JP2002168666A - Electromagnetic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic flowmeter for calculating adhered amount of an adhered insulating adhered. SOLUTION: As shown in Fig. (a), an excitation current is non-excited during periods K1, K3 and K5, excited positively during a period K2, and excited negatively during a period K4; and a flow rate electromotive force, having a signal voltage component and a ramp-like noise voltage component, is generated. As shown in Fig. (b), the signal voltage component is (differentiated noise component (e)+(adhesion influence component (n)) during the periods K1, K3 and K5 and e+n+(flow rate signal component (s)) during the periods K2 and K4. As shown in Fig. (c), the lamp-like noise voltage component is (fixed content (a)) during the period K1. Similarly, it is a+ (changing content 4b) during the period K5. Calculated results R1 to R3 are calculated, based on an amplitude of the electromotive force obtained from the periods K1 to K5, and (n) is obtained from the R1 to R3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic flowmeter, and more particularly, to an electromagnetic flowmeter for detecting an insulating substance attached to an electrode of an electromagnetic flowmeter.

[0002]

2. Description of the Related Art An electromagnetic flowmeter measures the flow rate of a liquid by detecting the magnitude of a fluid electromotive force generated in accordance with the conductivity of a liquid flowing in the pipe by passing an exciting current through an exciting coil to generate a magnetic field in the pipe. It is a type flow meter. Electromagnetic flowmeters can measure the flow rate without affecting the flow of liquid due to the structure without moving parts and obstacles in the pipe. It has the feature that the flow rate of liquid, high clay liquid, and highly corrosive liquid can be measured stably. For this reason, electromagnetic flowmeters are used for the treatment of wastewater leachate and concentrated sludge water in environmental facilities, mixed fluids of oil and water from oil wells in oil facilities, and insulating properties such as white mud and red mud in aluminum scouring in mining facilities. It is used to measure the flow rate of deposits.

FIG. 9 is a time chart of each signal handled by a conventional electromagnetic flow meter. As shown in FIG.
The electromagnetic flowmeter employs a high-frequency ternary excitation method including positive excitation by a positive excitation current, non-excitation by setting the excitation current to 0, and negative excitation by a negative excitation current. The high frequency excitation method has advantages of stability and high-speed response when measuring the flow rate of various fluids.

In FIG. 9, periods K ₁ , K ₃ and K ₅
Is a non-excitation period, the period K ₂ and K ₆ are positive exciting period, the period K ₄ is the negative exciting period. The detected fluid electromotive force consists of a signal voltage component and a ramp-like (slope) noise voltage component, which varies according to the flow rate of the liquid and the magnetic field in the tube. The fluid electromotive force is sampled immediately before the end time of each period, and its magnitude is measured.

As shown in FIG. 1B, the signal voltage component is composed of a flow signal component and a differential noise component, and changes in magnitude and direction based on the flow rate of the liquid and the magnetic field in the pipe. Assuming that the differential noise component is e and the flow signal component is s, the magnitudes of the signal voltage components are periods K ₁ , K ₃ , and
K ₅ in a e, the period K _2, K _4, and is a K ₆ e + s.

As shown in FIG. 1C, the magnitude of the ramp noise voltage component linearly increases in proportion to time. Here, the magnitude of the ramp-like noise voltage component of the start time of the period K ₁ to zero. The magnitude of the ramp noise voltage component is a fixed component of the magnitude of the ramp noise component, a
And then, a variation when is b, a a period K _1, the period K ₂ is a + b, a a + 2b in the period K _3, in the same manner, it is a + 5b period K _6.

The fluid electromotive force is the total voltage of the signal voltage component and the ramp-shaped noise voltage component, and the magnitude of the fluid electromotive force V _{91 to} V ₉₅ obtained from the excitation periods K _{1 to} K ₅ is given by the following equation:
From 91 to 95 are obtained. V ₉₁ = e + a ····· formula _{91 V 92 = e + s +} a + b ····· formula _{92 V 93 = -e + a +} 2b ····· formula _{93 V 94 = -e-s +} a + 3b ····· formula 94 V ₉₅ = E + a + 4b ... Equation 95

The calculation result R ₉ is obtained by adding Expressions 91 to ₉ to Expression 96 shown below.
Determined by substituting 5. R ₉ = −V ₉₁ + 2V ₉₂ −2V ₉₄ + V ₉₅ ... Equation 96 R ₉ = − (e + a) +2 (e + s + a + b) −2 (−e−s + a + 3b) + (e + a + 4b) = − e−a + 2e + 2s + 2a + 2b + 2e + 2s− 2a-6b + e + a + 4b = 4s + 4e Equation 97

[0009]

In the above conventional electromagnetic flow meter, as shown in equation 97, the operation result R ₉ includes the term of the differential noise component e, so that the excitation current of the low frequency is used instead of the high frequency. If adopted and the signal voltage component does not include the differential noise component, the flow rate signal component s can be immediately obtained from Expression 97, but the advantage of the high frequency excitation method is lost.

When an insulating deposit adheres to the inside of the detector tube of the electromagnetic flowmeter, an adhesion-influencing component that affects the fluid electromotive force is generated in accordance with the amount of the adhesion. Does not consider ingredients. In conventional electromagnetic flowmeters, the flow of fluid is temporarily stopped, the electromotive force of the fluid during movement is compared with that of the stopped fluid, and the component that affects the adhesion is detected.However, the flow of the fluid depends on the installation location of the electromagnetic flowmeter. In some cases, it was not possible to pause, which caused inconvenience.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and has as its object to provide an electromagnetic flowmeter for calculating the amount of adhered insulating deposits. And

[0012]

To achieve the above object, an electromagnetic flowmeter according to the present invention comprises: a magnetic field applying means for applying a magnetic field perpendicular to the moving direction of a conductive fluid moving in a pipe; An electromotive force measuring means for measuring an electromotive force generated in the conductive fluid by the magnetic field applying means, wherein the magnetic field applying means generates a magnetic field in one direction, a positive excitation, a non-excitation for stopping the magnetic field, and the one direction. An electromagnetic flowmeter that performs ternary excitation that repeats negative excitation that generates a magnetic field in the opposite direction to
Based on the electromotive force detected in advance by the electromotive force measuring means during the movement of the fluid in a state where the insulating deposit is not attached, and the electromotive force detected in the movement of the fluid in the state where the insulating deposit is attached. And calculating the amount of the attached insulating material attached to the electromagnetic flowmeter.

The electromagnetic flow meter of the present invention has a positive excitation, a non-excitation,
In addition, during each excitation period of the ternary excitation method of negative excitation, the adhesion influence component can be detected by calculating the electromotive force detected during the movement of the fluid. Can be performed.

In the electromagnetic flowmeter according to the present invention, the electromotive force detected in a state where the insulative deposit is not attached includes a differential noise component and a flow signal component, and is 3 in a state where the insulative deposit is not attached. It is preferable to obtain the differential noise component from the electromotive force measured by performing the value excitation. in this case,
If the electromotive force detected in a state where the insulating deposit is attached is obtained, and the differential noise component is subtracted, the amount of the insulating deposit attached to the electromagnetic flowmeter can be calculated.

The electromotive force detected at the time of continuous non-excitation, positive excitation, non-excitation, negative excitation, and non-excitation in a state where the insulative deposit does not adhere is V ₁₁ , V ₁₂ , and V _{13, respectively.} , V
₁₄ and V ₁₅ , the differential noise component is calculated as V _{11
/ 4-V 13/2 +} V 15/4 by obtaining, or,
In the state where the insulating deposit is attached, continuous de-excitation,
Positive excitation, non-excited, the negative excitation, and an electromotive force respectively V ₂₁ that is detected when the _{non-excited, V 22, V 23, V} 24 and,, V ₂₅
Then, the adhesion-influencing component of the insulating deposit is expressed as (V _{21/4
-V 23/2 + V 25/} 4) - (V 11/4-V 13/2 + V 15
/ 4) is also a preferred embodiment of the present invention. In this case, it is easy to calculate the amount of the adhered insulating substance in the ternary excitation method.

Also, the electromagnetic flowmeter of the present invention has a magnetic field applying means for applying a magnetic field perpendicular to the moving direction of the conductive fluid moving in the pipe, and measures an electromotive force generated in the conductive fluid by the magnetic field. And an electromagnetic flow rate for performing a binary excitation in which the magnetic field applying means repeats positive excitation for generating a magnetic field in one direction and negative excitation for generating a magnetic field in a direction opposite to the one direction. A first frequency and a second frequency lower than the first frequency during the movement of the conductive fluid, respectively, in a state where the insulative deposit is not attached in advance by the electromotive force measuring means. Each of the electromotive forces detected by repeating the binary excitation and the first electromotive force during the movement of the conductive fluid in a state where the insulating attachment is attached.
And calculating, based on each electromotive force detected by repeating the binary excitation at the second frequency, the amount of the insulating deposit attached to the electromagnetic flowmeter.

The electromagnetic flowmeter according to the present invention calculates the electromotive force detected during the movement of the fluid during each of the excitation periods of the binary excitation system of the positive excitation and the negative excitation at the first frequency and the second frequency. Thus, the adhesion-influencing component can be detected, so that a self-diagnosis for checking the amount of the adhered insulating substance can be performed.

In the electromagnetic flow meter according to the present invention, when the insulating deposit is not attached, the electromotive force detected at the first frequency includes a differential noise component and a flow signal component, and is detected at the second frequency. The generated electromotive force includes a flow signal component, and the differential noise component is obtained based on the both electromotive forces, or the electromotive force detected at the first frequency in a state where the insulating deposit is attached. The power includes a differential noise component, a flow signal component, and an adhesion-influencing component of the insulating deposit, and the electromotive force detected at the second frequency includes a flow signal component. It is preferable to obtain a noise component and an adhesion influence component. In this case, it is easy to calculate the amount of the adhered insulating substance in the binary excitation method.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electromagnetic flow meter according to the present invention will be described below with reference to the drawings based on an embodiment of the present invention. FIG. 1 is a time chart of each signal handled by the electromagnetic flow meter according to the first embodiment of the present invention. An electromagnetic flowmeter supplies an exciting current to an exciting coil, and creates a magnetic field in a direction perpendicular to the moving direction of the liquid flowing in the tube by a ternary excitation method. The detector of the electromagnetic flow meter detects a fluid electromotive force generated in a direction perpendicular to the moving direction of the liquid and the direction of the magnetic field according to the flow rate and conductivity of the liquid. The ternary excitation method is a positive excitation by a positive excitation current, a non-excitation with zero excitation current,
And, the negative excitation by the excitation current in the negative direction is repeated. In the electromagnetic flow meter of the present embodiment, the repetition period is shortened,
While improving stability and fast responsiveness in low conductivity fluids, a differential noise component is generated in the fluid electromotive force. The fluid electromotive force consists of a signal voltage component and a ramp noise voltage component.

FIG. 2A is a time chart of the exciting current. The periods K ₁ , K ₃ and K ₅ are non-excited,
Period K ₂ and K ₆ are positive excitation, the period K ₄ is the negative excitation.

FIG. 2B shows a time chart of the signal voltage component.
It is. The signal voltage component has a period K₁~ K₆Excitation current
The size and direction change in synchronization with
It changes greatly immediately after the start time and immediately before the end time of each period
To be stable. The differential noise component e is the excitation frequency of the excitation current
This occurs when a high frequency is used for the number, and increases according to the excitation frequency.
Add. Adhesion-influencing component n is insulated from the detector of the electromagnetic flowmeter
Generated when volatile deposits adhere, and increase according to the amount of the deposits
I do. The flow signal component s is generated when the liquid moves,
It increases with body flow and conductivity. The electromagnetic flow meter is
Sampling the signal voltage component just before the end time of each period
I do. The magnitude of the signal voltage component is equal to the period K ₁, K_Three,as well as,
K_FiveE + n and the period K_Two, K_FourAnd K₆E + n
+ S.

FIG. 3C is a time chart of the ramp noise voltage component. The magnitude of the ramp noise voltage component linearly increases in proportion to time. Electromagnetic flow meter, the start time of the non-magnetic-excitation period K _1, the magnitude of the ramp-like noise voltage component to zero, sampling the ramp-like noise voltage component just before the end time of each period. The size of the ramp-like noise voltage component, a fixed frequency is a, if the variation is is b, a a period K _1, a period K ₂ to a + b, a a + 2b in the period K _3, in the same manner Te, which is a + 5b in the period K _6.

In the state where the insulating deposit is attached, the fluid electromotive force is the total voltage of the signal voltage component and the ramp-shaped noise voltage component, and the magnitude of the fluid electromotive force obtained from the excitation periods K _{1 to} K _5. V _{21 to} V ₂₅ are as shown in the following formulas 1 to 5. V ₂₁ = e + n + a... Formula 1 V ₂₂ = e + n + s + a + b... Formula 2 V ₂₃ = −en−a + 2b... Formula 3 V ₂₄ = −en−s + a + 3b. Equation 4 V ₂₅ = e + n + a + 4b Equation 5

The calculation result R ₁ is obtained by adding Equations 1 to 5 to Equation 6 shown below.
Is obtained by substituting R ₁ = −V ₂₁ + V ₂₂ + V ₂₃ −V ₂₄ ... Equation 6 R ₁ = − (e + n + a) + (e + n + s + a + b) + (− en−a + 2b) − (− en−s + a + 3b) = − e −n−a + e + n + s + a + b−en−a + 2b + e + n + s−a−3b = 2s Equation 7 The calculation result R ₁ includes the term of the flow signal component s as shown in Equation 7.

The calculation result R ₂ is obtained by using the following equations 8 to 1 to 5
Is obtained by substituting R ₂ = (− V ₂₁ + 2V ₂₂ −2V ₂₄ + V ₂₅ ) / 2 Equation 8 R ₂ = ｛− (e + n + a) +2 (e + n + s + a + b) −2 (−en−s + a + 3b) + (e + n + a + 4b) )} / 2 = {- e -n-a + 2e + 2n + 2s + 2a + 2b + 2e + 2n + 2s-2a-6b + e + n + a + 4b} / 2 = 2s + 2e + 2n ····· formula 9 operation result R _2, as shown in equation 9, the flow rate signal component s, differential noise It consists of components e and adhesion-affecting components n.

In a state where the insulating deposits do not adhere,
Fluid electromotive force exciting period K ₁ ~K fluid electromotive force obtained from ₅ size V ₁₁ ~V ₁₅ is as shown in Equation 10 Equation 14 below. V ₁₁ = e + a ····· formula _{10 V 12 = e + s +} a + b ····· formula _{11 V 13 = -e + a +} 2b ····· formula _{12 V 14 = -e-s +} a + 3b ····· formula 13 V ₁₅ = E + a + 4b ... Equation 14

The operation result R ₃ is obtained by adding the following equation (10) to equation (15).
It is obtained by substituting equation 14. R ₃ = −V ₁₁ + V ₁₂ + V ₁₃ −V ₁₄ Formula 15 R ₃ = − (e + a) + (e + s + a + b) + (− e + a + 2b) − (− e−s + a + 3b) = − e−a + e + s + a + b− e + a + 2b + e + s-a-3b = 2s ····· formula 16 operation result R _3, as shown in equation 16, consisting of section of the flow signal component s.

The operation result R ₄ is obtained by adding the following equation (10) to equation (17).
It is obtained by substituting equation 14. R ₄ = (− V ₁₁ + 2V ₁₂ −2V ₁₄ + V ₁₅ ) / 2 Equation 17 R ₄ = {− (e + a) +2 (e + s + a + b) −2 (−es−a + 3b) + (e + a + 4b)} / 2 = {− ea−2e + 2s + 2a + 2b + 2e + 2s−2 a−6b + e + a + 4b} / 2 = 2s + 2e (18) The calculation result R ₄ is composed of the terms of the flow signal component s and the differential noise component e as shown in Expression 18. .

FIG. 2 is a flowchart of a preparation process executed by the electromagnetic flow meter of FIG. 1 before self-diagnosis. Electromagnetic flow meter, in a state not adhering to advance the insulating deposits detector, from Equation 15 of the operation result R ₃ seeking 2s of the flow signal component (step S11), and the flow rate from the equation 17 of the operation result R ₄ The signal component and the differential noise component 2s + 2e are obtained (step S12). Operation result by subtracting the calculation result R ₃ from R _4, obtains a differential noise component 2e, and stores this value in RAM variable A (step S13).

FIG. 3 is a flowchart of a self-diagnosis process executed by the electromagnetic flow meter of FIG. Operation result sought 2s of the flow signal component from Equation 6 R ₁ (step S21), and the flow rate signal component from the equation 8 of the operation result R _2, differential noise component, and obtains a 2s + 2e + 2n attachment influence component (step S22). Operation result by subtracting the calculation result R ₁ from R _2,
Find 2e + 2n of the differential noise component and the adhesion influence component,
This value is stored in RAM variable B. The value of the RAM variable A is subtracted from the value of the RAM variable B, 2n of the adhesion influence component is obtained and stored in the RAM variable C (step S23), and RA
It is determined whether or not the value of the M variable C is equal to or more than a predetermined value, and the influence amount of the insulating deposit is checked (step S24). If “NO”, the processing is continued from step S21 assuming that the adhesion affecting component is small, and if “YES”, an alarm is output assuming that the adhesion affecting component is large (step S2).
5) The process is continued from step S21.

[0031] The electromagnetic flowmeter, instead of the calculation procedure, the fluid electromotive force of magnitude V ₁₁ ~V ₁₅ in a state where the insulating deposit does not adhere stored therein, the insulating coating has attached When the magnitudes V _{21 to} V ₂₅ of the fluid electromotive force are obtained in the state, the adhesion influence component n can be directly obtained from the following formula.

Differential noise component and adhesion influence component e + n
, As shown in Equation 19 is calculated by subtracting the equation 6 of the operation result R ₁ from Equation 8 of the operation result R _{2. e + n = (- V 21} + 2V 22 -2V 24 + V 25) / 4 - (- V 21 + V 22 + V 23 -V 24) / 2 = V 21/4-V 23/2 + V 25/4 ····· formula 19

The differential noise component e is given by
Obtained by subtracting the formula 15 of the operation result R ₃ from Equation 17 of the operation result R _{4. e = (- V 11 + 2V} 12 -2V 14 + V 15) / 4 - (- V 11 + V 12 + V 13 -V 14) / 2 = V 11/4-V 13/2 + V 15/4 ····· formula 20

The adhesion-influencing component n is given by the following equation:
It is obtained by subtracting equation 20 from 19. _{n = (V 21/4-} V 23/2 + V 25/4) - (V 11/4-V 13/2 + V 15/4) · ···· formula 21

FIG. 4 is a time chart of an exciting current showing an application example of the electromagnetic flow meter of FIG. FIG. 7A is a first specific example showing an application example to a binary excitation method. In the excitation current of the first specific example, a ternary excitation period in which positive excitation, non-excitation and negative excitation are repeated is inserted in a binary excitation period in which positive excitation and negative excitation are repeated, and a cycle T ₁ for performing binary excitation. ,as well as,
It has a period T ₂ for performing ternary excitation. Electromagnetic flowmeter of FIG. 1, the period T ₂ to get the five flow electromotive force, performs a self-diagnosis for the adhesion amount of the insulating deposits.

FIG. 4B is a second specific example showing an example of application to a two-frequency excitation system. The exciting current of the second specific example has a low frequency component in which positive excitation and negative excitation are repeated at a long cycle T ₄ ,
It is a two-frequency excitation mode for superposing a high-frequency component to repeat the positive excitation and negative excitation in a short cycle T _3. In the vicinity of a change point in a low frequency portion of the exciting current, ternary excitation is performed. FIG.
Electromagnetic flow meter is a period K ₇ ~K ₉ is near the changing point five flow electromotive force respectively acquired, performs self-diagnosis for the deposition of insulating deposits.

According to the above embodiment, during each excitation period of the ternary excitation system of the positive excitation, the non-excitation, and the negative excitation, the electromotive force detected during the movement of the fluid is calculated, so that the adhesion effect is calculated. Since the components can be detected, a self-diagnosis for checking the amount of the insulating deposit can be performed.

FIG. 5 is a flowchart of a preparation process executed by the electromagnetic flow meter according to the second embodiment of the present invention. The electromagnetic flow meter according to the present embodiment is different from the first embodiment in that a binary excitation method is used instead of the ternary excitation method, and that the adhesion influence component of the insulating deposit is detected. The electromagnetic flowmeter performs a preparation process in a state where the insulating deposit is not attached to the detector in advance.

FIG. 6 is a time chart of each signal handled by the electromagnetic flow meter of FIG. Excitation current has a duration of the period of use excitation frequency f _H and the low excitation frequency f _L. As the low excitation frequency f _L , a frequency whose frequency is sufficiently lower than the used excitation frequency f _H is selected. Exciting current, the duration of use excitation frequency f _H, the positive excitation and negative excitation period T ₅ repeated i times, the period of the low excitation frequency f _L, the positive excitation and negative excitation period T ₆ is repeated j times. The signal voltage component of the flow electromotive force is
Magnitude and direction changes according to the exciting current, the duration of use excitation frequency f _H, consist differential noise component e and the flow rate signal components s _1, the periods of low excitation frequency f _L, the flow rate signal component s ₁ Become.

The electromagnetic flow meter, a period of use the excitation frequency f _H, i the signal voltage component of the positive excitation and negative excitation per period T ₅
Sampling times. The magnitude of the positive excitation signal voltage component and the magnitude of the negative excitation signal voltage component are added, and the i added values are summed and averaged (step S31). The averaging process F _H1 is shown below. F _H1 = {(e + s ₁ )-(− e−s ₁ ) + to + (e + s ₁ ) − (− e−s ₁ )} / i = 2e + 2s ₁ ...

During the period of the low excitation frequency f _L , the signal voltage components of the positive excitation and the negative excitation are sampled j times every cycle T ₆ .
The magnitude of the positive excitation signal voltage component and the magnitude of the negative excitation signal voltage component are added, and the j addition values are summed and averaged (step S32). The averaging process _FL1 is shown below. F _L1 = {(s ₁ ) − (− s ₁ ) + to + (s ₁ ) − (− s ₁ )} / j = 2s ₁ Equation 23

The averaging process from the process value of the averaging process F _H1 F
_The differential noise component e is obtained by subtracting the processing value of _L1 ,
It is stored in the variable A (step S33). This processing is described below. A = F _H1 −F _L1 = 2e + 2s ₁ −2s ₁ = 2e Equation 24

FIG. 7 is a flowchart of a main process executed by the electromagnetic flow meter after the preparation process of FIG. The electromagnetic flow meter executes the main process when the differential noise component e is obtained by the preparation process of FIG. FIG. 8 is a time chart of each signal handled by the electromagnetic flow meter that executes the main process of FIG. The exciting current flows as in FIG. Signal voltage components of the flow electromotive force, the duration of use excitation frequency f _H,
Differential noise component e, adhesion influence component n and consists flow signal component s _2, the periods of low excitation frequency f _L, consisting of the flow rate signal component s _2.

The electromagnetic flow meter determines whether it is time to detect an adhesion affecting component (step S41). If "NO", processing continues from step S46, if "YES", the period of use excitation frequency f _H, that i times sampling of the signal voltage component of the positive excitation and negative excitation per period T ₅ . The magnitude of the positive excitation signal voltage component and the magnitude of the negative excitation signal voltage component are added, and the i added values are summed and averaged (step S42). The averaging process F _H2 is shown below. F _H2 = {(e + n + s ₂ )-(− en−s ₂ ) + to + (e + n + s ₂ ) − (− en−s− ₂ )} / i = 2e + 2n + 2s ₂ ...

During the period of the low excitation frequency f _L , the signal voltage components of the positive excitation and the negative excitation are sampled j times every cycle T ₆ . The magnitude of the negative excitation signal voltage component is subtracted from the magnitude of the positive excitation signal voltage component, and the j subtracted values are summed and averaged (step S43). The averaging process _FL2 is shown below. F _L2 = {(s ₂ ) − (− s ₂ ) + to + (s ₂ ) − (− s ₂ )} / j = 2s ₂ ...

Averaging processing F The averaging processing F is calculated from the processing value of _H2.
By subtracting the processing value of _L2 , the differential noise component e and the adhesion influence component n are obtained and stored in the RAM variable B (step S4).
4). This processing is described below. B = F _H2 −F _L2 = 2e + 2n + 2s ₂ −2s ₂ = 2e + 2n Equation 27

The RAM-variable A is subtracted from the RAM-variable B to determine the adhesion-influencing component, and it is determined whether or not the adhesion-affecting component is greater than a predetermined value, and the influence of the insulating adhered matter is checked (step S45). This processing is described below. BA = 2e + 2n-2e = 2n Equation 28

If the determination in step S45 is "NO", the flow rate is measured according to a predetermined procedure assuming that the adhesion affecting component is small (step S46), and it is determined whether it is time to detect the adhesion affecting component (step S46). S47).
If “NO”, the process is continued from step S46,
If "YES", the process is continued from step S42. If the determination in step S45 is "YES", an alarm is output assuming that the adhesion affecting component is large.

According to the above-described embodiment, the electromotive force detected during the movement of the fluid is calculated in each of the excitation periods of the binary excitation method of the positive excitation and the negative excitation at the first frequency and the second frequency. Thus, the adhesion-influencing component can be detected, so that a self-diagnosis for checking the amount of the adhered insulating substance can be performed.

Although the present invention has been described based on the preferred embodiment, the electromagnetic flow meter of the present invention is not limited to the configuration of the above-described embodiment, but may be of the above-described embodiment. Electromagnetic flowmeters with various modifications and alterations from are also included in the scope of the present invention.

[0051]

As described above, according to the electromagnetic flowmeter of the present invention, the electromotive force detected during the movement of the fluid during each of the three excitation periods of the positive excitation, the non-excitation, and the negative excitation. Is calculated, the adhesion-influencing component can be detected, so that a self-diagnosis for examining the amount of the adhered insulating substance can be performed.

Further, by calculating the electromotive force detected during the movement of the fluid in each of the excitation periods of the binary excitation method of the positive excitation and the negative excitation at the first frequency and the second frequency, the adhesion influence component is calculated. Can be detected, so that a self-diagnosis can be performed to check the amount of the attached insulating substance.

[Brief description of the drawings]

FIG. 1 is a time chart of each signal handled by an electromagnetic flow meter according to a first embodiment of the present invention.

FIG. 2 is a flowchart of a preparation process executed by the electromagnetic flow meter of FIG. 1 before self-diagnosis.

FIG. 3 is a flowchart of a self-diagnosis process executed by the electromagnetic flow meter of FIG. 1;

FIG. 4 is a time chart of an exciting current showing an application example of the electromagnetic flow meter of FIG. 1;

FIG. 5 is a flowchart of a preparation process executed by the electromagnetic flow meter according to the second embodiment of the present invention.

6 is a time chart of each signal handled by the electromagnetic flow meter of FIG.

FIG. 7 is a flowchart of a main process executed by the electromagnetic flow meter after the preparation process of FIG. 5;

8 is a time chart of each signal handled by the electromagnetic flow meter that executes the main processing of FIG. 7;

FIG. 9 is a time chart of each signal handled by a conventional electromagnetic flow meter.

[Explanation of symbols]

 e Differential noise component n Adhesion effect component s Flow rate signal component a, b Ramp noise component

Claims (7)

[Claims] A magnetic field applying means for applying a magnetic field perpendicular to the moving direction of the conductive fluid moving in the pipe; and an electromotive force measuring means for measuring an electromotive force generated in the conductive fluid by the magnetic field. An electromagnetic flowmeter that performs ternary excitation in which the magnetic field applying means repeats positive excitation for generating a magnetic field in one direction, non-excitation for stopping the magnetic field, and negative excitation for generating a magnetic field in a direction opposite to the one direction. In the above, the electromotive force detected during the movement of the fluid in a state where the insulative deposit is not attached in advance by the electromotive force measuring means, An electromagnetic flowmeter, which calculates the amount of the insulating deposit attached to the electromagnetic flowmeter based on the following formula. 2. An electromotive force detected in a state in which the insulating substance is not attached includes a differential noise component and a flow signal component, and is measured by performing ternary excitation in a state in which the insulating substance is not attached. The electromagnetic flowmeter according to claim 1, wherein the differential noise component is obtained from the obtained electromotive force. 3. The electromotive force detected at the time of continuous non-excitation, positive excitation, non-excitation, negative excitation, and non-excitation in a state where the insulative deposit is not adhered is V ₁₁ , V ₁₂ , respectively. V _13, V
₁₄ and V ₁₅ , the differential noise component is calculated as V ₁₁ / 4−V _13/2 + V _15/4
3. The electromagnetic flow meter according to claim 2, wherein the flow rate is determined by: 4. An electromotive force detected at the time of continuous non-excitation, positive excitation, non-excitation, negative excitation, and non-excitation in a state where the insulating deposit is adhered, is V ₂₁ , V ₂₂ , respectively. V ₂₃ ,
Assuming that V ₂₄ and V ₂₅ , the adhesion-influencing component of the insulating deposit is (V ₂₁ / 4−V <sub>23/2)
+ V 25/4) - (</sub> V 11/4-V 13/2 + V 15/4) determined by an electromagnetic flowmeter according to claim 3. 5. A magnetic field applying means for applying a magnetic field perpendicular to the moving direction of a conductive fluid moving in a pipe, and an electromotive force measuring means for measuring an electromotive force generated in the conductive fluid by the magnetic field. An electromagnetic flowmeter that performs a binary excitation in which the magnetic field applying means repeats positive excitation for generating a magnetic field in one direction and negative excitation for generating a magnetic field in a direction opposite to the one direction; The first frequency during the movement of the conductive fluid, in a state where the insulating deposit is not attached beforehand,
And, at a second frequency lower than the first frequency, each electromotive force detected by repeating the binary excitation, and a state in which an insulating adhered substance is attached, while the conductive fluid is moving, At the first and second frequencies, based on the respective electromotive forces detected by repeating the binary excitation, the amount of the insulating deposit attached to the electromagnetic flowmeter is calculated. Electromagnetic flow meter. 6. In a state where the insulating deposit is not attached,
The electromotive force detected at the first frequency includes a differential noise component and a flow signal component, and the electromotive force detected at the second frequency includes a flow signal component. The electromagnetic flowmeter according to claim 5, wherein the component is determined. 7. An electromotive force detected at the first frequency in a state where the insulating deposit is attached, includes a differential noise component, a flow signal component, and an adhesion affecting component of the insulating deposit.
The electromagnetic flowmeter according to claim 6, wherein the electromotive force detected at the second frequency includes a flow signal component, and the differential noise component and the adhesion influence component are obtained based on the two electromotive forces.