JPS635217A - Ultrasonic current meter - Google Patents

Abstract

PURPOSE:To accurately measure a flow speed free of the effect of sonic velocity, by constituting the title current meter of a transmitter circuit, first and second transducers, a forward direction/reverse direction change-over circuit, a phase detector and an operator etc. CONSTITUTION:Transmitter circuits TXA, TXB alternately output the transmitting signal TA corresponding to an oscillation signal ZA and the transmitting signal TB corresponding to an oscillation signal ZB with frequency close to that of the signal ZA. Subsequently, a forward direction/reverse direction change-over circuits SW1 alternately changes over transducers P1, P2 to perform the transmission and reception of the first transmitting-receiving wave of a forward direction corresponding to the signal TA, that of the second transmitting- receiving wave of the forward direction corresponding to the signal TB, that of the first transmitting-receiving wave in a reverse direction corresponding to the signal TA and that of the transmittint-receiving wave in the reverse direction corresponding to the transmitting- receiving wave in the reverse direction corresponding to the signal TB. Phase detectors PDA, PDB calculate the phase difference of the first transmitting-receiving wave in the forward direction, that of the first transmitting-receiving wave in the reverse direction, that of the second transmitting-receiving wave in the forward direction and that of the second transmitting-receiving wave in the reverse direction and an operator CAL calculates the flow velocity of a fluid on the basis of each phase difference.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic current meter that propagates ultrasonic waves in a fluid and measures the flow velocity of the fluid from the phase difference between transmitted and received waves.

[Prior Art] Conventionally, this type of ultrasonic current meter transmits continuous (or burst wave) ultrasonic waves from a wave transmitting transducer,
There is a method that measures the flow velocity of a fluid by determining the phase difference between a wave propagated in a fluid and received by a transfer transducer with respect to a transmitted wave.

FIG. 6 is a block diagram of such a conventional ultrasonic current meter.

In FIG. 6, TX is a transmission circuit that outputs a transmission signal (electrical signal), 1 is a flow tube through which fluid flows in the direction of arrow F,
Pl and P2 are transmission waves T(
A transducer that transmits ultrasonic waves (ultrasonic waves) and receives received waves R corresponding to the transmitted waves, SL propagates the transmitted waves (received waves) in the forward direction along the fluid flow or in the reverse direction against the fluid flow, A forward/reverse switch that switches transducers P1 and P2 to obtain a forward received wave R and a reverse received wave Ru; RX is a receiving circuit that receives a received signal corresponding to the received wave R; , CAL is an arithmetic unit that calculates the fluid flow velocity based on the phase difference between the transmitted wave T and the received wave R;
TIM is a timer that outputs a signal that controls the operation of each part.

In such a conventional ultrasonic current meter, the transmitted wave T is determined by the mounting interval L between the transducers P1 and P2, and the fluid flow velocity by
, the sound speed is C1, and the angular frequency of the ultrasonic wave is ω, then T= E, sin (+1 t
(1), and the received wave Rd in the forward direction and the received wave Ru in the reverse direction are respectively Rd=E), sin ω(t-td) (
2) Ru=ERsinω ft −tu)
It is expressed as (3). However, t and tu are t, = -(S)C-■. Therefore, the phase difference Δ between the received wave R4 and the received wave R
φ becomes Δφ=ω (tu td ). As shown in Equation 6, the phase difference Δφ is a periodic function whose period is 2π. The detection range of phase difference Δφ is 0 to 2π
When the flow velocity V becomes large, the phase difference Δφ becomes Δφ=2nyr+Δφ (7), and it is necessary to separately detect n.

[Problems to be Solved by the Invention] By the way, the conventional ultrasonic current meter with the above configuration measures a flow velocity corresponding to a phase difference of 2π or more (actually π/2) between the transmitted wave T and the received wave R. There was a problem in that it was difficult to measure, and the measured values were affected by the speed of sound.

Note that in order to expand the measurement range, there is a method in which the transmitted wave T is modulated with a low frequency, but the circuit becomes multiple R1t.

The present invention has been made to solve the above problems,
It is an object of the present invention to provide an ultrasonic current meter that allows measurement values to be accurately measured without being influenced by the speed of sound, even when the phase difference between the transmitted wave T and the received wave R corresponds to 2π or more. .

[Means for solving the problem] Therefore, in the present invention, a first transmission signal corresponding to a first oscillation signal of a predetermined frequency and a second oscillation signal corresponding to a frequency close to the first oscillation signal are provided. A transmission circuit that alternately outputs a second transmission signal is arranged at a predetermined distance from a flow tube through which fluid is flowing in a predetermined direction, and each transmits a transmission wave corresponding to a human-powered transmission signal into the flow tube. At the same time, a first transducer and a second transducer each receive a received wave corresponding to a transmitted wave, and the first transducer and the second transducer each receive a first transmitted signal. Transmission of a first transmitted wave in a forward direction along the fluid flow corresponding to the first transmitted wave in the forward direction, reception of a first received wave in the forward direction corresponding to the first transmitted wave in the forward direction, and an order corresponding to a second transmitted signal. transmitting a second transmitted wave in the forward direction, receiving a second received wave in the forward direction corresponding to the second transmitted wave in the forward direction, and receiving a first wave in the reverse direction against the fluid flow corresponding to the first transmitted signal. transmission of a transmission wave in the opposite direction, reception of a first reception wave in the opposite direction corresponding to the first transmission wave in the opposite direction, and reception of a second reception wave in the opposite direction corresponding to the second transmission signal.
a transducer switching circuit that alternately switches a first transducer and a second transducer to transmit a transmitted wave and receive a received wave corresponding to a second transmitted wave in the opposite direction; The phase difference between the first transmitted wave in the direction and the first received wave in the forward direction, the phase difference between the first transmitted wave in the opposite direction and the first received wave in the opposite direction, and the second transmission in the forward direction a phase detector that calculates the phase difference between the wave and the second received wave in the forward direction, and the phase difference between the second transmitted wave in the opposite direction and the second received wave in the opposite direction; , and an arithmetic unit that calculates the flow velocity of the fluid, constitute an ultrasonic current meter.

[Function] In the ultrasonic current meter having the above configuration, the transmission circuit transmits a first transmission signal corresponding to the first oscillation signal and a second oscillation signal corresponding to the second oscillation signal having a frequency close to the first oscillation signal. The transducer switching circuit alternately outputs the transmission signals of the first transducer and the second transducer, and the first transducer and the second transducer output the first transducer. Transmission of a first transmission wave in the forward direction corresponding to the transmission signal; first transmission wave in the forward direction corresponding to the first transmission wave in the forward direction;
reception of a received wave in the forward direction, transmission of a second forward transmission wave corresponding to the second transmission signal, reception of a second forward reception wave corresponding to the second transmission wave in the forward direction, reception of a second reception wave in the forward direction corresponding to the second transmission wave in the forward direction, Transmission of a first transmission wave in the opposite direction corresponding to the transmission signal, reception of a first reception wave in the opposite direction corresponding to the first transmission wave in the opposite direction, and reception of the first reception wave in the opposite direction corresponding to the second transmission signal. 2 transmission wave transmission, the second transmission wave in the opposite direction
A second received wave in the opposite direction corresponding to the transmitted wave is received, and the phase detector detects the phase difference between the first transmitted wave in the forward direction and the first received wave in the forward direction, and the second received wave in the opposite direction. The phase difference between the first transmitted wave and the first received wave in the opposite direction, and the second transmitted wave in the forward direction;
The phase difference with the second received wave in the injection direction and the phase difference between the second transmitted wave in the opposite direction and the second received wave in the opposite direction are calculated, and the calculation unit calculates the flow rate of the fluid based on each phase difference. Calculate the flow velocity.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of an ultrasonic current meter according to the present invention. In Fig. 1, 0SCA is the oscillation signal Z of frequency fA.
A system oscillator that constantly outputs A, 05CB has a frequency f
The B-system oscillators GA and G, which constantly output an oscillation signal 2 with a frequency f close to A, are an A-system gate circuit and a B-system gate that output burst signals corresponding to the oscillation signal ZA and the oscillation signal Z8, respectively. The circuits TxA and TX8 are an A-system transmitting circuit and a B-system transmitting circuit, 5W, which amplify the burst signals output by the A-system gate circuit GA and B-system gate circuit G, respectively, and output transmission signals TA and TIl, respectively.
2 is a transmission signal TA and T8 and a reception signal RA which will be described later.
A system/Japanese system switching circuit that alternately outputs R8 and R8, Sl#
1 is a forward/reverse direction switching circuit, 1 is a flow tube in which fluid flows in the direction of the arrow ■, P and R2 are transducers arranged at a distance in the flow tube 1, RxA and RX, is A
system receiving circuit and B system receiving circuit, PDA is A system phase detector, PD is B system phase detector, SHA is A system phase detector P
A sample and hold circuit samples and holds a signal corresponding to the phase difference outputted by the DA, 5Hll is a sample and hold circuit that samples and holds a signal corresponding to the phase difference outputted from the B-system phase detector poa, and C
AL is an arithmetic unit that calculates the fluid flow velocity V based on the phase difference input from the sample and hold circuits SHA and SHB, and Ilo is an analog indicator that gives an analog indication or a digital indicator that displays the calculation result of the arithmetic unit CAL. TIM is a timer that generates a forward/reverse switching signal X, an A/B switching signal X2, and a transmission control signal Only the main signals are shown in the figure.

Next, we will discuss the operation of the ultrasonic current meter according to the present invention in the second section.
This will be explained with reference to the timing chart shown in the figure. First, A
+Gate circuit GA and B-system gate circuit GI3 are opened and closed by the transmission control signal X3 with period T3 shown in FIG. The signal zB is sampled and a burst signal is output. A system gate circuit GA
In synchronization with the operation of the A-system/B-system gate circuit G and the B-system gate circuit G, the A-system/B-system switching circuit SW2 switches between the A-system/B-system gate circuits and the B-system gate circuit G with a cycle T2 shown in FIG. 2(b).
It is switched by the B-system switching signal x2, and as shown in FIG.
) The transmission signals TA and T8 shown in FIG.

Next, the forward/reverse switching circuit SW is shown in FIG. 2(a).
Switching is performed by a forward/reverse direction switching signal XI having a cycle T1 that is twice the cycle T2 shown in FIG. A system/B system switching circuit S
By switching W2 and the forward/reverse switching circuit SW1, the transducer P1 and the transducer P2 perform the following transmission wave transmission and reception wave reception. Firstly 1. Forward/reverse switching circuit SW, or D'Jji
l C head direction side), A system/B system switching circuit SW2 or A system side is switched respectively, transducer P1
is the forward direction transmission wave TAd corresponding to the transmission signal TA of system A
The transducer P2 receives the A-system forward direction received wave RAd. Second, when the forward/reverse switching circuit SW is switched to the D side and the A system/B system switching circuit SW2 is switched to the B system side, the transducer P1 responds to the B system transmission signal T8. ;Forward transmission wave TBd
The transducer P2 receives the B-system forward direction reception wave RBd. Third, the forward direction/reverse direction switching circuit SW is placed on the U side (reverse direction side), and the A system/B system switching circuit SW is connected to the U side (reverse direction side).
2 are respectively switched to the A system side, transducer P2 transmits a transmission wave TAu in the opposite direction corresponding to the transmission signal TA of system A, and transducer P2 transmits a reception wave RAu in the opposite direction of system A. receive. Fourth, when the forward/reverse switching circuit SW is switched to the U side and the A/B switching circuit SW2 is switched to the B side, the transducer P
Transducer 2 transmits a transmission wave T, 4 in the opposite direction of the B system, and transducer P1 receives a reception wave RBu in the opposite direction of the B system.

Here, the forward direction transmission wave TAd and the reverse direction transmission wave TAu of the A system and the forward direction transmission wave T8 . and the reverse direction transmission wave T[lu are respectively T Ad= T Au=
5in(2rtfAt) (8)
Tad=Tau=sin(2gf,t) (
9). Also, the received wave RA in the 1st term direction of the A system
d and the backward received waves R,, u, and the forward received wave RBd and backward received wave RBu of system B have a phase delayed by the time required to propagate the distance signal, respectively, = sin (2rt f , t −ΦAd)
flO)=sin(2rc f A t
−ΦAu) (11)=sin(2rt
f, −Φad) (12)=sin
(2n f Bt −Φ[LLI)
It can be expressed as (13). However, Φ, 4, ΦAi1
,Φ8. and Φ8U are the forward phase difference of 1. A phase difference in the backward direction of the H system, a forward phase difference in the B system, and a phase difference in the reverse direction of the B system.

Next, the A-system receiving circuit RX receives the forward direction received wave R of the A-system.
The B-system receiving circuit RX8 receives the reception signal RA corresponding to Ad and the A-system backward reception wave R81, and the B-system reception circuit RX8 receives the reception signal RA corresponding to the B-system forward reception wave R11d and the B-system reverse reception wave RBu. Receive signal R8.

Next, the A-system phase detector PDA detects the signal corresponding to the phase difference ΦAd between the transmitted wave TAd and the received wave RAd and the transmitted wave TA.
A signal corresponding to the phase difference ΦA, J between LL and the received wave RAu is output. Similarly, the B-system phase detector PD, transmits the transmitted wave T
Phase difference Φ3 between Bd and received wave Red. , and a signal corresponding to the phase difference ΦBLI between the transmitted wave Tau and the received wave Rau.

Next, the sample hold circuit SHA is controlled by the A system/B system switching signal x2, and the phase difference Φ1 and Φ output by the A system phase detector PDA. Sample and hold the signal corresponding to . In addition, the sample hold circuit SOB is controlled by the A system/B system switching signal X2, and the B system phase detector PDB
The signals corresponding to the phase difference Φ3° and ΦBU outputted by are sampled and held. Sample hold circuit S
The HA and 5l18 each generate a lamp voltage having the same period as the period of the transmitted wave, perform coral ringing at the zero-crossing point of the received wave, and hold it.

Next, the arithmetic unit CAL uses the sample and hold circuits SHA and SH! by an appropriate timing signal. Based on the phase differences ΦAd, ΦAu, Φ, d and Φau manually input from l,
Calculate the fluid flow velocity ■.

Here, the average value R6 of the received waves RAd and RBd of the A system and the average value Ru of the received waves RAu and R11u of the B system are as follows. Rd=−(RAd+Rad) ΦAd×Φ1id = sin(π(f A + f a)t −)・cos
(rr(fA-f,)t-"'-"') (14)R
u = (RAll” RBu)ΦAu+Φ,
U = si (π (f A + f 8) t −) Φ.

−Φ.

・cos(π(f A −f A) t −)
f15). In addition, the low frequency component Rd of the average value R4 of the received waves of the A system and the low frequency component Ru of the average value Ru of the received waves of the B system are respectively ΦAd - ΦBd R1 = cos (π (f A - f a) t −)=c
os (2πfo −Φdl (16)Φ
Au-ΦBu Ru= CO3(π (fA-fa)t-)= cos
(2πfot−Φu) (17).

However, ΦAd−Φ, d Φd = (18)
Φ. −ΦBuΦ, = (19)
fA-f.

f0=(20). Note that the low frequency component Rd of the 16th equation and the low frequency component Ru of the 17th equation are the encompassing lines of the 14th equation and the 15th equation, and are fo, Φ, and Φ. are the frequency of the envelope, the difference in forward phase difference, and the difference in phase difference in the reverse direction, respectively.

On the other hand, the frequency fA of the A-system oscillator 05CA and the B-system oscillator O
Taking the difference from the frequency f of SC, corresponds to finding the phase of the beat wave. Therefore, the A system oscillator 0SC
If the frequency fA of A and the frequency fB of the B-system oscillator OSC are selected close to each other, the frequency of the beat wave can be made different, and over a wide range of flow velocities, Φd × 2π (21) and Φ5 × 2π ( 22) can be maintained.

Here, the wavelengths λd, λ1 and the phase differences Φ1, Φ when separated by a distance 1i1L. Which relationship is L/λd:=:Φd
/2π (23)L/λ1=Φu/2π
(24). Also, the speed of sound C and the wavelength λ
The relationship between d and λ is λd = (c+V)/fo
(25)λ, = (CV)/
fO(26). Therefore, from Equations 16, 17, 23, and 24, Φd L−λ, □ 2π Φ6. -Φ,d” (C0V) (27)2
π (fA fa) Φ.

shi=λ, □ 2π Φ＾1−Φ8u = (C−V) (28
)2π (fA-fa).

Calculator CAL calculates the flow velocity V from the 27th to 28th equations, ■=
Calculated by πL(fA-fa). Distance ML and A-system oscillator OS [: Difference between frequency fA of A and frequency fll of B-system oscillator O5 (:!l (f A - f a) (
30) is a constant, the arithmetic unit CAL calculates the forward direction phase difference ΦAd of the A system and the forward direction phase difference Φad(Φ1−
Φaa) (31)
and the phase difference Φ in the opposite direction of the A system. and the phase difference in the opposite direction of the B system Φh, (Φ0−Φau) (32)
From this, the flow velocity ■ can be calculated.

The flow velocity V is independent of the sound velocity as shown in Equation 29. Therefore, if the frequency fA of the A-system oscillator 03CA and the frequency f of the B-system oscillator OSC are appropriately selected, the forward phase difference Φ of the A system can be obtained. , the phase difference Φ in the opposite direction of the A system. , even if the forward phase difference Φ, d of system B and the reverse phase difference Φ, U of system B each exceed
/ 2 (33) and 1Φ0−Φaul<π/2 (34)
It is possible to maintain the flow rate and measure the flow rate over a wide range.

In the conventional ultrasonic current meter, the ultrasonic frequency f=40KH
z, sound speed C=340m/S, transducer P1
and P2 which distance 211 L = 0.2m, flow velocity v =
tom/S, the forward direction phase difference of the A system is Φ6. = 2.77π (rad) > 2 rt
(35). However, in the ultrasonic current meter according to the present invention, the oscillation frequency f A of the A-system oscillator 05CA
= 4OK) Iz, when the oscillation frequency f of the B system oscillator 05Cts is 40.4 Hz, the forward phase difference Φ of the A system
Ad, phase difference Φ in the opposite direction of the A system. , the forward direction phase difference ΦBd of the B system, and the forward direction phase difference Φ of the B system are, respectively, and Φ□−ΦAd=2.78π (40
) Φ, U-ΦB, = 2.80π
(41), whereas 1ΦAd−Φaa l = 0.46π×π/2
(42) 1Φ□−Φaul=0.49π×π/2
(43), which is less than π/2.

Note that the outflow may be calculated by multiplying the flow velocity V by a predetermined coefficient.

Next, the input/output circuit I10 outputs the calculation result of the arithmetic unit CAL to an analog indicator that provides an analog instruction or a digital display that provides a digital display (not shown).

Note that the switching sea fences of the forward/reverse switching circuit SW, A system/B system switching circuit SW2 do not necessarily have to be in this order as long as the forward/reverse direction and the A system/B system are switched equally. .

Next, FIG. 3 is a block diagram showing another embodiment of the ultrasonic current meter according to the present invention. In addition, in Fig. 3, the first
Parts that perform the same functions as those in the figures are designated by the same reference numerals, and their explanations will be omitted.

In this embodiment, one set of oscillators 05CA, 05C0, sample bold circuits 28S1 (A and 5llTh) are provided as in the above embodiment, but gate circuits 5!8G, transmission circuit TX,
The receiver circuit RX and phase detector PD are configured with one piece. As a result, the A system and the B system operate in common, which not only reduces the number of components, but also compensates for variations and drifts in the characteristics of the hardware of the A system and B system. However, since the transmitting circuit TX and the receiving circuit Rx need to operate in the same manner for the frequencies fA and fa, the first
A wider band than that shown in the figure is required.

Next, FIGS. 4 and 5 are block diagrams of main parts showing other embodiments of the ultrasonic current meter according to the present invention. In the embodiment shown in FIG. 4, a single oscillator OSC is used instead of a set of oscillators oscA and osc, and frequencies fA and f6 are generated by changing the division ratio of the frequency divider DIV according to the signal of the timer TIM. It is something that makes you

In the embodiment shown in FIG. 5, a Funi's lock loop consisting of a voltage variable frequency oscillator VCO, a phase comparator, a controller C0NT including a filter and an amplifier, and a counter CNT is used in place of the frequency divider DIV.

In the above embodiment, two sets of sample and hold circuits are used, but four sets of sample and hold circuits can be used and used exclusively for each of the A system/B system and the forward direction/reverse direction. It is also possible to alternately use exactly one sample and hold circuit.

[Effects of the Invention] As explained above, according to the present invention, the phase difference Φ between the transmitted wave and the received wave corresponding to the first frequency transmitted in the forward direction
Ad, the phase difference ΦAu between the transmitted wave and the received wave corresponding to the first frequency transmitted in the reverse direction, the first frequency transmitted in the forward direction;
The phase difference between the transmitted wave and the received wave corresponding to a second frequency close to the frequency of Φ8. Based on the phase difference Φau between the transmitted wave and the received wave corresponding to the second frequency transmitted in the opposite direction, the fluid flow velocity ■ is calculated by V=izL (fA-fa), so the sound velocity It is possible to obtain an ultrasonic current meter that can measure flow velocity over a wide range without being affected by.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an ultrasonic current meter according to the present invention, Fig. 2 is a block diagram of an ultrasonic current meter according to the present invention;
The figure is a timing chart showing the operation of the ultrasonic anemometer shown in Fig. 1, Fig. 3 is a block diagram showing another embodiment of the ultrasonic anemometer according to the present invention, and Figs. FIG. 6 is a block diagram of the main parts of another embodiment of the ultrasonic current meter according to the invention, and FIG. 6 is a block diagram of a conventional ultrasonic current meter. In each figure, 05CA and 05Ca are oscillators, GA%G is a gate circuit, TXA and TXa are transmitting circuits, sw is a forward/reverse switching circuit, SW2 is an A system/B system switching circuit,
1 is the flow tube, P2 is the transducer, RXA,
Rxa is a receiving circuit, PDA is a phase detector,
SHA%SHa is a sample hold circuit, CAL is an arithmetic unit, TIM is a timer, and Ilo is an input/output circuit. Agent Patent Attorney Tadashi Sato Figure 1 TXA, TXa: kit tiil k
SHA, SHB: ? ”z7'llz;
l';- Root circuit SWI: ++1 member r3 same/Gyakumaran>n all circuit HiL:, Tora calculation SW2: A/B 9F circuit TIM Kuimer I10. Input/output times
& Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] a transmission circuit that alternately outputs a first transmission signal corresponding to a first oscillation signal of a predetermined frequency and a second transmission signal corresponding to a second oscillation signal of a frequency close to the first oscillation signal; They are arranged at a predetermined distance from each other in a flow tube through which fluid is flowing in a predetermined direction, and each transmits a transmission wave corresponding to an input transmission signal into the flow tube, and receives a reception wave corresponding to each transmission wave. A first transducer and a second transducer that receive a first transmitting wave in a forward direction along the flow of the fluid corresponding to the first transmitting signal, the first transducer and the second transducer respectively transmission, reception of a first received wave in the forward direction corresponding to the first transmitted wave in the forward direction, transmission of a second transmitted wave in the forward direction corresponding to the second transmitted signal, in the order receiving a second received wave in the forward direction corresponding to a second transmitted wave in the direction; transmitting a first transmitted wave in the opposite direction against the flow of the fluid corresponding to the first transmitted signal; receiving a first received wave in the opposite direction corresponding to the first transmitted wave in the opposite direction; transmitting a second transmitted wave in the opposite direction corresponding to the second transmitted signal; and transmitting a second transmitted wave in the opposite direction corresponding to the second transmitted signal. a transducer switching circuit that alternately switches the first transducer and the second transducer to receive a received wave corresponding to the transmitted wave; a phase difference between the received wave, a phase difference between the first transmitted wave in the opposite direction and the first received wave in the opposite direction, and a phase difference between the second transmitted wave in the forward direction and the second received wave in the forward direction. and a phase detector that detects the phase difference between the second transmitted wave in the opposite direction and the second received wave in the opposite direction, and calculates the flow velocity of the fluid based on each of the phase differences. An ultrasonic current meter characterized by comprising a computing unit that performs the following steps.