JP2006038708A - Ultrasonic flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out an intermittent ultrasonic pulse drive operation for an ultrasonic transducer on a transmission side, in order to reduce its power consumption without lowering accuracy in flow rate measurements. <P>SOLUTION: An intermittent drive control section 111 outputs a forward direction clock selecting signal CS<SB>j</SB>and a reverse direction clock selecting signal CS<SB>g</SB>each having a several clock duration such that an intermittent period is interposed between them, when measuring a forward direction transmission frequency and a reverse direction transmission frequency. A transmission frequency switching section 9 applies a forward direction clock CLK<SB>j</SB>and a reverse direction clock CLK<SB>g</SB>which are selected from the forward direction clock selecting signal CS<SB>j</SB>and the reverse direction clock selecting signal CS<SB>g</SB>, to the ultrasonic transducer on the transmission side, as a transmission wave pulse group into which the intermittent period is interposed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an ultrasonic flow meter, and more particularly to an ultrasonic flow meter that measures the flow velocity and flow rate of a fluid such as city gas, LPG, and water using ultrasonic waves.

As an example of a conventional ultrasonic flowmeter, one using a phase-locked loop (PLL) is known (see, for example, Patent Document 1). The measurement principle in this type of ultrasonic flowmeter is that a pair of ultrasonic transducers is provided on the upper side and lower side in the fluid flow direction of the flow path, and ultrasonic waves are predetermined between the pair of ultrasonic transducers by the PLL. The number of waves (hereinafter referred to as the lock wave number) is controlled so that the ultrasonic transducer on the upper side in the flow direction (hereinafter referred to as the forward ultrasonic transducer) and the ultrasonic transducer on the lower side in the flow direction (hereinafter referred to as the super Transmission frequency (hereinafter referred to as forward transmission frequency) when emitting ultrasonic waves toward the ultrasonic transducer) and transmission frequency when ultrasonic waves are emitted from the reverse ultrasonic transducer toward the forward ultrasonic transducer (Hereinafter referred to as reverse transmission frequency) and the measured forward transmission frequency and reverse direction Determine the average flow velocity of the fluid flowing through the flow path based on signal frequency, a method of obtaining the flow rate by multiplying the flow path cross-sectional area more average flow velocity.

Now, as shown in FIG. 2, the lock wave number is N, the forward transmission frequency is f _j , the reverse transmission frequency is f _g , and the distance between the forward ultrasonic transducer 2a and the reverse ultrasonic transducer 2b (hereinafter referred to as propagation). L is the length) and V is the flow velocity of the fluid. The measurement when the ultrasonic wave is propagated from the forward ultrasonic transducer 2a to the reverse ultrasonic transducer 2b (hereinafter referred to as forward measurement) 1) is obtained, and the following expression (2) is obtained by measurement when ultrasonic waves are propagated from the backward ultrasonic transducer 2b to the forward ultrasonic transducer 2a (hereinafter referred to as reverse direction measurement).

L / (C + V) = N / f j → Lf j / N = C + V ··· (1)
L / (C−V) = N / f _g → Lf _g / N = C−V (2)

The following formula (3) is obtained from the formula (1) -the formula (2), and the following formula (4) is obtained from the formula (1) + the formula (2).

V = (L / 2N) × (f _j −f _g ) (3)
C = (L / 2N) × (f _j + f _g ) (4)

Then, the flow rate Q is obtained by the following equation (5) using a correction coefficient H that takes into account the cross-sectional area S of the flow path, the measurement time interval (hereinafter referred to as interval time) Δ, and the like.

Q = V · S · H (5)

Further, if the integrated flow ΣQ ₀ up to the previous time is used, the integrated flow ΣQ ₁ can be obtained by ΣQ ₁ = ΣQ ₀ + Q.

Furthermore, since the temperature τ is obtained from the sound velocity C obtained by the equation (4) by the simple equation C = 331.68 + 0.61τ, the temperature τ can be corrected.
Japanese Patent Publication No. 3-39246

By the way, in the conventional ultrasonic flowmeter, during the measurement of the ultrasonic propagation time T _j from the forward ultrasonic transducer 2a to the reverse ultrasonic transducer 2b (hereinafter referred to as the forward propagation time) T _j and the reverse ultrasonic transducer. forward ultrasound transducer 2a ultrasound propagation time to the 2b (hereinafter, backward propagation time hereinafter) during the measurement of the T _g, the pair of ultrasonic transducers 2a, continuously transmits an ultrasonic pulse between 2b I kept doing it. That is, the driving pulse is continuously applied to the ultrasonic transducer on the transmission side. For this reason, the ultrasonic transducer on the transmission side has to continue to emit ultrasonic pulses, which causes a problem of consuming a lot of power. For ultrasonic flowmeters that must operate for a long time with a limited power source such as a battery, the number of drive pulses (number of drive pulses) applied to the ultrasonic transducer on the transmission side to minimize power consumption It was desirable to suppress M.

In the conventional ultrasonic flowmeter, the measurement accuracy of the flow rate Q often becomes a problem, but in order to improve the measurement accuracy of the flow rate Q, it is necessary to increase the number of times of measurement. However, when the number of times of measurement is increased, there is a problem that the measurement time becomes longer and power consumption increases. Therefore, it has been difficult to increase the measurement accuracy by increasing the number of measurements in an ultrasonic flowmeter that is required to operate without battery replacement for many years.

In view of the above problems, the present invention makes it possible to obtain excellent flow rate measurement accuracy while suppressing an increase in power consumption by intermittently emitting ultrasonic pulses from the ultrasonic transducer on the transmission side. An object of the present invention is to provide an ultrasonic flowmeter.

Means for Solving the Problems and Effects of the Invention

The ultrasonic flowmeter according to claim 1 is provided with a pair of ultrasonic transducers on the upper side in the flow direction and the lower side in the flow direction in the flow path through which the fluid flows, and ultrasonic waves are predetermined between the pair of ultrasonic transducers. In an ultrasonic flowmeter that controls the forward transmission frequency and the reverse transmission frequency so as to achieve the specified lock wave number, and obtains the flow velocity and flow rate based on the forward transmission frequency and the reverse transmission frequency at that time, the forward transmission frequency In addition, the intermittent drive control unit that outputs a clock selection signal for several clocks with an intermittent time when measuring the reverse transmission frequency, and the clock selected by the clock selection signal from the intermittent drive control unit with an intermittent time A transmission frequency changeover switch unit to be applied to the ultrasonic transducer on the transmission side as a transmission wave pulse group, Characterized in that the intermittent operation by the transmission wave pulse group sandwiching the intermittent time the driving of the ultrasonic transducers of the transmitting side in. According to the ultrasonic flowmeter of the first aspect, the drive of the ultrasonic transducer on the transmission side in one transmission frequency measurement is an intermittent operation by the transmission wave pulse group with the intermittent time interposed therebetween. The number of times of driving the large ultrasonic transducer is reduced, and the power consumption of the ultrasonic flowmeter can be reduced accordingly.

The ultrasonic flowmeter according to claim 2 is the ultrasonic flowmeter according to claim 1, further comprising a counter that continues to count the clock during the intermittent time. According to the ultrasonic flowmeter according to claim 2, by continuously counting the clock during the intermittent time, it becomes possible to continue to estimate the flow velocity during the intermittent time, and the flow rate is highly accurate even with low power consumption. Measurement can be realized.

The ultrasonic flowmeter according to claim 3 is the ultrasonic flowmeter according to claim 1 or 2, further comprising an interval control unit for controlling an interval time between transmission frequency measurements. According to the ultrasonic flowmeter of claim 3, since the interval control unit is provided so as to control the interval time between transmission frequency measurements, the interval time is shortened at a high flow rate and the interval time at a low flow rate. Can be lengthened.

The ultrasonic flowmeter according to claim 4 is the ultrasonic flowmeter according to any one of claims 1 to 3, wherein the interval control unit controls the interval time according to the measured flow rate. It is characterized by. According to the ultrasonic flowmeter of claim 4, by controlling the interval time according to the flow rate, the interval time is lengthened at a low flow rate, the number of drive pulses per unit time is reduced, and the power consumption is reduced. Can be realized.

The ultrasonic flowmeter according to claim 5 is the ultrasonic flowmeter according to any one of claims 1 to 3, further comprising a flow rate determination unit that variably controls the intermittent time according to the measured flow rate. It is characterized by that. According to the ultrasonic flowmeter of claim 5, by controlling the intermittent time according to the flow rate, the intermittent time is lengthened at a low flow rate, the number of drive pulses per unit time is reduced, and the power consumption is reduced. Can be realized.

The ultrasonic flowmeter according to claim 6 is the ultrasonic flowmeter according to claim 5, wherein the flow rate determination unit calculates a temperature based on a sound velocity obtained by measuring a transmission frequency, It is characterized by performing flow rate correction. According to the ultrasonic flowmeter of the sixth aspect, by calculating the temperature based on the speed of sound obtained by measuring the transmission frequency, it is possible to reduce the number of components and low power consumption without arranging the thermometer. The measurement accuracy of the flow rate can be improved.

The ultrasonic flowmeter according to claim 7 is the ultrasonic flowmeter according to any one of claims 1 to 6, wherein the pair of ultrasonic transducers has a low Q value representing mechanical resonance sharpness and It is characterized by frequency impedance characteristics close to low spurious single resonance characteristics. According to the ultrasonic flowmeter of claim 7, by using an ultrasonic transducer having a frequency impedance characteristic close to a single resonance characteristic having a low Q value representing a mechanical resonance sharpness and a low spurious characteristic, a drive pulse is obtained. Since the reception points are stable even if the number is small, it is possible to improve the measurement accuracy of the ultrasonic flowmeter and reduce power consumption.

The ultrasonic flowmeter according to claim 8 is the ultrasonic flowmeter according to any one of claims 1 to 7, wherein the transmission is applied to the ultrasonic transducer on the transmission side according to the transmission frequency of the clock. A drive pulse number control unit that variably controls the number of drive pulses of the wave pulse group is provided. According to the ultrasonic flowmeter of claim 8, since the number of drive pulses of the transmission wave pulse group is variably controlled according to the transmission frequency of the clock, even if the transmission frequency of the clock changes, the flow rate Measurement accuracy can be maintained.

The ultrasonic flowmeter according to claim 9 is the ultrasonic flowmeter according to any one of claims 1 to 8, wherein the ultrasonic flowmeter is measured by the ultrasonic transducer on the receiving side according to the transmission frequency of the clock. A reception point management unit for changing the reception point of the reception wave pulse group is provided. According to the ultrasonic flowmeter of claim 9, the measurement accuracy is improved in accordance with the driving of the ultrasonic transducer with low power consumption by changing the reception point according to the forward transmission frequency or the reverse transmission frequency. Can be achieved.

An ultrasonic flowmeter according to a tenth aspect is the ultrasonic flowmeter according to any one of the first to ninth aspects, wherein the lock wave number is changed according to a measurement fluid. According to the ultrasonic flowmeter of the tenth aspect, the type of fluid (for example, gas type) can be determined by propagation time measurement or an external switch, and the lock wave number can be changed and managed using the same frequency region. Therefore, the measurement accuracy is improved, and at the same time, it is not necessary to provide an ultrasonic transducer for each type of fluid.

The ultrasonic flowmeter according to claim 11 is the ultrasonic flowmeter according to any one of claims 1 to 10, wherein marker pulse synthesis is performed in which marker pulses are mixed in a clock selected by the transmission frequency changeover switch unit. The marker pulse is propagated in a cycle corresponding to a predetermined lock wave number, and the wave number of the ultrasonic wave between the pair of ultrasonic transducers is set to a predetermined lock wave number based on the marker pulse. A reception measurement management unit for coarsely controlling the frequency of the clock is provided. According to the ultrasonic flowmeter of the eleventh aspect, since the phase greatly deviated can be phase-matched by a rough control step, the wave number can be quickly locked even for a sudden change in flow rate, so that low power consumption is achieved. Leads to. In addition, since the phase rotation management is performed by attaching the marker pulse, it is possible to measure the flow rate over a wide range with high accuracy.

The ultrasonic flowmeter according to claim 12 is the ultrasonic flowmeter according to any one of claims 1 to 11, wherein the reception measurement management unit eliminates the phase shift in the coarse control. The frequency of the clock is finely controlled between the pair of ultrasonic transducers so that the wave number of the ultrasonic wave becomes a predetermined lock wave number. According to the ultrasonic flowmeter of the twelfth aspect, since the fine adjustment control for adjusting the phase roughly adjusted by the coarse adjustment control by the fine control step with higher accuracy is performed, the flow measurement with high accuracy can be performed.

The ultrasonic flowmeter according to claim 13 is the ultrasonic flowmeter according to any one of claims 1 to 12, wherein the pair of ultrasonic transducers switches between a forward propagation time and a backward propagation time. When measuring, the forward transmission frequency and the reverse transmission frequency at the previous measurement are memorized, and the forward transmission frequency and the reverse transmission frequency at the next measurement are memorized and the forward transmission at the previous measurement stored. It starts with a frequency and a reverse transmission frequency. According to the ultrasonic flowmeter of claim 13, since the VCO that consumes a large amount of current consumption is stopped during measurement, the forward transmission frequency at that time is stopped before the measurement operation is stopped in the direction in which measurement is not performed. And stores the reverse transmission frequency. By measuring from the forward transmission frequency and reverse transmission frequency stored at low power consumption when starting forward measurement and reverse measurement, the forward transmission frequency and reverse transmission frequency can be adjusted quickly, Low power consumption. It is also conceivable to store the voltage value input to the VCO.

The ultrasonic flowmeter according to claim 14 is the ultrasonic flowmeter according to any one of claims 1 to 13, wherein the third-order reflection of the ultrasonic flowmeter after the direct wave of the reception wave pulse group by the transmission wave pulse group arrives. In the time period until a wave appears, the next received wave pulse group by the next transmitted wave pulse group is received. According to the ultrasonic flowmeter of claim 14, by setting the time zone until the tertiary reflected wave appears as a reception point after reception, the tertiary reflected wave is removed in advance from the measurement of the transmission frequency, and the flow rate is measured. Accuracy can be improved.

The ultrasonic flowmeter according to claim 15 is provided with a pair of ultrasonic transducers on the upper side in the flow direction and the lower side in the flow direction in the flow path through which the fluid flows, and ultrasonic waves are predetermined between the pair of ultrasonic transducers. In the ultrasonic flowmeter that controls the forward transmission frequency and the reverse transmission frequency so as to obtain the lock wave number, and obtains the flow velocity and flow rate based on the forward transmission frequency and the reverse transmission frequency at that time, The phase of the clock that drives the sonic transducer and the phase of the received wave converted signal converted by the ultrasonic transducer on the receiving side is compared, and a phase-locked loop that outputs a clock with a transmission frequency that matches the phase is output from the phase-locked loop. Lock wave number clock that outputs phase comparison timing signal when clock count value becomes lock wave number A clock management unit, a transmission / reception control unit that outputs a clock selection signal for several clocks with an intermittent time according to a phase comparison timing signal from the lock wave number clock management unit, and a clock selection signal from the transmission / reception control unit A transmission frequency changeover switch unit that applies the clock for several clocks to the ultrasonic transducer on the transmission side as a transmission wave pulse group with an intermittent time, and a counter that continues to count the clock during the intermittent time; An interval control unit that controls the interval time between the measurement of the forward transmission frequency and the measurement of the reverse transmission frequency according to the measured flow rate, and the flow rate determination that variably controls the intermittent time according to the measured flow rate And the transmission-side ultrasonic transducer on the transmission side according to the transmission frequency of the clock from the phase-locked loop A drive pulse number control unit that variably controls the number of drive pulses of a transmission wave pulse group to be applied to the sensor, and reception that is measured by an ultrasonic transducer on the reception side according to the transmission frequency of the clock from the phase locked loop A reception point management unit that changes a reception point of a wave pulse group, a marker pulse synthesis unit that mixes a marker pulse from the transmission / reception control unit with a clock selected by the transmission frequency changeover switch unit, and a predetermined marker pulse. The frequency of the clock is coarsely controlled so that the wave number of the ultrasonic wave becomes a predetermined lock wave number between the pair of ultrasonic transducers based on the marker pulse by propagating at a period corresponding to the lock wave number determined. Then, after eliminating the phase shift in the coarse adjustment control, the ultrasonic wave is predetermined between the pair of ultrasonic transducers. And a reception measurement management unit that finely controls the frequency of the clock so as to obtain a lock wave number. According to the ultrasonic flowmeter of claim 15, an ultrasonic wave with high power consumption can be obtained by driving the ultrasonic transducer on the transmission side in the measurement of the transmission frequency to an intermittent operation using a transmission wave pulse group with an intermittent time in between. The number of times the transducer is driven is reduced, and accordingly, the power consumption of the ultrasonic flowmeter can be reduced.

Flow rate measurement accuracy is achieved by dividing the ultrasonic pulse group transmitted and received between a pair of ultrasonic transducers into an ultrasonic pulse group with intermittent time in between, and intermittently operating the ultrasonic pulse drive of the ultrasonic transducer on the transmitting side. The power consumption can be reduced without reducing the power consumption.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit block diagram showing the configuration of the ultrasonic flowmeter according to the first embodiment of the present invention. The ultrasonic flowmeter according to the first embodiment includes a flow path 1, an ultrasonic transducer (a forward ultrasonic transducer) 2 a installed on the upper side in the flow direction in the flow path 1, and a flow direction in the flow path 1. The ultrasonic transducer (reverse ultrasonic transducer) 2b installed on the lower side, the transmission / reception switching unit 3 connected to the forward ultrasonic transducer 2a and the reverse ultrasonic transducer 2b, and the transmission / reception switching unit 3 were connected. The phase comparison changeover switch SWa, the phase comparison changeover switch SWb to which the transmission / reception changeover unit 3 is connected, the phase comparison changeover switch SWa and a voltage control oscillator (VCO) 6a described later are connected to the input terminal, and the control terminal will be described later. Phase comparator 4a to which microcomputer 11 is connected, phase comparison changeover switch SWb, and voltage control oscillator to be described later VCO) 6b is connected to the input terminal, a phase comparison unit 4b having a control terminal connected to a microcomputer 11 described later, a low-pass filter (LPF) 5a to which the output terminal of the phase comparison unit 4a is connected, and a phase comparison unit The low-pass filter (LPF) 5b to which the output terminal 4b is connected, the voltage control oscillator (VCO) 6a to which the LPF 5a is connected, the voltage control oscillator (VCO) 6b to which the LPF 5b is connected, and the VCO 6a are connected. Counter (hereinafter referred to as forward counter) 7a, counter (hereinafter referred to as reverse counter) 7b to which VCO 6b is connected, lock wave number clock management unit 8a to which VCO 6a is connected, and lock wave number to which VCO 6b is connected. The clock management unit 8b is connected to the VCO 6a and VCO 6b and the microcomputer 11. And a transmission frequency switching unit 9, a marker pulse synthesis unit 10 to the transmission frequency switching unit 9 and the microcomputer 11 is connected, a microcomputer 11 serving as a transmission control unit, a main part is configured.

In the flow path 1, the flow direction axis is linear between the forward ultrasonic transducer 2a and the reverse ultrasonic transducer 2b, and the shape and cross-sectional area of the axial cross section are the same in the flow direction. When the measurement fluid is a gas, the axial cross-sectional shape of the flow path 1 may be any shape that forms a space closed by a wall, and for example, any one of a circular shape, an elliptical shape, a square shape, a rectangular shape, etc. is adopted. May be.

The forward ultrasonic transducer 2a and the reverse ultrasonic transducer 2b are ultrasonic transducers configured using piezoelectric elements, diaphragms, electrodes, etc., and have a low Q value representing mechanical resonance sharpness and low spurious. This is a frequency impedance characteristic close to a single resonance characteristic. Transmission / reception switching of the forward ultrasonic transducer 2a and the reverse ultrasonic transducer 2b is performed by a transmission / reception switching unit 3 constituted by an analog switch or the like.

The transmission / reception switching unit 3 includes transmission means (not shown) including a driving voltage circuit for emitting an ultrasonic pulse group from the forward ultrasonic transducer 2a and the reverse ultrasonic transducer 2b, and forward ultrasonic waves. Receiving means (not shown) including a voltage detection circuit for detecting the received wave conversion signal of the transducer 2a and the reverse direction ultrasonic transducer 2b, and switching between transmission and reception from the microcomputer 11 Switching between transmission / reception of the forward ultrasonic transducer 2a and the reverse ultrasonic transducer 2b is controlled according to ON / OFF (high level / low level) of the signal SR. For example, in the case of forward measurement in which the transmission wave pulse group TP _j is transmitted from the forward ultrasonic transducer 2a toward the reverse ultrasonic transducer 2b, the forward ultrasonic transducer 2a becomes the transmission side (source). Therefore, the transmission / reception switching unit 3 connects the transmission unit and the forward ultrasonic transducer 2a, and connects the reception unit and the reverse ultrasonic transducer 2b. On the other hand, when the backward ultrasonic transducer 2b reverse measurement for transmitting a transmission wave pulse group TP _g toward the forward ultrasound transducer 2a is reverse ultrasound transducer 2b is the transmission side (firing source) Therefore, the transmission / reception switching unit 3 connects the transmission unit and the backward ultrasonic transducer 2b, and connects the reception unit and the forward ultrasonic transducer 2a.

The phase comparison switch SWa switches between outputting a received wave conversion signal from the transmission / reception switching unit 3 and outputting a forward clock CLK _j from the VCO 6a in accordance with a switch switching signal SC _j from the microcomputer 11. .

Phase comparison selector switch SWb, in accordance with the switching signal SC _g from the microcomputer 11, or outputs the received wave conversion signals from the reception switching unit 3 switches whether to output the reverse clock CLK _g from VCO6b .

The phase comparator 4a, LPF 5a, and VCO 6a constitute a so-called phase locked loop (PLL).

Phase comparing unit 4a outputs a reception wave converted signal or a forward clock CLK _j from the phase comparator selector switch SWa, by comparing the forward clock CLK _j from VCO6a, the phase difference voltage signal corresponding to the phase difference To do. The forward phase set signal PS _j input from the microcomputer 11 informs the phase comparison unit 4a whether to perform phase comparison of the coarse adjustment marker pulse MP or to perform phase comparison of the fine adjustment received wave conversion signal. Signal.

The LPF 5a receives the phase difference voltage signal from the phase comparison unit 4a, averages the phase difference voltage signal, and outputs it. The LPF 5a serves to determine the loop characteristics of the PLL.

The VCO 6a receives the voltage signal from the LPF 5a, and if there is a phase shift between the received wave conversion signal and the forward clock CLK _j in the phase comparator 4a, the forward clock CLK so that the phase shift becomes zero. change the forward transmission frequency f _j of the _j, adjust the phase such that the predetermined lock wavenumber N. Specifically, as shown in FIG. 4 (a), the VCO 6a has the order adjusted to the forward transmission frequency f _j necessary for adjusting the phase of the phase shift compared with the received wave converted signal by the phase comparison unit 4a. The direction clock CLK _j is output to the lock wave number clock management unit 8a.

The phase comparison unit 4b, the LPF 5b, and the VCO 6b also constitute a so-called phase locked loop (PLL).

Phase comparator 4b is output and received wave converted signal or a reverse clock CLK _g from the phase comparator selector switch SWb, by comparing the reverse clock CLK _g from VCO6b, the phase difference voltage signal corresponding to the phase difference To do. Incidentally, the forward phase set signal PS _g being input from the microcomputer 11 informs whether the marker pulse MP for rough tuning for phase comparison, whether to phase comparing the received wave conversion signal for fine adjustment to the phase comparator 4b Signal.

The LPF 5b receives the phase difference voltage signal from the phase comparison unit 4b, averages the phase difference voltage signal, and outputs it. The LPF 5b serves to determine the loop characteristics of the PLL.

The VCO 6b receives the voltage signal from the LPF 5b, and if there is a phase shift between the received wave conversion signal and the reverse clock CLK _g in the phase comparator 4b, the reverse clock CLK so that the phase shift becomes zero. change the reverse transmission frequency f _g of _g, adjust the phase such that the predetermined lock wavenumber N. For more information, VCO6b is reverse clock CLK _g lock wavenumber clock management unit that is adjusted in the reverse transmission frequency f _g required for the phase shift amount to the phase adjustment as compared to the received wave converted signal by the phase comparator 4b Output to 8b.

The forward counter 7a counts the forward clock CLK _j having the forward transmission frequency f _j (estimates the flow velocity V even while not measuring). Specifically, the forward counter 7a takes in the count value as the forward count value K _j in synchronization with the turn-off of the transmission / reception switching signal SR, and is then cleared to zero to count the forward clock CLK _j . Resume.

Reverse counter 7b is (estimates the flow velocity V also while not measured) to reverse transmission counts the reverse clock CLK _g of a frequency f _g. Specifically, reverse counter 7b is synchronized with the ON transmission and reception switch signal SR is taken into the microcomputer 11, the count value as an inverted count value K _g, the count of the reverse clock CLK _g is cleared to zero thereafter Resume.

The lock wave number clock management unit 8a performs management (the count of the lock wave number N, the forward phase) for setting the wave number (lock wave number) to be locked in the space between the forward ultrasonic transducer 2a and the reverse ultrasonic transducer 2b to N. The comparison timing signal CT _j is triggered). The lock wave number clock management unit 8a counts the forward clock CLK _j from the VCO 6a and compares the phase from several times before the count value becomes the lock wave number N ((N-2) in FIG. 4B). A forward phase comparison timing signal CT _j (see FIG. 4B) for notifying the unit 4a of the phase comparison timing between the received wave conversion signal and the forward clock CLK _j from the VCO 6a is transmitted to the microcomputer 11. Furthermore, the lock wave number clock management unit 8a transmits forward clocks CLK _{j corresponding} to several clocks at the forward transmission frequency f _j changed by the VCO 6a for the next phase adjustment. Note that the type of fluid (for example, gas type) may be determined, and the lock wave number N may be changed and managed using the same frequency region by measuring propagation time or using an external switch.

The lock wave number clock management unit 8b performs management (counting of the lock wave number N, reverse phase) for setting the wave number (lock wave number) to be locked in the space between the backward ultrasonic transducer 2b and the forward ultrasonic transducer 2a. performing trigger, etc.) comparing timing signal CT _g. Lock wavenumber clock management unit 8b is reverse clock CLK from the reverse clock CLK _g received wave converted signal count value has been counted from several before the lock wavenumber N to the phase comparison unit 4b and VCO6b from VCO6b transmit reverse phase comparison timing signal CT _g informing the phase comparison timing with the _g to the microcomputer 11. Further, the lock wave number clock management unit 8b transmits reverse clocks CLK _{g corresponding} to several clocks at the reverse transmission frequency f _g changed by the VCO 6b for the next phase adjustment. Note that the type of fluid (for example, gas type) may be determined, and the lock wave number N may be changed and managed using the same frequency region by measuring propagation time or using an external switch.

The transmission frequency changeover switch unit 9 selects a signal selected from the forward clock CLK _j (see FIG. 3A) by the forward clock selection signal CS _j (see FIG. 3B) as a transmission wave pulse group TP (see FIG. 4). (See (g)) to the marker pulse synthesizer 10. Further, the transmission frequency changeover switch unit 9 selects a signal selected from the backward clock CLK _g (see FIG. 3D) by the backward clock selection signal CS _g (see FIG. 3E) as the transmission wave pulse group TP ( As shown in FIG. 4G, the data is output to the marker pulse synthesizing unit 10.

The marker pulse synthesizing unit 10 synthesizes the applied voltage so that the transmission wave pulse group TP (see FIG. 4G) includes the marker pulse MP (see FIG. 4E). Specifically, the marker pulse synthesizing unit 10 outputs the marker pulse MP at the timing of the transmission wave pulse group TP (see FIG. 4G) and while the marker pulse MP (see FIG. 4E) is on. A high voltage is output to the transmission / reception switching unit 3 as the included transmission wave pulse group TP (see FIG. 4H).

The microcomputer 11 includes an intermittent drive control unit 111, an interval control unit 112, a flow rate determination unit 113, a reception measurement management unit 114, a drive pulse number control unit 115, and a reception point management unit 116. ing.

The microcomputer 11 controls the forward clock selection signal CS _j (see FIG. 3B) and the reverse for controlling the number of pulses (number of drive pulses) M of the transmission wave pulse group TP output from the transmission frequency changeover switch unit 9. The direction clock selection signal CS _g (see FIG. 3E) is output to the transmission frequency changeover switch unit 9. Incidentally, a condition in FIG. 4 (d), the because backward clock selection signal CS _g is off, selects the forward clock CLK _j from VCO6a.

The microcomputer 11, based on reverse phase comparison timing signal CT _g from the forward phase comparison timing signal CT _j and lock wavenumber clock management unit 8b from the lock wavenumber clock management unit 8a, the forward ultrasound transducer 2a And marker pulse MP (refer FIG.4 (e)) superimposed on the transmission wave pulse group TP (refer FIG.4 (g)) at the time of the drive of the reverse direction ultrasonic transducer 2b is output to the marker pulse synthetic | combination part 10. FIG.

Further, the microcomputer 11 outputs the forward switching signal SC _j (see FIG. 4 (f)) to the phase selector switch SWa, and outputs the backward switching signal SC _g to the phase selector switch SWb. The forward switch switching signal SC _j switches whether the phase comparator 4a compares the forward clock CLK _j from the VCO 6a with the received wave conversion signal or the forward clock CLK _j . During the phase comparison between the forward clock CLK _j from the VCO 6a and the received wave conversion signal (because intermittent transmission is performed), the phase shift is adjusted by controlling the forward switch switching signal SC _j. Thus, the forward clock CLK _j having the forward transmission frequency f _j is output, and the VCO 6a is locked at the adjusted forward transmission frequency f _j immediately before the forward clock CLK _j from the VCO 6a is compared. It becomes a state. Further, backward switching signal SC _g, the phase comparator portion 4b or to compare the backward clock CLK _g and the received wave conversion signal from VCO6b, switches whether to compare the backward switching signal SC _g together. The control of the reverse switching signal SC _g, (because of the intermittent transmission) while the reverse clock CLK _g has a phase comparison between the received wave conversion signal from VCO6b adjusts the phase shift amount Thus, the reverse clock CLK _g having the reverse transmission frequency f _g is output, and the VCO 6 b is locked at the adjusted reverse transmission frequency f _g immediately before the reverse clock CLK _g from the VCO 6 b is compared. It becomes a state.

The intermittent drive control unit 111 variably controls the forward intermittent time δ _j and the reverse intermittent time δ _g according to the obtained flow rate Q. That is, when the flow rate Q is low, the forward intermittent time δ _j and the reverse intermittent time δ _g are lengthened.

The interval control unit 112 variably controls the interval time Δ according to the obtained flow rate Q. That is, when the obtained flow rate Q is a low flow rate, the interval time Δ is lengthened. The interval time Δ is equal to or longer than the standby time W (see FIG. 3 (h)), which is the sum of the forward propagation time T _j or the backward propagation time T _g and the reverberation time. In order to reduce it, it is desirable to set it to approximately three times or more of the forward propagation time T _j or the backward propagation time T _g .

The flow rate determination unit 113 obtains the flow rate Q based on the measured forward transmission frequency f _j and reverse transmission frequency f _g , and determines the forward intermittent time δ _j and the reverse intermittent time δ _g according to the flow rate Q. Variable control. In addition, the flow rate determination unit 113 transmits the transmission wave pulse group TP _j from the forward ultrasonic transducer 2a to the reverse ultrasonic transducer 2b, and performs the forward direction measurement and the transmission wave pulse group TP from the reverse ultrasonic transducer 2b. _The temperature τ is obtained based on the sound velocity C obtained by the backward measurement performed by transmitting _g to the forward ultrasonic transducer 2a, and the flow rate Q is corrected with respect to the temperature τ.

The reception measurement management unit 114 propagates the marker pulse MP in a cycle corresponding to a predetermined lock wave number N, and performs super-operation between the forward ultrasonic transducer 2a and the reverse ultrasonic transducer 2b based on the marker pulse MP. order to instruct to coarse controlling reverse transmission frequency f _g of the forward clock CLK forward transmit frequency of the _j f _j and the reverse clock CLK _g as the wave number of the acoustic wave becomes a predetermined lock wavenumber N The direction phase set signal PS _j and the reverse direction phase set signal PS _g are output to the phase comparison unit 4b and the phase comparison unit 4a. Further, the reception measurement management unit 114 eliminates the phase shift by the coarse adjustment control, and then the lock wave number N in which the ultrasonic wave number is determined in advance between the forward ultrasonic transducer 2a and the reverse ultrasonic transducer 2b by the fine adjustment control. become way forward clock CLK _j forward transmit frequency f _j and the reverse clock CLK _g forward phase set signal PS _j and reverse phase set signal reverse transmission frequency f _g instructing to control fine adjustment of the PS _g is output to the phase comparison unit 4b and the phase comparison unit 4a.

The driving pulse number control unit 115, the transmission wave in accordance with the uplink transmission frequency f _g of the forward clock CLK forward transmit frequency of the _j f _j and the reverse clock CLK _g, is applied to the transmitting-side ultrasonic transducer of the receiving side The number M of drive pulses of the pulse group TP is variably controlled.

Receiving point management unit 116, in accordance with the uplink transmission frequency f _g of the forward clock forward transmit frequency of the CLK _j f _j and the reverse clock CLK _g, received wave pulse group to measure the reception side ultrasonic truss juicer Change the RP reception point.

FIG. 3 shows a timing chart when the forward intermittent time δ _j and the reverse intermittent time δ _g are provided in the ultrasonic flowmeter according to the first embodiment of the present invention (intermittent mode). In this case, the control works so as to eliminate the phase shift between the received wave pulse groups RP _j1 and RP _j2 received by the backward ultrasonic transducer 2b and the forward clock CLK _j, and the received wave received by the forward ultrasonic transducer 2a. Control is performed so as to eliminate the phase shift between the pulse groups RP _g1 and RP _g2 and the backward clock CLK _g .

Next, the operation of the ultrasonic flowmeter according to the first embodiment configured as described above will be described with reference to the flowcharts of FIGS.

(1-1) Transmission operation of first transmission wave pulse group TP _j1 in forward measurement (see the transmission flowchart of FIG. 5)

First, the microcomputer 11 causes the interval control unit 112 to start forward measurement based on whether or not the interval time Δ has elapsed since the end time of the previous backward measurement (forward measurement start time). It is determined whether or not (step S101). Specifically, the interval control unit 112 measures the forward direction based on whether or not the interval time Δ has elapsed since the completion (falling) of the output of the second reverse clock selection signal CS _g (see FIG. 3E). Determine the start time.

If the forward measurement start time has come (YES in step S101), the microcomputer 11 determines whether the measurement to be performed from now is forward measurement or reverse measurement (step S102).

Since the forward measurement is now performed (Yes in step S102), the microcomputer 11 instructs the transmission / reception switching unit 3 to turn off the transmission / reception switching signal SR (see FIG. 3G) to enter the forward measurement mode. (Step S103). Then, the transmission / reception switching unit 3 connects the transmission unit and the forward ultrasonic transducer 2a, and connects the reception unit and the reverse ultrasonic transducer 2b based on the fact that the transmission / reception switching signal SR is OFF. That is, the transmission / reception switching unit 3 sets the forward ultrasonic transducer 2a to the transmission side and sets the reverse ultrasonic transducer 2b to the reception side.

Subsequently, the microcomputer 11 determines whether or not the forward clock CLK _j (FIG. 3) based on whether or not the forward clock selection signal CS _j (see FIG. 3B) output to the transmission frequency changeover switch unit 9 is ON. It is determined whether or not it is time (drive time) to apply (see (a)) as the first transmission wave pulse group TP _j1 to the forward ultrasonic transducer 2a (step S105).

If the forward clock selection signal CS _j is off (No in step S105), the microcomputer 11 sets the non-measurement mode in which the forward clock CLK _j is not applied to the forward ultrasonic transducer 2a (step S106).

If the forward clock selection signal CS _j is on (Yes in Step S105), the microcomputer 11 determines whether or not it is the marker pulse transmission timing for coarse adjustment control by the reception measurement management unit 114 (Step S107). ).

If it is the marker pulse transmission timing for coarse adjustment control (Yes in step S107), the microcomputer 11 transmits the marker pulse MP (see FIG. 4E) and the drive pulse number M by the marker pulse synthesizing unit 10. The head pulse (see FIG. _4G) of the wave pulse group TP _j1 is superimposed to synthesize a transmission wave pulse (applied voltage) including the marker pulse MP as shown in FIG. The forward ultrasonic transducer 2a is applied via the unit 3 (step S108).

On the other hand, if it is not the marker pulse transmission timing for coarse adjustment control (No in step S107), the microcomputer 11 causes the marker pulse synthesizing unit 10 to transmit the transmission wave pulse via the transmission / reception switching unit 3 to the forward ultrasonic transducer. Apply to 2a (step S109).

Next, the microcomputer 11 determines whether or not the number of transmission wave pulses applied to the forward ultrasonic transducer 2a has reached the number M of drive pulses by the drive pulse number control unit 115 (step S110). If it is not M, control is returned to step S107, and steps S107 to S110 are repeated.

When the number of transmission wave pulses reaches the drive pulse number M in step S110, the microcomputer 11 ends the transmission operation of the first transmission wave pulse group TP _{j1 in} the forward measurement.

In this manner, the forward ultrasonic transducer 2a transmits the first transmission wave pulse group TP _j1 having the number M of drive pulses toward the reverse ultrasonic transducer 2b.

(1-2) Reception operation of the first received wave pulse group RP _j1 in forward measurement (see the reception flowchart in FIG. 6).

The microcomputer 11 propagates the distance of the propagation length L after the first transmission wave pulse group TP _j1 is emitted from the forward ultrasonic transducer 2a by the reception measurement management unit 114, and receives the first reception wave pulse group RP. It is determined whether or not the time (forward measurement start time) to be received by the backward ultrasonic transducer 2b as _j1 has come (step S201).

If the forward measurement start time is not reached (if it is time when the first received wave pulse group RP _j1 has not yet reached the backward ultrasonic transducer 2b), the microcomputer 11 sets the non-measurement mode ( Step S202).

If the forward measurement start time is reached (if it is time when the first received wave pulse group RP _j1 has already arrived at the backward ultrasonic transducer 2b), the microcomputer 11 uses a marker for coarse adjustment control. It is determined whether it is a pulse waiting time (step S203).

If it is the marker pulse waiting time (Yes in step S203), the microcomputer 11 turns on the reverse phase set signal PS _g (see FIG. 3 (j)) by the reception measurement management unit 114 so that the marker 11 and controls the phase comparator 4b for pulse waiting, by turning on the reverse switching signal SC _g, coarse adjustment control by the phase comparator 4b for adjusting marker pulse receiving and marker pulse (phase adjustment (Step S204). By adjusting the phase with the received wave pulse group RP _j1 (coarse harmonic wave) including the marker pulse MP, the phase shift due to the steep change in the flow rate Q becomes faster (to perform large phase correction), and the phase shift due to the phase shift Can be corrected.

If the coarse adjustment control has already been completed and the measurement is in the fine adjustment control (NO in step S203), the microcomputer 11 causes the reception measurement management unit 114 to wait for the received wave pulse group RP _{j1 to} wait for the phase comparison unit. The control 4b is performed, and since the coarse adjustment control has already been completed and the measurement is performed in the fine adjustment control, the fine adjustment control (phase adjustment) is performed (step S205).

Next, the microcomputer 11 determines whether or not a phase shift due to a steep change in the flow rate Q has occurred (step S206). If the phase shift is large, the next time, the coarse adjustment control is used for measurement. Preparation is made (step S207), and if the phase shift is small, the next time preparation is made to perform measurement by fine control (step S208).

Subsequently, the microcomputer 11 controls the phase comparison unit 4b so as to be a reception point of the received wave pulse group RP _j1 corresponding to the forward transmission frequency f _j (step S209) (according to the forward transmission frequency f _j ). The phase comparison unit 4b is prepared in order to obtain a reception point).

(1-3) Transmission operation of the second transmission wave pulse group TP _j2 in forward measurement (see the transmission flowchart of FIG. 5)

After the transmission operation of the first transmission wave pulse group TP _{j1 in} the forward direction measurement, the microcomputer 11 causes the intermittent drive control unit 111 to intermittently forward from the trailing edge of the first transmission wave pulse group TP _j1. The time δ _j is counted, and the transmission flowchart (steps S101 to S110) of FIG. 5 is repeated again after the elapse of the forward intermittent time δ _j , thereby transmitting the second transmission wave pulse group TP _{j2 in} the forward measurement. Perform the action.

As shown in FIG. 3B, in the first forward measurement by the transmission operation of the first transmission wave pulse group TP _{j1 and} the transmission operation of the second transmission wave pulse group TP _j2 in the forward measurement, Transmission wave pulse groups TP _j1 and TP _j2 having the number M of drive pulses (here, 3) are transmitted across the forward intermittent time δ _j .

(1-4) Reception operation of second received wave pulse group RP _j2 in forward measurement (refer to the reception flowchart in FIG. 6)

After the transmission operation of the second transmission wave pulse group TP _{j2 in} the forward direction measurement, the microcomputer 11 repeats the reception flowchart (steps S201 to S209) in FIG. 6 to receive the second reception in the forward direction measurement. The receiving operation of the wave pulse group RP _j2 is performed.

As shown in FIG. 3 (f), in the first forward measurement by the reception operation of the first received wave pulse group RP _j1 and the second received wave pulse group RP _j2 in the forward measurement, The received wave pulse groups RP _j1 and RP _j2 are received with the forward intermittent time δ _j interposed therebetween.

(2-1) Transmission operation of the first transmission wave pulse group TP _{g1 in} the reverse direction measurement (see the transmission flowchart in FIG. 5)

First, the microcomputer 11 uses the interval control unit 112 to start reverse measurement based on whether or not the interval time Δ has elapsed from the end time of the previous forward measurement (reverse measurement start time). It is determined whether or not (step S101). Specifically, the interval control unit 112 performs backward measurement based on whether or not the interval time Δ has elapsed since the completion (falling) of the second forward clock selection signal CS _j (see FIG. 4B). Determine the start time.

If the reverse measurement start time has come (Yes in step S101), the microcomputer 11 determines whether the measurement to be performed from now on is forward measurement or reverse measurement (step S102).

Since the measurement is in the reverse direction (No in step S102), the microcomputer 11 instructs the transmission / reception switching unit 3 to turn on the transmission / reception switching signal SR (see FIG. 3 (g)) to enter the reverse direction measurement mode. (Step S104). Then, the transmission / reception switching unit 3 connects the transmission unit and the backward ultrasonic transducer 2b, and connects the reception unit and the forward ultrasonic transducer 2a based on the fact that the transmission / reception switching signal SR is ON. That is, the transmission / reception switching unit 3 sets the backward ultrasonic transducer 2b to the transmission side and sets the forward ultrasonic transducer 2a to the reception side.

Subsequently, the microcomputer 11 determines whether the backward clock CLK _g (FIG. 3) is based on whether the backward clock selection signal CS _g (see FIG. 3E) output to the transmission frequency changeover switch unit 9 is ON. It is determined whether it is time (drive time) to apply (see (d)) as the first transmission wave pulse group TP _g1 to the backward ultrasonic transducer 2b (step S105).

If reverse clock selection signal CS _g is OFF (NO at step S105), the microcomputer 11 sets the non-measurement mode without applying a reverse clock CLK _g to reverse ultrasonic transducer 2b (step S106).

If reverse clock selection signal CS _g is on (YES in step S105), the microcomputer 11, the reception measurement management unit 114 determines whether the marker pulse transmission timing for the coarse control (step S107 ).

If it is the marker pulse transmission timing for coarse adjustment control (Yes in step S107), the microcomputer 11 transmits the marker pulse MP (see FIG. 4E) and the drive pulse number M by the marker pulse synthesizing unit 10. The head pulse of the wave pulse group TP _g1 (see FIG. _4G ) is superimposed to synthesize a transmission wave pulse including the marker pulse MP as shown in FIG. And applied to the reverse ultrasonic transducer 2b (step S108).

On the other hand, if it is not the marker pulse transmission timing for coarse adjustment control (No in step S107), the microcomputer 11 causes the marker pulse synthesizing unit 10 to transmit the transmission wave pulse via the transmission / reception switching unit 3 to the reverse ultrasonic transducer. 2b (step S109).

Next, the microcomputer 11 determines whether or not the number of transmission wave pulses applied to the backward ultrasonic transducer 2b has reached the driving pulse number M by the driving pulse number control unit 115 (step S110). If it is not M, the control is returned to step S107, and steps S107 to S110 are repeated.

When the number of transmission wave pulses reaches the number of drive pulses M in step S110, the microcomputer 11 ends the transmission operation of the first transmission wave pulse group _{TPg1 in} the reverse direction measurement.

In this manner, the backward ultrasonic transducer 2b transmits the first transmission wave pulse group _TPg1 having the number M of drive pulses toward the forward ultrasonic transducer 2a.

(2-2) Reception operation of the first received wave pulse group _{RPg1 in} the reverse direction measurement (see the reception flowchart in FIG. 6).

The microcomputer 11 propagates the distance of the propagation length L after the first transmission wave pulse group _TPg1 is emitted from the backward ultrasonic transducer 2b by the reception measurement management unit 114, and the first reception wave pulse group RP. It is determined whether or not the time (reverse direction measurement start time) to be received by the forward ultrasonic transducer 2a has come as _g1 (step S201).

If the reverse measurement start time is not reached (if the first received wave pulse group _RPg1 has not yet reached the forward ultrasonic transducer 2a), the microcomputer 11 sets the non-measurement mode ( Step S202).

If it is the reverse measurement start time (if it is time when the first received wave pulse group _RPg1 has already reached the forward ultrasonic transducer 2a), the microcomputer 11 will use a marker for coarse adjustment control. It is determined whether it is a pulse waiting time (step S203).

If it is the marker pulse waiting time (Yes in step S203), the microcomputer 11 turns on the forward phase set signal PS _j (see FIG. 3 (i)) by the reception measurement management unit 114, thereby setting the marker The phase comparison unit 4a is controlled for waiting for a pulse, and the forward switch switching signal _SCj is turned on, so that the phase comparison unit 4a is used for receiving a marker pulse and for adjusting a marker pulse phase. (Step S204). By adjusting the phase with the received wave pulse group RP _g1 (coarse harmonic wave) including the marker pulse MP, the phase shift due to the steep change in the flow rate Q becomes faster (to perform large phase correction), and the phase shift due to the phase shift. Can be corrected.

If the coarse adjustment control has already been completed and the measurement is being performed in the fine adjustment control (NO in step S203), the microcomputer 11 causes the reception measurement management unit 114 to wait for the received wave pulse group RP _{g1 to} wait for the phase comparison unit. The control of 4a is performed, and since the coarse adjustment control has already been completed and the measurement is performed in the fine adjustment control, the fine adjustment control (phase adjustment) is performed (step S205).

Next, the microcomputer 11 determines whether or not a phase shift due to a steep change in the flow rate Q has occurred (step S206). If the phase shift is large, the next time, the coarse adjustment control is used for measurement. Preparation is made (step S207), and if the phase shift is small, preparation is made to perform measurement by fine adjustment next time (step S208).

Subsequently, the microcomputer 11 controls the phase comparator 4a so as to receive point of the received wave pulse group RP _g1 corresponding to reverse transmission frequency f _g (step S209) (combined in reverse transmission frequency f _g The phase comparison unit 4a is prepared in order to obtain a reception point).

(2-3) Transmission operation of the second transmission wave pulse group TP _{g2 in} the reverse direction measurement (see the transmission flowchart in FIG. 5).

After the transmission operation of the first transmission wave pulse group TP _{g1 in} the reverse direction measurement, the microcomputer 11 causes the intermittent drive control unit 111 to _perform reverse intermittent operation from the trailing edge of the first transmission wave pulse group TP _g1. By counting the time δ _g and repeating the reverse intermittent time δ _g , the transmission flowchart (steps S101 to S110) in FIG. 5 is repeated again, thereby transmitting the second transmission wave pulse group TP _{g2 in} the reverse direction measurement. Perform the action.

The first transmitting operation and the second transmission operation of the transmission wave pulse group TP _g2 of the transmitted wave pulse group TP _g1 on the reverse measurement, the reverse measurement once, as shown in FIG. 3 (f), Transmission wave pulse groups TP _g1 and TP _g2 having the number M of drive pulses (here, 3) are transmitted across the forward intermittent time δ _j .

(2-4) Reception operation of the second received wave pulse group RP _{g2 in} the reverse direction measurement (see the reception flowchart in FIG. 6).

After the transmission operation of the second transmission wave pulse group TP _{g2 in} the backward direction measurement, the microcomputer 11 repeats the reception flowchart (steps S201 to S209) in FIG. 6 to receive the second time in the backward direction measurement. The receiving operation of the wave pulse group _RPg2 is performed.

As shown in FIG. 3C, in the first backward measurement, the reception operation of the first received wave pulse group RP _g1 and the second received wave pulse group RP _g2 in the reverse direction measurement. The received wave pulse groups RP _g1 and RP _g2 are received with the forward intermittent time δ _j interposed therebetween.

(3) Calculation of the flow rate Q (refer to the flow rate calculation flowchart of FIG. 7)

The microcomputer 11 starts the forward measurement, ends the backward measurement, and starts the next forward measurement (forward measurement time interval U _j + reverse measurement time interval U _g (FIG. 3 (g))) and the count value K _j of the forward counter 7a counted in the meantime, the forward transmission frequency f _j is obtained (step S301). That is, f _j = K _j / (U _j + U _g ) is obtained.

Further, the microcomputer 11 starts the forward measurement, ends the backward measurement, and starts the next forward measurement (forward measurement time interval U _j + reverse measurement time interval U _g the count value _{K g} (FIG. 3 (g) refer)) and counted during inverse direction counter 7b, obtaining the reverse transmission frequency _{f g} (step S301). That is, f _g = K _g / (U _j + U _g ) is obtained.

Next, the microcomputer 11 uses the flow rate determination unit 113 to calculate the flow velocity V based on the following equation (4) (step S302).

V = (L / 2N) × (f _j −f _g )

Subsequently, the microcomputer 11 causes the flow rate determination unit 113 to multiply the flow velocity V by the pipe cross-sectional area S, multiply the measurement unit time, or correct the correction coefficient H according to the temperature / pressure, the measurement fluid, and the obtained flow velocity V. To obtain the flow rate Q (step S303). In addition, the microcomputer 11 adds the flow rate Q just measured to the integrated flow rate ΣQ ₀ accumulated so far by the flow rate determination unit 113 to obtain the total flow rate ΣQ ₁ = ΣQ ₀ + Q.

Then, the microcomputer 11 causes the intermittent drive control unit 111 to increase the forward intermittent time δ _j and the reverse intermittent time δ _g according to the flow rate Q just measured, for example, if the flow rate is low. The power consumption is reduced (step S304). Furthermore, if the low flow rate continues for a certain period of time, the microcomputer 11 increases the interval time Δ by the interval control unit 112 by increasing not only the forward intermittent time δ _j and the reverse intermittent time δ _g. The direction measurement time interval U _j (see FIG. _3G ) and the reverse direction measurement time interval U _g (see FIG. 3G) are lengthened to further reduce consumption. Further, the microcomputer 11 divides the forward intermittent time δ _{j, the} reverse intermittent time δ _g, and the interval time Δ into several stages, and measures the forward measurement time interval U _j (see FIG. _3G ) and the reverse measurement time. It may be possible to further reduce power consumption by controlling the interval U _g (see FIG. 3G).

In the ultrasonic flowmeter according to the first embodiment, the forward direction measurement is first performed and then the backward direction measurement is performed. However, the measurement order may be reversed.

Further, in the ultrasonic flowmeter according to the first embodiment, a rectangular wave is applied as the transmission wave pulse group TP, but it may be driven by a sine wave, step driving, or burst driving.

Furthermore, in the ultrasonic flowmeter according to the first embodiment, the first transmission wave pulse group TP _j1 and the second transmission wave pulse group TP _{j2 in} the forward direction measurement, and the first transmission wave pulse in the backward direction measurement. The group TP _g1 and the second transmission wave pulse group TP _g2 are fired. However, the number of firings of the transmission wave pulse group TP in the forward direction measurement and the backward direction measurement is not limited to two times. Or three or more times may be sufficient.

As mentioned above, although the Example of this invention was described, this is only an illustration, this invention is not limited to this, Based on the knowledge of those skilled in the art, unless it deviates from the meaning of a claim Various changes are possible.

1 is a circuit block diagram showing a configuration of an ultrasonic flow meter according to Embodiment 1 of the present invention. FIG. 3 is a diagram for explaining a principle of measuring a flow velocity in the ultrasonic flowmeter according to the first embodiment. 3 is a timing chart showing a flow rate measurement procedure in the ultrasonic flowmeter according to the first embodiment. 3 is a timing chart showing a flow rate measurement procedure in the ultrasonic flowmeter according to the first embodiment. 3 is a flowchart illustrating a transmission operation in the ultrasonic flowmeter according to the first embodiment. 3 is a flowchart illustrating a reception operation in the ultrasonic flowmeter according to the first embodiment. 3 is a flowchart illustrating a flow rate calculation operation in the ultrasonic flowmeter according to the first embodiment.

Explanation of symbols

1 Channel 2a Forward Ultrasonic Transducer (Ultrasonic Transducer)
2b Reversed Ultrasonic Transducer (Ultrasonic Transducer)
3 Transmission / reception switching unit 4a, 4b Phase comparison unit 5a, 5b Low pass filter (LPF)
6a, 6b Voltage controlled oscillator (VCO)
7a Forward counter 7b Reverse counter 8a, 8b Lock wave number clock management unit 9 Transmission frequency changeover switch unit 10 Marker pulse synthesis unit 11 Microcomputer (transmission control unit)
111 Intermittent drive control unit 112 Interval control unit 113 Flow rate correction unit 114 Reception measurement management unit 115 Drive pulse number control unit 116 Reception point management unit

Claims (15)

A pair of ultrasonic transducers is provided on the upper and lower sides in the flow direction in the flow path through which the fluid flows, and forward transmission is performed so that the ultrasonic wave has a predetermined lock wave number between the pair of ultrasonic transducers. In the ultrasonic flowmeter that controls the frequency and the reverse transmission frequency, and obtains the flow velocity and the flow rate based on the forward transmission frequency and the reverse transmission frequency at that time,
An intermittent drive control unit that outputs a clock selection signal for several clocks with an intermittent time when measuring the forward transmission frequency and the reverse transmission frequency;
A transmission frequency changeover switch unit that applies the clock selected by the clock selection signal from the intermittent drive control unit to the ultrasonic transducer on the transmission side as a transmission wave pulse group with an intermittent time;
An ultrasonic flowmeter characterized in that driving of the ultrasonic transducer on the transmission side in transmission frequency measurement is an intermittent operation by a group of transmission wave pulses sandwiching an intermittent time. The ultrasonic flowmeter according to claim 1, further comprising a counter that continues to count the clock during the intermittent time. The ultrasonic flowmeter according to claim 1, further comprising an interval control unit that controls an interval time between measurement of transmission frequencies. The ultrasonic flowmeter according to claim 1, wherein the interval control unit controls the interval time in accordance with the measured flow rate. The ultrasonic flowmeter according to any one of claims 1 to 4, further comprising a flow rate determination unit that variably controls the intermittent time according to the measured flow rate. The ultrasonic flowmeter according to claim 5, wherein the flow rate determination unit calculates a temperature based on a sound speed obtained by measuring a transmission frequency, and performs flow rate correction on the temperature. 7. The pair of ultrasonic transducers according to any one of claims 1 to 6, wherein the pair of ultrasonic transducers has a frequency impedance characteristic close to a single resonance characteristic having a low Q value representing mechanical resonance sharpness and low spurious. The described ultrasonic flowmeter. 2. A drive pulse number control unit for variably controlling the number of drive pulses of a transmission wave pulse group applied to the ultrasonic transducer on the transmission side according to the transmission frequency of the clock. Item 8. The ultrasonic flowmeter according to any one of Items 7. 9. The reception point management unit for changing a reception point of a reception wave pulse group measured by the ultrasonic transducer on the reception side according to a transmission frequency of the clock. The ultrasonic flowmeter according to any one of the above. The ultrasonic flowmeter according to any one of claims 1 to 9, wherein the lock wave number is changed according to a measurement fluid. A marker pulse synthesizing unit that mixes a marker pulse with a clock selected by the transmission frequency changeover switch unit is provided, and the marker pulse is propagated in a cycle according to a predetermined lock wave number, and the marker pulse is used as the basis of the marker pulse. The reception measurement management unit for coarsely controlling the frequency of the clock so that the wave number of the ultrasonic wave between the pair of ultrasonic transducers becomes a predetermined lock wave number is provided. The ultrasonic flowmeter according to any one of 10 above. The reception measurement management unit finely controls the frequency of the clock so that the wave number of the ultrasonic wave becomes a predetermined lock wave number between the pair of ultrasonic transducers after eliminating the phase shift in the coarse adjustment control. The ultrasonic flowmeter according to claim 11. When switching between the forward propagation time and the backward propagation time with the pair of ultrasonic transducers, the forward transmission frequency and the reverse transmission frequency at the previous measurement are stored, and the order at the next measurement is stored. The ultrasonic flow rate according to any one of claims 1 to 12, wherein the directional transmission frequency and the reverse transmission frequency are started from the stored forward transmission frequency and reverse transmission frequency at the previous measurement. Total. The next received wave pulse group by the next transmitted wave pulse group is received in the time zone from when the direct wave of the received wave pulse group by the transmitted wave pulse group arrives until the third reflected wave appears. The ultrasonic flowmeter according to claim 1, wherein: A pair of ultrasonic transducers is provided on the upper and lower sides in the flow direction in the flow path through which the fluid flows, and forward transmission is performed so that the ultrasonic wave has a predetermined lock wave number between the pair of ultrasonic transducers. In the ultrasonic flowmeter that controls the frequency and the reverse transmission frequency, and obtains the flow velocity and the flow rate based on the forward transmission frequency and the reverse transmission frequency at that time,
A phase-locked loop that compares the phase of the clock that drives the ultrasonic transducer on the transmitting side and the received wave converted signal converted by the ultrasonic transducer on the receiving side, and outputs a clock with a transmission frequency that matches the phase, and
A lock wave number clock management unit that outputs a phase comparison timing signal when the count value of the clock from the phase locked loop becomes a lock wave number;
A transmission / reception control unit that outputs a clock selection signal for several clocks with an intermittent time according to the phase comparison timing signal from the lock wave number clock management unit,
A transmission frequency changeover switch unit that applies a clock of several clocks to the ultrasonic transducer on the transmission side as a transmission wave pulse group with an intermittent time based on a clock selection signal from the transmission / reception control unit;
A counter that continues to count the clock during the intermittent time;
An interval control unit for controlling an interval time between measurement of the forward transmission frequency and measurement of the reverse transmission frequency according to the measured flow rate;
A flow rate determination unit that variably controls the intermittent time according to the measured flow rate,
A drive pulse number control unit that variably controls the drive pulse number of the transmission wave pulse group to be applied to the ultrasonic transducer on the transmission side according to the transmission frequency of the clock from the phase-locked loop;
A reception point management unit that changes a reception point of a reception wave pulse group measured by the ultrasonic transducer on the reception side according to the transmission frequency of the clock from the phase-locked loop;
A marker pulse synthesizing unit that mixes a marker pulse from the transmission / reception control unit in the clock selected by the transmission frequency changeover switch unit;
The marker pulse is propagated at a period corresponding to a predetermined lock wave number, and the clock frequency is set so that the ultrasonic wave number becomes a predetermined lock wave number between the pair of ultrasonic transducers based on the marker pulse. Receive measurement that finely controls the frequency of the clock and finely controls the frequency of the clock so that the ultrasonic wave has a predetermined lock wave number between the pair of ultrasonic transducers after the phase adjustment is eliminated by the coarse control. An ultrasonic flowmeter comprising a management unit.

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