JPS59122914A - Electromagnetic flowmeter - Google Patents

Abstract

PURPOSE:To find cleaning timing without removing the main body of a flowmeter, by separating a pair of electrodes from a signal conversion part, connecting the electrodes to a DC power source, applying DC power across said pair of the electrodes, and measuring the change in transient phenomenon. CONSTITUTION:When the presence or absence of attached material is detected by an electromagnetic flowmeter shown in the Figure, switches 32a-32c in a switching part 40 are switched to the sides of an attached material diagnosing part 50 from the flow rate measuring state shown in the Figure. At the same time, a clock signal is imparted to a hold circuit 61 and the attached material diagnosing part 50 from a clock signal source 62. As a result, a signal converting part 20 holds a value before DC power is applied. Meanwhile, a battery power source 31 is applied to a pair of electrodes 2a and 2b from a measuring part 17 of the attached material diagnosing part 50. A hold circuit 51 holds the signal voltage. After a specified period is elapsed, a second hold circuit 52 holds the signal voltage across the pair of the electrodes 2a and 2b. Based on both hold values and a preset value SV, attaching degree, i.e., the cleaning timing on the inner surface of a pipe to be measured is obtained.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention detects whether or not deposits that have a characteristic of changing the impedance between electrodes are attached to the inner surface of a measuring tube, and provides measures and instructions for removing the deposits. This article relates to an electromagnetic flowmeter that allows measures to be taken to compensate for the meter's indication.

[Technical background of the invention and its problems]

An electromagnetic flowmeter consists of a measuring tube with a pair of electrodes, an excitation coil that applies magnetic flux to the fluid flowing inside the measuring tube, and a signal output from the weight of the meter. It consists of a signal converter that converts the flow rate into the required signal and instructs the indicator as a flow rate signal.
If a deposit that has a characteristic of changing the impedance between the pair of electrodes adheres to the inner surface of the measuring tube, the indicated value of the indicator will differ from that of the flow meter. However, simply measuring the impedance between the electrodes cannot detect the presence of deposits on the surface of the electrodes, or deposits on the inner wall of the measurement tube that may cause a change in the impedance. Unable to check.

Conventionally, when the flowmeter's cutting edge is too small, the electromagnetic flowmeter is removed from the plant and checked.

However, when the diameter of the measurement tube of the electromagnetic flowmeter exceeds 1 m, the removal work is extremely difficult. In fact, there are only a few problems with output reduction found using this method.
This is a serious problem considering that the percentage is as high as 0%. Also,
On the other hand, if there were no abnormalities, significant man-hours associated with removal, etc., and damage due to plant stoppages would occur, and a solution to this problem was desired.

[Object of the Invention] The present invention is capable of detecting the presence or absence of deposits that change the impedance between electrodes on the inner surface of a measuring tube without stopping the fluid or removing the flow meter main body from the plant. To provide an electromagnetic flowmeter that enables prompt removal of deposits and indication compensation means of an indicator.

[Summary of the invention]

The present invention is an electromagnetic flowmeter that applies DC power between a pair of electrodes, detects the presence or absence of deposits that change the impedance between the electrodes from temporal changes in the transient phenomenon, and takes appropriate compensation. be.

[Embodiments of the invention]

In explaining the present invention in detail below, first, the schematic structure of an electromagnetic flowmeter including a flowmeter main body and a flowmeter main body will be explained with reference to FIGS. 1 to 7. The main body of the flowmeter can be schematically illustrated as shown in FIG. 1, except for the excitation coil. 1 in the diagram
is a measuring tube through which fluid flows, 2m and 2b are a pair of electrodes provided insulated from the measuring tube 1, and Jan3b is a pair of electrodes 2.
This is a signal output line that takes out the signal voltage between a and r 21). The measuring tube 1 may be, for example, a conductive conduit 1a with a lining 1b as shown in FIG. 2, or an insulating conduit 1c as shown in FIG.

In addition, as shown in FIG. 4, a pair of electrodes 2a, 2b are attached to the conductive conduit 1a via an insulator 4, and the conduit 1a near the pair of electrodes 2a, 2b and the pair of electrodes 2g, 2b. There is a configuration in which the potential distribution between potential electrodes 5a and 5b in contact with the outer surface is amplified by operational amplifiers 6a and 6b, respectively, and applied to the outer surface of the conduit 1a by the current supply electrodes 7... The tube shown in FIG. 4 has the same function as a measuring tube with an insulating wall (lining) by providing a potential distribution to the conductive tube 1a. 2o is a signal converter having a differential amplifier 21;

Next, FIGS. 5 to 7 show a schematic configuration and its equivalent circuit when the signal voltage is considered. First, when a magnetic flux generator (not shown) applies magnetic flux in a direction perpendicular to the line connecting the pair of electrodes 2a and 2bf and the fluid flow direction as shown in FIG. 5(,), the magnetic flux as shown in FIG. 5(b) is applied. It can be expressed by an equivalent circuit. In the figure, 10 indicates a signal (including noise) according to the flow rate, and 1 indicates fluid resistance. 6th
In Figure (a), the ground wire 3e is taken out of the measuring tube 1 and introduced into the signal converter 20 together with the signal output lines 3a + 3b, and its equivalent circuit is shown in Figure (b).

In the figure, 10a and 10b are signals corresponding to the flow rate between the measuring tube 1 and each electrode 2a and 2b, and ll&+11b is a fluid resistance.

FIG. 7 shows a specific example where the ground point 13 of the ground wire 3e is brought into contact with the fluid 14.

Next, the detection principle and its equivalent circuit when a deposit that changes the interelectrode impedance is attached to the measuring tube 1 will be explained with reference to FIGS. 8 to 12. The electromagnetic flowmeter of the present invention detects the presence or absence of deposits in the measuring tube by applying DC power between both electrodes, and one of its basic configurations is as shown in FIG. It is.

FIG. 8 shows first and second switches 32a that operate in conjunction to manually or automatically switch and select the signal converter 20 and battery power source 31 at the ends of the signal take-out lines Ja, 9b;
32bf is provided, and the first and second switches 32a are provided during actual flow rate measurement.

32b is connected to the signal converter 20 side, and when checking whether conductive or insulating deposits 15 are attached to the inside of the measuring tube 1, it is connected to the battery power source (DC power source) 30 side. After DC power is applied between the pair of electrodes, the magnitude of the current output from the pair of electrodes 2a, 2b or the temporal change in the magnitude of the current is observed using, for example, a voltmeter 33. When detecting this deposit 15, the third switch 31c is activated to connect a required resistor 3 between the input terminals of the signal converter 20.
Insert 4.

FIG. 9 is a diagram showing the same principle configuration, in which a battery power source 3 is connected to signal take-out lines Ja and 3b via a switch 32.
1 is inserted, and a signal output line 3a is inserted in the signal converter 20.

Coupling capacitor 32a at each output terminal of 3b.

32b is provided. In this case, when the switch 31 is closed, DC power is applied between the pair of electrodes from the battery power source 31, and the DC power from the battery power source 31 is supplied to the coupling capacitor 32a.

32b, it does not affect the signal converter 20 in any way. Then, by opening the switch 31 after applying DC power between the pair of electrodes, it is possible to extract signal changes between the pair of electrodes 2ae2b.

Further, FIG. 10 is a diagram similarly showing the principle configuration,
When measuring the flow rate, a signal corresponding to the flow rate obtained by the pair of electrodes 2a and 2b is directly supplied to the signal converter 20, and when detecting the presence or absence of deposits 15, the switch 32a,
32b and wait for the pair of electrodes 2h and 2bf, insert the measuring tube 1 into one side of the bridge circuit 16,
a, 2. The measurement unit 17 measures the change in impedance between
You can also measure it as follows. z1 to z3 are known impedances, and 31 is a battery power source.

FIG. 11 is an equivalent circuit diagram based on the principle configuration shown in FIGS. 8 to 10. In the figure, Ro is a pair of electrodes 2 a
*Resistance between 2b and the conductive reef body, R2 is the resistance between both electrodes 2a and 2b of the conductive fluid, and R3 is the resistance between the pair of electrodes 2a on the inner surface of the measuring tube 1.

This is a short resistor that shorts between 2b.

1l-i3 is the current flowing through the circuit. C is a capacitor.

FIG. 12 is a diagram showing an impedance measurement circuit,
17a is an indicator of the measuring section 17.

The reason why the capacitor C is connected to the resistor R2 in FIGS. 11 and 12 is as follows. Now, if we consider electrochemically, the water in the conductive liquid is ionized and R20
→H” + OH.Now, the battery power source E
When voltage is applied from b to both electrodes 2a and 2b, a large amount of e- is supplied from E to one electrode, resulting in 2+2C-+H2, and countless microbubbles of R2 adhere to the electrode surface, and current no longer flows. . So-called polarization occurs.

Next, when the polarity of the battery power source E is changed and the voltage is reapplied, the current flows well and eventually functions as a so-called capacitor C which becomes polarized.

The present invention was discovered through the following specific phenomenon. When I was measuring the flow rate of wastewater containing metal hydroxides and oxides using an electromagnetic flowmeter with a measuring tube 1 as shown in Figure 2, I noticed that the indicated value gradually decreased to about the same level over a period of about one year. I went down to When the resistance between both electrodes 2a + 2b was measured with a commercially available tester, the resistance between both electrodes 2a and 2b was measured with a stable indication like a normal fixed resistance. After cleaning the inside of the measuring tube 1, the resistance between the electrodes 2a*2b was measured and showed 2 Ω, which rose to 6 Ω after a few seconds, and the speed of indication change became slow. When the polarity of the battery power supply Eb was reversed, the indication rapidly decreased below 2Ω, and after a few seconds, the indication changed slowly to 6Ω and up to 9. From this, in the case of FIGS. 2 and 3, if the conductive deposit 15 is attached, the fluctuation of the indication becomes slow (the time constant is large) and the width of the indication change becomes small. Since capacitor C is given a small amount of air for a long time and is photoelectrically charged to the capacitor, charging is completed while the range of change in the tester's indication is small, and even in the case of electrochemical polarization, the range of change in indication is small for a long time. to complete polarization.

From this, in order to know the presence or absence of deposits 15 and the timing of cleaning the inner surface of the measuring tube 1, it is necessary to check the changes in electrical specifications (especially transient phenomena) shown in FIG. It can be known by changes etc.

Therefore, the following can be understood from FIGS. 1 to 12. When deposits 15 adhere to the inner surface of the measuring tube 1, both electrodes 2a.

The impedance between 2b changes and direct current power is transferred to both electrodes 2.
The magnitude of the current flowing when applied between m and 2b changes over time. From this temporal change, the presence or absence of deposits 15 and, in turn, the timing of cleaning the inside of the measuring tube can be known.

For example, when a conductive deposit 15 adheres to the inner surface of the measuring tube 1 shown in FIGS. 2 and 3, the resistances R1 and Rs (generally Rs>R1) shown in the equivalent circuit of FIG. 11 change significantly. In the example shown in FIG. 4, if the conductivity of the conductive conduit 1a is different, even if the conductive conduit 1a has a conductive deposit, the insulating deposit 1
5, the resistance R3 changes.

Next, in the CR series/parallel circuit of the equivalent circuit in Figure 6, 1=
Find the current flowing through the circuit when DC power is applied to 0,
Calculate the time constant. However, it is assumed that there is no residual charge in the capacitor.

RI L1+R3is = E...song...song□song (sR2,2+bow j2dt=R・2・ (2)
11=i2+i3 ・・・・・・・・・
・・・・・・・・・−(3)(1), From equation (3), i
Eliminating s (J +Rs)jx R312=B
・If you delete is from equations (4) (2) and (3), ° hi(R2+R3) zz+2 dt R311=0 ・
・・・・・・(5) C (4) If il is deleted from equation (5), here, a
=RIR2+R2R3+RsRII Q2 is a charge and K is a constant.

Since the initial condition 1=0 and q==Q, from equation (2), the time constant T becomes. When we insert the measurement results into this formula, we find that deposits 15
The adhesion tendency is clearly visible.

Next, first to third embodiments of the present invention will be described. FIG. 13 is a diagram showing a first embodiment of the electromagnetic flow meter according to the present invention, in which 40 denotes signal output lines Ja, 3b.
is connected to the signal converter 2° and the deposit diagnosis unit 5o, and the deposit diagnosis unit 5o detects changes in the specifications shown in FIG. 11 and FIG. A foot measuring section 17 for measurement and a pair of electrodes 2a.

Electrical specifications when DC power is applied between 2b and i'> t=n1 For example, the first hold circuit 5 holds the voltage between signal take-out lines 3a and 3b, and the predetermined time after applying DC power. Electrical specifications after 2 lapses of t = n For example, the difference between the hold values of the second hold circuit 52 that holds the voltage between the signal output lines 9a and 3b and both hold circuits 51 and 52, and the predetermined set value SV. Compare the deposits 15
and a comparator 53 that outputs a signal S1 indicating the degree of adhesion and the timing of cleaning the inner surface of the measuring tube. In the figure, 6 is a signal hold circuit, and 62 is a clock signal source.

When detecting the presence or absence of deposits 15 in the electromagnetic flowmeter shown in FIG. Switch by means. When switching the switches 138 to 13cf, the clock signal source 62
A clock signal is given to the hold circuit 6 and the deposit diagnosis unit 50 from the hold circuit 6 . As a result, the signal conversion section 20 holds the value before applying DC power, while the deposit diagnosis section 5
The battery power supply 31 is connected to the pair of electrodes 2a, 2 from the measurement unit 17 of
b. Immediately or after a certain period of time has elapsed after this battery power supply 31 is applied, the first hold circuit 51 holds the signal voltage between the pair of electrodes 2a r 2 b, and after a predetermined period of time after this holding, the second hold circuit 52 The signal voltage between the pair of electrodes 2a and 2b' is held. Then, the degree of adhesion and the timing for cleaning the inner surface of the measuring tube are obtained from both hold values and the set value SV.

Next, FIG. 14 is a diagram showing a second embodiment of the electromagnetic flowmeter according to the present invention. This is achieved by providing a switch circuit 19 between the excitation coil 18a and the excitation power supply 18b, and
During measurement, the excitation current is completely cut off by a signal from the clock signal source 62. With this configuration, the first
Compared to Figure 3, the measurement accuracy can be improved.

Next, FIG. 15 is a diagram showing a third embodiment of the electromagnetic flowmeter according to the present invention. In this case, the compensation circuit 23 is connected to the signal conversion section 20, and the output of the deposit diagnosis section 50 is transferred to the compensation circuit 23.
This is to input and compensate. Therefore, the compensation circuit 23 compensates for the decrease in the output signal due to the deposit 15 with the output S1 of the deposit diagnosis section 50, and outputs the correct flow rate value Sz'c.

Note that the present invention is not limited to the above embodiments.

Although the above embodiment was applied to an example using two electrodes 2a and 2b, it can be similarly applied to an example using multiple electrodes. Further, a flow rate change monitoring circuit having a timer is provided on the output side of the signal converting section 2o, and this monitoring circuit detects when the flow rate is stable in cycles or months and gives a deposit detection command to the clock signal source 62. You can do it like this. Furthermore, when the deposit 15 is detected, a check signal may be input to the input terminal of the signal converter 20 to diagnose the converter 20. In addition, the present invention can be implemented with various modifications without departing from the gist thereof.

〔Effect of the invention〕

As described in detail above, according to the present invention, a pair of electrodes is disconnected from the signal converter and connected to a DC power source, and DC power is applied between the pair of electrodes, and from the change in the transient phenomenon, the measurement tube is Since it is possible to know the degree of deposits on the inner surface of the measuring tube and the timing for cleaning the inside of the measuring tube, it is possible to know the presence or absence of deposits and the timing for cleaning without stopping the fluid or removing the flow meter body from the sensor. be able to.

We also provide an electromagnetic flowmeter that can request measures such as water or chemical cleaning from the cleaning nozzle, addition of all compensation elements, adhesion removal measures, indication compensation measures, etc., depending on the degree of adhesion. can.

[Brief explanation of the drawing]

Figures 1 to 4 are diagrams showing the configuration of the measuring tube, Figure 5
Figures 7 to 7 are block diagrams and equivalent circuit diagrams when all signal voltages are considered, Figures 8 to 10 are diagrams showing the principle configuration for detecting deposits, and Figure 11 is the principle configuration. The equivalent circuit diagram, FIG. 12 is a configuration diagram of the measurement circuit, and FIGS. 13 to 15 are the first diagrams of the electromagnetic flowmeter according to the present invention.
It is a block diagram which shows the 3rd Example. 1...Measurement tube, 2a8, 2b...--pair electrode, 3
a. 3b...Signal take-out line, 18a...Exciting coil, 18
b... Excitation power supply, 19... Switch circuit, 20...
・Signal converter, 32a to 32c...switch, 40・
...Switching unit, 50...Adherence diagnostic unit, 62...Clock signal source. Applicant's representative Patent attorney Takehiko Suzue Figure 9, Figure 9, Figure 11, Figure 10, Figure 121* Commissioner of the Patent Office Kazuo Wakasa 1. Indication of the case Japanese Patent Application No. 57-233508 2, Name of the invention Electromagnetic flowmeter 3, Person making the amendment Relationship to the case Patent applicant (307) Higashi 5J Shiba Yudenki Co., Ltd. 4, Agent

Claims (3)

[Claims] (1) A flowmeter main body that applies a magnetic flux to the fluid flowing in the measuring tube and extracts a signal proportional to the fluid flow velocity using at least one pair of electrodes, and a flowmeter main body that extracts a signal proportional to the flow velocity of the fluid through at least one pair of electrodes, and a In an electromagnetic flowmeter having a signal conversion section that converts into a signal, the electrode is provided between the pair of electrodes and the signal conversion section, and the electrode is normally connected to the signal conversion section side;
a switching unit that disconnects from the signal converting unit when detecting deposits in the measurement tube; a DC power supply that applies DC power to the pair of electrodes that are connected by disconnecting from the signal converting unit by the switching unit; 1. An electromagnetic flowmeter comprising: a deposit diagnosis means for determining the state of deposits from changes in signals obtained between a pair of electromagnetic poles by applying power to the pair of electrodes. (2) The deposit diagnosis means holds two 12 signals output from a pair of electrodes during a certain period of time, and determines the adhesion state of deposits from the hold difference and set value. An electromagnetic flowmeter according to claim 1. (3) The electromagnetic flowmeter according to claim 1, wherein the supply of magnetic flux to the measuring tube is cut off when a deposit is detected.