JP5034510B2 - Flow velocity or flow rate measuring device and its program - Google Patents

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.

  Conventionally, as this type of flow rate measurement device, a vibrator is provided in a flow path in the flow direction, and the velocity of the fluid is calculated from the difference in ultrasonic propagation time (see, for example, Patent Document 1).

  FIG. 11 is a block diagram showing a configuration of a conventional ultrasonic flowmeter. In FIG. 11, a first vibrator 5 that transmits ultrasonic waves and a second vibrator 6 that receives ultrasonic waves are disposed in the flow direction in the middle of the fluid conduit 4. 7 is a transmission circuit to the first vibrator 5, and 8 is an amplification circuit for the signal received by the second vibrator 6. The amplified signal is compared with the reference signal by the comparison circuit 9, and is equal to or higher than the reference signal. When the signal is detected, the repeating unit 11 activates the trigger circuit 12 by the number of times set by the number setting circuit 10, and after delaying the signal by the delay unit 13, the ultrasonic signal is repeatedly transmitted.

When the repetition starts, the timer counter of the time measuring means 14 is started. When the number of repetitions set by the number setting circuit 10 is completed, the timer counter of the time measuring means 14 is stopped and the time is measured. Next, transmission / reception of the first vibrator 5 and the second vibrator 6 is switched by the switching means 15, and an ultrasonic signal is transmitted from the second vibrator 6 to the first vibrator 5, that is, from downstream to upstream. Is repeated as described above, and the time is counted. From the time difference, the flow rate calculation means 16 determines the flow rate value in consideration of the size of the pipe line and the flow state.
Japanese Patent Laid-Open No. 9-280917

  However, in the conventional flow rate measuring device, an operation for switching between the transmission-side transducer and the reception-side transducer is entered, and a time lag occurs because a switching operation is performed between measurements such as measurement-switching-measurement. In addition, each measurement before and after the switching operation can measure only one-way information, and if there is a lapse of time across the switching operation process, the measured information will be shifted, causing a measurement error. There is a possibility.

  The present invention solves the above problem, and the flow rate is controlled based on the time value of the time measuring means for measuring the propagation time of the ultrasonic signal reflected between the transducers at least twice so as not to cause a large time shift. The purpose is to calculate. This timekeeping value includes information that is a pair of propagation directions.

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 transmits / receives ultrasonic waves, and a transmission unit that drives the transmission-side transducer. Receiving means for converting an output signal of the receiving-side vibrator into an electrical signal, switching means for switching transmission / reception of the vibrator, and the ultrasonic wave output from the vibrator on the transmitting side is at least between the vibrators. Time measuring means for measuring the time from two reflections to propagation to the vibrator on the receiving side, flow rate calculating means for calculating a flow rate based on the time value of the time measuring means, the vibrator and the transmitting means And a control means for controlling at least one of the receiving means, the time measuring means, and the flow rate calculating means.

The flow rate measuring device of the present invention calculates a flow rate using a direct wave propagating between a pair of transducers arranged in a flow path and transmitting and receiving ultrasonic waves and a propagation time of an ultrasonic signal reflected at least twice.

  For this reason, since the propagation time measured before and after the switching operation of the vibrator includes information that is a pair of propagation directions, the average flow velocity can be obtained accurately even if the time elapses before and after the switching operation occurs. it can.

According to a first aspect of the present invention, a pair of transducers arranged in a flow path through which a fluid to be measured flows transmits / receives ultrasonic waves, transmission means for driving the transmission-side transducer, and an output signal of the reception-side transducer as an electrical signal Receiving means for converting, switching means for switching transmission / reception of the transducer, and the ultrasonic wave output from the transducer on the transmission side is reflected at least twice between the transducers and then transmitted to the transducer on the reception side Time measuring means for measuring time until propagation, flow rate calculating means for calculating a flow rate based on a time value of the time measuring means, the vibrator, the transmitting means, the receiving means, the time measuring means, and the flow rate calculating means It is a flow measurement device provided with the control means which controls at least one.

  Then, the flow rate is calculated based on the time measured by the time measuring means for measuring the propagation time of the ultrasonic signal reflected between the transducers at least twice. As a result, the propagation time measured before and after the switching operation of the transducer includes information that is a pair of propagation directions, so that the average flow velocity can be obtained accurately even if the time elapses before and after the switching operation occurs. Can do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the present embodiment.

(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 the present 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. The transmitter 34 for installing and driving the first vibrator 32, the receiver 35 for receiving the reception signal of the second vibrator 33 and determining the reception timing, and the first vibrator 32 by the transmitter 34 Directly from the start of driving, the propagation wave of the ultrasonic wave reaches the second vibrator 33, is reflected by the second vibrator 33, is reflected by the first vibration 32 again, and then reaches the second vibrator 33. And a time measuring means 36 for measuring the propagation time via the receiving means 35, and a flow rate calculating means 37 for calculating the flow rate between the vibrators based on the time value of the time measuring means 36 and obtaining the flow rate therefrom. is there.

  Further, a switching unit 38 is provided between the transmission unit 34 and the first transducer 32, and between the second transducer 33 and the reception unit 35, and transmission / reception of ultrasonic waves is performed between the first transducer 32 and the second transducer. 33 are alternately performed. The control means 39 controls at least one of the transmission means 34, the reception means 35, the timing means 36, the flow rate calculation means 37, and the switching means 38.

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

  Upon receiving the start signal from the control means 39, the transmission means 34 pulse-drives the first vibrator 32 for a fixed time, and at the same time, the time measuring means 36 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 this ultrasonic wave is determined, the operation of the time measuring means 36 is stopped, and the flow velocity is obtained from the time information t according to (Equation 1). Here, the measurement time obtained from the time measuring means 36 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)
In many cases, the receiving means 35 is configured to compare the reference voltage and the received signal by a normal comparator.

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

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

t1 = L / (c + v * cosφ) (Equation 2)
t2 = L / (c−v * cos φ) (Equation 3)
v = (L / 2 * cosφ) * ((1 / t1) − (1 / t2)) (Expression 4)
According to this method, the flow velocity 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.

  Although the flow velocity and flow rate can be obtained in this way, when an operation for switching between the transmitting-side transducer and the receiving-side transducer is entered, a switching operation is entered between the measurements, such as measurement-switching-measurement. Deviation has occurred. In addition, each measurement before and after the switching operation can measure only one-way information, and when there is a lapse of time across the switching operation processing, the measured information is shifted and measurement error is caused. It can also be a factor.

  Therefore, a method for calculating the flow rate based on the time value of the time measuring means 36 for measuring the propagation time of the ultrasonic signal reflected at least twice between the transducers 32 and 33 will be described. In this method, since the propagation time measured before and after the switching operation of the vibrators 32 and 33 includes information that is a pair of propagation directions, the average flow velocity can be accurately obtained even if the passage of time before and after the switching operation occurs. Can be requested.

  Normal operation is as shown in the timing diagram of FIG. That is, measurement is started from the start signal at time t 0 by the control means 39 and the first vibrator 32 is driven via the transmission means 34. The ultrasonic signal generated there propagates through the flow path 31 and reaches the second transducer 33 at time t1, and when the reception means 35 detects the reception point, the signal is amplified and then received in advance. The reception of the ultrasonic wave is determined at the signal level. The time measuring means 36 measures the propagation time of the propagation wave of the ultrasonic wave directly reaching the second vibrator 33 from the start of driving of the first vibrator 32 by the transmission means 34 via the receiving means 35. Thus, the propagation time from upstream to downstream can be obtained.

  When the ultrasonic wave reaches the second vibrator 33, the ultrasonic wave is reflected there and propagates in the direction of the first vibrator 32. This is the propagation of ultrasonic waves from downstream to upstream. Further, the propagation signal that has reached the first vibrator 32 is similarly reflected there and propagates in the direction of the second vibrator 33. This is the same direction as the first direct propagation.

  FIG. 3 shows the process of propagation with the horizontal axis time and the vertical axis as the channel width. This will be described together with the timing chart of FIG. When there is no flow, the propagation time is the same regardless of the propagation direction.

In FIG. 3, an ultrasonic signal is transmitted from the first transducer (transmission-side transducer) 32 at t0. The ultrasonic signal propagated through the flow path 31 reaches the second transducer (receiving transducer) 33 at time t1. The reflected ultrasonic signal returns to the first transducer 32 at time t2, is reflected there again, and reaches the second transducer 33 at time t3. Since the output of the second vibrator 33 on the receiving side is connected to the receiving means 35, signals at time t1 and time t3 can be captured, but time t2 cannot be obtained directly.

  However, as shown in FIG. 3, the velocity of the ultrasonic wave flowing through the flow path 31 from t0 to t1 and the reflected wave in the same direction from t2 to t3 fluctuate faster as the propagation time changes. If not, the two propagation times can be set equal to T1.

  By subtracting T1 that is twice the total time T3, it is possible to obtain the propagation time T2 from the downstream to the upstream that is the opposite wave. Although this operation is basic, in this embodiment, the propagation time is obtained only from the reflected wave without using the direct wave.

  The case where there is a flow will be described with reference to FIG. In FIG. 4, the flow direction of the fluid is from left to right. Measurement is started from the start signal at time t0 by the control means 39, and the first vibrator 32 is driven via the transmission means. The ultrasonic signal generated there propagates through the flow path 31 and reaches the second vibrator 33 at time t1 '.

  In this case, since the ultrasonic signal is along the flow of the fluid, it reaches the second vibrator earlier than time t1 in FIG. The ultrasonic wave propagation signal reflected here reaches the first vibrator 32 at time t2 ′, but this propagation time is opposed to the flow of the fluid, so that it is longer than the time from t1 to t2 in FIG. It depends. This is the propagation time from downstream to upstream, but this time cannot be measured directly. Similarly, the ultrasonic wave reflected by the first vibrator 32 propagates in the direction of the second vibrator 33. This is in the same direction as the first direct propagation, and the total propagation time T3a is measured by the time measuring means 37 via the receiving means 35.

  T3a obtained by the time measuring means 36 has the following relationship.

2 * T1a + T2a = T3a (Equation 5)
Further, using the switching unit 38, the transmission-side vibrator is the second vibrator 33 and the reception-side vibrator is the first vibrator 32. The operation is shown in FIG. Since the transmission side is installed downstream, the propagation time T1b is longer than T1a in FIG. Similarly, the time T2b of the reflected wave is shorter than T2a. Although T2b cannot be obtained directly, T3b obtained by the timing means 36 has the following relationship.

2 * T2b + T1b = T3b (Equation 6)
When obtaining the average flow velocity before and after the operation of the switching means 38, assuming that there is no sudden flow velocity change, the following equation is established.

T1a = T1b = T1 (Equation 7)
T2a = T2b = T2 (Equation 8)
Substituting (Expression 7) and (Expression 8) into (Expression 5) and (Expression 6) yields the following.

2 * T1 + T2 = T3a (Equation 5 ')
2 * T2 + T1 = T3b (Equation 6 ')
When (Equation 5 ′) and (Equation 6 ′) are added and rearranged, the result is as follows.

T1 + T2 = (T3a + T3b) / 3 (Expression 7)
T1 can be obtained from (Expression 5 ′) − (Expression 7).

T1 = (2 * T3a-T3b) / 3 (Expression 8)
Moreover, T2 can be calculated | required from (Formula 5 ')-(Formula 7).

T2 = (2 * T3b-T3a) / 3 (Equation 9)
By substituting T1 for t1 and T2 for t2 into (Equation 4), the flow velocity v can be obtained. 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.

  In the description of the present embodiment, the reflected wave is based on two-time reflection. However, the present invention is not limited to this, and the same relationship can be derived even when four or six times of reflected waves are used. it can.

  As described above, the flow rate is calculated based on the time value of the time measuring means for measuring the propagation time of the ultrasonic signal reflected at least twice between the transducers 32 and 33 before and after the switching means 39 is operated. If only the propagation time from the upstream to the downstream direction is obtained before the switching means 38, and the propagation time from the downstream to the upstream direction is obtained after the operation of the switching means 38, a deviation occurs in what is measured before and after the switching.

  On the other hand, the time information of T3a and T3b includes information that becomes a pair in each propagation direction. For this reason, obtaining T1 and T2 from T3a and T3b includes arrival times in the propagation direction as a pair before and after the operation of the switching means 38, so that it is possible to obtain an accurate flow velocity without any loss of information. .

  As a result, the propagation time measured before and after the switching operation of the transducer includes information that is a pair of propagation directions, so that the average flow velocity can be obtained accurately even if the time elapses before and after the switching operation occurs. Can do.

  In addition, when determining the propagation arrival time, the zero cross point ta of a waveform exceeding a certain reference voltage Vref is often used as the arrival position of the received wave, for example, as shown in FIG. It is also possible to use an average of four points ta, tb, tc, and td instead of using one point ta. The ultrasonic waveform directly propagating from the first transducer 32 to the second transducer 33 is reflected twice when the amplitude is A1 as shown in FIG. Since the signal arriving at is attenuated, the amplitude is as small as A0 as shown in FIG. 7B. In this case, there is a possibility that the receiving point ta cannot be obtained by the receiving means 35. A method for avoiding this will be described with reference to FIG.

  When the control means 39 detects that the time propagation means 36 has directly received the propagation wave, the control means 39 increases the gain of the amplification means 43 in the preceding stage of the reception means 35 via the gain change means 42. For example, the amplitude A0 of the reflected wave in FIG. 7B is increased to A1. By doing so, the reflection that is otherwise attenuated and difficult to capture is amplified, and the time measuring means 36 can measure the propagation time by the reflected wave as a reception point. When the control means 39 detects the arrival of the reflected wave by the signal from the time measuring means 36 or the flow rate calculating means 37, the gain is returned to the initial state in order to receive the next direct wave through the gain changing means 42. Thus, the state of the amplifying means 43 is adjusted.

  Thus, by having the gain changing means, it becomes possible to correctly capture the propagation signal whose amplitude is reduced by reflection.

  Since the transmission / reception direction is reversed by the operation of the switching means 38, the control means 39 can make further adjustment by having the gain of the amplification means 43 in each transmission direction, and can accurately adjust the signal whose amplitude is reduced by reflection. It becomes possible to capture well.

Further, when the propagation arrival time of the reflected wave is obtained, it cannot be expected that the amplitude of the reflected wave is increased by the amplification means 43 to be exactly the same as the waveform of the direct wave. Therefore, it is necessary to adjust the reference voltage Vref even with the same amplitude A1.

  When the control means 39 detects that the propagation wave has been received directly by the time measuring means 36, the control means 39 increases the gain of the amplification means 43 in the preceding stage of the reception means 35 via the gain change means 42 and sets the reference voltage change means 44. Accordingly, the comparison voltage of the comparison means 45 located after the amplification means 43 of the reception means 35 is adjusted. This adjustment can be performed when the control unit 39 automatically obtains the time when the reflected wave originally arrives, or when the value obtained through an experiment or the like is stored in advance and adjusted while the value is exchanged.

  As a result, the reflection that is normally attenuated and difficult to capture is amplified, and even if the waveform shape changes by adjusting the reference voltage, the time measuring means 36 can measure the propagation time using the reflected wave as a reception point. To. When the control means 39 detects that the reflected wave has arrived based on the signal from the time measuring means 36 or the flow rate calculating means 37, the reference means returns the reference voltage to the initial state in order to receive the next direct wave. The state of the comparison means 45 is adjusted via the voltage changing means 44.

  As described above, by including the reference voltage changing unit 44 that changes the reference voltage of the receiving unit 35 in order to receive the reflected wave, it is possible to correctly capture the reception point of the propagation signal whose amplitude is reduced by reflection. Become.

  Since the transmission / reception direction is reversed by the operation of the switching means 38, the control means 39 can make further adjustments by having the reference voltage of the comparison means 45 for each transmission direction, and the signal whose amplitude is reduced by reflection. Can be accurately captured.

  Further, in the method of obtaining T2 from T1 and T3 in FIG. 3, the propagation times from the reflected wave times t2 to t3 are made equal to the times t0 to t1. However, if the gain of the receiving means 35 is changed or the waveform of the reflected wave itself is deformed, it is necessary to correct this assumption. Therefore, when T2 obtained from the calculation is close to T1 (when the flow velocity becomes almost zero), the flow rate calculation means 37 outputs a signal to the control means 39, and the control means calculates the flow rate when the flow velocity is almost lost. By correcting the coefficient L / 2 * cosφ of the equation 4 used in the means 37, adjustment is performed so that an operation for reducing the error can be performed. This adjustment can be realized by automatically performing, storing a previously obtained value, or adjusting the value while exchanging the value.

  It is also possible to adjust the flow velocity to zero by closing the flow channel 31 from the outside. In that case, it is possible to increase the accuracy by inputting the fact that the flow rate is zero to the control means by the communication means or the like. In this case, the switching means 38 is operated to reverse the transmission / reception direction, and the coefficient of (Equation 4) used in the flow rate calculation means 37 can be corrected for each transmission direction.

  As described above, by including the calculation correction unit that corrects the calculation coefficient of the flow rate calculation unit 37 using the output signal of the timing unit 36 when there is no flow rate by the output of the flow rate calculation unit 37 or an external signal, The error can be adjusted when there is no flow rate.

  Further, when the difference between T3a and T3b obtained as shown in FIGS. 4 and 5 becomes smaller, the flow velocity becomes almost zero. In this case, when the flow rate is obtained, the operation time is long until the transmission direction is switched using the switching means 38, and the operation time becomes long, and this is wasteful from the viewpoint of power saving. Therefore, a method for shortening the measurement time will be described. When T3a and T3b are equal to or less than a predetermined value, the flow velocity becomes slow and there is almost no flow rate, so the switching means 38 is fixed and the upstream vibrator is set to the transmission side. The operation will be described with reference to FIG.

  Measurement is started from the start signal at time t0 by the control means 39, and the upstream first vibrator 32 is driven via the transmission means 34. The ultrasonic signal generated there propagates through the flow path 31, reaches the second transducer 33 on the downstream side at time t1, and when the reception point is detected by the receiving means 35, the signal is amplified and then predetermined. The reception of the ultrasonic wave is determined at the signal level of the received reception timing. The time measuring means 36 measures the propagation time of the propagation wave of the ultrasonic wave directly reaching the second vibrator 33 from the start of driving of the first vibrator 32 by the transmission means 34 via the receiving means 35. Thus, the propagation time from upstream to downstream can be obtained.

  When the ultrasonic wave reaches the second vibrator 33 on the downstream side, it is reflected and propagates in the direction of the first vibrator 32 on the upstream side. This is the propagation of ultrasonic waves from downstream to upstream. The propagation signal that has reached the upstream first vibrator 32 is similarly reflected there and propagates in the direction of the second vibrator 33 on the downstream side. This is the same direction as the first direct ultrasound propagation. In FIG. 3, an ultrasonic signal is transmitted from the first transducer (transmission-side transducer) 32 at t0. The ultrasonic signal propagated in the flow path reaches the second transducer (reception-side transducer) 33 at time t1. The reflected ultrasonic signal returns to the first transducer 32 at time t2, is reflected there again, and reaches the second transducer 33 at time t3.

  Since the output of the second vibrator 33 on the receiving side is connected to the receiving means 35, signals at time t1 and time t3 can be captured, but time t2 cannot be obtained directly. However, as shown in FIG. 3, the velocity of the fluid flowing in the flow path 31 fluctuates faster as the propagation time changes between the ultrasonic direct wave from t0 to t1 and the reflected wave in the same direction from t2 to t3. If not, the two propagation times can be set equal to T1. By subtracting T1 that is twice the total time T3, it is possible to obtain the propagation time T2 from the downstream to the upstream that is the opposite wave. The time measuring means 36 measures the propagation time T1 of the direct wave and the propagation time T3 including the reflected wave. By sending T1 and T3 obtained by the time measuring means 36 to the flow rate calculating means 37, T2 can be obtained from (Equation 10).

T2 = T3-2 * T1 (Equation 10)
By substituting T1 for t1 and T2 for t2 into (Equation 4), the flow velocity v can be obtained. 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.

  In the description of the present embodiment, the reflected wave is based on two-time reflection. However, the present invention is not limited to this, and the same relationship can be derived even when four or six times of reflected waves are used. it can.

  As described above, the flow rate is calculated using the time directly propagated between the transducers 32 and 33 and the propagation time of the ultrasonic signal reflected between the transducers 32 and 33 at least twice, so that the transducers 32 and 33 are calculated. It is not necessary to perform transmission / reception operations by switching the switching means 38, and the relative propagation time can be obtained, whereby the flow velocity can be obtained. When the switching means 38 is fixed, if the flow rate is even a little, the time of T3 including the reflection is shorter when transmitting from the upstream than when transmitting from the downstream.

  For this reason, when there is no flow rate, the operation time of the propagation time measurement is shortened by having the transmission direction designating means that gives priority to the upstream side that has the shorter propagation time at the output of the time measuring means and fixes the transmitting side transducer. Thus, power saving operation is possible.

  Further, as described above, the flow rate can be obtained by fixing the transmitting-side vibrator when the flow rate is small without using the switching unit 38 and using the direct wave and the reflected wave on the receiving-side vibrator. Is possible. However, in order to perform more accurate measurement, it is better to obtain time measurement by bidirectional transmission by switching the switching means 38. This will be described with reference to FIG.

  Therefore, the main control means 39 a inside the control means 39 obtains the propagation time information from the signal from the time measuring means 36. When it is desired to improve the accuracy of the propagation time, the switching unit 38 is operated via the accuracy request unit 46. When the switching means 38 is operated, the information is sent to the flow rate calculation means 37, and the flow velocity and flow rate are obtained using T3a and T3b. Normally, considering power saving, the accuracy request means 46 can fix the switching means 38 and measure, for example, using the direct wave and the reflected wave by using (Expression 10) with the upstream side as the transmission side vibrator.

  As described above, when the accuracy is required, the switching unit 38 is operated and the accuracy request unit 46 for measuring the propagation time is provided, so that the measurement accuracy can be improved and the power saving operation can be performed.

  Also, the receiving means 35 at the subsequent stage of the switching means 38 has a reception characteristic due to the disposition of the signal propagation distance (path) from the first vibrator 32 and the second vibrator 33 is not equal or due to aging. Changes may occur. If a time delay occurs due to a difference in sensitivity or path of the receiving means 35 when measuring the propagation time with high accuracy, for example, even if there is no flow velocity, there may be a calculation such that there is a flow due to the time difference. is there.

  Therefore, as shown in FIG. 10, reception switching means 47 is provided, and at least two reception means 35 are provided. For example, when the second vibrator 33 is a receiving-side vibrator, the reception switching means 47 selects the first receiving means 35a as the receiving means 35 and sends a vibrator signal. It is sent to the time measuring means 36.

  Next, when a transmission wave is output from the transmission unit 34 and the second transducer 33 is a reception-side transducer again, the reception switching unit 47 selects the second reception unit 35b and similarly detects the reception point. The switching of the receiving means 35 is performed so that the characteristics of the receiving system are leveled as much as possible, such as simple switching by the control means 39 or switching once after two consecutive times. Similarly, when the transmission-side transducer is the second transducer 33, the control unit 39 controls the reception switching unit 47 to adjust the path so that the signal is not biased toward the specific reception unit 35.

  By having the reception switching means 47 that operates so as not to connect the reception means 35 fixed to the vibrator by switching at least two reception means 35 in this way, even when there is a wiring path delay to the reception means 35, etc. It is possible to level the delay error by switching so that the receiving means 35 is not biased. By leveling, it becomes possible to reduce the offset of the flow velocity caused by the delay time due to the path difference.

(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 control means 39 is provided with a measurement time adjusting means 48. The operation will be described with reference to FIGS. 1, 3, 4, 5 and 11.

  The propagation time measurement when there is no flow is the same even if T3 switches the switching means 38 and the transmission and reception side transducers are reversed as shown in FIG. When there is a flow, T3a and T3b have different times as shown in FIGS. As the flow velocity decreases, the values of T3a and T3b are gradually approaching. Therefore, when the signal difference (time difference) is smaller than a predetermined value based on the signal from the time measuring means 36 or the flow rate calculating means 37, the control means 39 determines that there is almost no flow velocity. In such a case, even if it is frequently measured, there is little change, so that the time interval for transmission to the transmission unit 34 via the measurement time adjustment unit 48 is adjusted to be long.

  For example, when the control means 39 outputs a drive signal to the transmission means 34 every 1 second and the flow velocity is measured, the measurement changes every 5 seconds when the difference between T3a and T3b becomes smaller than a certain value. In addition, if the difference does not increase even in the measurement every 5 seconds, it is possible to further widen the measurement time interval.

  As described above, when the control means 39 has the measurement time adjusting means 48 for adjusting the measurement time interval when the signal difference of the time measuring means 36 is smaller than a predetermined value, the measurement operation is performed by increasing the measurement interval when the flow rate is small. Reduce the number of times to enable power-saving operation.

  Conversely, the difference between the propagation times T3a and T3b including the reflected wave may suddenly increase. This is a case where sudden use of fluid occurs on the downstream side of the flow path 31. In such a case, when operating at normal propagation time measurement intervals, it may not be possible to measure that the flow velocity frequently changes. When the difference in flow velocity change cannot be detected, a large integrated error occurs when the integrated flow rate is measured.

  Therefore, when the signal difference (time difference) is larger than a predetermined value based on a signal from the time measuring means 36 or the flow rate calculating means 37, the control means 39 determines that the flow velocity is large and the change degree is likely to be severe. In such a case, it is necessary to measure frequently by shortening the measurement interval to correctly detect a large change. The control means 39 adjusts the time interval for transmission to the transmission means 34 via the second measurement time adjustment means 49 so as to shorten it. For example, normally, when the control means 39 outputs a drive signal to the transmission means 34 and measures the flow velocity every second, if the difference between T3a and T3b exceeds a certain value, the second measurement time It changes to measurement every 0.5 seconds via the adjusting means 49.

  As described above, when the signal difference of the time measuring means 36 is larger than a predetermined value by the control means 39, the second measurement time adjusting means 49 for adjusting the measurement time interval is provided. It is possible to increase the number of times of measurement by shortening and to accurately measure changes in flow velocity.

(Embodiment 3)
A flow velocity or flow rate measuring apparatus of the present invention relating to Embodiment 3 will be described. The difference from the first embodiment is that the control means 39 controls at least one of the vibrators 32 and 33, the transmission means 34, the reception means 35, the first time measurement means 36, the flow rate calculation means 37 and the switching means 38. That is, a storage medium 50 having a program for causing a computer to function in order to ensure the operation is used.

  In FIG. 4, in order to perform the operation of the control means 39 shown in the first embodiment, the correction coefficient of (Equation 4) is obtained in advance through experiments or the like, or the operation is performed with respect to aging, temperature change, and system stability. Correlation such as timing is obtained, and software is stored in the storage medium 50 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 depending on the operation of the switching means 38, the number of condition settings and the like increases, but this can be easily realized by adjusting this by an operation by a computer. As described above, when the operation of the control means 39 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 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 39 may be performed by a program using a microcomputer or the like.

As a result, the control means 39 is configured to have a program for causing the computer to function, and it is possible to easily set and change the operation of the measurement method, and to flexibly cope with aging, etc. Accuracy can be improved.

  In addition, as shown in FIG. 12, after receiving the direct wave and the reflected wave by the receiving means 35, it is also possible to repeat the transmission and reception by driving the first vibrator again by the transmitting means 34 via the repeating means 41. It is. Then, after repeating a predetermined number of times, it is possible to perform a more accurate flow velocity calculation by obtaining an average of the obtained direct wave propagation time and reflected wave propagation time.

  Moreover, as shown in FIG. 13, when the delay means 42 is used, transmission / reception can be repeated at a time when there is no influence even when n reflections remain as reverberation.

  As described above, the flow velocity or flow rate measuring device according to the present invention switches the transmission-side transducer and the reception-side transducer using the switching unit, and reflects the ultrasonic signal at least twice between the transducers from the output of the reception unit. The flow rate is calculated on the basis of the time value of the time measuring means for measuring the propagation time.

  As a result, the propagation time measured before and after the switching operation of the vibrator includes information that is a pair of propagation directions, so that the flow rate and flow rate calculation results can be obtained accurately even if the passage of time before and after the switching operation occurs. It can be applied to household and industrial gas meters as gas flow meters and water meters as liquid flow meters.

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 propagation operation in the same measuring device Timing chart showing propagation operation in the same measuring device Timing chart showing propagation operation in the same measuring device Timing chart showing received waves in the same measuring device (A) Timing diagram showing a received wave in the measuring device (b) Timing diagram showing a reflected wave in the measuring device Block diagram showing the periphery of the control means in the same measuring device Block diagram showing the periphery of the control means in the same measuring device Overall block diagram showing other operations of the flow velocity or flow rate measuring device of the present invention Block diagram showing the periphery of the control means in the same measuring device Overall block diagram of a measuring apparatus showing another operation of the present invention Overall block diagram of a measuring apparatus showing another operation of the present invention Overall block diagram of a conventional flow measurement device

Explanation of symbols

31 Flow path 32 First vibrator 33 Second vibrator 34 Transmitting means 35 Receiving means 36 Timing means 37 Flow rate calculating means 38 Switching means 39 Control means 42 Gain changing means 43 Amplifying means 44 Reference voltage changing means 45 Comparison means 46 Accuracy request means 47 Reception switching means 48 Measurement time adjustment means 49 Second measurement time adjustment means 50 Storage medium

Claims (1)

A pair of transducers arranged in the flow path of the fluid to be measured and transmitting and receiving ultrasonic waves;
Transmitting means for driving the transmitting-side vibrator;
Receiving means for converting an output signal of the receiving-side vibrator into an electrical signal;
Switching means for switching between transmission and reception of the resonator,
Clocking means for timing the time from when the ultrasonic wave output from the transducer on the transmitting side is reflected at least twice between the transducers to propagate to the transducer on the receiving side ;
Flow rate calculating means for calculating a flow rate based on the time value of the time measuring means;
A flow rate measurement apparatus comprising: the vibrator, the transmission unit, the reception unit, the time measurement unit, and a control unit that controls at least one of the flow rate calculation units.

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