JP5228462B2 - Fluid flow measuring device - Google Patents

Description

  The present invention relates to a fluid flow measuring apparatus that measures the flow velocity and flow rate of a fluid such as a gas or a liquid using an ultrasonic wave using a vibrator.

  A conventional fluid flow measuring device will be described with reference to FIG. 9. A pair of ultrasonic vibrators 102 and 103 are arranged on the upstream side and the downstream side of a flow path 101 through which a fluid flows, and the ultrasonic waves are fluidized. Is crossed diagonally.

  Then, the flow velocity of the fluid is measured from the difference in propagation time of the ultrasonic wave propagating between the pair of ultrasonic transducers 102 and 103, and the flow rate is calculated based on this. For example, the flow velocity can be calculated from the propagation time difference, and the flow rate value can be calculated in consideration of the size of the pipeline and the flow state.

In addition, the solid line arrow 104 in a figure shows the direction through which a fluid flows, and the broken line arrow 105 has shown the direction through which an ultrasonic wave propagates. The direction in which the fluid flows and the direction in which the ultrasonic waves propagate intersect at an angle θ (for example, see Patent Document 1).
JP 2002-13958 A

  However, in the conventional measuring apparatus, the ultrasonic wave is propagated from the upstream ultrasonic transducer 102 to the downstream ultrasonic transducer 103 to determine the ultrasonic propagation time Tud and the downstream ultrasonic transducer. The ultrasonic wave is propagated from 103 to the upstream ultrasonic vibrator 102, the ultrasonic propagation time Tdu is measured alternately, the time difference is calculated using the measured ultrasonic propagation times Tud, Tdu, and the flow rate is calculated. It was.

  At this time, a reference level is set to a received waveform portion where a predetermined amplitude can be obtained as a trigger level, and a propagation time is measured. Therefore, the propagation time of the ultrasonic wave cannot be measured using the zero cross point before the trigger level.

  For this reason, an uncertain time is included in the arrival time of the ultrasonic wave, which may cause an error, and there is a problem that high-precision flow measurement cannot be realized.

  That is, the ultrasonic reception waveform generally rises at a frequency driven by a drive circuit, and sequentially changes to a vibration frequency unique to the ultrasonic transducer.

  Alternatively, since the reception waveform of the ultrasonic wave is affected by the reflected wave from the side wall of the flow path or the like, the frequency at the rising portion near the reception point is stable, but the trigger level is relatively high. In the portion where the reception amplitude is large, a difference occurs in the waveform received between the upstream side and the downstream side, which is detected as an error in propagation time.

  In addition, since the ultrasonic wave reflected by the side wall of the channel 101 arrives at the received wave with a slight delay and is received as the received wave, a zero cross point that passes through the zero point when the received waveform is subtracted from the offset is obtained. Sometimes it was uncertain.

  Furthermore, the measurement for a longer time than the arrival time originally has the problem of increasing the current consumption because the measurement device is operated extra for that time.

  The present invention solves the above-described conventional problem, and uses at least two arrival times of the zero cross point of the received ultrasonic wave before the trigger level, and calculates the average value to determine the ultrasonic wave arrival time. An object of the present invention is to realize a power saving operation while realizing high-accuracy measurement while reducing the error included in the propagation time of ultrasonic waves so that measurement can be performed.

In order to solve the above-described conventional problems, the flow velocity or flow rate measuring device of the present invention is arranged in a flow path through which a fluid to be measured flows , and a pair of transducers that transmit and receive ultrasonic waves and a transmission that drives one transducer Means, a receiving means for converting the output signal of the other receiving-side transducer into an electric signal, a received wave judging means for outputting a signal when the signal of the receiving means reaches a predetermined value, and a signal of the receiving means is a zero cross point predetermined and reception point detection unit for outputting a signal to become time the ranges, at least two or more reception point storage means stores as the elapsed time from the transmission start an output of the reception point detection unit, said reception point storage as Measuring means for measuring the propagation time of the ultrasonic signal propagated between the transducers using the elapsed time stored in the means , and the propagation time from the upstream to the downstream and the propagation time from the downstream to the upstream obtained by the timing means. Based on time difference And flow rate calculation means to calculate the flow rate, at least one of the previous SL transmitting means and the receiving means and the reception wave determination unit and the reception point detection unit and the reception point storage means said clock means and said flow rate calculation means and control means for controlling, the control means, the output of the reception wave determination unit, selects a plurality of elapsed time stored in the reception point storage unit climbed reverse as many predetermined for the operational propagation time Receiving point selecting means is provided, and the receiving point storing means is overwritten and updated until there is an output signal of the received wave determining means.

  With this configuration, the propagation time of the ultrasonic wave propagating between the ultrasonic transducer on the upstream side and the ultrasonic transducer on the downstream side, that is, the arrival time of the ultrasonic wave is set to zero of the received ultrasonic wave before the trigger level. Use at least two cross-point arrival times, find the average value and measure the ultrasonic arrival time, reduce errors contained in the ultrasonic propagation time, and perform highly accurate measurements. Power saving operation can be realized while realizing it.

  The flow velocity or flow rate measuring device according to the present invention uses at least two arrival times of the received ultrasonic zero crossing point before the trigger level and calculates the average value to measure the ultrasonic arrival time. Can do. For this reason, the error included in the propagation time or arrival time of the measured ultrasonic wave can be reduced by using the average value of multiple zero cross points, and power saving operation is achieved while realizing highly accurate flow measurement. it can.

1st invention is arrange | positioned at the flow path through which the to-be-measured fluid flows , a pair of vibrator | oscillator which transmits / receives an ultrasonic wave, the transmission means which drives one vibrator | oscillator, and the output signal of the other receiving side vibrator | oscillator is an electrical signal Receiving means for converting the signal to the receiving means, a received wave determining means for outputting a signal when the signal of the receiving means reaches a predetermined value, and a reception point detection for outputting a signal each time the signal of the receiving means falls within a predetermined range as a zero cross point. Means, at least two or more reception point storage means for storing the output of the reception point detection means as an elapsed time from the start of transmission, and propagation between the transducers using the elapsed time stored in the reception point storage means a counting means for counting the propagation time of the ultrasonic signal, and flow rate calculation means to calculate the flow rate from the propagation time and the downstream from upstream to downstream, determined by the clock means based on the time count difference of the propagation times to the upstream, the reception of the previous Symbol transmission means And control means for controlling at least one of the stages and the received wave determining means and the reception point detection unit and the reception point storage means, said clock means and said flow rate calculation means, said control means, said reception wave determination A receiving point selecting means for selecting a plurality of elapsed times stored in the receiving point storage means that has been reversed by a predetermined number by the output of the means for calculating the propagation time, and the receiving point storage means includes the received wave Overwriting is updated until there is an output signal from the judging means.

With this configuration, the propagation time of the ultrasonic wave propagating between the ultrasonic transducer on the upstream side and the ultrasonic transducer on the downstream side, that is, the arrival time of the ultrasonic wave is set to zero of the received ultrasonic wave before the trigger level. Use at least two cross-point arrival times, find the average value and measure the ultrasonic arrival time, reduce errors contained in the ultrasonic propagation time, and perform highly accurate measurements. Power saving operation can be realized while realizing it.

The second aspect of the invention is particularly the invention of the first aspect , wherein the control means starts energization of the reception point storage means from a time point sufficiently shorter than a propagation time estimated in advance only for the first time, and determines the received wave By having power supply means that stops after the output of the means, it is possible to reliably capture the received wave by preparing to store the output of the received wave detection means before the received wave originally arrives at the time of the first measurement Is possible.

A third invention is the control means, especially in the first invention, second and subsequent energization to the reception point storage means, said power supply means so as to start from a slower than the first time based on the previous propagation time By adjusting the timing, preparation for storing the output of the reception wave detection means immediately before the reception wave arrives makes it possible to reliably capture the reception wave and to save power.

The fourth invention is particularly the first invention , wherein the control means has trigger means for outputting a signal when the output of the reception point detection means exceeds a predetermined number of times, and the power supply means is based on the output of the trigger means. by starting the energization of the reception point storage unit, a shorter time with improved reliability by preparing for storing output of the reception wave detection means after confirming that the received reliably wave reaches Power saving operation by operation becomes possible.

The fifth invention is particularly configured to have a program for causing a computer to function as the control means in any one of the first invention to the fourth invention, thereby making it easy to set and change the operation of the measurement method. In addition, since it can flexibly cope with aging, etc., it is possible to improve the measurement accuracy and power saving operation more flexibly.

  Embodiments of the present invention will be described below with reference to the drawings. Note that the embodiments described below do not limit the present invention.

(Embodiment 1)
In FIG. 1, a first vibrator 32 and a second vibrator 33 are installed on the upstream side and the downstream side of the flow path 31 through which the fluid to be measured flows, and the supersonic wave that propagates between the vibrators 32 and 33. The sound wave is set so as to cross the channel 31 obliquely.

  In addition, transmission means 34 for driving the first vibrator 32 and the second vibrator 33, and reception for receiving signals received by the first vibrator 32 and the second vibrator 33 and amplifying the signals. Means 35, a received wave determination means 36 that outputs a signal when the signal of the receiving means 35 reaches a predetermined value, a reception point detection means 37 that outputs a signal when the signal of the receiving means 35 falls within a predetermined range, and the reception Two reception point storage means 38 for storing the output of the point detection means 37; time measurement means 39 for measuring the propagation time of the ultrasonic signal propagated between the transducers using the signal of the reception point storage means 38; And a flow rate calculating means 40 for calculating a flow rate based on the time difference of the time measuring means 39.

  Further, a switching means 41 is provided between the transmission means 34 and the first vibrator 32, and between the second vibrator 33 and the reception means 35, and the first vibrator 32 and the second vibrator 33 are ultrasonic waves. It operates by switching between transmission and reception.

  The reception point storage means 38 has at least two or more storage units, and after the start of storage, it is overwritten and updated until there is an output signal of the reception wave determination means 36.

  The control means 42 includes the transmission means 34, the reception means 35, the reception wave determination means 36, the reception point detection means 37, the reception point storage means 38, the timing means 39, the flow rate calculation means 40, and the switching. Control at least one of the means 41.

  Further, the control means 42 has a reception point selection means 43, and when the reception wave determination means 36 detects that the ultrasonic wave has arrived at the receiving-side transducer, it goes back to a time close to the original reception wave arrival point. At least two or more values are selected from the reception point data stored in the storage means 38 for calculating the propagation time, and sent to the time measuring means 39 for measuring the propagation time.

  The time measuring means obtains the propagation time using the average value of the received reception point data and passes the value to the flow rate calculating means 40.

  The flow rate calculation means 40 obtains the flow rate based on the difference in propagation time, that is, the difference between the propagation time from the upstream side and the propagation time from the downstream side, and obtains the flow rate from the product of the cross-sectional area of the flow path.

  A normal flow rate or flow rate measurement operation will be described.

  Upon receipt of the start signal from the control means 42, the transmission means 34 pulse-drives the first vibrator 32 for a certain time, and at the same time, the time measuring means 39 starts measuring time. An ultrasonic wave is transmitted from the pulse-driven first vibrator 32.

  The ultrasonic wave transmitted from the first vibrator 32 propagates through the fluid to be measured and is received by the second vibrator 33.

  The reception output of the second vibrator 33 amplifies the signal by the receiving means 35 and then determines the reception of the ultrasonic wave at the signal level at a predetermined reception timing.

  When the reception of the ultrasonic wave is determined, the operation of the time measuring means 39 is stopped, and the flow velocity is obtained from the time information t according to (Equation 1).

  The measurement time obtained from the time measuring means 39 is t, the effective distance in the flow direction between the ultrasonic transducers is L, the angle is φ, the sound velocity is c, and the flow velocity of the fluid to be measured is v.

v = (1 / cosφ) * (L / t) −c (1)
The receiving means 35 is usually configured to compare the reference voltage and the received signal by a comparator.

  Further, the transmission and reception directions of the first ultrasonic transducer 32 and the second ultrasonic transducer 33 are switched, and the respective propagation times of the fluid under measurement from upstream to downstream and from downstream to upstream are measured. The speed v can be obtained from (Expression 2), (Expression 3), and (Expression 4).

  Note that the measurement time from upstream to downstream is t1, and the measurement time from downstream to upstream is t2.

t1 = L / (c + v * cosφ) (2)
t2 = L / (c−v * cos φ) (3)
v = (L / 2 * cos φ) * [(1 / t1) − (1 / t2)] (4)
According to this method, the flow rate can be measured without being affected by the change in the sound speed, and thus it is widely used for measuring the flow velocity, the flow rate, the distance, and the like.

  When the flow velocity v is obtained, the flow rate can be derived by multiplying it by the cross-sectional area of the flow path 31.

  The conventional operation will be described with reference to FIGS.

  Measurement is started from the start signal at time t0 by the control means 42, and the first ultrasonic transducer 32 is driven via the transmission means 34.

  The ultrasonic signal generated there propagates through the flow path, and the ultrasonic wave emitted from the first ultrasonic transducer 32 reaches the second ultrasonic transducer 33 at time t1.

  The received signal is amplified by the receiving means 35, and when the signal level reaches a predetermined value (Vref), the received wave determining means 36 determines that the received wave has arrived and outputs a signal. Based on this signal, the reception point detection means 37 starts to operate, outputs a signal with the first zero cross point after Vref as the reception point, and the time until this point is obtained by the time measurement means 39.

  The switching means 41 switches between transmission and reception to perform the same operation, and the flow rate calculation means 40 calculates the flow rate based on the difference between the time obtained by the time measuring means 39 and the time previously obtained.

  Here, the point ta in FIG. 3A is after Vref. This is because the value of Vref is used for reception wave determination, and the subsequent zero cross point ta is used as the reception point. For example, if the signal wave is 100 kHz and the propagation time is around 100 μs, a zero cross point such as ta occurs every 5 μs.

  As can be seen from FIG. 3, the received wave reaches before Vref. As the signal before Vref can be used, the arrival time of the ultrasonic wave is less likely to include an uncertain time. Further, if a signal before 5 μs can be used, the measurement time can be shortened by 5% when the propagation time of 100 μs is measured, and the current consumption can be reduced.

  Let p be the zero reference that is the reference for the zero crossing point. If the offset occurs on the plus side, the zero reference becomes q and the zero crossing point arrives earlier than originally intended.

  On the contrary, when the offset occurs on the minus side, the zero reference becomes r and the zero cross point occurs later than originally intended.

  Similarly, when noise occurs and the received waveform shifts to the plus side, the zero cross point arrives later than the original ta point, and conversely, if the received waveform shifts to the minus side due to noise or the like, the zero cross point becomes less than the original ta point. It will arrive early.

  In this way, it is conceivable that the reception time accuracy deteriorates due to disturbances such as offset and noise in the reception point determination of only one point.

  Therefore, a method will be described in which a zero cross point before Vref is detected, and a reception point is obtained systematically even when a disturbance such as an offset occurs.

  It suffices to simply obtain the point where the received wave arrives at the zero cross point, for example, the point a in FIG. 3, but in that case, Vref cannot be set. If the next b point close to it is a reception wave arrival point, Vref must be a broken line Vref-sub. In this case, since it is close to a zero signal, there is a possibility of erroneous detection by reacting with a change in waveform or a little noise when a flow rate flows.

  In order to avoid such a phenomenon and determine the arrival point of the received wave with higher accuracy than normal ta, two or more zero cross points are obtained continuously, and the average value is used to cancel the offset deviation. Can do.

  For example, as shown in FIG. 3B, the occurrence of an offset may cause the conventional zero cross point to shift from the ta point to the tb and tc points. In that case, the Ta time as a reception wave arrival point becomes very unstable.

  When the average is obtained using two zero cross points, tx is obtained with respect to ta, ty with respect to tb, and tz with respect to tc, and the average Ta 'becomes a constant value and is stabilized. Here, tb after Vref is used, but this operation has the same effect even if two zero cross points are used using a received wave before Vref.

  When an even number of zero cross points are used, it is possible to narrow down by averaging operation more than when two reception point fluctuations due to zero reference deviation are used.

  Therefore, a method of starting to detect the zero cross point before Vref will be described.

  It suffices to simply obtain the zero cross point from the point where the received wave arrives, for example, point a in FIG. 3, but in that case, Vref cannot be set.

  If the next b point close to it is a reception wave arrival point, Vref must be a broken line Vref-sub.

  In this case, since it is close to a zero signal, there is a possibility of erroneous detection by reacting with a change in waveform or a little noise when a flow rate flows.

  In order to avoid such a phenomenon and determine the arrival point of the received wave in a shorter time than the normal ta, it is only necessary to detect at least two zero cross points before Vref and take the average value.

  In order to realize this operation, measurement is started from the start signal at time t0 by the control means 42 and the first ultrasonic transducer 32 is driven via the transmission means 34.

  The ultrasonic signal generated there propagates through the flow path, and the ultrasonic wave emitted from the first ultrasonic transducer 32 reaches the second ultrasonic transducer 33 at time t1.

  The received signal is amplified by the receiving means 35, and when the signal level reaches a predetermined value (Vref), the received wave determining means 36 determines that the received wave has arrived and outputs a signal.

  For this reason, the reception point detecting means 37 that outputs a signal when it falls within a predetermined range as a zero cross point, for example, within plus 1 mV or minus 1 mV, starts operation.

  Then, when the point a in FIG. 4 is reached, the reception point detection unit 37 outputs a signal, and the reception point storage unit 38-1 stores the output. If the value to be stored is the elapsed time from the time of transmission or the number of pulses having a specific fixed time width in which the elapsed time can be measured, the subsequent calculation is facilitated.

  Next, at the point b, the reception point storage means 37 outputs a signal and stores it in the reception point storage means 38-2. Similarly, the reception point data at the next point c is sequentially stored in the reception point storage means 38-3.

  In this case, when the reception point data is larger than the number of reception point storage means 38, the control unit 46 may control the order of writing so that the oldest reception points are overwritten sequentially.

  For example, as shown in FIG. 4B, after storing up to the reception point storage unit 38-4, the next is to return to the reception point storage unit 38-1 and overwrite.

  The received wave determination means 36 outputs a signal for the first time when the received signal exceeds Vref.

When the signal is output from the reception wave determination unit 36, the control unit 46 prevents the reception point detection unit 37 from outputting a signal at the subsequent zero cross point, or writes to the reception point storage unit 38. Ban.

  Since at least one zero cross point up to tx is stored by performing this operation, two or more of the zero cross points up to tx are used, and the time measuring means 39 obtains the propagation time using the average value.

  At that time, the control means 42 uses the reception point selection means 43, and when the reception wave determination means 36 detects that the ultrasonic wave has reached the receiving-side transducer, the time close to the original reception wave arrival point, for example, FIG. ) From the received point data stored in the received point storage means 38 to the last stored point data for propagation time calculation, and at least two values as far as possible are selected and propagated. The time is sent to the time measuring means 39.

  The closer to point a in FIG. 4 (a), the more correctly received point can be detected without distortion of the received waveform. However, since the amplitude is small, it is easily affected by noise.

  Therefore, it is also possible to estimate the point a by subtracting a predetermined constant value from the average value as the propagation time using, for example, the points b and c several points before Vref.

  Since the receiving point storage means 38 is overwritten sequentially from the oldest one, the data next to the overwritten value is the oldest.

  The number going back is determined in advance by experiments, etc., or if data near the point a in FIG. 4 (a) is likely to cause a large error due to noise, it is determined several points before Vref. It may be set to a different value.

  Further, the reception point data (propagation time) used by the time measuring means 39 is useful because it is possible to cancel the offset when two continuous points or even numbers are used.

  However, it is also possible to use an odd number from the rising edge or an odd number from the falling edge depending on the characteristics of the flow path and the characteristics of the vibrator.

  With this configuration, the propagation time of the ultrasonic wave propagating between the ultrasonic transducer on the upstream side and the ultrasonic transducer on the downstream side, that is, the arrival time of the ultrasonic wave is set to zero of the received ultrasonic wave before the trigger level. By using at least two cross point arrival times in succession, the average value can be obtained and measured.

  For this reason, even if an offset or the like is superimposed, it is possible to cancel the rising zero point and the falling zero point.

  The switching means 41 switches between transmission and reception to perform the same operation, and the flow rate calculation means 40 calculates the flow rate based on the difference between the time obtained by the time measuring means 39 and the time previously obtained.

  As a result, the propagation time that has been required up to ta in FIG. 4 can be determined up to tx or the zero cross point before that.

  Specifically, the Ta-Tf time can shorten the measurement operation time of the propagation time by an integral number of the half cycle Tf of the transmission frequency.

  As it is, the propagation time is fixed at ta in FIG. 4A, but the influence of offset and the like cannot be avoided.

  In this method, by using the average value of a plurality of zero cross points, an error included in the propagation time or arrival time of the measured ultrasonic wave can be reduced, and highly accurate flow measurement can be realized. In addition, even in a state where the number of zero cross points increases, a plurality of zero cross points in the vicinity of the reception wave determination means can be reliably captured, and the number of reception point storage means can be appropriately reduced and overwritten sequentially. Power saving operation becomes possible.

  The reception point storage means 38 for storing the output of the reception point storage means 37 consumes power to perform the storage operation, but it is often unknown in advance from which time point the power supply can be energized.

  If it is turned on too early, power is wasted, and there is no point in energizing after passing the reception point.

  Therefore, as shown in FIG. 5, a power supply unit 44 is provided in the control unit 42 to perform power control. The timing will be described with reference to FIG.

  When measurement is started first, Ta is unknown. Although the approximate time can be estimated from the physical distance between the ultrasonic transducers 32 and 33, it is not certain.

  Therefore, the control unit 42 uses the power supply unit 44 to adjust the energization timing to the reception point storage unit 38.

  First, measurement is started from a start signal at time t 0 and the first ultrasonic transducer 32 is driven via the transmission unit 34.

  The ultrasonic signal generated there propagates through the flow path, and the ultrasonic wave emitted from the first ultrasonic transducer 32 reaches the second ultrasonic transducer 33 at time t1.

  At the previous time t2, energization to the reception point storage means 38 is started using the power supply means 43. t2 is a time sufficiently shorter than t1.

  In this way, the control means 42 has the power supply means 44 for energizing the reception point storage means 38 for storing the output of the reception point detection means 37 for a long time only for the first time. By preparing to store the output of the received wave detection means before the wave arrives, it is possible to reliably receive the received wave.

  In addition, the reception point is determined by the first time and the propagation time is obtained. In that case, it becomes easy to adjust the energization time after the second time.

  For example, the energization of the reception point storage unit 38 is first started at t2 in FIG. 6, but it is at t1 that the ultrasonic wave actually propagates and is received.

  In the next measurement, since the propagation time does not change significantly, the power supply means 44 in the control means 42 can wait for energization until t2 where the reception signal is not reached yet near t1. .

  The third time uses the second propagation time, or uses the first and second moving averages to predict the propagation time, thereby making it possible to shorten the energization time as much as possible.

  In this way, the control means 42 adjusts the timing of the power supply means 43 so that the reception point storage means 38 for storing the output of the reception point detection means 37 is energized for the second time and thereafter, based on the previous value. Thus, by preparing for storing the output of the reception wave detection means immediately before the reception wave arrives, the reception wave can be reliably captured and a power saving operation can be performed.

  In this description, only the energization time of the reception point storage means 38 is adjusted. However, if the operation downstream from the reception means 35 for amplifying the reception signal does not continue to be unstable for a long time when the power is turned on, a set of them or particularly If the power supply means 44 adjusts the energization of the part that requires power, further power saving can be achieved.

  Further, the state from the zero cross point a to d in FIG. 4A is equivalent to the enlarged state in the vicinity of t3 to t1 in FIG.

In this case, the reception unit 35 operates before the reception signal arrives, and the reception point detection unit 37 also operates to send a signal for each of a, b, c, and d.

In FIG. 7, the control means 42 counts the output signal of the reception point detection means 37, and if the number of times reaches a predetermined number of times, for example, twice, the trigger means 45 receives the signal via the power supply means 44 when the reception point reaches the point b. Energization of the point storage means 38 is started.

  The energization time until tx when reception is confirmed can be further shortened.

In this way, the control means 42 has the trigger means 45 that outputs a signal when the output of the reception point detection means 37 exceeds a predetermined number of times, and the power supply means 44 outputs the output of the reception point detection means 37 by the output of the trigger means. By starting energization to the reception point storage means 38 to be stored, the zero cross points from the reception point storage means 38 are stored up to the number of Vrefs or the number of reception point storage means 38 prepared in advance.

  And the propagation time is calculated | required using two continuous zero crossing point data from them. Thus, by confirming that the received wave has arrived reliably, and preparing to store the output of the received wave detecting means 37, the reliability is improved and a power saving operation by a shorter time operation becomes possible.

  In addition, the zero cross point in FIG. 4 is generated at a period substantially half the transmission frequency if noise is not superimposed on the received wave.

  However, when a fluid actually flows in the flow path, something is operating downstream by the fluid.

  A spike-like signal may be superimposed on the received wave due to this operation or other external noise. In this case, if the point where the noise crosses zero is taken as the reception point, the calculation of the propagation time will be greatly shifted. In order to prevent this, the time verification means 46 is provided in the control means 42 as shown in FIG.

  The operation will be described. First, similarly to FIG. 4, when the reception of the zero cross point starts, the reception point detection means 37 outputs a signal, and the output is stored in the reception point storage means 38-1.

  If the value to be stored is the elapsed time from the time of transmission or the number of pulses having a specific fixed time width in which the elapsed time can be measured, the subsequent calculation is facilitated.

  Next, when the point b is reached, the reception point storage unit 37 outputs a signal, and the reception point storage unit 38-2 stores the reception point data. After storing the points c and d and the point tx, the received signal exceeds Vref.

At this time, the reception wave determination means 36 outputs a signal for the first time. When a signal is output from the reception wave determination means 36, the control means prevents the reception point detection means 37 from outputting a signal at the subsequent zero cross point, or prohibits writing to the reception point storage means 38. To do.

  Then, the time of the next zero cross point ta is sent directly to the time verification means 46 of the control means without going through the reception point storage means 38. The time verification means 46 sequentially obtains the difference between the value of the reception point data in the reception point storage means 38 and the value of ta.

  If this difference is within a predetermined range, it is determined that the data at points a, b, c, and tx are not due to noise, and it is determined that the data can be adopted as a flow rate calculation. Then, the flow rate is calculated using two or more zero cross points among them.

  For example, if the transmission frequency is 100 kHz, the half of the cycle is 5 μs. Therefore, if tx-ta is within a predetermined vicinity of 5 μs, it is determined that tx is an effective reception point.

  Similarly, if a-ta is within the vicinity of an integer multiple of 5 μs, it is determined as an effective reception point. The same determination is made for points b, c, and d.

As described above, the control unit 42 includes the time verification unit 46 that calculates the difference between the output of the reception point detection unit 37 after the output of the reception wave determination unit 36 and the value of the reception point storage unit 38. If the value is within a predetermined value, measurement can be enabled to prevent false detection of the zero cross point due to noise, etc., and reliability can be improved by selecting an accurate zero cross point. become.

  Further, after the received signal exceeds Vref before the zero cross point tx in FIG. 4, the circuit subsequent to the receiving means 35 does not need to operate other than the time measuring means 39 and the flow rate calculating means 40.

  Therefore, when the received wave determination means 36 detects that the received wave exceeds Vref, the control means 42 stops the energization to the reception point storage means 38 to perform the power saving operation and perform the unnecessary energization operation of the receiving circuit. It is possible to stop.

  The time of stopping may be immediately after exceeding Vref, or noise may be generated by a signal at the time of stopping energization and the operation of the timing means 39 etc. may not be adversely affected, so that the next zero cross point ta is detected. The power supply may be stopped after that.

  In this way, the control means 42 stops the power supply to the reception point storage means 38 via the power supply means 43 after the elapse of a predetermined time after the output of the reception point detection means 37 after the output of the reception wave determination means 36. As a result, the operation of measuring and storing the extra zero cross point can be stopped, and the power saving operation can be realized.

  Although it has been described in FIG. 3B that the average value Ta ′ of the tx and ta2 points can be determined as the reception arrival point, it will be described because it may seem different from the conventional arrival point Ta. The original reception arrival point is point a in FIG.

  As described above, it is very difficult to detect only this point. Therefore, a time Ta to ta is obtained, and a time to point a is obtained by subtracting a predetermined constant.

  Therefore, when tx and ta are used, the time to the reception arrival point a can be calculated by adjusting a predetermined constant by a value of a quarter period (ta-tx) / 2 of the received wave. is there. Since Ta 'has less error than Ta, the time to a can be obtained stably.

  This explanation uses two zero cross points, but the case of an even number of zero cross points is similarly stable.

(Embodiment 2)
A fluid flow measuring apparatus according to the second embodiment will be described with reference to FIG.

  The difference from the first embodiment is that the signals of the reception wave determination means 36 and the reception means 35 that output signals when the signals of the vibrators 32 and 33, the transmission means 34, the reception means 35, and the reception means 35 reach predetermined values. Receiving point detecting means 37 that outputs a signal when it falls within a predetermined range, receiving point storing means 38 that stores the output of the receiving point detecting means 37, and the signal transmitted from the receiving point storing means 38 that has propagated between the transducers. At least one of a time measuring means 39 for measuring the propagation time of the sound wave signal, a flow rate calculating means 40 for calculating a flow rate based on a time difference of the time measuring means 39, a switching means 41 for switching between transmission and reception, and a receiving point selecting means 43. That is, the storage medium 47 having a program for causing a computer to function to ensure the operation of the control means 42 to be controlled is used.

  In order to perform the operation of the control means 42 shown in the first embodiment, the operation of the reception point storage means for obtaining tx and the energization method are obtained in advance by experiments or the like, the secular change, the temperature change, the stability of the system Correlation such as operation timing with respect to the degree is obtained, and software is stored in the storage medium 47 as a program.

  Usually, it is convenient to use an electrically writable memory such as a microcomputer memory or a flash memory.

  Since the direction of transmission / reception changes due to the operation of the switching means 41, the number of condition settings and the like increases, but this can be easily realized by adjusting this by operation by a computer.

  As described above, when the operation of the control means 42 can be performed by a program, it is possible to easily set, change and adjust the measurement interval of the correction coefficient for the flow rate calculation, and to flexibly cope with aging. Therefore, the accuracy of flow velocity or flow rate measurement can be improved more flexibly.

  In the present embodiment, operations other than the control means 42 may be performed by a program using a microcomputer or the like.

  As a result, it has a configuration that has a program for causing the computer to function as a control means, making it easy to set and change the operation of the measurement method and flexibly respond to secular changes, etc. It can be performed.

  The flow velocity or flow rate measuring apparatus of the present invention continues to store two or more zero cross points by overwriting, and stops the operation when there is an output signal in the received wave determining means indicating that the received wave has arrived reliably.

  As a result, the trigger point by the received wave determining means is set at a portion where the amplitude of the received waveform is relatively large, and the trigger is stably operated, and the average of two or more optimum zero cross points before that is averaged. Since the value can be used for the propagation time measurement, it is possible to measure the propagation time with few errors and to realize the power saving operation by shortening the measurement time.

FIG. 1 is an overall block diagram of a fluid flow measuring apparatus showing Embodiment 1 of the present invention. Timing chart of the measuring device Timing chart showing received waves in the same measuring device Timing chart showing measurement of received wave in the same measuring device Timing chart showing received waves in the same measuring device Timing chart showing the operation of the receiving point storage means in the same measuring device Overall block diagram showing another operation of the flow measuring device of the present invention Timing chart of the measuring device Overall block diagram showing another operation of the flow measuring device of the present invention Other operation | movement of the flow measuring apparatus of this invention, and the whole block diagram which shows Embodiment 2 Cross section of a conventional flow measurement device

Explanation of symbols

Reference Signs List 31 Flow path 32 First vibrator 33 Second vibrator 34 Transmitting means 35 Receiving means 36 Received wave determining means 37 Receiving point detecting means 38 Receiving point storage means 39 Timing means 40 Flow rate calculating means 41 Switching means 42 Control means 43 Reception point selection means 44 Power supply means 45 Trigger means 46 Time verification means 47 Storage medium

Claims (5)

A pair of transducers arranged in a flow path through which the fluid to be measured flows, for transmitting and receiving ultrasonic waves;
Transmission means for driving one vibrator;
Receiving means for converting the output signal of the other receiving-side vibrator into an electrical signal;
A received wave determining means for outputting a signal when the signal of the receiving means reaches a predetermined value;
A reception point detection means for outputting a signal each time the signal of the reception means falls within a predetermined range as a zero cross point ;
At least two or more reception point storage means for storing the output of the reception point detection means as an elapsed time from the start of transmission ;
Timing means for timing the propagation time of the ultrasonic signal propagated between the transducers using the elapsed time stored in the reception point storage means;
And flow rate calculation means to calculate the flow rate based on the time count difference of the propagation time from the propagation time and the downstream to the downstream to upstream from the upstream which has been determined by the clock means,
And control means for controlling at least one of the previous SL transmitting means and the receiving means and the reception wave determination unit and the reception point detection unit and the reception point storage means said clock means and said flow rate calculation means, said control means, the by the output of the reception wave determination unit has a reception point selection unit for selecting a plurality of elapsed time stored in the reception point storage unit climbed reverse as many predetermined for the operational propagation time, the reception The point storage means is a fluid flow measuring device that overwrites and updates until there is an output signal of the received wave determination means. It said control means, than the propagation time to be estimated in advance the power supply to the reception point storage unit for the first time only starting from sufficiently short time, according to claim 1, further comprising a power supply means for stopping after the output of the reception wave determination unit Fluid flow measuring device. Wherein the control means, said reception point second and subsequent energization of the storage means, fluid according to claim 2, wherein adjusting the timing of the power supply means to start from a later point in time than the first time based on the previous propagation time Flow measuring device. Wherein said control means includes a number becomes a trigger means for outputting a signal from the number of times the output is determined in advance the reception point detection unit, starting the energization of the reception point storage unit said power supply means by the output of said trigger means The fluid flow measuring device according to claim 3 . The program for functioning a computer as a control means of any one of Claims 1-4 .

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