JPH0862005A - Electromagnetic flow meter - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an electromagnetic flow meter capable of detecting the water level of a liquid in a pipeline stepwise. In an electromagnetic flowmeter, two or more insulating layers and conductive layers are alternately arranged in a radial pattern, and a pair of earth rings are provided at both ends of the conduit so that the insulating layers and the conductive layers face each other. A first multiplexer having a terminal connected to each of the conductive layers of one of the pair of ground rings, and a second multiplexer having a terminal connected to each of the conductive layers of the other ground ring of the pair of ground rings. The multiplexer and the first and second multiplexers are provided with liquid contact detection means for detecting the presence or absence of liquid contact of the conductive layers when the conductive layers facing each other at both ends of the conduit are sequentially and substantially simultaneously selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an electromagnetic flow meter, and more particularly to an electromagnetic flow meter capable of stepwise detecting a non-full state of a fluid in a pipe of an electromagnetic flow meter transmitter.

[0002]

2. Description of the Related Art Generally, when fluid is transported using a pump or the like for batch control, the inside of the pipe may become empty when the pump is stopped depending on the condition of the pipe. In such a case, there is a problem that an error occurs in the output value of the electromagnetic flow meter.

FIGS. 3, 4, and 5 are configuration diagrams showing a conventional example in which empty piping is detected. FIG. 3 is a side view showing a piping state of a general detector, 1 is a detector, 2 is an earth ring connected to a flange of the detector, and 4 is a pipe flange fixed to a pipe 5. The earth ring 2 is generally provided to block noise voltage coming from the pipe, and its structure is as shown in FIG.

FIG. 4 is a cross section of the ground electrode 2 shown in FIG. 3 in which the inner surface of the donut-shaped metal disk 201 is covered with a corrosion-resistant insulating member 202 such as Teflon, and a grounding electrode 6 is provided for the purpose of grounding. It is a figure. The grounding electrode 6 is an electrode supporting portion including a liquid contacting portion 601 that comes into contact with the liquid to be measured, a connecting rod 602 inserted into a hole provided in the metal disc 201 to support the liquid contacting portion 601, and insulating sleeves 603 and 604. When,
It is composed of a screw portion 605 for fixing this portion to the metal disc 201.

FIG. 5 is a cross-sectional view showing an example of an earth ring provided with a sky detection electrode. In the figure, two ground electrodes 6 are provided. Reference numerals 7 and 8 are empty detection electrodes, and the electrode 8 is arranged at the lowermost end of the metal disk 201, and the electrode 7 is arranged at a distance (angle θ) from the electrode 8. The structure of these electrodes is the same as the grounding electrode shown in FIG. A power source 9 is connected between the electrodes 7 and 8, and an exciting coil 10a of a relay 10 surrounded by a dotted line is inserted in this circuit. 11 is a bell, 12 and 1
Reference numeral 3 is a connection terminal.

According to the above configuration, the sky detection electrodes 7, 8
Is short-circuited with the liquid to be measured when the measured liquid F is filled in the pipe, but when the pump is stopped and the pipe is emptied, the water level in the pipe is changed according to the state of the pipe. Is determined, the sky detection can be performed by providing the sky detection electrode at a position corresponding thereto.

[0007]

By the way, the conventional sky detecting means has a problem that it is not possible to know how much the liquid level in the conduit is, since there is only one pair of detecting electrodes. An object of the present invention is to provide an electromagnetic flow meter capable of detecting the amount of liquid in a conduit stepwise by combining two or more detection electrodes and a multiplexer.

[0008]

In order to achieve this object, according to the present invention, in claim 1, a pair of exciting coils for generating a magnetic field in a direction perpendicular to a fluid flowing through a pipe, and the magnetic field. A pair of detection electrodes which are arranged on the pipe wall of the pipe line in a direction orthogonal to the direction and which detect electromotive force generated corresponding to the flow rate of the fluid, and a flow rate which calculates the flow rate based on a signal from the detection electrodes. In an electromagnetic flowmeter having a signal detection circuit, a pair of earths in which two or more insulating layers and conductive layers are alternately arranged in a radial pattern and the insulating layers and conductive layers are provided at opposite ends of the conduit so as to face each other. A ring, a first multiplexer having a terminal connected to each of the conductive layers of one of the pair of ground rings, and a terminal connected to each of the conductive layers of the other ground ring of the pair of ground rings. A second multiplexer, said first,
The second multiplexer is provided with a liquid contact detection means for detecting the presence or absence of liquid contact with the conductive layers when the conductive layers facing each other at both ends of the conduit are sequentially and substantially simultaneously selected. In the item 2, the liquid contact detection means for detecting the presence or absence of liquid contact of the conductive layer includes a voltage application means for applying a voltage to the conductive layer via the first and second multiplexers, and a voltage application means. It is characterized by comprising a voltage detection resistor connected in parallel to the conductive layer, and a voltage detection means for detecting a voltage generated in the voltage detection resistor. The liquid contact detection means for detecting the presence or absence of liquid contact in the conductive layer includes the first and second multiplexers having terminals connected to the conductive layers of the pair of earth rings and a common terminal grounded, and the detection electrodes. The signal of Is characterized in that it has and a commercial frequency detecting means for detecting a commercial frequency component included in the signal by Toki.

[0009]

In the above construction, when the pipelines are full, when the first and second multiplexers sequentially select the conductive layers facing each other at both ends of the pipelines simultaneously, the liquid contact detection means detects all the conductive layers. Detects that it is in contact with liquid. In the case of non-full water, the liquid contact detection means detects that part or all of the conductive layers are not in contact with liquid. In the second aspect, when the conduit is full, all the liquid contact electrodes are in contact with the opposite liquid contact electrodes through the fluid, so that the current flows to the fluid side. Therefore, the resistance between the liquid contact electrodes becomes zero, and when the opposing liquid contact electrodes are swept by the multiplexer, no current flows through the voltage detection resistor at any position (conductive layer), and the output of the voltage detection means becomes zero. When the conduit is not full and some of the wetted electrode pairs are not wetted and other wetted electrodes are wetted, the resistance value of the voltage detection resistor is detected when the multiplexer selects the wetted electrode. To be done. In claim 3, when the pipeline is full, all the conductive layers of the earth rings provided at both ends of the pipeline are grounded via the common terminal of the multiplexer, so piping (not shown)
Noise from the side (mainly commercial frequency component) does not enter the detection electrode side. When the conduit is not filled with water and some of the wetted electrode pairs are not wetted and other wetted electrodes are wetted, the conductive layer is not grounded when the multiplexer selects the wetted electrode. Therefore, the commercial frequency is mixed into the detection electrode. The commercial frequency detection means detects the commercial frequency to detect that the water is not full. Hereinafter, detailed description will be given based on examples.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of the essential structure of an embodiment of the present invention, in which an exciting coil, a housing and the like are omitted. In the figure, 30 is a conduit through which a measurement fluid flows, 31 is a flow rate detection electrode, and 32 is a flow rate signal detection circuit. Reference numeral 33 is an earth ring having flanges 30a formed at both ends of the pipeline and an insulating layer 33a and a conductive layer 33b sandwiched between mating pipes (not shown in the figure). For example, gold, platinum, copper, A conductive metal such as aluminum is radially formed at predetermined intervals by vapor deposition, sputtering, or the like. The ground rings at both ends are attached so that the conductive layers a and a ', b and b', c and c'are facing each other.
Here, 8 conductive layers are arranged in a radial pattern with the chi and chi 'points at the top.
It is formed in equal parts.

Numerals 34a and 34b are multiplexers, and terminals a and a'are conductive layers a and a'of earth rings b and b '.
Conductive layers b and b'are connected to c, and conductive layers c and c'are connected to c'corresponding to the number of conductive layers, respectively, and common terminals X and Y of the two multiplexers are opposite conductive layers. Sweep all conductive layers within a predetermined time so that they are selected by shifting for a short time (Note that staggering the selection of conductive layers for a short time results in non-grounding during switching when the multiplexers switch at the same time. This is to prevent the non-grounding). Dummy resistors R ₁ and R ₂ are connected in series between the common terminals X and Y with a voltage detection resistor R ₃ of several tens of MΩ interposed therebetween.

Reference numeral 35 is a common terminal X, Y of the multiplexer.
Is a constant current circuit that supplies a constant current via a sine wave having a frequency 10 times higher than the exciting current. Reference numeral 36 is a voltage detection means including buffer amplifiers 36a and 36b, a differential amplifier 36c, a detection circuit 36d, an A / D converter 36e and the like connected to both ends of the voltage detection resistor R ₃ .

In the above structure, the flow rate of the measuring fluid is detected by the flow rate detecting electrode 31 and the flow rate signal detecting circuit 32 by a known means. The conductive layer 33b of the earth ring is connected to the constant current circuit 35 by the multiplexer 34a,
Current is supplied through 34b. If the fluid flowing in the conduit is full, the opposite conductive layers are connected via the fluid, so that the conductivity of the measurement fluid is 5 μS, for example.
/ Cm, the resistance between the conductive layers is about 1 MΩ, and the current flowing through the resistors R ₁ , R ₂ , and R ₃ connected in parallel is extremely small. Therefore, the output of the voltage detecting means becomes a value close to zero.

Next, when the flow rate flowing through the pipeline decreases and a portion where no fluid exists in the pipeline, the resistance of the conductive layer located at the uppermost portion (conductive layer indicated by chi, chi 'in the figure) becomes infinite. Since it becomes large, the current flows to the resistors R ₁ , R ₂ and R ₃ side. Voltage Voltage sensing means 36 is generated across the resistor R ₃ (R ₃ · i ...
i = constant current value) is detected. Further, if the water level in the conduit decreases and becomes lower than the conductive layers a, b ', and t', the resistance R ₃ is selected when three pairs of conductive layers are selected, including the conductive layers indicated by d and d '. Voltage is generated.

Next, another embodiment of the present invention will be described with reference to FIG. In FIG. 2, 30 is a conduit through which the measurement fluid flows, 31 is a flow rate detection electrode, and a buffer amplifier 30b is connected to this electrode. 30c is a buffer amplifier 30
This is a differential amplifier to which the output of b is input, and the output of this differential amplifier 30c is input to a known signal detection circuit 32 to obtain a signal corresponding to the flow rate. 33 is 8 as in FIG.
Each of the conductive layers is a ground ring that is arranged equidistantly on the apex.

34a and 34b are multiplexers, and terminals a and a'are conductive layers a and a'of earth rings b and b '.
Conductive layers b and b'are connected to c, and conductive layers c and c'are connected to c'corresponding to the number of conductive layers, respectively, and common terminals X and Y of the two multiplexers are opposite conductive layers. Are simultaneously selected and all the conductive layers are swept within a predetermined time. The common terminals X and Y are grounded.

Reference numeral 40 denotes a commercial frequency detecting means for branching the output of the differential amplifier 30c and inputting it to detect the commercial frequency contained in the flow rate signal component. The commercial frequency bandpass filter 40a inputs its output and amplifies it. It is composed of an amplifier 40b, a clear circuit 40c for inputting and rectifying its output, and a low-pass filter 40d.

In the above structure, the flow rate of the measurement fluid is detected by the known means of the flow rate detection electrode 31 and the flow rate signal detection circuit 32. At the same time, the commercial frequency detecting means 40 branches the output of the differential amplifier 30c and inputs it to detect the commercial frequency contained in the flow rate signal component. If the fluid flowing in the pipeline is full, the common terminal of the multiplexer is grounded through the common terminal regardless of which conductive layer (eg, chi, chi ') is selected, so the commercial frequency from the piping side The noise is short-circuited and the output of the commercial frequency detecting means 40 becomes zero.

Next, when the flow rate in the pipeline decreases and a portion where no fluid exists in the pipeline, the multiplexer selects the conductive layer located at the top (the conductive layer indicated by chi, chi 'in the figure). At this time, the commercial frequency noise from the piping side is not short-circuited, so that it is superimposed on the detection electrode and output. Therefore, an output signal appears in the commercial frequency detecting means 40. When the water level further decreases and, for example, the conductive layers (i), (i) and (t) are exposed, the ground of the terminal of the multiplexer connected thereto is not short-circuited via the common terminal, so that the commercial frequency detecting means 40 is provided. The output signal appears.

In the conventional example and the configuration of FIG. 1, since a current is passed through the liquid through the empty detection electrode (conductive layer), metal ions are eluted from the electrode and the chemical properties of the process fluid are changed. However, in the embodiment of FIG. 2, empty detection can be performed without passing an electric current through the liquid.

According to the configurations shown in FIGS. 1 and 2, eight conductive layers are radially formed on the ground rings on both sides, and these conductive layers are arranged to face each other. Therefore, the multiplexer sweeps these conductive layers. By doing so, the water level of the fluid in the pipe can be detected. The number of conductive layers is not limited to this embodiment, and the more the conductive layers are, the finer the water level can be detected. In the configuration of FIG. 1, the function as an earth ring can be satisfied by grounding the common terminal of the multiplexer on one side.

[0022]

As described above, according to the present invention, in an electromagnetic flowmeter, two or more insulating layers and conductive layers are alternately arranged in a radial pattern, and the insulating layers and conductive layers are provided at both ends of the conduit. A pair of grounding rings provided so as to face each other; a first multiplexer having terminals connected to the respective conductive layers of one grounding ring of the pair of grounding rings; and the other grounding ring of the pair of grounding rings. When the second multiplexer having a terminal connected to each of the conductive layers and the conductive layers facing each other at both ends of the conduit are sequentially and substantially simultaneously selected by the first and second multiplexers, the presence or absence of liquid contact with the conductive layer is determined. Since it is equipped with liquid contact detection means for detection,
It is possible to realize an electromagnetic flow meter that can detect the water level of a liquid in a pipeline stepwise.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 3 is an explanatory diagram of a configuration of a conventional example that is generally used in the past.

FIG. 4 is a cross-sectional view of an earth ring that has been commonly used in the past.

5 is a cross-sectional view showing the structure of sky detection means using the earth ring shown in FIG.

[Explanation of symbols]

 30 ... Pipeline 31 ... Flow rate detecting electrode 32 ... Flow rate signal detecting circuit 33 ... Earth ring 33a ... Insulating layer 33b ... Conductive layer 34 ... Multiplexer 35 ... Constant current circuit 36 ... Voltage detecting means 40 ... Commercial frequency detecting means

Claims (3)

[Claims] 1. A pair of exciting coils for generating a magnetic field in a direction perpendicular to a fluid flowing in a pipe, and a pair of exciting coils arranged on a pipe wall of the pipe in a direction perpendicular to the magnetic field and corresponding to a flow rate of the fluid. In an electromagnetic flowmeter having a pair of detection electrodes for detecting an electromotive force generated and a flow rate signal detection circuit for calculating a flow rate based on a signal from the detection electrodes, two or more insulating layers and conductive layers are alternately arranged in a radial pattern. A terminal is connected to each of a pair of grounding rings arranged at both ends of the conduit so that the insulating layer and the conductive layer face each other, and a conductive layer of one of the grounding rings of the pair of grounding rings. The first multiplexer, the second multiplexer having terminals connected to the conductive layers of the other earth ring of the pair of earth rings, and the first and second multiplexers paired at both ends of the conduit. An electromagnetic flowmeter, comprising: a liquid contact detection means for detecting the presence or absence of liquid contact of the conductive layers when the conductive layers facing each other are sequentially and substantially simultaneously selected. 2. The liquid contact detection means for detecting the presence or absence of liquid contact of the conductive layer includes voltage application means for applying a voltage to the conductive layer via the first and second multiplexers, and the voltage application means. The electromagnetic flowmeter according to claim 1, further comprising a voltage detection resistor connected in parallel to the conductive layer, and a voltage detection unit that detects a voltage generated in the voltage detection resistor. 3. The liquid contact detection means for detecting the presence or absence of liquid contact with the conductive layer, wherein the first and second multiplexers have terminals connected to the conductive layers of the pair of earth rings and a common terminal grounded. 2. An electromagnetic flowmeter according to claim 1, further comprising: a commercial frequency detecting unit that branches a signal from the detection electrode to detect a commercial frequency component included in the signal.