JP5292798B2 - Flow measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem in finding the propagation time of an ultrasonic wave that a difference arises between a waveform received on the upstream side and one on the downstream side in a portion where a received amplitude is comparatively large and that the difference is to be detected as an error in propagation time. <P>SOLUTION: A received signal is amplified by a reception means 35 while a receiving point storing means 38 causes the latest receiving point data to be stored in order in a plurality of storage parts until the level of the signal reaches a previously determined value (Vref). The average value of a plurality of zero crossing points in the vicinity of Vref can be used as a reception point, making it possible to measure the propagation time with errors reduced such as an upper or lower offset and to materialize power saving operation through the shortening of measurement time. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a flow rate measuring apparatus that uses a vibrator or the like and measures a flow rate of a gas or a liquid using ultrasonic waves.

  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 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 rate value can be calculated in consideration of the size of the pipeline and the flow state by obtaining the flow velocity from the time difference.

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, an ultrasonic wave is propagated from the upstream ultrasonic transducer 102 to the downstream ultrasonic transducer 103, and the ultrasonic propagation time Tud is determined. The ultrasonic wave is propagated from the ultrasonic wave to the ultrasonic transducer 102 on the upstream side, the ultrasonic wave propagation time Tdu is measured alternately, and the flow rate is calculated by calculating the time difference using the measured ultrasonic wave propagation times Tud and Tdu. 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 continuous arrival times of the received ultrasonic zero crossing point before the trigger level, and obtains an average value of the ultrasonic wave. An object of the present invention is to realize a power saving operation while realizing a highly accurate measurement by reducing the error included in the propagation time of the ultrasonic wave so that the arrival time can be measured.

In order to solve the above-described conventional problems, the flow velocity or flow rate measuring device according to the present invention includes a pair of transducers that are arranged in a flow path through which a fluid to be measured flows and that transmits and receives ultrasonic waves, and a transmission unit that drives one transducer. Receiving means for converting the output signal of the other receiving-side transducer into an electrical signal, received wave determining means for outputting a signal when the signal of the receiving means reaches a predetermined value, and a zero cross signal determined by the signal of the receiving means. Receiving point detecting means for outputting a signal every time a point is determined as a point ; receiving point storing means for storing a plurality of output signals output by the receiving point detecting means before signal output of the received wave determining means ; A time measuring means for measuring the propagation time of the ultrasonic signal propagated between the transducers by averaging two or more even number signals stored in the receiving point storage means , and a flow rate based on the time difference of the time measuring means. A flow rate calculating means for calculating Control means for controlling at least one of the transmission means, reception means, reception wave determination means, reception point detection means, reception point storage means, timing means, and flow rate calculation means, and the reception point storage means Overwriting is updated until there is an output signal from the received wave determination means, and the arrival times of the zero cross points of the received ultrasonic waves are sequentially stored in the plurality of reception point storage 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. Using at least two cross point arrival times in succession, the average value can be obtained and the ultrasonic arrival time can be measured to reduce the error contained in the ultrasonic propagation time and achieve high accuracy. Power saving operation can be realized while realizing simple measurement.

  The flow velocity or flow rate measuring apparatus according to the present invention uses at least two continuous arrival times of the received ultrasonic zero crossing points before the trigger level and obtains an average value to obtain the ultrasonic arrival time. Can be 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. Also, by using the average value of multiple zero cross points, the error included in the measured ultrasonic propagation time or arrival time can be reduced, and power saving operation can be realized while realizing highly accurate flow measurement. .

According to a first aspect of the present invention, a pair of transducers arranged in a flow path through which a fluid to be measured flows transmits / receives ultrasonic waves, a transmission unit that drives one transducer, and an output signal of the other reception-side transducer as an electrical signal A receiving means for converting the signal into the signal, a received wave determining means for outputting a signal when the signal of the receiving means reaches a predetermined value, and a receiving point for outputting the signal each time the signal of the receiving means falls within a predetermined range for determining a zero-cross point. Detection means; reception point storage means for storing a plurality of output signals output from the reception point detection means before signal output from the reception wave determination means; and two or more even numbers stored in the reception point storage means Measuring means for measuring the propagation time of the ultrasonic signal that has propagated between the transducers by averaging the signals of, the flow rate calculating means for calculating the flow rate based on the time difference of the time measuring means, the transmitting means, the receiving means, Received wave judgment means, reception point detection And a control means for controlling at least one of a stage, a reception point storage means, a timing means, and a flow rate calculation means, and the reception point storage means overwrites and updates until there is an output signal of the reception wave determination means It is a thing.

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. Also, by using the average value of multiple zero cross points, the error included in the measured ultrasonic propagation time or arrival time can be reduced, and power saving operation can be realized while realizing highly accurate flow measurement. .

The second 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 the reception point detection means by the output of the trigger means. By starting energization to the reception point storage means for storing the output of the received signal, reliability is improved by making sure that the received wave has arrived and preparing for storing the output of the received wave detection means. At the same time, a power saving operation by a short time operation becomes possible.

The third invention is particularly the first invention, wherein the control means calculates the difference between the value of the reception point storage means and the output of the reception wave judgment means which is reversed by a predetermined number based on the output of the reception wave judgment means. If the value of the time verification means is within a predetermined value, the measurement can be validated to prevent erroneous detection of the zero cross point due to noise, etc. By doing so, reliability can be improved.

The fourth aspect of the invention is particularly the first aspect of the invention, in which the control means supplies power to the reception point storage means via the power supply means after the elapse of a predetermined time after the output of the reception point detection means after the output of the reception wave determination means. By stopping, it is possible to stop the operation of measuring and storing an extra zero cross point, and to realize a power saving operation.

(Embodiment 1)
In FIG. 1, an ultrasonic flowmeter of the present invention includes a flow path 31 through which a fluid to be measured flows, a first vibrator 32 and a second vibrator 33 that transmit and receive ultrasonic waves arranged in the flow path 31. Installed, a transmission means 34 for driving the first vibrator 32 and the second vibrator 33, and received signals of the first vibrator 32 and the second vibrator 33, amplifies the signal. Receiving means 35, received wave determining means 36 for outputting a signal when the signal of the receiving means 35 reaches a predetermined value, receiving point detecting means 37 for outputting a signal when the signal of the receiving means 35 falls within a predetermined range, Two reception point storage means 38 for storing the output of the reception point detection means 37; a 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; The flow rate is calculated based on the time difference of the time measuring means 39. Those having a quantity computing means 40.

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.

  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).

  However, 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 accuracy 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 (Expression 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 Equations 2, 3, and 4).

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

t1 = L / (c + v * cosφ) (Equation 2)
t2 = L / (c−v * cos φ) (Equation 3)
v = (L / 2 * cosφ) * ((1 / t1) − (1 / t2)) (Expression 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, flow rate, 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 operation will be described with reference to the timing chart of FIG. 2 and the received waveform of FIG. Measurement is started from the start signal at time t 0 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 consecutive zero cross points are obtained, and the average value is used to cancel the offset deviation. be able to.

  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. 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 an even number of 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 means 36, the control means 46 prevents the reception point judging means 37 from outputting a signal at the subsequent zero cross point, or writes to the reception point storage means 38. Ban.

  Since at least one zero crossing point up to tx is stored by performing this operation, two or more even numbers are used among them, and the propagation time is obtained by the time measuring means 39 using the average value. .

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 a 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.

  Although the propagation time was fixed at ta in FIG. 4 as it was, the influence of offset and the like was inevitable. 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 surely captured, and the number of reception point storage means can be appropriately reduced and overwritten sequentially. Power operation becomes possible.

  In addition, the reception point storage unit 38 that stores the output of the reception point storage unit 37 consumes power to perform the storage operation, but it is often not known in advance from which point in time it may 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 means 43 is provided in the control means 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 means 42 uses the power supply means 43 to adjust the energization timing to the reception point storage means 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.

  As described above, the control means 42 has the power supply means 43 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, in FIG. 6, at first, energization to the reception point storage unit 38 is started at t2, but it is at t1 that the ultrasonic wave actually propagates and is received.

Next the control unit 42 since it is not the propagation time varies considerably in measuring the power supply means 43 to be capable of waiting for energizing until t 3 when yet received signal closer to t1 has not reached Become.

  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 43 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 determination 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 determination means 37, and when the number of times reaches a predetermined number of times, for example, twice, the trigger means 44 receives via the power supply means 43 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.

  As described above, the control means 42 has the trigger means 44 for outputting a signal when the output of the reception point detection means 37 exceeds the predetermined number of times, and the power supply means 43 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 45 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 reception point storage means 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, when the point b is reached, the reception point storage means 37 outputs a signal, and the reception point storage means 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 the signal is output from the reception wave determination unit 36, the control unit prevents the reception point determination unit 37 from outputting a signal at the subsequent zero cross point or prohibits writing to the reception point storage unit 38. To do.

  Then, the time of the next zero cross point ta is sent directly to the time verification means 45 of the control means without going through the reception point storage means 38.

  The time verification means 45 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 even-numbered zero cross points in succession.

  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 means 42 has the time verification means 45 for calculating the difference between the output of the reception point detection means 37 after the output of the reception wave determination means 36 and the value of the reception point storage means 38, and the time verification means 45. 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, the time Ta to ta is obtained, and the 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 flow rate measuring apparatus according to Embodiment 2 will be described. 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. Operation of control means 42 for controlling at least one of time measuring means 39 for measuring the propagation time of the sound wave signal, flow rate calculating means 40 for calculating the flow based on the time difference of the time measuring means 39, and switching means 41 for switching between transmission and reception. The storage medium 46 having a program for causing the computer to function is ensured.

  In FIG. 1, in order to perform the operation of the control unit 42 shown in the first embodiment, the operation of the reception point storage unit for obtaining tx and the energization method are obtained in advance by experiments or the like, the secular change, the temperature change. Correlation such as operation timing is obtained with respect to the stability of the system, and the software is stored in the storage medium 46 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.

  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. 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 such as a microcomputer.

  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 reception wave determining means is set at a portion where the amplitude of the reception waveform is relatively large, and the trigger is stably operated. Can be used for the propagation time measurement, so that it is possible to measure the propagation time with little error and to reduce the measurement time, thereby realizing a power saving operation.

Overall block diagram of the flow velocity or flow rate measuring device of the present invention (A) is a timing diagram showing the operation of the measurement control means in the measuring device, (b) is a timing diagram showing the operation of the transmitted wave in the measuring device, and (c) is the operation of the received wave and the reflected wave in the measuring device. Timing diagram showing 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 other operations of the flow velocity or flow rate measuring device of the present invention (A) is a timing diagram showing the operation of the measurement control means in the measuring device, (b) is a timing diagram showing the operation of the transmitted wave in the measuring device, and (c) is the operation of the received wave and the reflected wave in the measuring device. Timing diagram showing Overall block diagram showing other operations of the flow velocity or flow rate measuring device of the present invention Overall block diagram showing other operations of the flow velocity or flow rate measuring device of the present invention Sectional view 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 Power supply means 44 Trigger means 45 Time verification means 46 Storage medium

Claims (4)

A pair of transducers arranged in the flow path of the fluid to be measured and 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 range determined as a predetermined zero-cross point ;
Receiving point storing means for storing a plurality of output signals output by the receiving point detecting means before the signal output of the received wave determining means ;
Time measuring means for measuring the propagation time of the ultrasonic signal that has averaged two or more signals stored in the receiving point storage means and propagated between the transducers;
Flow rate calculation means for calculating a flow rate based on the time difference of the time measuring means;
Control means for controlling at least one of the transmission means, reception means, reception wave determination means, reception point detection means, reception point storage means, timing means, and flow rate calculation means,
The reception point storage means is a flow rate measurement device that overwrites and updates until there is an output signal of the received wave determination means. The control means includes 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 supplies the reception point storage means for storing the output of the reception point detection means by the output of the trigger means. The flow rate measuring device according to claim 1 which starts energization. The control means has time verification means for calculating the difference between the output of the reception point detection means after the output of the reception wave determination means and the value of the reception point storage means, and the value of the time verification means is within a predetermined value. The flow rate measuring device according to claim 1, wherein if present, measurement is effective. 2. The flow rate measuring device according to claim 1, wherein the control means stops power supply to the reception point storage means via the power supply means after elapse of a predetermined time after output of the reception point detection means after output of the reception wave determination means.

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