JP5292797B2 - Flow measuring device - Google Patents

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 flow rate measuring device will be described with reference to FIG. 9. A pair of ultrasonic transducers 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 slant the fluid. It crosses over to.

  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 problems, and measures at least two arrival times of the zero cross point of the received ultrasonic wave continuously, and measures the ultrasonic wave arrival time using the average value. The purpose of this is to reduce the error included in the propagation time of the ultrasonic wave so as to realize high-accuracy measurement and to realize the power saving operation.

In order to solve the above-described conventional problems, a flow rate measuring device according to the present invention includes a pair of transducers 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. A 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, and a zero-cross point at which the signal of the receiving means is determined in advance Receiving point detecting means for outputting a signal every time the range is determined, and the first zero cross point after the signal output of the received wave determining means and the output signal of the receiving point detecting means at the previous zero cross point are stored . Based on the time difference between the reception point storage means, the time measurement means for averaging the two signals stored in the reception point storage means and measuring the propagation time of the ultrasonic signal propagated between the transducers, and the time difference between the time measurement means Flow rate calculation to calculate flow rate Control means for controlling at least one of 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 two receptions The arrival time at the zero cross point of the received ultrasonic waves is sequentially stored in the 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 averaged from the two zero cross points before and after the trigger level. Can be measured. For this reason, the error contained in the propagation time or arrival time of the measured ultrasonic wave can be reduced, and power saving operation can be realized while realizing highly accurate flow measurement.

  The flow velocity or flow rate measuring device of the present invention can measure using the average value of the zero cross points before and after the trigger level. 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. Further, by using the average value of the two points, an error included in the propagation time or arrival time of the measured ultrasonic wave can be reduced, and a power saving operation can be realized while realizing a highly accurate flow measurement.

1st invention is arrange | positioned at the flow path through which a to-be-measured fluid flows, is arrange | positioned at the flow path through which to-be-measured fluid flows, a pair of vibrator | oscillator which transmits / receives an ultrasonic wave, The transmission means which drives one vibrator, A receiving means for converting the output signal of the other receiving-side transducer into an electrical signal; a received wave determining means for outputting a signal when the signal of the receiving means reaches a predetermined value; and a zero-cross point at which the signal of the receiving means is predetermined. a reception point detection unit for outputting a signal each time it is a range determined, the reception for storing an output signal of the reception point detection unit of the signal output after the first zero-crossing point and its preceding zero-crossing point of the reception wave determination unit A point storage means, a timing means for averaging the two signals stored in the reception point storage means and measuring the propagation time of the ultrasonic signal propagated between the transducers, and a flow rate based on the time difference between the timing means Flow rate calculating means for calculating A 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 two reception point storage means The arrival time of the received ultrasonic zero-cross point is sequentially stored.

  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 averaged from the two zero cross points before and after the trigger level. Can be measured. For this reason, the error contained in the propagation time or arrival time of the measured ultrasonic wave can be reduced, and power saving operation can be realized while realizing highly accurate flow measurement.

A second invention is, in particular, in the first inventions, the control means receiving the power supply means includes a trigger means for issuing a number becomes the signal from the number of times the output is predetermined reception point detection unit by the output of said trigger means By starting energization to the reception point storage means for storing the output of the point detection means, it is possible to reliably confirm that the reception wave has arrived and to prepare for storing the output of the reception wave detection means. As a result, the power saving operation by the short time operation becomes possible.

A third invention is, in particular, in the first inventions, the reception point storage means control means by having a storage control unit for adjusting so that is sequentially overwritten from the oldest data, such as zero crossing point is increased Even in the state, a plurality of zero cross points in the vicinity of the received wave determining means can be reliably captured, and a power saving operation can be performed by sequentially overwriting with a reduced number of received point storage means.

A fourth invention is, in particular, power to the first inventions with control means receiving path determination unit reception point storage means via the power supply means in a predetermined time after the inhibitor output of the reception point detection unit after output of By stopping the supply, it is possible to stop the operation of measuring and storing an extra zero cross point, and to realize a power saving operation.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
In FIG. 1, the ultrasonic flowmeter of the present embodiment includes a flow path 31 through which a fluid to be measured flows, a first vibrator 32 that is disposed in the flow path 31 and transmits / receives ultrasonic waves, and a second vibration. Receiving element 33, transmitting means 34 for driving the first vibrator 32 and the second vibrator 33, and receiving signals of the first vibrator 32 and the second vibrator 33 for amplifying the signal. Receiving 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, Two reception point storage means 38 for storing the output of the reception point detection means 37; and a timing 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 flow rate computation 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 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).

(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).
(Measurement time from upstream to downstream is t1, and 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. 3 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. 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 for detecting the zero cross point with high accuracy and obtaining the reception point even when there is such a disturbance will be described.

  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 zero cross points can be obtained continuously and the average value can be used to cancel the offset deviation. .

  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.

  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 this phenomenon and determine the arrival point of the received wave in a shorter time than the normal ta, at least one zero cross point before Vref is detected, and the zero cross point after the Vref arrival point is detected. What is necessary is just to take an average value in pairs.

  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 detection 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, when the point b is reached, the reception point storage unit 37 outputs a signal and overwrites the reception point storage unit 38-1.

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

  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 stores the next zero cross point in the storage means 28-2 and then the reception point judging means 37 does not output a signal at the subsequent zero cross point. Or writing to the reception point storage means 38 is prohibited.

  Since the zero cross point of tx and ta is stored by performing this operation, the propagation time is obtained by the time measuring means 39 using two averages.

  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 reception arrival point can be determined at two points tx and ta. Until now, the propagation time was determined at ta in FIG. 4, but the influence of offset or the like was inevitable.

  In this method, the 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.

  Further, every time the zero cross point arrives from the point of FIG. 4a, the reception point storage means 38-1 and 38-2 write the reception point data alternately, and the operation is stopped when the reception signal exceeds Vref. Then, an average process is performed using d and tx, and the reception arrival point can be determined.

  By such processing, the propagation time that has been taken up to ta in FIG. 4 can be determined at an earlier point, so that the measurement operation time of the propagation time can be shortened, and the power saving operation can be performed. realizable. Specifically, the measurement time can be shortened for Tf in FIG.

  In the above description, the configuration using two reception point storage means 38 has been described. However, the configuration is such that two or more reception point storage means 38 are sequentially stored, and the propagation time is determined using two consecutive zero cross points. It may be confirmed.

  In this case, even if data at one zero cross point is defective due to noise or the like, measurement can be continued by using a pair of zero cross points that are continuous from the remaining received data.

  The arrival time of the ultrasonic waves can be measured by averaging from any two continuous zero cross points.

  For this reason, the error contained in the propagation time or arrival time of the measured ultrasonic wave can be reduced, and power saving operation can be realized while realizing highly accurate flow measurement.

  The zero cross point selected as the receiving point is, for example, a distance from Vref, such as a pair of point a and point b, and selecting a correct value as the arrival point results in small waveform distortion and an error included in the propagation time or arrival time of the ultrasonic wave. The power saving operation can be realized while realizing a highly accurate flow measurement.

  However, in this case, the error in the propagation time can be further reduced, but it is easily affected by noise.

  If tx close to Vref is selected, there is a possibility that the received waveform is distorted, but a value with higher reproducibility can be obtained without being affected by noise or the like.

  Considering high accuracy and high reproducibility, changing the reception point according to the state of measurement and the signal classification such as noise state becomes a more convenient system.

  By storing a plurality of zero cross points in this way, it is possible to obtain a flow measurement by obtaining a propagation time using a reception point that is reverse by a predetermined number from Vref.

  That is, the propagation time of the ultrasonic wave propagating between the upstream ultrasonic transducer and the downstream ultrasonic transducer, that is, the arrival time of the ultrasonic wave can be measured before Vref which is the trigger level. .

  For this reason, the error contained in the propagation time or arrival time of the measured ultrasonic wave can be reduced, and power saving operation can be realized while realizing highly accurate flow measurement.

  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 of the reception point storage means 38 is started at t2, but it is at t1 that the ultrasonic wave has actually propagated and 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, it is assumed that the state of the zero cross points a to d in FIG. 4 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 point, for example, twice, the trigger means 44 passes the power supply means 43 through the power supply means 43 when the reception point reaches the point b. Energization of the 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.

  Then, the propagation time is obtained using two consecutive zero cross point data. Thus, after 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 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 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 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.

In FIG. 3B, the reception arrival point has been described as being able to determine the average value Ta ′ of the tx and ta2 points, but 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.

(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. 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 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 according to the present invention overwrites and memorizes two zero cross points, and stops its 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,
The trigger can be operated stably, and the average value of the two optimal points among the previous zero cross points can be used for the propagation time measurement, so that the propagation time with less error can be measured and the measurement can be performed. Since the time can be shortened, it is possible to realize a power saving operation.

Overall block diagram of a flow rate measuring apparatus showing an embodiment 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 Overall block diagram showing the operation of the flow measurement device and others (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 the operation of the flow measurement device and others Overall block diagram showing the operation of the flow measurement device and others 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 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 range determined as a predetermined zero-cross point ;
Receiving point storage means for storing the output signal of the receiving point detection means at the first zero cross point after the signal output of the received wave determination means and the zero cross point immediately before that;
Time measuring means for measuring the propagation time of the ultrasonic signal propagated between the transducers by averaging the two signals stored in the receiving point storage means;
Flow rate calculation means for calculating a flow rate based on the time difference of the time measuring means;
A flow rate measurement apparatus comprising: a control unit that controls at least one of the transmission unit, the reception unit, the reception wave determination unit, the reception point detection unit, the reception point storage unit, the time measurement unit, and the flow rate calculation unit. 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. 2. The flow rate measuring apparatus according to claim 1, wherein the control means includes accumulation control means for adjusting the reception point storage means so that the oldest data is sequentially overwritten. 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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