JP2003090749A - Electromagnetic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an accurate flowmeter measurement result by removing the influence of electric resistance in an electric cable for connecting a measurement unit and a control unit. SOLUTION: The electromagnetic flowmeter comprises a measurement unit 20 including a detector 21 for allowing fluid to be measured to flow in a magnetic field that is generated by an excitation coil 26 and for generating a voltage corresponding to the flow rate of the fluid, and a voltage-current conversion circuit 22 for converting the voltage to a corresponding current for outputting, and a control unit 40 that includes an excitation circuit 41 for supplying an excitation current to the excitation coil 26 and an operation means 43 for calculating the flow rate of the fluid to be measured based on the output current of the voltage-current conversion circuit 22, and is connected to the measurement unit 20 via an electric cable 32.

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 for measuring the flow rate of liquid.

[0002]

2. Description of the Related Art In a rotary type beverage filling machine, in order to fill an appropriate amount of beverage into a container (glass bottle, PET bottle, etc.), the flow rate of the beverage to be filled is measured by a flow meter,
The filling amount of the beverage in the container is controlled. An electromagnetic flow meter that electromagnetically measures the flow rate is suitable as the flow meter. This electromagnetic flowmeter has a measurement unit arranged at the detection site. This measuring unit includes a detection tube through which a beverage flows, a pair of electrodes arranged so as to face each other with a flow path of the detection tube interposed therebetween, and 90 ° in the circumferential direction of the detection tube from each of the electrodes.
And a pair of electromagnetic coils arranged opposite each other at a shifted position.

When each electromagnetic coil of this measuring unit is excited by a sine wave or rectangular wave excitation signal, a voltage corresponding to the fluid velocity and the magnetic field strength is generated between the electrodes based on the so-called Faraday's law of electromagnetic induction. . Therefore,
The flow rate of the beverage flowing through the detection tube can be calculated based on the voltage generated between the electrodes, and the filling amount of the beverage in the container can be known by integrating the flow rate.

[0004]

When the flow rate is detected using the measuring unit, an exciting current is supplied to the exciting coil, and the flow rate and filling of the beverage are based on the voltage output from the electrode. A control unit for calculating the quantity is connected to the measuring unit. However, in the beverage filling machine in which a large number of the measuring units are arranged in close proximity,
From the standpoint of space, it is difficult to provide the control unit near the corresponding measurement unit. Therefore, the control unit is disposed at a site distant from the measurement unit, and these are elongated (for example, They are connected by an electric cable of several meters).

Since the electric cable is laid in a narrow place, it is required to have a wire diameter as small as possible in order to facilitate the wiring work. However, a cable with a small wire diameter is affected by noise. Easy to receive and high in electrical resistance.
For this reason, conventionally, there has been a problem that an accurate flow rate measurement result cannot be obtained with a cable having a small wire diameter due to the influence of the electric resistance of the electric cable.

In view of such a situation, an object of the present invention is to
It is an object of the present invention to provide an electromagnetic flow meter capable of obtaining an accurate flow rate measurement result by removing the influence of the electric resistance of an electric cable connecting a measurement unit and a control unit.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a detector for causing a fluid to be measured to flow in a magnetic field generated by an exciting coil to generate a voltage corresponding to the flow velocity of the fluid, and the voltage to a corresponding current. A flow rate of the fluid to be measured is calculated based on a measuring unit including a voltage-current conversion circuit for converting and outputting, an exciting circuit for supplying an exciting current to the exciting coil, and an output current of the voltage-current converting circuit. And a control unit that includes a computing unit and is connected to the measuring unit via an electric cable.

In an embodiment of the present invention, the measurement unit is provided with a temperature detector for detecting the ambient temperature of the voltage-current conversion circuit, and the arithmetic means of the control unit is provided with an ambient temperature of the voltage-current conversion circuit. Correction means for correcting the conversion error due to the change of the temperature based on the temperature detected by the temperature detector.

In the embodiment of the present invention, the housing of the measuring unit is made of austenite ferrite stainless steel, and the opening of the housing is made of the austenite ferrite stainless steel or the inner surface side is made of a material having high magnetic permeability. The outer surface side is covered with a lid formed of austenitic stainless steel.

In the embodiment of the present invention, the coil exciting circuit switches a constant current circuit whose setting of a constant current value can be changed based on a command signal from the outside, and a constant current output from the constant current circuit. And a switching circuit for supplying the exciting coil to the exciting coil.

In an embodiment of the invention, the control unit comprises wireless communication means.

According to an embodiment of the present invention, the control unit is configured to generate a valve closing signal for stopping the flow of the fluid to be measured when the flow rate is integrated and the integrated flow rate value reaches a predetermined value. ing.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an electromagnetic flow meter according to the present invention will be described below with reference to the drawings. Figure 1
FIG. 1 shows an example of the configuration of a rotary beverage filling machine to which the electromagnetic flow meter according to the present invention is applied.

This rotary beverage filling machine comprises a filling liquid tank 1 which is open to the atmosphere. This tank 1
Is partitioned into an upstream chamber 1A and a downstream chamber 1B by a partition plate 1C whose upper end portion constitutes a weir. Upstream room 1A
Is connected to a liquid storage tank (not shown) via a supply pipe 2, and one end of a discharge pipe 3 is connected to the bottom of the downstream chamber 1B. The partition plate 1C has a through hole that connects the upstream chamber 1A and the downstream chamber 1B, and the pump 4 is provided in this through hole. The pump 4 is driven by a motor 5 provided outside the tank 1.

The beverage (filling liquid) stored in a liquid storage tank (not shown) is supplied to the upstream chamber 1A of the filling liquid tank 1 via the supply pipe 2 and the flow rate adjusting valve 6. The upstream chamber 1A is provided with a float 7 that moves up and down together with the liquid surface, and liquid level sensors 8 and 9 that detect the height of a detection member that extends upward from the float 7. Control device 10
Controls the flow rate adjusting valve 6 provided in the supply pipe 2 based on the detection signals of the liquid level sensors 8 and 9 so that the liquid level in the upstream chamber 1A of the tank 1 is higher than the suction port of the pump 4. To do. Further, the control device 10 drives the pump motor 5 to constantly send the liquid in the upstream chamber 1A of the tank 1 to the downstream chamber 1B. Thereby, the downstream chamber 1
The liquid in B overflows from the weir of the partition plate 1C into the upstream chamber 1A, and the liquid level in the tank downstream chamber 1B, that is,
The upper limit height of the filling hydraulic head is kept constant.

It should be noted that by the pump 4, the tank upstream chamber 1
When the flow rate of the beverage fed from the A to the tank downstream side chamber 1B Q _1N, the flow rate of the beverage to be discharged from the tank downstream side chamber 1B to the discharge piping 3 and Q _OUT, when the state of the Q _1N> Q _OUT is satisfied Then, the liquid overflows from the weir of the partition plate 1C.

The discharge pipe 3 having one end connected to the tank downstream chamber 1B has the other end connected to the fixed portion 11A of the rotary joint 11. Rotary joint 1
1, the rotating portion 11B is connected to the center vertical portion of the rotary pipe 12, and the slip ring 13 is provided between the fixed portion 11A and the rotating portion 11B. A flow rate adjusting valve 15 driven by a motor with an encoder 14 is provided in the middle of the discharge pipe 3.

Both ends of the horizontal portion of the rotary pipe 12 are connected to the inside of the annular chamber 16. This chamber 1
A large number of supply pipes 16a are hung at the bottom of the chamber 6 at equal intervals in the circumferential direction of the chamber 16.
A filling nozzle 17 is attached to the lower end of each of the above, and a measuring unit 20 and an on-off valve 18 of the electromagnetic flow meter according to the present invention described later are provided in the middle of each of the supply pipes 16a.

In this rotary beverage filling machine, the chamber 16 rotates in the horizontal plane about the vertical portion of the rotary pipe 12 as a center of rotation, and when a certain filling nozzle 17 passes a predetermined filling start position, this nozzle is rotated. The container 19 is filled with the beverage in the chamber 16 via 17.

Next, the electromagnetic flowmeter according to the present invention applied to the rotary type beverage filling machine will be described. The electromagnetic flowmeter according to the present invention includes a measurement unit 20 interposed between the chamber 16 and the opening / closing valve 18, and a control unit 40 connected to the measurement unit 20, as shown in FIG. Is equipped with. Measuring unit 20
Has a configuration in which the detector 21 and the voltage-current conversion circuit 22 are arranged in the housing 23.

The detector 21 includes a detection tube 24 made of ceramic, a pair of electrodes 25-1 and 25-2 facing each other with a channel 24a in the detection tube 24 interposed therebetween, and the outside of the detection tube 24. A pair of exciting coils 26 arranged opposite to each other
-1, 26-2 are provided. The exciting coil 26
-1, 26-2 are provided at positions shifted by 90 ° from the electrodes 25-1, 25-2 in the circumferential direction of the detection tube 24.

The voltage signals from the electrodes 25-1 and 25-2 of the detector 21 are transmitted to the voltage-current conversion circuit 22 in the same housing via the shielded wire, and the conversion circuit 2
A preamplifier circuit (not shown) in 2 amplifies the voltage until it reaches a sufficient voltage value (usually several tens of dB).
However, the amplification factor depends on the strength of the applied magnetic field, the distance between the electrodes, etc., and cannot be generally stated). This allows
Even if electric noise is mixed in from the outside during signal transmission, a sufficient S / N ratio can be obtained, so that the noise can be easily removed by the amplifier 42 section described later.

[0023] Voltage - current conversion circuit 22, as an example of the configuration in FIG. 3, electric current I ₀ flowing through the load R _L to the reference resistor R _S, the voltage appearing across this reference resistance R _S is It is controlled so as to be equal to the input voltage V _i .
In this voltage-current conversion circuit 22, the operational amplifier A
The voltage of the _first output terminal and fed back to the inverting input terminal of the operational amplifier A _1, and fed back to the non-inverting input of the operational amplifier A ₁ a voltage of the output terminal via the operational amplifier A ₂ in the same feedback ratio Therefore, the output current I ₀ corresponds to the input voltage V _i as shown in the following equation. I ₀ = V _i / (nR _S ) ... (1) Here, R _{1 to} R ₄ are resistors, and n = R ₁ / R ₂ = R ₃ / R ₄ .

The voltage-current conversion circuit 22 is composed of the circuit 2
The differential amplification control is performed so that the voltage across the reference resistance R _S is always constant even if the load R _L including the line resistance of the cable connecting the control unit 40 and the load resistance of the other party changes. Output current. Therefore, even if the line resistance of the cable changes to some extent, the electrodes 25-1 and 25-2 of the detector 21 are
A signal corresponding to the voltage signal from 5-2 can be transmitted to the control unit 40 that is not affected by the line resistance. Although the operational amplifier A ₂ operates as a voltage follower, it may be omitted because it is merely provided as a protection means. If the output of the operational amplifier A ₁ is not sufficient, the output transistor may be connected to the subsequent stage. That is, for example, when a PNP type transistor is used as the output transistor, the base of the transistor is connected to the output of the operational amplifier A ₁ and the collector of the transistor is connected to the power supply, and the base voltage of the transistor is connected. The emitter output of the transistor under the control of the operational amplifier A ₁ may be fed back to the resistor R ₂ .

In the housing 23 of the measuring unit 20, the openings located on the sides of the portions where the exciting coils 26-1 and 26-2 are arranged are covered with lids 27-1 and 27-2, respectively, and voltage-current conversion is performed. It has a configuration in which the opening located on the side of the arrangement portion of the circuit 22 is covered with a lid 27-3. In the voltage-current conversion circuit 22, a temperature detector 28 (for example, a thermistor is applied to detect the ambient temperature on the substrate, the housing 23, the screw portion fixing the housing 23 and the substrate, the detection tube 24, or the like. ) Is attached.

The voltage-current conversion circuit 22 has its input connected to the electrodes 25-1 and 25-2 and its output connected to the waterproof connector 29. Further, the exciting coils 26-1, 26-2 and the temperature detector 28 are
It is connected to the waterproof connector 29 via the substrate of the voltage-current conversion circuit 22. Further, an electric shield member 30 is arranged on the outer periphery of the detection tube 24, and an electromagnetic shield member 31 is arranged on the outer periphery of the exciting coils 26-1 and 26-2.

The control unit 40 is provided at a position apart from the corresponding measurement unit 20 due to the arrangement space, and is connected to the measurement unit 20 via the electric cable 32 and the waterproof connector 29. In this embodiment, as shown in FIG. 1, the control unit 40 is fixedly installed on the horizontal portion of the rotary pipe 12. The control unit 40 includes the exciting coils 26-1, 26-
2, a coil exciting circuit 41 for outputting an exciting current to the second coil, and an amplifier 42 for amplifying the output voltage of the electrodes 25-1, 25-2.
And a microcomputer 43 that outputs a current value command signal to the coil excitation circuit 41 and processes the output of the amplifier.

As shown in FIG. 4, the coil excitation circuit 41
Has a switching circuit 44 and a constant current circuit 45. The switching circuit 44 includes bridge-connected switch elements 44a to 44d. In the switching circuit 44, the common connection point of the switch elements 44a and 44c is connected to the power supply line 46, the common connection point of the switch elements 44b and 44d is connected to the constant current circuit 45, and the switch elements 44a and 44b are further connected. And a common connection point of the switch elements 43c and 43d are connected to one end and the other end of the exciting coils 26-1 and 26-2 connected in series, respectively.

The switch elements 44a to 44d include a pair of switch elements 44a and 44d, a switch element 44b, and a switch element 44b.
A switch control pulse signal of a predetermined frequency is applied from the microcomputer 43 so that the pair of 44c are alternately opened and closed. That is, the control pulse signal is applied to the switch elements 44a and 44d via the inverter 47, and the control pulse signal is directly applied to the switch elements 44b and 44c.

The constant current circuit 45 includes an operational amplifier 45a,
A transistor 45b connected to the output of the operational amplifier 45a and an operational amplifier 45a are provided. The collector of the transistor 45b has the switching circuit 4 described above.
4 is connected. Also, the emitter is a resistor 45c.
Is grounded through and is connected to the negative input of the operational amplifier 45a.

In the constant current circuit 45, the microcomputer 4 is connected to the non-inverting input of the operational amplifier 45a.
The current value command voltage output from the D / A conversion unit 43a built in 3 is applied. As a result, the transistor 45b is driven by the output of the operational amplifier 45a, and a current corresponding to the current value command voltage flows through the switching circuit 44. At that time, the voltage (resistor 45
The terminal voltage of c) is fed back to the inverting input of the operational amplifier 45a. Therefore, a constant current corresponding to the current value command voltage always flows through the switching circuit 44.

According to the coil exciting circuit 41, the value of the constant current flowing through the switching circuit 44, that is, the value of the exciting current flowing through the exciting coils 26-1 and 26-2 is output from the microcomputer 43 as a current value. It can be arbitrarily set by changing the command voltage.

When the exciting coils 26-1 and 26-2 are excited by the alternating constant current output from the coil exciting circuit 41, a predetermined alternating magnetic field acts on the beverage flowing through the detecting tube 24 shown in FIG. A voltage based on the so-called Faraday's law of electromagnetic induction is generated between the electrodes 25-1 and 25-2. For example, if the inner diameter of the detection tube 24 is d (m), the magnetic flux density given by each electromagnetic coil is B (T), and the average flow velocity of the fluid to be measured is v (m / s), the magnetic field is When the flow velocity is uniform and the inside of the detection tube has an axisymmetric flow velocity distribution, a voltage e (v) represented by the following equation is generated in the measured fluid 2. e = B · d · v (2)

As is clear from the above equation (2), the voltage e induced between the electrodes 25-1 and 25-2 corresponds to the average flow velocity v of the beverage flowing through the detection tube 24. The voltage e is converted into a corresponding current by the voltage-current conversion circuit 22 arranged in the measuring unit 20. The output current of the voltage-current conversion circuit 22 is input to the amplifier 42 of the control unit 40 via the electric cable 32, where it is converted into a corresponding voltage and amplified,
It is added to an A / D converter (not shown) built in the microcomputer 43.

The operation of the electromagnetic flowmeter according to this embodiment will be described below. The control panel 50 fixedly installed outside the filling machine transmits data indicating a target filling amount suitable for the container 19 and a filling timing signal to the control unit 40 by infrared rays via the infrared port 51, while The microcomputer 43 of the control unit 40 takes in the target filling amount data and the filling timing signal via the infrared port 44. Therefore, the microcomputer 43
Based on the filling timing signal, the filling valve 18
A valve opening signal for opening the container is output to start filling the container 19 with the beverage.

Further, the microcomputer 43 causes the flow rate v of the beverage which is A / D converted by the A / D converter.
The flow rate of the beverage (flow velocity × internal cross-sectional area of the detection tube 24) is calculated based on the data indicating, and the flow rate is integrated to measure the filling amount of the beverage in the container 19. Then, the filling amount is compared with the target filling amount, and when the former coincides with the latter, a valve closing signal is output and the filling valve 18 is closed. As a result, the container 19 is filled with the target filling amount of the beverage.

Further, the microcomputer 43 calculates the time required for the filling amount to reach the target filling amount (filling time) based on the flow rate, and the data indicating the filling time is transmitted via the infrared port 44. It is transmitted to the control panel 51. The control panel 51 receives the data indicating the filling time and determines whether the filling time is proper or not. Then, when the filling time is not proper, it is displayed on a display means (not shown), and the flow rate adjusting valve 15 is controlled so that the filling time is proper.

By the way, since the distance between the measuring unit 20 and the control unit 40 is several meters, for example, the cable 32 connecting them has a large electric resistance.
Further, when the cable 32 having a wire diameter is used, a high shield effect cannot be obtained because the amount of the shield member for enhancing the shield effect against electric noise from the outside is small. Therefore, the electrodes 25-1, 25-2 are simply
When the output voltage is transmitted to the control unit 40 via the cable 32, an accurate measurement result cannot be obtained due to the influence of the electric resistance of the cable 32 and electric noise.

However, according to the above embodiment, in the measuring unit 20, the output voltage of the electrodes 25-1 and 25-2 is converted into the corresponding current by the voltage-current conversion circuit 22, so that the output voltage is changed. Is transmitted to the control unit 40 without being affected by the electric resistance (line resistance) of the cable 32, and as a result, an accurate flow rate measurement result can be obtained.

On the other hand, the detection tube 24 made of ceramic is
Due to its low coefficient of thermal expansion, it is not affected by the temperature of the beverage being filled.
It is hard to get rid of. However, the voltage-current conversion of the measuring unit 20
The circuit 22 includes an amplifier (for example, the
Preamplifier circuit, operational amplifier A ₁, A₂) Amplification is above
Material temperature (low temperature is around 5 ℃, high temperature is under 100 ℃)
Fluctuates under the influence of. This change in the amplification factor is caused by the voltage-current change.
The fluctuation of the output current of the conversion circuit 22, that is,
Data indicating the flow rate v of the beverage taken into the computer 43
Bring fluctuations. Also, the specific gravity of the beverage depends on the temperature
The weight will change even if the same volume of beverage is filled.
To do.

The relationship between the ambient temperature of the voltage-current conversion circuit 22 and the fluctuation value of the data indicating the flow velocity v can be known in advance by experiments or the like. If the relationship between the ambient temperature and the variation value of the data indicating the flow velocity v is known, the correction value of the data corresponding to the ambient temperature is also known. Therefore, in this embodiment, the correction value of the flow velocity data corresponding to the ambient temperature is set to the microcomputer 43.
Stored in advance in a memory (not shown).

Based on the ambient temperature detected by the temperature detector 28, the microcomputer 43 reads out a correction value corresponding to this ambient temperature change from the memory, and outputs the correction value from the amplifier 42 according to this correction value. The flow velocity data is corrected, and the beverage filling flow rate and the beverage filling amount into the container 19 are calculated based on the corrected flow velocity data. Therefore, according to this embodiment,
It is possible to improve the measurement accuracy of the filling flow rate and the filling amount.

Next, the measuring unit 20 will be described. A large number of measurement units 20 are arranged along the circumference of the annular chamber (the arrangement intervals are, for example, 100 mm).
Therefore, the exciting coil 2 of the adjacent measuring unit 20 is
It is necessary to take care so that the magnetic fields generated by 6-1 and 26-2 do not interfere with each other. In order to suppress the above interference, the housing 23 of the measurement unit 20 and the lids 27-1 to 27-.
3 may be formed of a material having a high magnetic permeability such as pure iron.
However, this material such as pure iron has a drawback that it is easily rusted.

Therefore, the housing 23 in this embodiment is cast and formed using a material having excellent corrosion resistance and magnetic permeability, for example, SCS11 which is austenitic ferrite stainless steel. In addition, the lids 27-1 and 27
-2 and 27-3 are materials having excellent magnetic permeability, for example,
A plate made of ferritic stainless steel SUS430, pure iron, carbon steel, electromagnetic steel or the like is used as a core, and a plate made of a material excellent in corrosion resistance, for example, austenitic stainless steel SUS316 is pressed on the outer surface of the core. It is formed by applying such means.

Housing 23 and lids 27-1 to 27-27
If -3 is formed of the above material, rust is prevented from being generated on these surfaces, and electromagnetic interference between adjacent measurement units 20 is suppressed. of course,
The lids 27-1, 27-2 and 27-3 may be formed by casting using SCS11 which is austenitic ferrite stainless steel, or may be formed by processing a plate made of austenitic ferrite stainless steel SUS329J1. good.

By the way, a large number of electromagnetic flow meters in which the measuring unit 20 and the control unit 40 are combined are arrayed in the filling machine (the number of arrays is from about 48 to 160).
However, these flowmeters have individual differences even if the number of turns of the exciting coil 26 of each measuring unit 20 is the same. This is because the flowmeters have variations in the mounting position of the excitation coil 26 with respect to the detection tube 24 and variations in the internal resistance of the excitation circuit 41 and the amplifier 42.

The individual difference of each of the above flowmeters causes variations in their flow rate measuring functions. Therefore, it is conceivable to adjust the sensitivity of the amplifier 42 of each control unit 40 using a variable resistor to eliminate the variation in the measurement result. However, variable resistors have the drawback of lacking long-term reliability, and it is therefore desirable to avoid their use.

As shown in the equation (1), since the voltage output from the electrode 25 is proportional to the magnetic flux density of the magnetic field generated by the exciting coil 26, changing the exciting current of the coil 26 is substantially effective. It is equivalent to adjusting the sensitivity of the amplifier 42. As described above, the constant current circuit 45 shown in FIG.
The constant current value supplied to the switching circuit 44, that is, the value of the exciting current of the exciting coil 26 can be arbitrarily set by the current value command voltage output from 3a.

The current value command voltage can be changed purely electronically in the microcomputer 43. Therefore, in the flowmeter according to this embodiment, the detection sensitivity can be arbitrarily and easily adjusted without using a variable resistor, which is extremely advantageous in adjusting the sensitivity of each flowmeter. The sensitivity of the flowmeter is adjusted before shipment from the factory, and the adjustment data is stored in the memory of the microcomputer 43.

By the way, as described above, in this embodiment, the control panel 5 fixedly installed outside the filling machine.
Infrared ports 51 and 44 are used as communication means between 0 and the microcomputer 43 of the control unit 40, and data indicating a target filling amount, a filling timing signal, and the like are transmitted from the control panel 50 to the control unit 40 by infrared rays. The data indicating the actual filling time is stored in the control unit 40.
From the control panel 50 by infrared rays.

Therefore, according to this embodiment, it is not necessary to transmit the communication data via the slip ring 13 shown in FIG. 1, and therefore the reliability of data transmission can be improved. The slip ring 13
Is used exclusively as a power supply means. Further, instead of the infrared rays, other wireless transmission media such as radio waves can be used. The electromagnetic flowmeter according to the present invention can be applied to flow rate measurement of liquids other than beverages.

[0052]

According to the invention of claim 1, the output voltage of the detector is amplified and converted into a corresponding current in the same housing in which the detector is provided. The signal corresponding to is transmitted to the control unit without being affected by the electric resistance (line resistance) of the cable, and as a result, an accurate flow rate measurement result can be obtained.

According to the invention of claim 2, the voltage-
Since the error due to the ambient temperature of the current conversion circuit is corrected,
It is possible to improve the measurement accuracy of the filling flow rate and the filling amount.

According to the third aspect of the present invention, since the housing and the lid of the measuring unit are made of a material having excellent corrosion resistance and magnetic permeability, it is possible to suppress the generation of rust. Further, when a large number of measurement units 20 are adjacent to each other, electromagnetic interference between them can be suppressed.

According to the invention of claim 4, since the value of the exciting current of the exciting coil of the measuring unit can be changed arbitrarily and purely electronically, the detection sensitivity can be easily adjusted and the reliability can be improved. Can be planned.

According to the invention of claim 5, since the control unit is provided with the wireless communication means, it is not necessary to transmit the communication information through the slip ring when applied to the rotary type liquid filling machine. . Therefore, the reliability of transmission of communication information can be improved.

According to the sixth aspect of the invention, the control unit generates the valve closing signal for stopping the flow of the fluid to be measured when the flow rates are integrated and the integrated flow rate reaches a predetermined value. Therefore, it is not necessary to provide means for integrating the flow rates to generate a valve closing signal outside the control unit.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a beverage filling machine to which an electromagnetic flow meter according to the present invention is applied.

FIG. 2 is a block diagram showing an embodiment of an electromagnetic flow meter according to the present invention.

FIG. 3 is a circuit diagram showing an example of a voltage-current conversion circuit.

FIG. 4 is a circuit diagram showing an example of a coil excitation circuit.

[Explanation of symbols] 1 Filling liquid tank 3 discharge piping 16 liquid chamber 17 Filling nozzle 18 Filling valve 19 containers 20 measuring units 21 detector 22 Voltage-current conversion circuit 23 housing 24 Detector tube 25 electrodes 26 Excitation coil 27 Lid 28 Temperature detector 32 cables 40 control unit 41 coil excitation circuit 42 amplifier 43 Microcomputer 44 infrared port 50 control panel 51 infrared port

Claims (6)

[Claims] 1. A detector for causing a fluid to be measured to flow in a magnetic field generated by an exciting coil to generate a voltage corresponding to the flow velocity of the fluid, and a voltage-current for converting the voltage into a corresponding current and outputting the converted current. A measuring unit including a converting circuit; an exciting circuit that supplies an exciting current to the exciting coil; and a calculating unit that calculates the flow rate of the fluid to be measured based on the output current of the voltage-current converting circuit. And a control unit connected to the electric flowmeter via an electric cable. 2. The measurement unit is provided with a temperature detector for detecting the ambient temperature of the voltage-current conversion circuit, and the arithmetic unit of the control unit is provided with a conversion error due to a change in the ambient temperature of the voltage-current conversion circuit. The electromagnetic flowmeter according to claim 1, further comprising a correction unit that corrects the temperature based on the temperature detected by the temperature detector. 3. The housing of the measuring unit is formed of austenite ferrite stainless steel, and the opening of the housing is formed of the austenite ferrite stainless steel, or the inner surface side is made of a material having high magnetic permeability and the outer surface side is austenite. The electromagnetic flowmeter according to claim 1 or 2, wherein the electromagnetic flowmeter is covered with a lid formed of stainless steel. 4. A constant current circuit in which the coil exciting circuit is capable of changing the setting of a constant current value based on a command signal from the outside, and the constant current output from the constant current circuit is switched to switch the exciting coil. The electromagnetic flowmeter according to any one of claims 1 to 3, further comprising a switching circuit for supplying the electromagnetic flowmeter to the electromagnetic flowmeter. 5. The electromagnetic flowmeter according to claim 1, wherein the control unit includes a wireless communication unit. 6. The control unit is configured to integrate a flow rate and generate a valve closing signal for stopping the flow of the fluid to be measured when the integrated flow rate value reaches a predetermined value. The electromagnetic flowmeter according to any one of claims 1 to 5.