ultrasonic transducer respectively among Fig. 1; V represents the flow velocity of fluid media (medium); C represents the velocity of sound of ultrasonic signal in fluid media (medium); α represents the angle of the direction of propagation of the flow velocity direction of fluid media (medium) and ultrasonic signal, when α is acute angle, is referred to as following current, when α is the obtuse angle, is referred to as adverse current; D represents the diameter of pipeline; θ represents that ultrasonic signal enters the incident angle of fluid media (medium); T1 represent s1 as emission ultrasonic transducer, s2 when receiving ultrasonic transducer, ultrasonic signal is in the ducted travel-time, i.e. the following current time; T2 represent s2 as emission ultrasonic transducer, s1 when receiving ultrasonic transducer, ultrasonic signal is in the ducted travel-time, i.e. the adverse current time.Its principle of work is: ultrasonic signal is in fluid media (medium) (being dynamic media), compare with static medium (flow velocity is zero), the velocity of propagation of ultrasonic signal increases during following current, travel-time reduces, the velocity of propagation of ultrasonic signal reduces during adverse current, travel-time increases, thereby makes that the travel-time life period of concurrent-countercurrent direction ultrasonic signal is poor.Time difference ultrasonic flowmeter exists the linear relationship principle to measure according to the flow velocity and the mistiming of fluid media (medium), therefore as long as accurately measure following current time and adverse current time, flow velocity and the linear relationship of following current time and adverse current time according to fluid media (medium), the flow velocity of fluid media (medium) can be obtained, and then instantaneous delivery can be obtained.The note mistiming is Δ T,
Wherein,
τ represents the time delay of ultrasonic signal in ultrasonic transducer and hardware circuit.Because the velocity of sound of ultrasonic signal in common fluid media (medium) be greater than 1000m/s, and the flow velocity of these common fluid media (medium)s is usually less than 10m/s, i.e. C
2＞＞V
2, therefore can obtain
Thereby can obtain the flow velocity of fluid media (medium)
The note instantaneous delivery is Q,
Wherein, K represents the velocity flow profile correction factor of fluid media (medium), and S represents the sectional area of pipeline.
In theory, under the static situation of fluid media (medium) (flow velocity that is fluid media (medium) is 0m/s), following current time t1 and adverse current time t2 that time difference ultrasonic flowmeter is measured should equate that mistiming Δ T should be 0.But because parameters such as the sensitivity of two ultrasonic transducers that adopt, mechanical-electric coupling can not be identical, Δ T generally changes in a scope under the quiescent conditions, according to
Instantaneous delivery Q under static as can be known should fluctuate in a scope.Ultrasonic flowmeter is to the measurement of mobile fluid media (medium), and referred to herein as dynamic measurement, dynamically the instantaneous delivery note is made Q
dSuppose that it is q that time difference ultrasonic flowmeter will satisfy the boundary flow
t, and precision is 1%, then must satisfy at Δ T of following mistiming of quiescent conditions | Δ T|≤ξ, ξ are a precision threshold parameter (by boundary flow and precision decision), so static instantaneous delivery Q
sSatisfy | Q
S|≤δ, δ=f (ξ).As static instantaneous delivery Q
sDo not satisfy | Q
S| during≤δ, claim that at this this situation is a static drift.
The static drift problem is the bottleneck of time difference ultrasonic flowmeter precision improvement always, static drift and ultrasonic signal are accurately judged closely related, the industry spot circumstance complication that ultrasonic flowmeter is measured, the ultrasonic signal that receives is smaller, be subject to disturb, solid particle in the fluid media (medium) and electromagnetic wave very easily make the ultrasonic signal amplitude that receives change in addition, cause measuring inaccurate and measuring accuracy decline, therefore the basic skills that solves static drift is to judge the due in of ultrasonic signal accurately, promptly obtain time of following current accurately and adverse current time, and then it is poor to obtain correct time.
In time difference ultrasonic flowmeter, judge that the most frequently used method of due in of ultrasonic signal is the threshold value relative method.Shown in Fig. 2 a and Fig. 2 b, among Fig. 2 b, DS represents to launch the pulse drive signal of ultrasonic transducer emission to threshold ratio than ratio juris; TS represents to receive the ultrasonic signal that ultrasonic transducer receives; T represents the following current time (adverse current time); T express time coordinate axis; Z represents the hardware threshold value, in case set, its value remains unchanged; A, b, c, d represent 4 moment point of the second period of the ultrasonic signal that receives successively, and a is a zero crossing.Suppose among Fig. 2 a and Fig. 2 b, the ultrasonic signal that the ultrasonic signal that ultrasonic transducer receives receives when being a static measurement, hardware threshold value Z is the c point with this ultrasonic signal cutting first constantly, and the following current time (adverse current time) that the ultrasonic flowmeter of this moment records is T, and the mistiming is Δ T.If the amplitude of the ultrasonic signal that receives is bigger or little than the amplitude of the ultrasonic signal that this time receives next time, then hardware threshold value Z can move forward with the moment point c point of this ultrasonic signal cutting first or after move, cause following current time (adverse current time) of measuring bigger than normal or less than normal.Because ultrasonic signal is fainter, be vulnerable to the influence of solid particle, external environment and electronic devices and components aging action in the fluid media (medium), thereby the amplitude of the ultrasonic signal that receives is changed, the moment point c point that hardware threshold value Z and ultrasonic signal are cut first can move forward or after move, following current time and adverse current time measurement are inaccurate.Under quiescent conditions, following current time and adverse current time all are the ms levels, and both sizes are very approaching, make that mistiming Δ T is the ps level, occurs three kinds easily and makes static drift | Q
S| the situation of＞δ:
1) big if the amplitude of the ultrasonic signal that receives becomes, hardware threshold value Z be the b point of second round constantly with the ultrasonic signal cutting that receives first, records the following current time (adverse current time) at this moment to be designated as T
1, the mistiming is Δ T
1, | Δ T
1|＞| Δ T|, thereby | Q
S|＞δ;
2) if the amplitude of the ultrasonic signal that receives diminishes, hardware threshold value Z is the d point of second period constantly with the ultrasonic signal cutting that receives first, and following current time this moment (adverse current time) is designated as T
2, the mistiming is Δ T
2, | Δ T
2|＞| Δ T|, thereby | Q
S|＞δ;
3) very big if the amplitude of the ultrasonic signal that receives becomes degree big or that diminish, hardware threshold value Z constantly may be a certain moment point in first cycle or the 3rd cycle with the ultrasonic signal cutting that receives first so, make the static measurement mistiming increase or reduce one-period, following current time of Ce Lianging or adverse current time are wrong like this, thereby the mistiming is wrong, causes static instantaneous delivery measurement result mistake.
To sum up, when ultrasonic transducer receives ultrasonic signal, because ultrasonic transducer needs the regular hour by static to concussion is stable, above-mentioned threshold value relative method adopts the second period signal as the sign of judging the ultrasonic signal due in point that receives, though can stablize the needed time by fine removal ultrasonic signal, but when the big minor swing of amplitude of ultrasonic signal, the threshold value relative method can not be judged the due in of ultrasonic signal very accurately, produce the static drift problem, this has had a strong impact on the dynamic measurement precision of time difference ultrasonic flowmeter, even produces the metering mistake.
Summary of the invention
Technical problem to be solved in the utility model provides and a kind ofly can effectively reduce static drift, improves the inhibition model of the measuring accuracy of time difference ultrasonic flowmeter.
The utility model solves the problems of the technologies described above the technical scheme that is adopted: a kind of static drift of time difference ultrasonic flowmeter suppresses model, comprise the amplification filtering circuit, first comparer, second comparer with latch function, the 3rd comparer, counter, phase inverter and logic and operation unit, described first comparer has Q1 output terminal and the non-output terminal of Q1, described second comparer has Q2 output terminal and the non-output terminal of Q2, described the 3rd comparer has Q3 output terminal and the non-output terminal of Q3, the input end of described amplification filtering circuit is connected with the reception ultrasonic transducer, the ultrasonic signal that described amplification filtering circuit receives the reception ultrasonic transducer carries out amplification filtering to be handled, ultrasonic signal after the output terminal output amplification filtering of described amplification filtering circuit, the in-phase input end of the in-phase input end of described first comparer and described second comparer all is connected with the output terminal of described amplification filtering circuit, ultrasonic signal after the access amplification filtering, the inverting input of the inverting input of described first comparer and described second comparer all inserts the hardware threshold value, the Q1 output terminal of described first comparer is connected with the input end of described counter, the pulse number of the pulse train of the Q1 output terminal output of described first comparer of described counter accumulative total, the output terminal output pulse number of described counter, the non-output terminal of the Q2 of described second comparer is connected with the input end of described phase inverter, the output terminal of described phase inverter is connected with the LE pin of described second comparer, the Q2 output terminal output latch signal of described second comparer, the inverting input of described the 3rd comparer is connected with the output terminal of described amplification filtering circuit, ultrasonic signal after the access amplification filtering, the in-phase input end ground connection of described the 3rd comparer, the Q2 output terminal of described second comparer is connected with the input end of described logic and operation unit respectively with the Q3 output terminal of described the 3rd comparer, the output terminal output of described logic and operation unit is used for as the stop signal of judging the sign that ultrasonic signal arrives, the output terminal of described logic and operation unit is connected with timing chip in the time difference ultrasonic flowmeter metering circuit, the microprocessor controls pulse signal generating circuit of described timing chip in the time difference ultrasonic flowmeter metering circuit picks up counting when exporting drive pulse signal, described timing chip stops timing after receiving stop signal, described counter is connected with described microcontroller respectively with described timing chip.
The size of the ultrasonic signal of the reality that the size of described hardware threshold value receives according to different reception ultrasonic transducers is regulated, described hardware threshold value was a fixed voltage value after adjusting was finished, the ultrasonic signal of described hardware threshold value after greater than amplification filtering first positive period signal peak, and less than the ultrasonic signal after the amplification filtering second positive period signal peak.
Described microcontroller is that model is the single-chip microcomputer of MSP430.
The model of described second comparer is MAX963.
The model of described timing chip is TDC_GP2.
Compared with prior art, advantage of the present utility model is that second comparer that utilizes first comparer and have latch function carries out the hardware threshold ratio, utilize the 3rd comparer to carry out zero balancing, by the hardware threshold ratio mode that zero balancing combines with mistake, the voltage magnitude that can be good at solving owing to ultrasonic signal changes the problem that causes the misjudgement of ultrasonic signal due in, obtain the moment that ultrasonic signal arrives exactly, thereby can accurately record following current time and adverse current time, reduced static drift greatly, the utility model can be got rid of the misdata that measures by the mode of step-by-step counting simultaneously, has greatly improved the measuring accuracy of time difference ultrasonic flowmeter.
Description of drawings
Fig. 1 is the metering circuit synoptic diagram of time difference ultrasonic flowmeter;
Fig. 2 a is that existing threshold ratio is than the ratio juris synoptic diagram;
Fig. 2 b is the enlarged drawing of the interior part of frame of broken lines among Fig. 2 a;
Fig. 3 suppresses the circuit theory diagrams of model for the utility model;
Fig. 4 a is the oscillogram of the ultrasonic signal that receives ultrasonic transducer and receive;
Fig. 4 b is the oscillogram of pulse train of the Q1 output terminal output of first comparer;
Fig. 4 c is the oscillogram of latch signal of the Q2 output terminal output of second comparer;
Fig. 4 d is the oscillogram of signal of the Q3 output terminal output of the 3rd comparer;
Fig. 4 e is the oscillogram of stop signal of the output terminal output of logic and operation unit;
Fig. 5 suppresses the basic procedure block diagram that model suppresses method accordingly for the utility model;
Fig. 6 is the big logotype of hardware threshold value.
Embodiment
Embodiment describes in further detail the utility model below in conjunction with accompanying drawing.
The static drift of time difference ultrasonic flowmeter that the utility model proposes suppresses model, as shown in Figure 3, it comprises amplification filtering circuit 1, first comparer 2, second comparer 3 with latch function, the 3rd comparer 4, counter 5, phase inverter 6 and logic and operation unit 7, first comparer 3 has Q1 output terminal and the non-output terminal of Q1, second comparer 4 has Q2 output terminal and the non-output terminal of Q2, the 3rd comparer 5 has Q3 output terminal and the non-output terminal of Q3, the input end of amplification filtering circuit 1 is connected with the reception ultrasonic transducer, the ultrasonic signal that 1 pair of reception ultrasonic transducer of amplification filtering circuit receives carries out amplification filtering to be handled, ultrasonic signal after the output terminal output amplification filtering of amplification filtering circuit 1, the in-phase input end of the in-phase input end of first comparer 2 and second comparer 3 all is connected with the output terminal of amplification filtering circuit 1, ultrasonic signal after the access amplification filtering, the inverting input of the inverting input of first comparer 2 and second comparer 3 all inserts hardware threshold value Z, the Q1 output terminal of first comparer 2 is connected with the input end of counter 5, the pulse number of the pulse train of the Q1 output terminal output of counter 5 accumulative totals first comparer 2, the output terminal output pulse number of counter 5, the non-output terminal of the Q2 of second comparer 3 is connected with the input end of phase inverter 6, the output terminal of phase inverter 6 is connected with the LE pin of second comparer 3, the Q2 output terminal output latch signal of second comparer 3, the inverting input of the 3rd comparer 4 is connected with the output terminal of amplification filtering circuit 1, ultrasonic signal after the access amplification filtering, the in-phase input end ground connection of the 3rd comparer 4, the Q2 output terminal of second comparer 3 is connected with the input end of logic and operation unit 7 respectively with the Q3 output terminal of the 3rd comparer 4, the output terminal output of logic and operation unit 7 is used for as the stop signal of judging the sign that ultrasonic signal arrives, the output terminal of logic and operation unit 7 is connected with timing chip 8 in the time difference ultrasonic flowmeter metering circuit, microcontroller 9 control waves of timing chip 8 in the time difference ultrasonic flowmeter metering circuit pick up counting when producing circuit output drive pulse signal, timing chip 8 stops timing after receiving stop signal, counter 5 is connected with microcontroller 9 respectively with timing chip 8, carry out pulse number accumulative total by microcontroller 9 control counters 5, microcontroller 9 reads the pulse number that counter 5 is added up from counter 5, picked up counting by microcontroller 9 control timing chips 8, microcontroller 9 reads from timing chip 8 between 8 timing of timing chip.
For different emission ultrasonic transducers, under the identical situation of drive pulse signal, emission ultrasonic transducer ultrasonic waves transmitted signal is different, so the voltage amplitude size for the received ultrasonic signal of different reception ultrasonic transducers also is that difference is very big, hardware threshold value Z is according to a pair of emission ultrasonic transducer and to receive ultrasonic transducer be changeless in the present embodiment, but concerning different a pair of emission ultrasonic transducers and reception ultrasonic transducer, hardware threshold value Z is different, therefore inhibition model of the present utility model is in order to use at different ultrasonic transducers, this hardware threshold value Z can regulate, for fixing a pair of emission ultrasonic transducer and reception ultrasonic transducer, after in a single day hardware threshold value Z regulates, this hardware threshold value Z has just immobilized, in fact this hardware threshold value Z is exactly a fixed voltage value, but the size of this hardware threshold value Z must be greater than the ultrasonic signal after the amplification filtering first positive period signal peak, and less than the ultrasonic signal after the amplification filtering second positive period signal peak, as shown in Figure 6, the size of hardware threshold value Z be in ultrasonic signal after the amplification filtering first positive period signal peak and the second positive period signal peak between.
In this specific embodiment, amplification filtering circuit 1 adopts prior art; It is the single-chip microcomputer of MSP430 that microcontroller can adopt model; It is the comparer of MAX963 that second comparer 3 can adopt model, also can adopt other to have the comparer of latch function; First comparer 2 and the 3rd comparer 4 can adopt the comparer of existing any maturation, can be common comparer, also can have the comparer of latch function; It is the timing chip of TDC_GP2 that timing chip 8 adopts model, also can adopt other timing chips.
Inhibition model of the present utility model utilizes the voltage magnitude size of the ultrasonic signal after first comparer 2 and second comparer, 3 comparison hardware threshold value Z and the amplification filtering, in conjunction with utilizing the relatively voltage magnitude size of the ultrasonic signal after zero levels and the amplification filtering of the 3rd comparer 4, can alleviate the shortcoming that existing threshold value relative method exists well, reduce static drift greatly, thereby improved the measuring accuracy of time difference ultrasonic flowmeter.
Utilize inhibition model of the present utility model suppress static drift method FB(flow block) as shown in Figure 5, carry out following current with time difference ultrasonic flowmeter and be measured as example, concrete inhibition method may further comprise the steps:
The output terminal that 1. will receive ultrasonic transducer is connected with the input end of amplification filtering circuit 1, with the output terminal of amplification filtering circuit 1 respectively with the in-phase input end of first comparer 2, the inverting input of the in-phase input end of second comparer 3 and the 3rd comparer 4 is connected, hardware threshold value Z is inserted the inverting input of first comparer 2 and the inverting input of second comparer 3 respectively, in-phase input end ground connection with the 3rd comparer 4, the Q1 output terminal of first comparer 2 is connected with the input end of counter 5, the non-output terminal of Q2 of second comparer 3 is connected with the input end of phase inverter 6, the output terminal of phase inverter 6 is connected with the LE pin of second comparer 3, the Q2 output terminal of second comparer 3 and the Q3 output terminal of the 3rd comparer 4 are connected with the input end of logic and operation unit 7 respectively, the output terminal of logic and operation unit 7 is connected with timing chip 8 in the time difference ultrasonic flowmeter metering circuit, counter 5 and timing chip 8 are connected with microcontroller 9 in the time difference ultrasonic flowmeter metering circuit respectively.
When 2. the pulse signal generating circuit in microcontroller 8 control time difference ultrasonic flowmeter metering circuits was exported drive pulse signal, microcontroller 9 control timing chips 8 picked up counting.Pulse signal generating circuit output drive pulse signal and timing chip 8 pick up counting and carry out synchronously, can make the mistiming that finally calculates more accurate.
3. receive ultrasonic transducer and receive the ultrasonic signal that the emission ultrasonic transducer is launched, and give amplification filtering circuit 1 with the ultrasound signal transmission that receives, 1 pair of ultrasonic signal of amplification filtering circuit carries out amplification filtering to be handled, and the ultrasonic signal after the transmission amplification filtering is given in-phase input end, the in-phase input end of second comparer 3 and the inverting input of the 3rd comparer 4 of first comparer 2.The ultrasonic signal that the reception ultrasonic transducer receives is shown in Fig. 4 a.
4. first comparer 2 compares the voltage magnitude of ultrasonic signal and the size of hardware threshold value Z, when the voltage magnitude of ultrasonic signal during greater than hardware threshold value Z, the Q1 output terminal output high level of first comparer 2, when the voltage magnitude of ultrasonic signal during less than hardware threshold value Z, the Q1 output terminal output low level of first comparer 2; Then, the pulse train of being made up of high level and low level of its Q1 output terminals output of first comparer 2 transmission is given the input end of counter 5, and counter 5 is the pulse number of pulse trains totally.At this, pulse number by counter 5 pulse sequence is counted, can solve the very violent problem of voltage amplitude variation that is caused the ultrasonic signal that receives by the environmental interference signal well, the following current time or the adverse current time that can fine judgement measure are correct data.The waveform of pulse train shown in Fig. 4 b of the Q1 output terminal output of first comparer 2.
5. second comparer 3 compares the voltage magnitude of ultrasonic signal and the size of hardware threshold value Z, when the voltage magnitude of ultrasonic signal during greater than hardware threshold value Z, the non-output terminal output low level of the Q2 of second comparer 3, when the voltage magnitude of ultrasonic signal during less than hardware threshold value Z, the non-output terminal output of the Q2 of second comparer 3 high level; Then, the pulse train of being made up of high level and low level of the non-output terminal output of its Q2 of second comparer 3 transmission is to the input end of phase inverter 6, the signal of the output terminal output of phase inverter 6 inserts the LE pin of second comparer 3, the signal of the Q2 output terminal output of second comparer 3 is latched, the Q2 output terminal output latch signal of second comparer 3, and the transmission latch signal is given the input end of logic and operation unit 7.At this, utilize second the comparer 3 relatively voltage magnitude and the size of hardware threshold value Z of the ultrasonic signal after the amplification filtering, can get rid of ultrasonic signal well and arrive and receive ultrasonic transducer undesired signal before, the error that reduces to measure.The waveform of latch signal shown in Fig. 4 c of the Q2 output terminal output of second comparer 3.
6. the 3rd comparer 4 compares the voltage magnitude of ultrasonic signal and the size of zero level, when the voltage magnitude of ultrasonic signal during less than zero level, the Q3 output terminal output high level of the 3rd comparer 4, when the voltage magnitude of ultrasonic signal during greater than zero level, the Q3 output terminal output low level of the 3rd zero comparator 4; Then, the pulse train of being made up of high level and low level of its Q3 output terminals output of the 3rd comparer 4 transmission is to the input end of logic and operation unit 7.At this, the voltage magnitude of the ultrasonic signal after utilizing the 3rd comparer 4 relatively amplification filtering being handled and the size of zero level can solve existing threshold value relative method well and cause measuring inaccurate problem because of the variation of the voltage magnitude of ultrasonic signal.The waveform of signal shown in Fig. 4 d of the Q3 output terminal output of the 3rd comparer 4.
7. the pulse train of 7 pairs of latch signals in logic and operation unit and 4 outputs of the 3rd comparer is carried out logic and operation, its output terminal output is used for as the stop signal of judging the sign that ultrasonic signal arrives, and transmitting stop signal to the timing chip, timing chip 8 stops timing after receiving stop signal.At this, utilize the signal of the Q3 output terminal output of the signal of Q2 output terminal output of second comparer 3 and the 3rd comparer 4 to carry out the logical and operation, can suppress the static drift problem well.The S waveform of stop signal shown in Fig. 4 e.
8. microcontroller 9 reads the pulse number of counter 5 accumulative totals from counter 5, judges the fixed value whether pulse number equals to set then, if then read between 8 timing of timing chip the T shown in Fig. 4 e
3, with this time T that reads
3As the following current time, otherwise, give up this time timing, repeat then 2. to process 9..
9. measure identical mode with above-mentioned following current and record the adverse current time, be designated as T '
3, microcontroller is according to the following current time T
3With the adverse current time T '
3Can accurately calculate both mistiming Δ T, Δ T=|T
3-T '
3|.
10. microcontroller calculates instantaneous delivery according to the mistiming.
For further reducing static drift, improve the antijamming capability of time difference ultrasonic flowmeter, can in the detailed process of inhibition method, increase the software smooth filtering method, to reduce of the influence of random disturbance signal to hardware system, reject the error information (promptly rejecting too small or excessive data in the measurement) in the measuring process, make the flow of measuring more near actual value, improve measuring accuracy.The implementation procedure of software smooth filtering method is: repeat N step 1.～9., realize the identical measurement of N group, obtain the N group mistiming, the N group mistiming is carried out The disposal of gentle filter, obtain that more precise time is poor, and then calculate more accurate instantaneous flow.At this, the value of N is big more, and the degree of accuracy of the final mistiming that then obtains is high more, but simultaneously computation complexity can be than higher, and the value of N is too little, the final mistiming that then obtains accurately relatively low.In the present embodiment, can when one-shot measurement, measure 60 groups of mistiming data, then these 60 groups of mistiming data are sorted, remove minimum and maximum each 10 groups of mistiming data, 40 groups of mistiming data to the centre are averaged then, realize The disposal of gentle filter, with the mean value that obtains as the final mistiming, because this mistiming is more near actual value, this mistiming is more accurate, and therefore the instantaneous delivery that calculates according to this mistiming is also more accurate.
In this specific embodiment, the size of the fixed value of setting is to determine according to the size of the size of hardware threshold value Z and the ultrasonic signal after the amplification filtering, for a pair of specific emission ultrasonic transducer and reception ultrasonic transducer, the voltage magnitude of the ultrasonic signal after the amplification filtering is fixed, and hardware threshold value Z is in case after determining well, the pulse number of the pulse train of the Q1 output terminal of first comparer output has also just been determined so, pulse number is a fixed value, pulse train as Fig. 4 a, this fixed value can be made as 5, counter paired pulses number is counted, and when following current time or adverse current time being measured, microcontroller reads this count value and fixed value compares at every turn, if not etc., this group data are abandoned in measuring, if equate that microcontroller reads following current time or the adverse current time in the timing chip.
For ultrasonic transducer, if under the certain situation of drive pulse signal, the waveform that the reception ultrasonic transducer receives ultrasonic signal is constant, number by counter pulse totally is constant, the value of supposing constant number is the fixed value in the present embodiment, when carrying out one-shot measurement so, when if the pulse number of accumulative total is this fixed value, then measure next time, when if the pulse number of accumulative total is not this fixed value, then give up the data of this time measurement, remeasure.
Claims (4)
1. a static drift of time difference ultrasonic flowmeter suppresses model, it is characterized in that comprising the amplification filtering circuit, first comparer, second comparer with latch function, the 3rd comparer, counter, phase inverter and logic and operation unit, described first comparer has Q1 output terminal and the non-output terminal of Q1, described second comparer has Q2 output terminal and the non-output terminal of Q2, described the 3rd comparer has Q3 output terminal and the non-output terminal of Q3, the input end of described amplification filtering circuit is connected with the reception ultrasonic transducer, the ultrasonic signal that described amplification filtering circuit receives the reception ultrasonic transducer carries out amplification filtering to be handled, ultrasonic signal after the output terminal output amplification filtering of described amplification filtering circuit, the in-phase input end of the in-phase input end of described first comparer and described second comparer all is connected with the output terminal of described amplification filtering circuit, ultrasonic signal after the access amplification filtering, the inverting input of the inverting input of described first comparer and described second comparer all inserts the hardware threshold value, the Q1 output terminal of described first comparer is connected with the input end of described counter, the pulse number of the pulse train of the Q1 output terminal output of described first comparer of described counter accumulative total, the output terminal output pulse number of described counter, the non-output terminal of the Q2 of described second comparer is connected with the input end of described phase inverter, the output terminal of described phase inverter is connected with the LE pin of described second comparer, the Q2 output terminal output latch signal of described second comparer, the inverting input of described the 3rd comparer is connected with the output terminal of described amplification filtering circuit, ultrasonic signal after the access amplification filtering, the in-phase input end ground connection of described the 3rd comparer, the Q2 output terminal of described second comparer is connected with the input end of described logic and operation unit respectively with the Q3 output terminal of described the 3rd comparer, the output terminal output of described logic and operation unit is used for as the stop signal of judging the sign that ultrasonic signal arrives, the output terminal of described logic and operation unit is connected with timing chip in the time difference ultrasonic flowmeter metering circuit, the microprocessor controls pulse signal generating circuit of described timing chip in the time difference ultrasonic flowmeter metering circuit picks up counting when exporting drive pulse signal, described timing chip stops timing after receiving stop signal, described counter is connected with described microcontroller respectively with described timing chip.
2. a kind of static drift of time difference ultrasonic flowmeter according to claim 1 suppresses model, it is characterized in that described microcontroller is that model is the single-chip microcomputer of MSP430.
3. a kind of static drift of time difference ultrasonic flowmeter according to claim 2 suppresses model, and the model that it is characterized in that described second comparer is MAX963.
4. a kind of static drift of time difference ultrasonic flowmeter according to claim 3 suppresses model, and the model that it is characterized in that described timing chip is TDC_GP2.
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| CN2010202242515U CN201795819U (en) | 2010-06-10 | 2010-06-10 | Static drift rejection model of time difference method ultrasonic flowmeter |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101886939A (en) * | 2010-06-10 | 2010-11-17 | 宁波大学 | Inhibition model and inhibition method for static drift of time difference ultrasonic flowmeter |
| CN102323585A (en) * | 2011-08-30 | 2012-01-18 | 广州优创电子有限公司 | Treatment method for ultrasonic wave |
| CN103542900A (en) * | 2012-07-12 | 2014-01-29 | 成都科盛石油科技有限公司 | Oil field petroleum flow measurement system based on TDC-GP2 |
| CN104034375A (en) * | 2014-06-27 | 2014-09-10 | 苏州东剑智能科技有限公司 | Method for adopting ultrasonic waves to measure flow |
| CN104236646A (en) * | 2013-06-19 | 2014-12-24 | 财团法人工业技术研究院 | Ultrasonic flowmeter and ultrasonic flow measuring method |
| WO2022041582A1 (en) * | 2020-08-31 | 2022-03-03 | 宁波飞芯电子科技有限公司 | Drive circuit and drive method |
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2010
- 2010-06-10 CN CN2010202242515U patent/CN201795819U/en not_active Expired - Fee Related
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101886939A (en) * | 2010-06-10 | 2010-11-17 | 宁波大学 | Inhibition model and inhibition method for static drift of time difference ultrasonic flowmeter |
| CN102323585A (en) * | 2011-08-30 | 2012-01-18 | 广州优创电子有限公司 | Treatment method for ultrasonic wave |
| CN103542900A (en) * | 2012-07-12 | 2014-01-29 | 成都科盛石油科技有限公司 | Oil field petroleum flow measurement system based on TDC-GP2 |
| CN104236646A (en) * | 2013-06-19 | 2014-12-24 | 财团法人工业技术研究院 | Ultrasonic flowmeter and ultrasonic flow measuring method |
| CN104236646B (en) * | 2013-06-19 | 2017-07-14 | 财团法人工业技术研究院 | Ultrasonic flowmeter and ultrasonic flow measuring method |
| CN104034375A (en) * | 2014-06-27 | 2014-09-10 | 苏州东剑智能科技有限公司 | Method for adopting ultrasonic waves to measure flow |
| CN104034375B (en) * | 2014-06-27 | 2017-02-15 | 苏州东剑智能科技有限公司 | Method for adopting ultrasonic waves to measure flow |
| WO2022041582A1 (en) * | 2020-08-31 | 2022-03-03 | 宁波飞芯电子科技有限公司 | Drive circuit and drive method |
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