JP2010223658A - Device for measuring flow velocity or flow rate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem herein a difference arises in a received waveform between the upstream side and the downstream side, in a portion where a reception amplitude is relatively large and the difference is detected as error in the propagation time of ultrasonic waves, on the occasion of determining the propagation time. <P>SOLUTION: In this device for measuring flow velocity or a flow rate, a received signal is amplified by a receiving means 35 and a receiving point storage means 38 sequentially stores updated receiving point data in a plurality of storage parts until the maximum value of the signal comes between VH and VL. Since storage is stopped, when the value becomes between VH and VL, an arbitrary zero crossing point before the maximum amplitude point of a received wave can be made a receiving point, it is possible to measure the propagation time with a reduced error and to attain a power-saving operation by shortening the measurement time. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  A conventional fluid flow measuring device will be described with reference to FIG. 10. 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 are fluidized. (See, for example, Patent Document 1).

  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. The amplitude is adjusted by an auto gain amplifier so that the received wave has a constant amplitude.

  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. In addition, a trigger level setting / determination circuit is required.

  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. In addition, there is a problem that an extra circuit for setting the trigger level is necessary.

  The present invention solves the above-mentioned conventional problem, measures at least one arrival time of the zero cross point of the received ultrasonic wave, eliminates the trigger-level circuit, and eliminates the peak value of the received wave. Power saving operation while achieving high-accuracy measurement while reducing the error included in the ultrasonic propagation time by measuring the arrival time of the ultrasonic wave using one of the zero cross points The purpose is to realize a circuit that can be measured even without a trigger level.

  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 vibrators 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 of the vibrators. A receiving means for converting the output signal of the other receiving-side transducer into an electric signal, a received wave maximum value judging means for detecting a maximum value of the signal of the receiving means and outputting a signal, and a signal of the receiving means are predetermined. A reception point detection means for outputting a signal when the range is reached, at least one reception point storage means for storing the output of the reception point detection means, and signals transmitted from the reception point storage means. Time measuring means for measuring the propagation time of the ultrasonic signal, flow rate calculating means for calculating a flow rate based on the time difference of the time measuring means, the transmitting means, the receiving means, the received wave maximum value detecting means, and the receiving point detection Means and said reception point storage Control means for controlling at least one of the stage, the time measuring means, and the flow rate calculating means, and the reception point storage means sequentially overwrites and updates until there is an output signal of the received wave maximum value judging means. Is.

  With this configuration, the propagation time of the ultrasonic wave that propagates 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 the zero crossing point before the maximum amplitude of the received wave. It is possible to measure using one of these. For this reason, the error included in the propagation time or arrival time of the ultrasonic waves measured by simplifying the circuit 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 one of the zero cross points before the amplitude maximum value of the received wave. For this reason, the error included in the propagation time or arrival time of the measured ultrasonic waves can be reduced, realizing high-accuracy flow measurement, and further eliminating the circuit for setting the trigger level to achieve power-saving operation it can.

A first invention is a pair of vibrators arranged in a flow path through which a fluid to be measured flows and transmits and receives ultrasonic waves,
Transmitting means for driving one vibrator, receiving means for converting the output signal of the other receiving-side vibrator into an electrical signal, and received wave maximum value judging means for detecting the maximum value of the signal of the receiving means and outputting the signal When,
Using the reception point detection means for outputting a signal when the signal of the reception means falls within a predetermined range, at least one reception point storage means for storing the output of the reception point detection means, and the signal of the reception point storage means Measuring means for measuring the propagation time of the ultrasonic signal propagated between the transducers, flow rate calculating means for calculating a flow rate based on the time difference of the time measuring means, the transmitting means, the receiving means, and the maximum received wave Control means for controlling at least one of a value detection means, a reception point detection means, the reception point storage means, the time measurement means, and the flow rate calculation means, wherein the reception point storage means is the received wave maximum value determination means. Are overwritten and updated sequentially until there is an output signal.

As a result, the determination point by the reception wave maximum value determination means is set at the maximum amplitude portion of the reception waveform, and the reception wave determination is stably operated, and propagation is performed using one of the zero cross points before that. Since it can be used for time measurement, it is possible to measure a propagation time with few errors and to realize a power saving operation by shortening the measurement time. Furthermore, a power saving operation can be realized by omitting a circuit for setting the trigger level.

  According to a second aspect of the invention, in particular, in the first aspect of the invention, the control means has power supply means for energizing the reception point storage means for storing the output of the reception point detection means for a long time only for the first time. It is possible to reliably capture the received wave by preparing for storing the output of the received wave detecting means before the received wave originally arrives.

  According to a third aspect of the present invention, in particular, the power supply means in the first aspect of the invention supplies the energization to the reception point storage means for storing the output of the reception point detection means by the control means for the second and subsequent times based on the previous value. 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.

  According to a fourth aspect of the present invention, in particular, in the first aspect, 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 detects the reception point by the output of the trigger means. By starting energization to the receiving point storage means that stores the output of the means, it is confirmed that the received wave has arrived reliably, and then preparing to store the output of the received wave detection means, thereby improving the reliability In addition, a power saving operation by a short time operation becomes possible.

According to a fifth aspect of the present invention, there is provided a storage control means for adjusting so that the oldest data is sequentially overwritten when the number of zero cross points written in at least one receiving point storage means by the control means is large. By having
Even in a situation where there are many zero cross points, it is possible to reliably capture multiple zero cross points in the vicinity of the received wave maximum value judging means and reduce the number of receiving point storage means to save power by sequentially overwriting Is possible.

  The sixth aspect of the invention is a reception point selection that selects the value of the reception point storage means that has been reversed by a predetermined number based on the output of the reception wave maximum value determination means in the control means in the first invention. By having a means, it becomes possible to use an arbitrary zero cross point considerably before the signal output from the received wave maximum value judging means as a reception point, and to the measured ultrasonic propagation time or arrival time. The included error can be reduced, and power saving operation can be realized while realizing highly accurate flow measurement.

According to a seventh aspect of the invention, in particular, the difference between the value of the reception point storage means and the output of the reception wave determination means, which is reversed by a predetermined number, is calculated by the output of the reception wave maximum value determination means by the control means in the first invention. If there is a time verification means, and if the value of the time verification means is within a predetermined value, it is possible to prevent erroneous detection of the zero cross point due to noise, etc. Reliability can be improved by selecting points.

  According to an eighth aspect of the present invention, in particular, in the first aspect, the control means supplies 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 maximum value determination means. By stopping the power supply, it is possible to stop the operation of measuring and storing an extra zero cross point, and to realize a power saving operation.

  The ninth aspect of the invention is a configuration having a program for causing a computer to function as the control means in any one of the first to eighth aspects of the invention. It can be done easily, and it can flexibly cope with aging, etc., so that the measurement accuracy can be improved and the power saving operation can be performed more flexibly.

(Embodiment 1)
The flow velocity or flow rate measuring apparatus and instrument discrimination method of the present invention relating to Embodiment 1 will be described. FIG. 1 is a block diagram of a flow velocity or flow rate measuring apparatus showing the configuration of this embodiment. 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. A receiving means 35, a receiving point detecting means 37 for outputting a signal when the signal of the receiving means 35 falls within a predetermined range, at least one receiving point storing means 38 for storing the output of the receiving point detecting means 37, A time measuring means 39 for measuring the propagation time of the ultrasonic signal propagated between the transducers using the signal of the receiving point storage means 38; a flow rate calculating means 40 for calculating a flow rate based on the time difference of the time measuring means 39; It is what has. In addition, a reception wave maximum value determination unit 43 that detects the maximum signal of the reception unit 35 is provided.

  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 point detection means 37, the reception point storage means 38, the timing means 39, the flow rate calculation means 40, the switching means 41, and the reception. At least one of the wave maximum value judging means 43 is controlled.

  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, 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.

  Usually, before this operation, an auto gain operation is performed in order to make the magnitude of the received wave constant to some extent. This operation will be described including the receiving means 35 of FIG.

The receiving means uses an amplifying means 35-1 for amplifying the signal of the ultrasonic transducer on the receiving side, an output of the amplifying means, a received wave determining means 36 for outputting a signal when the received wave signal reaches a certain level, There are reception point detection means 37 for determining the zero cross point by output and reception wave maximum value determination means 43 for detecting the maximum value of the reception wave by the output of the amplification means.

  The received wave determining means 36 compares the trigger level setting means 36-1 for setting the trigger level for determining that the received wave has arrived, and the outputs of the trigger level determining means 36-1 and the amplifying means 35-1. Reception wave arrival comparison means 36-2 for sending a reception wave arrival signal.

  The reception point detecting means 37 compares the outputs of the zero reference means 37-1 for determining the zero cross point and the zero reference means 37-1 and the amplifying means 35-1 to send out a signal which becomes the zero cross point. Comparing means 37-2.

  The received wave maximum value determining means 43 switches between the first maximum value determining means 43-1 and the second maximum value determining means 43-2 for determining the maximum value of the received wave, and the maximum value determining means. Determination value switching means 43-3 and received wave maximum value comparison means 43-4 for comparing the output signal from the determination value switching means 43-3 with the output of the amplifying means 35-1 and sending the received wave maximum value signal. Consists of.

  The operation of the auto gain is performed using the received wave maximum value judging means 43. The control means 42 has an automatic gain adjustment means 42-1. First, the auto gain adjusting means 42-1 switches the determination switching means 43-3 to the second maximum value determining means 43-2 side. The second maximum value determining means outputs VL in FIG. 3 as a voltage value. If the maximum value of the received wave is smaller than VL when the received wave is amplified by the amplifying unit 35-1 and reaches the received wave maximum value comparing unit 43-4, the output of the received wave maximum value comparing unit 43-4 does not change. For this reason, the auto gain adjusting means 42-1 outputs a signal so as to increase the amplification degree of the amplifying means 35-1. If the amplification is increased until the maximum value of the received wave becomes larger than VL, the signal of the output of the received wave maximum value comparing means 43-4 changes when the received wave reaches VL. As a result, the magnitude of the received wave can be made larger than a certain level.

  However, if the amplification degree of the received wave is too large, the waveform is distorted or the power of the receiving circuit is consumed excessively, which is inappropriate. For this reason, once the received signal exceeds VL, the automatic gain adjusting means 42-1 switches the determination switching means 43-3 to the first maximum value determining means 43-1 side. The first maximum value determination means outputs VH in FIG. 3 as a voltage value. If the maximum value of the received wave is smaller than VH when the received wave is amplified by the amplifying unit 35-1 and reaches the received wave maximum value comparing unit 43-4, the output of the received wave maximum value comparing unit 43-4 does not change. In this case, the maximum value of the received signal is adjusted between VH and VL.

  However, if the auto gain adjusting means 42-1 increases the amplification degree of the amplifying means 35-1 too much, the maximum value of the received wave becomes larger than VH, and when the received wave arrives, the received wave maximum value comparing means 43-4 The signal changes when the output exceeds VH. Since this indicates that the maximum value of the received wave has become too large, the auto gain adjusting means 42-1 reduces the amplification degree of the amplifying means 35-1. By performing this operation, the auto gain operation adjusts the amplitude of the received wave so that the maximum value of the received wave always falls between VL and VH.

  After the size of the received waveform becomes constant to some extent by the auto gain operation, the reception point is determined using the received wave determination means 36. The output of the trigger level setting means 36-1 is set to Vref.

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 becomes Vref which is the output of the predetermined trigger level setting means 36-1, the received wave determining means 36 determines that the received wave has arrived and outputs the signal. put out. 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, in order to obtain the ta point after Vref in FIG. 3, it is necessary to prepare trigger level setting means 36-1 for outputting the Vref signal and received wave arrival comparing means 36-2 as the received wave determining means 36.

  Further, in order to ensure that Vref is applied to the received wave, the maximum amplitude of the received wave needs to be constant, so the received wave maximum value determining means is essential.

  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.

  Therefore, a method for detecting the zero cross point before Vref without using the reception wave determination means 36 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, at least one zero cross point before the maximum value of the received wave (received wave entering between VH and VL) is detected, and the received wave is detected. One point before the point where the maximum value is reached may be set as a detection point. For example, the immediately preceding zero cross point ty may be detected. By doing so, a configuration in which the reception wave determination means 36 is omitted can be realized.

  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 amplifying means 35-1 in the receiving means 35, and when the peak value of the signal reaches a predetermined value (between VH and VL), the received wave maximum value judging means 43 has reached the received wave. Is determined and a signal is output.

  Before that, the reception point detection means 37 which 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 next reception point storage means 38-2. Similarly, the reception point data at the next point c is sequentially stored in 38-3.

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

  Then, the peak value of the received wave enters between VH and VL, and the received wave maximum value determining means 43 determines that the received wave has arrived and outputs a signal. When this signal is received by the automatic gain adjusting means 42-2, the control means prevents the reception point judging means 37 from outputting a signal at the zero crossing point to go, or writes to the reception point storage means 38. Ban. By performing this operation, the time until ty is stored in the reception point storage means, so the time measuring means 39 obtains the propagation time. 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 up to ta in FIG. Specifically, the time of Ta + Tf increases the measurement operation time of the propagation time by the half period Tf of the transmission frequency, but the circuit constituting Vref can be omitted.

  The zero-cross point selected as the reception point is far from the maximum value of the received wave, for example, as point a in FIG. 5. If a correct value is selected as the arrival point, the waveform distortion is small and included in the propagation time or arrival time of the ultrasonic wave Error can be reduced, and power saving operation can be realized while realizing 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 ty close to the maximum value of the received wave 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 by using a reception point that is reverse by a predetermined number from the maximum value of the reception wave.

  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 the reception wave maximum value point. 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 by omission of a circuit or the like can be realized while realizing highly accurate flow measurement.

  Further, even in a state where the number of zero cross points increases, it is possible to reliably capture a plurality of zero cross points in the vicinity of the received wave maximum value determining means, and to sequentially overwrite with the number of receiving point storing means being appropriately reduced. 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. 6, 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 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 44. t2 is a time sufficiently shorter than t1.

In this way, the control means 42 receives the reception point storage means 38 that stores the output of the reception point detection means 37.
By having the power supply means 44 for energizing the first time only for the first time, it is ensured by preparing for storing the output of the reception wave detection means before the reception wave originally arrives at the first measurement. It becomes possible to catch 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. 7, at first, energization of the reception point storage unit 38 is started at t2, but it is at t1 that the ultrasonic wave has actually propagated and 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, it is assumed that the state of the zero cross points a to d 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. 8, 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 45 passes the power supply means 44 through the power supply means 44 when the reception point reaches b point. Energization of the 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, a plurality of zero cross points from there, the number of reception wave maximum value points, or the number of reception point storage means 38 prepared in advance. Remember. Thus, by confirming that the reception wave has arrived reliably and preparing for storing the output of the reception point detection means 37, the reliability is improved and a power saving operation by a short time operation becomes possible.

  In addition, the zero cross point in FIG. 5 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 receiving point, the calculation of the propagation time will deviate greatly. In order to prevent this, the control means 42 is provided with a time verification means 46 as shown in FIG. The operation will be described.

First, similarly to FIG. 5, when 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 3
8-2 stores the reception point data. After storing the points c and d and the point of ty, the received signal enters between VH and VL.

  At this time, the received wave maximum value judging means 43 outputs a signal for the first time. When a signal is output from the received wave maximum value determining means 43, the control means 42 prevents the reception point detecting means 37 from outputting a signal at the subsequent zero cross point, or outputs the signal to the reception point storage means 38. Prohibit writing.

  Then, the time of the next zero cross point tb 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 one of the zero cross points.

  For example, if the transmission frequency is 100 kHz, the half of the period 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.

  Thus, the control means 42 has the time verification means 46 for calculating the difference between the output of the reception point detection means 37 after the output of the received wave maximum value determination means 43 and the value of the reception point storage means 38, and the time verification If the value of the means 46 is within a predetermined value, it is possible to prevent erroneous detection of the zero cross point due to noise or the like by enabling the measurement, and to improve reliability by selecting an accurate zero cross point. Is possible.

  Further, after the received signal is between VH and VL before the zero cross point ty in FIG. 5, 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 maximum value judging means 43 detects that the received wave has entered from VL to V L, the control means 42 stops the energization to the receiving point storage means 38 to perform power saving operation and the unnecessary receiving circuit of the receiving circuit. The energization operation can be stopped. The time of stopping may be immediately after exceeding the interval between VH and VL, or noise may be generated by the signal at the time of stopping energization, and the operation of the timing means 39 and the like may not be adversely affected. The energization may be stopped after detecting the zero cross point tb.

In this way, the control means 42 stops the power supply to the reception point storage means 38 via the power supply means 44 after elapse of a predetermined time after the output of the reception point detection means 37 after the output of the reception wave maximum value determination means 43. By doing so, it is possible to stop the operation of measuring and storing the extra zero cross point, and to realize the power saving operation.

  If the flow path and transmission method are known in advance, the wave number that becomes the maximum value point of the received wave is known in advance, so the zero crossing point immediately before that is used as having transmitted the same propagation distance even if switched upstream and downstream It is possible.

(Embodiment 2)
The flow velocity or flow rate measuring apparatus of the present invention relating to the second embodiment will be described. The difference from the first embodiment is that the signals of the received wave maximum value determining means 43 and the receiving means 35 that output signals when the signals of the vibrators 32 and 33, the transmitting means 34, the receiving means 35, and the receiving means 35 reach the maximum values are obtained. 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 order to perform the operation of the control unit 42 shown in FIG. 1 in FIG. 1, the operation of the receiving point storage unit for obtaining ty by an experiment or the like, the energization method, the secular change, the temperature change, Correlation such as operation timing is obtained with respect to the stability of the system, and 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, 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. The accuracy of flow velocity or flow rate measurement can be improved more flexibly. In this 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 device of the present invention continues to overwrite and memorize the zero cross point, and stops its operation when there is an output signal in the received wave maximum value judging means indicating that the received wave has surely arrived.

  As a result, the trigger point by the received wave maximum value judging means is set to the large amplitude part of the received waveform, the trigger is operated stably, and the optimal point among the previous zero cross points is measured for propagation time. Therefore, it is possible to measure a propagation time with little error and to realize a power saving operation by simplifying the circuit.

Overall block diagram of the flow velocity or flow rate measuring device of the present invention (A) Timing diagram showing the operation of the measurement control means in the measuring device (b) Timing diagram showing the operation of the transmitted wave in the measuring device (c) Timing diagram showing the operation of the received wave and the reflected wave in the measuring device Timing chart showing received waves in the same measuring device Block diagram around the receiving means in the same measuring device Timing chart showing received waves 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) Timing diagram showing the operation of the measurement control means in the measuring device (b) Timing diagram showing the operation of the transmitted wave in the measuring device (c) Timing diagram showing the operation of the received wave and the reflected wave in the measuring device 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

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 Received wave maximum value judging means 44 Power supply means 45 Trigger means 46 Time verification means 47 Storage medium

Claims (9)

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 maximum value determining means for detecting the maximum value of the signal of the receiving means and outputting a signal;
A receiving point detecting means for outputting a signal when the signal of the receiving means falls within a predetermined range;
At least one reception point storage means for storing the output of the reception point detection means;
Time measuring means for measuring the propagation time of the ultrasonic signal propagated between the transducers using the signal of the receiving point storage means;
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, the reception means, the received wave maximum value detection means, the reception point detection means, the reception point storage means, the time measurement means, and the flow rate calculation means;
The reception point storage means is a flow velocity or flow rate measuring device that sequentially overwrites and updates until there is an output signal of the received wave maximum value determination means. 2. The flow velocity or flow rate measuring device according to claim 1, wherein the control means has power supply means for energizing the reception point storage means for storing the output of the reception point detection means for a long time only for the first time. The flow rate or flow rate according to claim 1, wherein the control means adjusts the timing of the power supply means so that the receiving point storage means for storing the output of the receiving point detection means is energized for the second time and thereafter, based on the previous value. Measuring device. 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 velocity or flow rate measuring device according to claim 1, wherein energization is started. 2. The flow velocity or flow rate measuring device according to claim 1, wherein the control means has accumulation control means for adjusting the reception point storage means so that the oldest data is sequentially overwritten. 2. The flow velocity or flow rate measurement according to claim 1, wherein the control means includes reception point selection means for selecting a value of the reception point storage means that is reversed by a predetermined number for the calculation of the propagation time based on the output of the reception wave maximum value determination means. apparatus. The control means has time verification means for calculating a difference between the value of the reception point storage means and the output of the reception wave determination means which is reversed by a predetermined number based on the output of the reception wave maximum value determination means, and the time verification means The flow velocity or flow rate measuring device according to claim 1, wherein the measurement is valid if the value is within a predetermined value. 2. The flow rate according to claim 1, wherein the control means stops the power supply 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 maximum value determination means. Flow measurement device. The program for functioning a computer as a control means of any one of Claims 1-8.

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