JP3869899B2 - Ultrasonic flow meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic flow meter.
[0002]
[Prior art]
In FIG. 4 , assuming that the sound velocity in the static fluid is C and the fluid flow velocity is V, if the propagation direction of the sound wave coincides with the direction along the flow (hereinafter referred to as the forward direction), the propagation velocity is (C + V In the case of the direction against the flow (hereinafter referred to as the reverse direction), (CV).
[0003]
When a pair of transducers 1 and 2 are arranged at a distance L apart from the upstream and downstream of the flow tube 3 and an ultrasonic pulse is transmitted from one transducer 1 in the forward direction, the other transducer is transmitted and received. The propagation time required for the ultrasonic pulse to reach the transducer 2 is t ₁ , and the propagation time required for the ultrasonic pulse to reach the transducer ₁ when the ultrasonic pulse is transmitted in the reverse direction from the transducer 2. Let t ₂ be
t ₁ = L / (C + V)
t ₂ = L / (C−V)
It becomes.
[0004]
In a conventional ultrasonic flowmeter, each propagation time (hereinafter also referred to as arrival time) of ultrasonic pulses t ₁ and t ₂ is measured, and a flow velocity V is calculated therefrom, and further, a flow rate and an integrated flow rate (fluid volume) are calculated. Was.
[0005]
For example, from the arrival times t ₁ and t ₂
(1 / t ₁ ) − (1 / t ₂ ) = 2 V / L
Since there is a relationship of
V = (L / 2) {(1 / t ₁ ) − (1 / t ₂ )}
Was asking.
[0006]
If the flow rate change range exceeds the measurement range of one flow meter, it is possible to combine the large (parent) and child (child) ultrasonic flow meters to increase the flow measurement range as a single meter. It is done.
[0007]
As a method of an ultrasonic flowmeter using such a parent-child meter, two methods, a summation formula and a separate formula, can be considered.
Summing equation a compact meter (child meter) 6 connected in parallel to the series connection of the large meter (parent Meter) 4 and an automatic valve 5 as shown in FIG. When the flow rate is small and less than a certain value, the automatic valve 5 is closed, and integration is performed only with the small meter (child meter) 6. When the flow rate is large and exceeds a certain level, the automatic valve 5 is opened and integrated even with a large meter (parent meter). The sum of the large meter (parent meter) 4 and the small meter 6 is the integrated flow rate.
[0008]
As shown in FIG. 6 , a small meter (child meter) 6 is connected in parallel to an automatic valve 5 connected in series to a large meter (parent meter) 4 as shown in FIG. When the flow rate is small and less than a certain value, the automatic valve 5 is closed and integrated with a small meter (child meter) 6. When the flow rate is large and exceeds a certain level, the automatic valve 5 is opened. At that time, the large meter (parent meter) 4 performs integration.
[0009]
[Problems to be solved by the invention]
The ultrasonic flowmeter using the parent-child meter has a problem that two sets of ready-made meters are combined, so that two sets of electronic units are required, resulting in high costs. Furthermore, there is a problem in that an electronic circuit portion for displaying as one meter such as a sum is required, resulting in an increase in current consumption.
[0010]
The measuring units of the large and small meters have different reception wave sizes due to different distances between the transducers and the like, and cannot be received using a common receiving unit. From this aspect, there is a problem that the cost is increased and the current consumption is increased.
[0011]
Therefore, an object of the present invention is to provide an ultrasonic flowmeter that expands the flow rate measurement range while suppressing an increase in cost and current consumption.
[0012]
[Means for solving the problems and their functions]
In order to achieve the object, the invention of claim 1
In a flowmeter that aims to increase the flow rate measurement range by combining a large flow rate measurement unit and a small flow rate measurement unit,
Each measurement unit is provided with a pair of ultrasonic transducers acting on the transmission side and the reception side on the upstream side and the downstream side, respectively, so that the fluid flow is superfluous from upstream to downstream and from downstream to upstream. Sending and receiving sound waves, and obtaining the flow rate of each measurement unit from the arrival time in each direction,
One electronic unit is provided for a total of two pairs of transducers, one pair of large flow rate measuring units and one pair of small flow rate measuring units, and this electronic unit drives the transmitter / receiver on the transmission side and receives and transmits on the reception side Receives the signal received from the wave detector, detects the arrival time, obtains the overall flow rate, and also displays the integrated display,
Select one pair of the two pairs of transducers with a switch so that they can be connected to the electronic unit,
When measuring with a large flow measurement unit, the pair of transducers of the large flow measurement unit is connected to the electronic unit,
When measuring with a small flow rate measurement unit, the pair of transducers of the small flow rate measurement unit is connected to the electronic unit,
A small flow rate measurement unit and a large flow rate measurement unit are connected in series, and the small flow rate measurement unit is provided with a bypass path that can be opened and closed with an automatic valve.The automatic valve is closed when the flow is small, and the automatic valve is opened when the flow is large.
When the automatic valve is closed, the switch is connected to a pair of transducers in the small flow rate unit, and when the automatic valve is open, a pair of transducers in the large flow rate measurement unit is connected to the electronic unit. Switch to measure and
The ultrasonic flowmeter is characterized in that the open / close state of the automatic valve is detected by an open / close detection means .
[0013]
In this invention, since one electronic part is selectively switched and connected to a pair of transducers of a large flow rate measuring part and a small flow rate measuring part by a switching device and performs measurement at a predetermined time interval, At the same time, the measurement is not performed at the same time, and after one is completed, the other is performed and the sampling method can be used.
[0014]
According to a second aspect of the present invention, in the ultrasonic flowmeter according to the first aspect, the valve opening / closing detection means comprises a magnet and a magnetic sensor.
[0015]
The invention of claim 3 is a flowmeter that aims to increase the flow rate measurement range by combining a large flow rate measurement unit and a small flow rate measurement unit,
Ultrasonic transducers that operate on both the transmitting and receiving sides are installed in the upstream and downstream sides of each measurement unit, and ultrasonic waves are transmitted and received in each fluid flow from upstream to downstream and from downstream to upstream. The flow rate of each measuring part is obtained from the arrival time in each direction,
One electronic unit is provided for the large flow rate measuring unit and the small flow rate measuring unit, and this electronic unit detects the arrival time by receiving the drive signal of the transmission side transducer and the reception signal from the reception side transducer. To find the overall flow rate,
A small flow rate measurement unit and a large flow rate measurement unit are connected in series, and the small flow rate measurement unit is provided with a bypass flow path that can be opened and closed with an automatic valve that opens at a small flow rate and the valve opens when the flow rate is large.
In addition, an ultrasonic flowmeter is provided with a valve opening / closing detection means, wherein when the valve is closed, measurement is performed by a small flow measurement unit, and when the valve is opened, measurement is performed by a large flow measurement unit. It is.
[0016]
According to a fourth aspect of the present invention, in the ultrasonic flowmeter according to the third aspect, the valve opening / closing detection means includes a magnet and a magnetic sensor.
[0017]
These invention, so to speak in a different formula, one of the two measuring portions of the transducer measured switched to connect to the electronic unit in response to the opening and closing of the valve. Therefore, the measurement range can be expanded advantageously in terms of current consumption.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 (a) (b) is a preferred embodiment of the present invention.
[0019]
A large flow rate measuring unit 4A and a small flow rate measuring unit 6A are connected in series, and there is a bypass path 7 that opens and closes a flow with an automatic valve (also simply referred to as a valve) 5 in parallel with the small flow rate measuring unit 6A. At a small flow rate, the valve 5 is closed, and all the gas as the fluid flows through the small flow rate measurement unit 6A to the large flow rate measurement unit 4A.
[0020]
When the flow rate becomes large, the valve 5 opens and flows through both the small flow rate measurement unit 6A and the bypass path 7 to the large flow rate measurement unit 4A. In this embodiment, measurement is performed at intervals of 2 seconds.
[0021]
Each measurement unit 4A, 6A has a pair of ultrasonic transducers that transmit and receive ultrasonic waves in the same direction as the flow in the fluid flow, and is arranged at a predetermined interval (for example, L). A switch 9 is provided so that either one of the pair is connected to the electronic unit 8, and the switch 9 is operated by a signal from the electronic unit 8 so that the selection can be made.
[0022]
4B is a transducer disposed upstream of the large flow rate measuring unit 4A, 4C is a transducer disposed downstream of the large flow rate measuring unit 4A, and 6B is a transducer disposed upstream of the small flow rate measuring unit 6A. , 6C is a transducer arranged downstream of the small flow rate measuring unit 6A.
[0023]
The electronic unit 8 outputs a reception wave detection signal when the reception-side transducer 6C or 4C of the pair of transducers 6B, 6C or 4B, 4C selected by the switch 9 is connected and detects a reception wave. A received wave detector 10;
Each time the measurement ON / OFF signal changes from the OFF side to the ON side, the transmitter-side transmitter / receiver 6B of the selected pair is driven. A transmitter driving unit 11 that stops driving when a received wave detection signal is input or a measurement ON / OFF signal is turned OFF;
When the received wave detection signal from the received wave detection unit 10 is input, the count starts from zero each time the measurement ON / OFF signal is turned on, detects the nth received wave detection signal, and receives the nth received wave. A first counter 12 for outputting a detection signal;
A second counter 13 that measures the time from when the measurement ON / OFF signal is turned ON until the nth received wave detection signal;
When the direction of transmission / reception is switched at intervals of 2 seconds and the measurement ON / OFF signal is changed from OFF side to ON side and the nth received wave detection signal is received, the measured value of the second counter 13 is read, and the flow rate, A control unit 14 is provided for calculating the integrated flow rate and the like.
[0024]
The received wave detection unit 10 includes an amplification unit and a comparison unit, and a signal from a reception-side transducer (for example, 6C) is first amplified and then compared with a reference voltage level. The point where the wave exceeding the reference voltage level passes the zero level next is the point where the received wave is detected, and the amplification unit has eight levels of amplification. One is selected by the amplification degree selection signal. Further, one of the eight reference voltage levels prepared by the reference voltage level selection signal of the control unit 14 is selected and used.
[0025]
FIG. 2 shows a specific example of the electronic circuit of the amplifying unit. Eight feedback resistors R20 to R27 are connected to the operational amplifier 15 through the analog switch 16, and the amplification degree selection signals S10, S11, and S12 from the control unit 14 are shown. By selecting any one of the analog switches 16 and turning it on, the amplification degree of the amplification unit is selected.
[0026]
V _in is input to the inverting input of the operational amplifier 15 through the resistor R1 in the reception wave signal from the receiving side of the transducer (e.g., 6C).
The resistance value of the feedback resistor is
R20 <R21 <... <R27
The degree of amplification is mutually determined,
(R20 / R1) <(R21 / R1) <... <(R27 / R1)
It becomes the relationship.
[0027]
FIG. 3 is a specific example of the electronic circuit of the comparison unit of the received wave detection unit 10, and the output V _out from the amplification unit of FIG. 2 is input to the non-inverting input of the comparator 17. The reference voltage level V _TH is input to the inverting input.
[0028]
S20, S21, and S22 are reference voltage level selection signals from the control unit 14, and any one of the eight resistors R40 to R47 is selected by selecting any one of the analog switches 18 and turning it on. The reference voltage level V _TH to be input to the inverting input of the comparator 17 is generated by dividing the constant reference voltage 19 with the resistor R3.
[0029]
The relationship between the resistance values of the eight resistors R40 to R47 is as follows:
R40 <R41 <R42 <... <R47
The analog switch 18 is selected by the reference voltage level selection signal from the control unit 14 to determine the reference voltage level V _TH .
[0030]
The state of the valve 5 (FIG. 1 ) is detected by a valve opening / closing detection means 20 including a magnet and a magnetic sensor (not shown) and is input to the control unit 14.
The control unit 14 is composed of a microcomputer and first checks the open / closed state of the valve 5 at intervals of 2 seconds based on the signal from the detection means 20.
[0031]
Transducer 6B of the switch 9 if a closed state in the state of FIG. 1 (a) (b) small flow measuring unit 6A, by selecting 6C was measured previously described, the switch 9 if the open state FIG. 1 (A) By switching from the state of (b), the transducers 4B and 4C of the large flow rate measuring unit 4A are selected and the above-described measurement is performed.
[0032]
The ultrasonic transmission / reception direction is alternately performed in the order of reverse, reverse, forward, and reverse regardless of whether the valve 5 is opened or closed. The switch 21 is a forward / reverse selector switch and is operated by a transmission / reception switching signal from the control unit 14.
[0033]
At this time, the amplification level selection signals S10, S11, S12 and the reference voltage level selection are sent from the control unit 14 to the received wave detection unit 10 so that the optimum amplification level and reference voltage level V _TH stored in advance are set. Signals S20, S21, and S22 are output.
[0034]
When the control unit 14 reads the measurement value t of the second counter 13 every 2 seconds, the control unit 14 calculates a reciprocal time value 1 / t from the value and calculates the product of the value and a constant corresponding to each measurement unit 6A or 4A. The difference from the previous calculation result is taken and the difference is integrated and displayed as the flow rate from the previous time to the current time.
The constants are determined for the small flow rate measuring unit or the large flow rate measuring unit based on the cross-sectional area of the flow tube, the transmitter / receiver interval, the flow velocity distribution of the flow tube cross-section, the measurement interval, and the like.
[0035]
【The invention's effect】
Since the ultrasonic flowmeter of the present invention is configured as described above and only one electronic unit is required, the configuration of the electronic circuit is simplified, current consumption can be reduced, and the battery for power supply can be reduced in size. And there exists an advantage which can suppress the increase in the cost of a flowmeter and can expand a measurement range.
[Brief description of the drawings]
1A is a schematic system diagram and FIG. 1B is a block diagram according to an embodiment of the present invention.
FIG. 2 is a specific example of an electronic circuit of an amplifier used in the embodiment of FIG.
3 is a specific example of an electronic circuit of a comparison unit used in the embodiment of FIG.
FIG. 4 is a schematic diagram illustrating the principle of an ultrasonic flow meter.
FIG. 5 is a schematic diagram of a parent-child meter.
FIG. 6 is a schematic view of the same parent-child meter.
[Explanation of symbols]
4A Small flow rate measurement unit 4B, 4C Transceiver 5 Valve (automatic valve)
6A Large flow rate measurement unit 6B, 6C Transmitter / receiver 7 Bypass path 8 Electronic unit 9 Switch 10 Received wave detection unit 11 Transmitter drive unit 12 First counter 13 Second counter 14 Control unit 20 Valve open / close detection means

Claims (4)

In a flowmeter that aims to increase the flow rate measurement range by combining a large flow rate measurement unit and a small flow rate measurement unit,
Each measurement unit is provided with a pair of ultrasonic transducers acting on the transmission side and the reception side on the upstream side and the downstream side, respectively, so that the fluid flow is superfluous from upstream to downstream and from downstream to upstream. Sending and receiving sound waves, and obtaining the flow rate of each measurement unit from the arrival time in each direction,
One electronic unit is provided for a total of two pairs of transducers, one pair of large flow rate measuring units and one pair of small flow rate measuring units, and this electronic unit drives the transmitter / receiver on the transmission side and receives and transmits on the reception side Receives the signal received from the wave detector, detects the arrival time, obtains the overall flow rate, and also displays the integrated display,
Select one pair of the two pairs of transducers with a switch so that they can be connected to the electronic unit,
When measuring with a large flow measurement unit, the pair of transducers of the large flow measurement unit is connected to the electronic unit,
When measuring with a small flow rate measurement unit, the pair of transducers of the small flow rate measurement unit is connected to the electronic unit,
A small flow rate measurement unit and a large flow rate measurement unit are connected in series, and the small flow rate measurement unit is provided with a bypass path that can be opened and closed with an automatic valve.The automatic valve is closed when the flow is small, and the automatic valve is opened when the flow is large.
When the automatic valve is closed, the switch is connected to a pair of transducers in the small flow rate unit, and when the automatic valve is open, a pair of transducers in the large flow rate measurement unit is connected to the electronic unit. Switch to measure and
An ultrasonic flowmeter characterized by detecting an open / close state of an automatic valve by an open / close detection means . 2. The ultrasonic flowmeter according to claim 1, wherein the valve opening / closing detection means comprises a magnet and a magnetic sensor. In a flowmeter that aims to increase the flow rate measurement range by combining a large flow rate measurement unit and a small flow rate measurement unit,
Ultrasonic transducers that operate on both the transmitting and receiving sides are installed in the upstream and downstream sides of each measurement unit, and ultrasonic waves are transmitted and received in each fluid flow from upstream to downstream and from downstream to upstream. The flow rate of each measuring part is obtained from the arrival time in each direction,
One electronic unit is provided for the large flow rate measuring unit and the small flow rate measuring unit, and this electronic unit detects the arrival time by receiving the drive signal of the transmission side transducer and the reception signal from the reception side transducer. To find the overall flow rate,
A small flow rate measurement unit and a large flow rate measurement unit are connected in series, and the small flow rate measurement unit is provided with a bypass flow path that can be opened and closed with an automatic valve that opens at a small flow rate and the valve opens when the flow rate is large.
In addition, an ultrasonic flowmeter is provided with a valve opening / closing detection means, wherein when the valve is closed, measurement is performed by a small flow measurement unit, and when the valve is opened, measurement is performed by a large flow measurement unit. . 4. The ultrasonic flowmeter according to claim 3, wherein the valve opening / closing detection means comprises a magnet and a magnetic sensor .

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