JPH06241855A - Electromagnetic flowmeter for not-fully-filled water - Google Patents

Abstract

PURPOSE:To obtain a flowmeter wherein its measuring accuracy is good and it can measure a water level and the conductivity of a fluid or a hydraulic grade by a method wherein exciting coils are installed on the upper side and the lower side of a flow passage, one pair of electrodes are installed on the right and the left of the flow passage and a voltage generated across the electrodes is amplified. CONSTITUTION:Exciting coils U, L are installed respectively on the upper side and the lower side of a flow passage 1, and one pair of electrodes 2 are installed on the right and the left of the flow passage 1. A voltage generated across the electrodes 2 is amplified by an amplifier 7, the value of its input impedance Z is changed, and two or more kinds of different values can be taken. When the exciting coils U, L are excited and the input impedance Z is set at a first value, an output voltage 1E, from the amplifier 7 is expressed by Ef=F(Q, h, g, C) as the function F of a flowing-down flow rate Q, a water level (h), a hydraulic grade (g) and the conductivity C of a fluid. When the input impedance is set at a second value, an output voltage Eg is expressed by Eg=G(Q, h), g, C) as the function G of the conductivity G of the fluid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic flow meter for measuring a flow rate, a water level, a hydraulic gradient and a conductivity of a fluid flowing in a non-full state of a flow path.

[0002]

2. Description of the Related Art The applicant has proposed an electromagnetic flowmeter for non-full water which measures the flow rate of a fluid flowing in a non-full state in a flow path by using the principle of an electromagnetic flow meter (Japanese Patent Application No. 3-335050).

This prior art had a structure as shown in FIG. 1 is a channel having a circular cross section, 2 and 2 are a pair of electrodes provided symmetrically with respect to a vertical line passing through the center of the channel 1, and U and L are respectively above and below the channel 1. The provided excitation coils are alternately excited to generate spatially different non-uniform magnetic flux density distributions during different periods. Reference numeral 4 indicates a flow rate detector having such a structure.

Reference numeral 5 denotes an exciting circuit, which alternately excites the upper and lower exciting coils U and L in response to a signal from the timing circuit 6. Reference numeral 7 is an amplifier for amplifying and outputting the voltage induced between the electrodes 2 and 2, and S ₁ is a changeover switch for changing over the excitation timing of the two exciting coils U and L by switching operation by the signal of the timing circuit 6. In synchronism with S ₂ , it is switched to the a side when the upper exciting coil U is excited and to the b side when the lower exciting coil L is excited.

Reference numerals 8A and 8B are sample & hold circuits for inputting and outputting the output voltages ε _U and ε _{L of the} contacts a and b of the changeover switch S ₁ , respectively, and 9 is a sample & hold circuit.
An A / D conversion circuit for converting an analog signal from the hold circuits 8A and 8B into a digital signal, 10 is a correction calculation circuit provided with a program for performing a correction calculation, and 11 is an output terminal for outputting a flow rate signal as a calculation result. .

Ratio of output voltage ε _U and ε _{L of} amplifier 7 ε _L
/ Ε _U has a constant relationship with the water level h. As shown in FIG. 4, when the water level h is plotted along the horizontal axis and the ratio ε _L / ε _U is plotted along the vertical axis, a single curve a indicating the relationship between the two is obtained. .

The ratio of the output voltage ε _U and the actual flow rate Q ε _U /
Q is the sensitivity of the flowmeter, and when this sensitivity is represented by k, the water level h and the sensitivity k have a functional relationship shown by a curve B as shown in FIG. 4 and 5, the water level h on the horizontal axis is represented by the ratio to the diameter (inner diameter) D of the flow path 1. And channel 1
6 is fixed to an appropriate gradient tan θ and is simply attached to the pipe, the water level h is changed from 0 to 1.0 D, the output ratio ε _L / ε _U and the sensitivity k are measured, and the curve a, B is obtained in advance.

Next, assuming that the output ratio is ε _L0 / ε _U0 = P ₀ when the flow rate detector 4 is connected to the pipe for measuring the flow rate, the water level h _{0 at} that time is shown in FIG. You can know it from the curve a. Further, from the curve B of FIG. 5, the water level h ₀
It is the gist of the prior art filed previously that the sensitivity calculation k ₀ at that time is determined and the true flow rate Q ₀ is calculated by the correction calculation circuit 10 as Q ₀ = ε _U0 / k ₀ .

However, the water level h
Since there is a one-to-one correspondence between the flow rate Q and the flow rate Q, the horizontal axis in FIG. 4 is considered to be replaced by the flow rate Q in the measured gradient, and FIG. did.

In the specific example of the prior art described above, instead of the curve a in FIG. 4, the output ratio ε _L / ε determined in advance is used.
_{The U} data is stored in the memory of the correction arithmetic circuit 10 together with the corresponding data of the flow rate Q on the horizontal axis of FIG. 7, and the true flow rate Q ₀ is calculated as follows using these stored data. .

That is, instead of the curve B in FIG. 5, as shown in FIG. 8, the horizontal axis represents the flow rate Q and the vertical axis represents the output.

[Outer 1]

Therefore, the output voltage ε _U and the corresponding flow rate Q are stored in the memory of the correction arithmetic circuit 10 as the output ratio ε.
It is stored as a numerical table together with _L / ε _U. As described above, in the conventional technique, the true flow rate Q ₀ is obtained without using the numerical value of the water level h specifically. The water level h in FIGS. 4 and 5 merely shows a role as an intervening term for obtaining the sensitivity k from the output ratio ε _L / ε _U for the purpose of conceptually explaining the purpose of the conventional technique. In the above-mentioned conventional technique, the true flow rate Q ₀ is calculated without using the water level h as described with reference to FIGS. 7 and 8.

This is because it was considered that the curve A in FIG. 4 and the curve in FIG. 7 were irrelevant to the pipeline gradient tan θ.

[0014]

SUMMARY OF THE INVENTION It is desirable for a flow meter to be able to perform measurement without causing obstacles in the flow path. In the above-mentioned conventional technique, the flow rate of the fluid in a non-full state can be measured without generating an obstacle such as a weir, and since the principle of the electromagnetic flow meter is used, there is an advantage that both forward flow and reverse flow can be measured.

However, the inventors of the present invention have made the following improvements by improving the above-mentioned conventional technique and making extensive studies to improve the accuracy of flow rate measurement. That is, when the pipeline gradient actually changes, the average flow velocity changes even at the same water level, so the flow velocity distribution changes subtly. Therefore, the curves in FIGS. 4, 5 and 7 change as the gradient of each conduit changes.

This change caused the flow rate measurement error. Further, in the above-mentioned conventional technique, the positional relationship between the electrode and the ground of the flow rate detector 4 used, and the relationship between the electrode shape and the exciting magnetic flux density distribution are liable to lose their symmetry. There was a problem that a flow rate measurement error occurred.

The electromagnetic flowmeter for non-full water according to the prior art is suitable for measuring the flow rate in sewers,
In these applications, it is desired to be able to measure the water level, the conductivity of a fluid, which is one of the indicators of water quality, and the gradient of the water surface, which is an indicator of the condition of the pipeline, that is, the hydraulic gradient.

Therefore, according to the present invention, the flow rate measurement accuracy is good,
Moreover, it is an object of the present invention to provide an electromagnetic flowmeter for non-filling water, which can measure even the water level, the conductivity of the fluid, and even the hydraulic gradient.

[0019]

In order to achieve the above-mentioned object, the electromagnetic flowmeter for non-full water of the present invention is constructed as follows.

That is, in the first invention, the exciting coil (U) provided on the upper side of the flow channel (1), the exciting coil (L) provided on the lower side, and the pair provided on the left and right sides of the flow channel (1). Amplifies the voltage generated between the electrodes (2), (2) and the electrodes (2), (2) and changes the value of its input impedance (Z) to take two or more different values. And an amplifier (7) capable of controlling the flow rate of the fluid flowing down the flow path (1) as Q, the water level as h, the fluid level gradient as the hydraulic gradient g, and the fluid When the conductivity is represented by C, the flow rate signals E _{f to} E _h shown in the following (a) to (c) are obtained as the output voltage of the amplifier 7.

A. Both excitation coils (U) (L) are excited,
The output voltage E _f of the amplifier (7) under the first measurement condition with the input impedance (Z) as one value is obtained. At this time, the output voltage E _f is expressed by the following first equation as a function F of the flow rate Q, the water level h, the hydraulic gradient g, and the conductivity C of the fluid.

E _f = F (Q, h, g, C) (1) b. The output voltage E _g of the amplifier (7) under the second measurement condition in which the value of the input impedance (Z) is changed to the other value with respect to the first measurement condition shown in (a) above is obtained. At this time, the output voltage E _g is expressed by the following equation (2) independent of the equation (1) as a function G of the flow rate Q, the water level h, the hydraulic gradient g, and the conductivity C of the fluid.

E_g= G (Q, h, g, C) (2) c. For the first measurement condition shown in (a) above, the lower excitation coil
Use the third measurement condition with the excitation of the coil (L) stopped.
Then, the function form of F is changed to obtain the following expression (3). E _hHako
Is the output voltage at.

E _h = H (Q, h, g, C) (3) d. Due to hydraulic requirements, there is a constant relationship between the flow rate Q, the water level h, and the hydraulic gradient g in a naturally flowing pipeline. The flow rate Q is calculated as a function q of the water level h and the hydraulic gradient g. It is expressed by equation (4).

Q = q (h, g) (4) E. The above-mentioned functions F, G, H and q are the known downflow rate Q.
-A numerical function is obtained in advance by actual measurement based on the water level h, the hydraulic gradient g, and the conductivity C of the fluid.

F. Four unknown quantities, downflow Q and water level h
In order to obtain the hydraulic gradient g and the conductivity C, the measurement conditions are changed from the first, second and third measurement conditions, and the output signals E _f , E _g , E _h corresponding to the flow rate are obtained, and The four unknown quantities were obtained by solving the four simultaneous equations (1) to (4).

By changing the combination of the excitation mode for determining the first, second, and third measurement conditions and the method for determining the value of the input impedance (Z), the second to ninth aspects are provided in addition to the first aspect of the invention. Inventions are conceivable. In these inventions as well, similar to the first invention, by solving four simultaneous equations, four unknown quantities, the flow rate Q, the water level h, the hydraulic gradient g, and the conductivity C of the fluid are obtained. be able to.

These second to sixth inventions correspond to claims 2 to 6, respectively, in the same manner as the first invention corresponds to claim 1, and are excitation modes for determining measurement conditions. When,
It is specified by selecting the input impedance (Z).

Therefore, these inventions are shown in Table 1 in the form of a table together with the first invention.

[0030]

[Table 1] Since the first to sixth inventions corresponding to claims 1 to 6 are specified in the above Table 1, these inventions will not be described at length in the text.

In summary, the first to sixth inventions fall under the first to sixth aspects. And 7th invention WHEREIN: (1) of any one invention among said 1st-6th invention-
By solving the four simultaneous equations in (4), instead of the unknown four quantities, the downflow rate Q and at least one of the water level h, the hydraulic gradient g, and the fluid flow rate C are obtained. I chose

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the first embodiment of FIG. 1, 1 is a channel having a circular cross section, 2 and 2 are a pair of electrodes provided on the left and right sides of the channel 1 at least near the bottom of the channel. The other end should be in contact with the flowing fluid even at the lowest water level to be measured.

The size of the electrode in the circumferential direction is the functional form F.
Affects the shape of GH. There is a difference in the ease of solving simultaneous equations depending on the functional form.

U is an upper exciting coil, L is a lower exciting coil, and 5 is an exciting circuit, which operates according to the signal of the timing circuit 6, and both exciting coils U under the first and second measurement conditions. And L is excited. Then, under the third measurement condition, the excitation of the lower excitation coil L is stopped and only the upper excitation coil U is excited.

Reference numeral 7 is an amplifier having a changeable input impedance Z, and the input impedance Z can take two or more different values. 9 is an A / D conversion circuit, 1
0 is an arithmetic circuit, 10A is a memory, 10B is an output circuit,
11 is an output terminal, 6 is a timing circuit, and an exciting circuit 5,
A synchronization signal is sent to the amplifier 7, the A / D conversion circuit 9 and the arithmetic circuit 10.

FIG. 2 differs from the first embodiment of FIG. 1 in that instead of the input impedance Z, a short-circuit resistance R and a switch S are provided between the two conductors from each electrode 2, 2 to the amplifier 7 and ground. Is provided and the switch S is opened / closed according to a signal from the timing circuit 6, so that the same operation as that when the input impedance of the amplifier 7 is changed is performed.

Therefore, the operation of the second embodiment of FIG. 2 will be described below. The exciting circuit 5 excites the upper and lower exciting coils U and L according to the signal from the timing circuit 6. Turn off the lower side excitation coil for a certain period.

The timing circuit 6 changes the input impedance of the amplifier 7 and the timing required for excitation, and
Generates timing required for / D conversion and signal processing of the arithmetic circuit.

The flow rate signal (output voltage of the amplifier 7) is A / D
It is converted and taken into the arithmetic circuit 10. Memory 10
In A, the functions F, G, H, and q are stored as a numerical table. Also, a program for solving the simultaneous equations (1) to (4) is stored.

The arithmetic circuit 10 solves the simultaneous equations (1) to (4) according to the above program. The output circuit 10B outputs the above calculation result to the outside in an appropriate form. (1) ~
To solve the simultaneous equations in (4), downflow rate Q, water level h,
It is necessary to change the measurement conditions to the first, second, and third within a short time so that the hydraulic gradient g and the electrical conductivity C of the fluid can be regarded as constant, and the timing circuit 6 operates as such.

The arithmetic circuit 10 generates a flow rate signal (output voltage) E _f · E _g ·, which is generated according to the first, second and third measurement conditions.
_Eh is distinguished and taken in. In the memory 10A, while setting appropriate values for the flow rate Q, the water level h, the hydraulic gradient g, and the conductivity C of the fluid, the numerical functions F, G, H of the numerical functions F, G, H obtained by actual measurement while varying the set values are set. The value is the set value Q
Stored and stored so that it can be pulled out by giving h, g, C.

There are various possible solutions to the simultaneous equations, but an example is given below. 1). First, in equation (1), an appropriate value for h · g · C is assumed. E _f = F (Q, h, g, C) (1) Here, in the comparison with E _f , Q satisfying the expression (1) is obtained from the numerical function F on the memory 10A.

That is, by assuming h, g, and C, the degree of freedom under the numerical function is only the one-dimensional flow rate Q.
Find Q such that the value of this function matches E _f . This can be easily done by using an appropriate interpolation operation or the like. The same can be said for the procedures (2) to 4) below. ) Write the value found there as Q ₀ . 2). Out of Q ₀ just obtained and h, g, and C initially assumed, g and C are substituted into the equation (2).

E _g = G (Q ₀ , h, g, C) (2) Here, h satisfying the equation (2) in comparison with E _g is obtained by the numerical function G on the memory 10A. The value obtained is written as h ₀ . 3). In this way, the obtained Q ₀ · h ₀ and g of h, g, and C initially assumed are substituted into the equation (2).

E _h = H (Q ₀ , h ₀ , g, C) (3) Here, in the comparison with E _h , C satisfying the expression (3) is obtained by the numerical function H on the memory 10A. . The value obtained is written as C ₀ . 4). The obtained Q ₀ and h ₀ are substituted into the equation (4).

Q ₀ = q (h ₀ , g) (4) Here, by the numerical function q on the memory 10A, (4)
Find g that satisfies the expression. Write the obtained value as g ₀ . 5). With this, all the values Q ₀ · h ₀ · g ₀ · C ₀ were obtained.

The steps 1) to 4) are made into one loop. Of the calculated Q ₀ · h ₀ · g ₀ · C ₀ , h ₀ · g
By assuming this value to be ₀ · C ₀ and turning this loop again, Q ₀ · h obtained when step 4) is completed
₀ · g ₀ · C ₀ approaches the true solution of the simultaneous equations. Such convergence calculation is repeated to obtain a falling rate Q ₀ · water level h _0, hydraulic gradient g conductivity C ₀ of ₀ · fluid with the necessary accuracy.

In the second to sixth inventions, four simultaneous equations
Four unknown quantities Q₀・ H₀・ G ₀・ C₀To ask for
Is similar to the solution in the first embodiment of the invention described above.
It is clear that it can be solved by the law, so please explain
Omit it.

[0049]

Since the electromagnetic flowmeter for non-full water of the present invention is configured as described above, it is possible to more accurately measure the flow-down flow rate of the pipe line flowing in non-full water. In addition, it is possible to measure the water level, the conductivity of the fluid, which is one of the indicators of water quality, and the hydraulic gradient, which is an indicator of the condition of the pipeline, together with the flow rate.

[Brief description of drawings]

FIG. 1 is a diagram of a first embodiment of the present invention.

FIG. 2 is a diagram of a second embodiment of the present invention.

FIG. 3 is a diagram of prior art.

FIG. 4 is a water level vs. output ratio diagram.

FIG. 5 is a water level vs. sensitivity diagram.

FIG. 6 is a schematic diagram illustrating a pipeline gradient.

FIG. 7 is a flow rate vs. output ratio diagram.

FIG. 8 is a flow rate vs. output diagram.

[Explanation of symbols]

 1 flow path 2 electrode 7 amplifier 10 arithmetic circuit 10A memory U, L exciting coil Z input impedance

Claims (7)

[Claims] 1. An exciting coil provided above a flow path (1)
(U), the exciting coil (L) provided on the lower side, and the flow path (1)
A pair of electrodes (2), (2) provided on the left and right of the
While amplifying the voltage generated between (2) and (2),
The input impedance (Z) value of
With an amplifier (7) that can take different values above
An electromagnetic flowmeter provided, wherein the flow rate of the fluid flowing down the flow path (1) is Q, the water level is h,
The gradient of the fluid surface is the hydraulic gradient g, and the conductivity of the fluid is C.
Flow rate signal E shown in the following_f~ E_hTo
It is calculated as the output voltage of the amplifier 7. I. Both excitation coils (U) and (L) are excited and input impedance
Under the first measurement condition where the dance (Z) is one value
Output voltage E of amplifier (7)_fAsk for. At this time, the output
Voltage E_fIs the flow rate Q, the water level h, the hydraulic gradient g, and the fluid
It is expressed as a function F of the conductivity C by the following first equation. E_f= F (Q, h, g, C) (1) b. Input impedance against the first measurement condition shown in b.
The second measurement condition in which the value of dance (Z) is changed to the other value
Output voltage E of amplifier (7)_gAsk for. this
When output voltage E_gIs the flow rate Q, water level h, hydraulic gradient g and
As a function G of the conductivity C of the fluid and the fluid,
It is represented by the expression (2). E_g= G (Q, h, g, C) (2) c. For the first measurement condition shown in (a) above, the lower excitation coil
Use the third measurement condition with the excitation of the coil (L) stopped.
Then, the function form of F is changed to obtain the following expression (3). E _hHako
Is the output voltage at. E_h= H (Q, h, g, C) (3) d. Due to hydraulic demand, the flow rate of natural flow down
There is a certain relationship between Q, water level h, and hydraulic gradient g.
And the flow rate Q is defined as the function q of the water level h and the hydraulic gradient g.
It is expressed by equation (4). Q = q (h, g) (4) E. The above-mentioned functions F, G, H and q are the known downflow rate Q.
・ Based on the water level h, hydraulic gradient g, and conductivity C of the fluid
It is obtained as a numerical function by actual measurement. F. Four unknown quantities, downflow Q, water level h, hydraulic gradient g
-To obtain the conductivity C of the fluid, the measurement conditions are
Output signal according to the flow rate by changing the second and third measurement conditions
E_f・ E_g・ E_hThe four of the above (1) to (4)
By solving the simultaneous equations, we obtain four unknown quantities.
Electromagnetic flow meter for non full water. 2. An electromagnetic flowmeter for non-full water, wherein only the upper side excitation coil (U) is excited in the second measurement condition shown in (b) of claim 1. 3. An electromagnetic flowmeter for non-full water, wherein only the lower side excitation coil (L) is excited in the third measurement condition shown in (c) of claim 1. 4. The second measurement condition shown in B of claim 1,
Of the third measurement conditions shown in the same C, an electromagnetic flowmeter for non-full water in which only the lower excitation coil (L) was used for excitation. 5. Of the first measurement conditions shown in claim 1, the excitation is limited to the upper side excitation coil (U), and the second measurement condition shown in (b) of the claim is set to excitation the upper side. The electromagnetic flowmeter for non-full water, in which only the exciting coil (U) is used, and in the third measurement condition shown in C of the same claim, only the lower exciting coil (L) is used for excitation. 6. Among the first measurement conditions shown in (a) of claim 1, only the upper side excitation coil (U) is excited, and the second measurement condition shown in (b) and the third measurement condition shown in (c). Of the above measurement conditions, the electromagnetic flowmeter for non-full water in which only the lower excitation coil (L) was used for excitation. 7. By solving the four simultaneous equations of (1) to (4), instead of the unknown four quantities, the downflow rate Q, the water level h, the hydraulic gradient g, and the conductivity C of the fluid are calculated. The electromagnetic flowmeter for non-full water according to any one of claims 1 to 6, wherein at least one of them is obtained.