JP5065620B2 - Electromagnetic flow meter - Google Patents

Description

  The present invention relates to a capacitive electromagnetic flow meter that detects a flow rate of a fluid to be detected.

  There are roughly two types of electromagnetic flowmeters that detect the flow rate of the fluid to be detected: a wetted electrode type and a non-wetted electrode type. A wetted electrode type electromagnetic flow meter (referred to as a wetted type or an electrode type electromagnetic flow meter or the like) directly detects an electromotive force generated in a fluid to be detected because the electrode is in direct contact with the fluid to be detected. On the other hand, a non-wetted electrode type electromagnetic flow meter (referred to as an (electrostatic) capacity type electromagnetic flow meter) has an electrode that does not directly contact the fluid to be detected and generates an electromotive force generated in the fluid to be detected. And detecting through the capacitance between the electrodes. Among these, in the liquid flow electrode type electromagnetic flow meter, since the electrode is always in contact with the liquid of the fluid to be detected, the electrode needs to be a liquid that does not corrode the electrode. In addition, there are problems such that the insulating deposit contained in the liquid adheres to the electrode and resistance increases, the electrode rusts, and the like, and a waterproof structure is required at the electrode arrangement portion.

  The configuration of the wetted electromagnetic flow meter 800 is shown in FIG. The electromagnetic flow meter 800 shown in this figure includes a flow rate detection means 801 comprising a measuring tube 811, an electrode 803, an excitation coil 822, etc., an AC amplifier 802, an excitation circuit 824, a synchronous rectification circuit 804, a timing pulse generation circuit 805, and an A / D. A converter 806, a control unit 840 such as a microcomputer for performing arithmetic processing, an output unit 808, a display unit 851, an AC power source 810, and the like are included. In the configuration of FIG. 26, the fluid to be measured flows in the measurement tube 811, and an alternating magnetic field is applied through the excitation circuit 824 and the excitation coil 822 perpendicularly to the direction in which the fluid flows. The excitation circuit 824 is driven by the excitation pulse from the timing pulse generation circuit 805. As a result, an electromotive force is generated between the pair of electrodes 803. The electromotive force is amplified by the AC amplifier 802 and synchronously rectified by the synchronous rectifier circuit 804. This synchronization is performed by a timing pulse given from the timing pulse generation circuit 805. The output of the synchronous rectifier circuit 804 is converted into a digital quantity by the A / D converter 806 and given to the control unit 840. The control unit 840 executes predetermined processing, outputs an instantaneous flow rate output or an integrated output via the output unit 808, and displays an instantaneous flow rate, an integrated flow rate, and the like on the display unit 851.

  In contrast, a capacitive electromagnetic flow meter generates an electromotive force that is proportional to the product of the strength of the applied magnetic field and the fluid flow velocity when a conductive fluid to be detected flows perpendicular to the magnetic field. Is attached to the outer surface of the measuring tube through which the fluid to be detected flows, and is detected based on the principle that the flow rate can be measured by detecting the capacitance with a pair of electrodes that are not in contact with the fluid to be detected. FIG. 23 shows an example of a block diagram of a capacitive electromagnetic flow meter. In this capacitive electromagnetic flow meter, an electrode 930 is attached to the outside of a measurement tube 910 through which a fluid to be detected flows, and a capacitor is formed with the pipe thickness of the measurement tube 910. A pair of exciting coils 922 are arranged in a direction orthogonal to the electric field detected by the electrodes 930, and an alternating magnetic field is generated by the exciting circuit 924. In this configuration, since the electrode 930 is not in contact with the fluid to be detected, it is difficult to be affected by the insulative deposits, and it is not necessary to consider the deterioration of the electrode 930 or the waterproof structure, and maintenance is easy. There is an advantage that the cause of leakage can be eliminated (see Patent Document 1).

This capacitive electromagnetic flow meter uses an exciting circuit to excite an exciting coil to generate an alternating magnetic field. FIG. 24 shows an example of a conventional excitation circuit. In an excitation circuit 924 shown in this figure, a constant voltage power source 927 and a constant current circuit 929 are connected to an excitation coil 922 via an excitation polarity switching circuit 928. A constant current circuit 929 generates a constant current by a DC constant voltage supplied from a constant voltage power supply 927, and switching is performed by an excitation polarity switching circuit 928 connected with a switch in a bridge shape to generate an alternating current. Energize.
JP-A-8-136307

  In general, the power source used for the exciting circuit of the exciting coil is a constant voltage power source with a fixed voltage value. The voltage value of the constant voltage power source is designed with a margin in consideration of the residual voltage of the constant current circuit, the direct current resistance of the exciting coil, and the like. On the other hand, depending on the application in which the electromagnetic flow meter is used, the required specifications, and the like, the diameters of the measurement pipes for flowing the fluid to be detected are different sizes. Even if the diameters of the measurement tubes are different, it is necessary to change the specifications such as the number of turns of the exciting coil and the wire diameter in order to generate a uniform magnetic flux in the flow path inside the measurement tube. Further, when the specification of the exciting coil is changed, the voltage value of the exciting circuit that excites it also differs. For this reason, it is necessary to redesign the power supply of the excitation circuit in accordance with the measuring tube used in the electromagnetic flow meter, and there is a problem that the manufacturing cost is extremely complicated.

  On the other hand, in the capacitive electromagnetic flow meter, detection is performed through the capacitance between the fluid to be detected and the electrode. This electrostatic coupling capacity is as small as about several tens of pF to several tens of pF. For this reason, in order to detect a signal reliably, it is necessary to raise the frequency of an alternating magnetic field and raise a signal level. However, if the same excitation coil is used to increase the excitation frequency, the inductance (L = jωL) increases, which makes it difficult for current to flow, resulting in a problem that the resulting magnetic flux decreases. In order to prevent this, as shown in FIG. 25, when the exciting coil is turned on, a higher voltage is applied to facilitate the flow of current, while after the current starts flowing, the voltage is decreased to maintain a constant low voltage. It is preferable to apply. As such an output variable power supply circuit, it is conceivable to use a linear power supply (series power supply). In the linear power supply, a constant voltage power supply is designed in accordance with a high voltage value in a required constant voltage, and the voltage value is adjusted using a variable resistor, a transistor, or the like. However, in this configuration, power loss always occurs in order to adjust the voltage value, resulting in poor efficiency, and the upper limit temperature of the fluid to be detected is limited due to heat generation. Since a mechanism for protecting circuit components is required, there is a problem that the apparatus becomes large and the cost is high.

The present invention has been made to solve such conventional problems. An object of the present invention is to provide an electromagnetic flow meter having a common excitation circuit regardless of a required voltage value. Another object of the present invention is to reduce heat generation by reducing the power loss of the electromagnetic flowmeter.

In order to achieve the above object, an electromagnetic flow meter according to a first aspect of the present invention is an electromagnetic flow meter for detecting a flow rate of a fluid to be detected, and a measurement tube that constitutes a flow path through which the fluid to be detected passes. , At least a pair of exciting coils arranged orthogonal to the flow path of the measurement tube, an excitation circuit for exciting the excitation coil, and a straight line connecting the flow path of the measurement tube and the pair of electrodes Based on at least a pair of electrodes arranged, a detection circuit capable of detecting a voltage signal detected by the electrodes, and a voltage signal detected by the detection circuit, the flow rate of the fluid to be detected passing through the flow channel of the measurement tube is determined. The excitation circuit is further connected in series with the excitation coil, and a constant voltage power source that can adjust and supply the output voltage value for exciting the excitation coil is connected in series with the excitation coil. Flow into the excitation coil A constant current circuit for regulating the current to a predetermined value, an excitation polarity switching circuit for switching the polarity of excitation, and a constant current circuit interposed between the excitation coil, the constant voltage power source and the constant current circuit. And the residual voltage detection circuit for detecting the residual voltage of the constant current circuit, the constant voltage power supply compares the residual voltage detected by the residual voltage detection circuit with a predetermined reference voltage, and the comparison result is minimized. The output voltage is controlled so that the constant voltage power supply includes a variable voltage DC / DC converter, and the variable voltage DC / DC converter applies a high voltage so that current can be easily passed when the excitation coil is turned on. On the other hand, after the current begins to flow, control is performed so that a constant low voltage is applied by dropping the voltage .

A capacitive electromagnetic flow meter according to a second aspect of the invention is a capacitive electromagnetic flow meter for detecting the flow rate of a fluid to be detected, comprising a measurement tube that constitutes a flow path through which the fluid to be detected is passed, and a flow of the measurement tube At least a pair of excitation coils arranged perpendicular to the path, an excitation circuit for exciting the excitation coil, and a straight line connecting the flow path of the measurement tube and the pair of electrodes, and to be detected At least a pair of electrodes coupled to the measurement tube in a non-contact state with the fluid, a detection circuit capable of detecting a voltage signal detected by the electrodes, and a flow path of the measurement tube based on the voltage signal detected by the detection circuit A constant voltage that can be supplied by adjusting an output voltage value that excites the excitation coil, and is further connected in series with the excitation coil. Connect the power supply and the excitation coil in series. A constant current circuit for prescribing the current flowing through the excitation coil to a predetermined value, and an excitation polarity switching circuit for switching the polarity of excitation interposed between the excitation coil, the constant voltage power source and the constant current circuit, A residual voltage detection circuit connected to the constant current circuit for detecting the residual voltage of the constant current circuit, and the constant voltage power source compares the residual voltage detected by the residual voltage detection circuit with a predetermined reference voltage The output voltage is controlled so that the comparison result is minimized , the constant voltage power supply includes a variable voltage DC / DC converter, and the variable voltage DC / DC converter supplies current when the excitation coil is turned on. While a high voltage is applied so as to facilitate the flow, control is performed so that a constant low voltage is applied by dropping the voltage after the current starts flowing .

  In the capacitive electromagnetic flow meter according to the third aspect of the invention, the constant voltage power source includes an input terminal for inputting a signal from the residual voltage detection circuit, and the residual voltage detection circuit includes a feedback circuit, and the feedback Connect the output side and input side of the circuit via a capacitor, input the difference between the residual voltage of the constant current circuit and the specified reference voltage to the input side, and connect the output side to the input terminal of the constant voltage power supply be able to.

  In the capacitive electromagnetic flow meter according to the fourth aspect of the invention, the constant voltage power source can include a DC / DC converter.

  In the capacitive electromagnetic flow meter according to the fifth aspect of the present invention, the excitation circuit can further include a switching circuit connected between the input terminal of the constant voltage power source and the residual voltage detection circuit. The capacitive electromagnetic flow meter according to the sixth aspect of the invention can use an analog switch for the switching circuit.

  An excitation circuit for a capacitive electromagnetic flow meter according to a seventh aspect of the present invention is a capacitive electromagnetic flow meter for detecting the flow rate of a fluid to be detected, for a capacitive electromagnetic flow meter for exciting an excitation coil that generates an alternating magnetic field. An excitation circuit that is connected in series with the excitation coil, adjusts the output voltage value that excites the excitation coil, can be supplied, and is connected in series with the excitation coil to reduce the current flowing through the excitation coil A constant current circuit for defining a predetermined value, an excitation coil, a constant voltage power source and a constant current circuit interposed between the excitation polarity switching circuit for switching the polarity of excitation, and the constant current circuit, And a residual voltage detection circuit for detecting the residual voltage of the constant current circuit. The constant voltage power supply is configured to be able to adjust the output voltage based on the residual voltage detected by the residual voltage detection circuit.

  An electromagnetic flow meter excitation method according to an eighth aspect of the present invention is an electromagnetic flow meter excitation method for detecting the flow rate of a fluid to be detected, wherein the residual voltage detection circuit defines the current flowing through the excitation coil to a predetermined value. A step of detecting a residual voltage of the constant current circuit, and a step of adjusting an output voltage by which the constant voltage power source excites the exciting coil based on the residual voltage detected by the residual voltage detection circuit.

  According to the first, second and seventh and eighth inventions, the output voltage can be adjusted based on the residual voltage of the constant current circuit. Can supply the correct voltage.

  According to the third aspect of the invention, the output voltage value of the constant voltage power supply is controlled so as to reduce this value in accordance with the residual voltage of the constant current circuit. An optimum voltage can be supplied.

  According to the fourth aspect of the present invention, it is possible to construct an excitation circuit that generates a necessary minimum output voltage using a DC / DC converter and has very little power loss. In particular, the DC / DC converter is a step-down converter that performs a switching operation, and has an advantage that power loss is small when voltage conversion is performed, and power loss can be extremely reduced.

  According to the fifth and sixth inventions, unnecessary signals can be cut, so that even if the residual voltage of the constant current circuit increases when a high voltage is applied in the initial stage of excitation, this signal can be eliminated.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiment described below exemplifies an electromagnetic flow meter for embodying the technical idea of the present invention, and the present invention does not specify the electromagnetic flow meter as follows. Further, the present specification by no means specifies the members shown in the claims to the members of the embodiments. In particular, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in the embodiments are not intended to limit the scope of the present invention unless otherwise specified, and are merely explanations. It is just an example. Note that the size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation. Further, in the following description, the same name and reference numeral indicate the same or the same members, and detailed description will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured such that a plurality of elements are constituted by the same member and the plurality of elements are shared by one member, and conversely, the function of one member is constituted by a plurality of members. It can also be realized by sharing.
(Capacitive electromagnetic flow meter)

1 to 19 show a capacitive electromagnetic flow meter 100 according to Embodiment 1 of the present invention. In these drawings, FIG. 1 is a block diagram showing a configuration of a capacitive electromagnetic flow meter 100, FIG. 2 is a cross-sectional view of a main body case, and FIG. 3 is a more detailed block diagram of a circuit configuration of the capacitive electromagnetic flow meter 100. 4 is a perspective view of the capacitive electromagnetic flow meter, FIG. 5 is an exploded perspective view of the capacitive electromagnetic flow meter of FIG. 4 with the display unit removed, and FIG. 6 is an exploded perspective view of the main body case of FIG. 7 is an exploded perspective view of a state in which the side cover is fixed by the main body cover, FIG. 8 is a sectional view of the state in which the housing is held by the main body cover, and FIG. 9 is a perspective view of the measuring tube and an exploded perspective view with the electrodes removed. 10 is an exploded perspective view of the main body case of FIG. 6, FIG. 11 is an exploded perspective view of the preamplifier module, FIG. 12 is a perspective view of the excitation module, FIG. 13 is a perspective view of the excitation plate, and FIG. 15 and 15 show the integrated display unit. FIG. 16 is a perspective view showing a state in which the display unit is fixed to the main body case, FIG. 17 is a perspective view of a capacitive electromagnetic flow meter using a separate display unit, and FIG. FIG. 19 is an exploded perspective view of the separation type display unit.
(Block Diagram)

  As shown in the block diagram of FIG. 1 and the cross-sectional view of the main body case of FIG. 2, the capacitive electromagnetic flow meter 100 is wound around the measurement tube 10 and the pole piece 178 that allow the fluid to be detected to pass through. An excitation coil 22 for applying a magnetic field to the fluid to be detected from outside, an excitation circuit 24 for generating an alternating magnetic field by the excitation coil 22, and a fluid to be detected passing through the magnetic field generated by the excitation coil 22 The electrode 30 for detecting the electromotive force generated, the detection circuit 34 for detecting the electromotive force via the electrode 30, the excitation circuit 24 and the detection circuit 34 are driven and controlled, and the flow rate is calculated from the detected signal. And a display unit 51 that displays the flow rate calculated by the control unit 40. The control unit 40 functions as a flow rate calculation unit capable of calculating the integrated flow rate based on the flow rate of the fluid to be detected detected by the main body case 110 constituting the flow rate detection means. If necessary, an output unit 60 for outputting an output signal, an input unit 70 for inputting various input signals such as an external reset signal, a setting unit 80 for performing various settings, and the like are provided. Also good. The control unit 40, the display unit 51, the output unit 60, the input unit 70, the setting unit 80, and the like are configured as a unit that is a separate member from the main body case 110 as the display unit 50.

  A more detailed block diagram of the circuit configuration of the capacitive electromagnetic flow meter 100 is shown in FIG. In this figure, each of the main body case 110 and the display unit 50 constituting the capacitive electromagnetic flow meter 100 shows the members constituting them. First, a pair of electrodes 30 and preamplifiers 163 are arranged on the measurement tube on the main body case 110 side. A differential amplifier 35, an amplifier 36, and a periodic reset circuit 37 are provided as a detection circuit 34 that detects an electromotive force at these electrodes 30. In the example of FIG. 3, the output of the preamplifier 163 is input to the differential amplifier 35 to detect the electromotive force generated between the electrodes 30. The output of the differential amplifier 35 is further amplified by the amplifier 36, A / D converted by the A / D converter 38 via the periodic reset circuit 37, and input to the control unit 40. The periodic reset circuit 37 is a circuit for receiving a reset signal periodically transmitted from the control unit 40 and resetting the detected voltage.

  On the other hand, as an excitation circuit 24 for generating a magnetic field in the measurement tube by the excitation coil 22, an excitation power source 25 for excitation, an excitation polarity switching circuit 28 that is interposed between the excitation coil 22 and the excitation power source 25 and switches the polarity of excitation. And a constant current circuit 29 for supplying a predetermined constant current to the exciting coil 22. In the excitation circuit 24, the excitation polarity switching circuit 28 switches the power supplied from the excitation power supply 25 and supplies an alternating current to the excitation coil 22 to generate an alternating magnetic field. In the example of FIG. 3, the excitation power supply 25 includes an initial excitation power supply 26 and an excitation continuation power supply 27, which are used by switching. That is, since a high voltage is required when the exciting coil 22 is started up, the initial exciting power source 26 that can obtain a higher output is used. When the excitation is stabilized, the voltage necessary for continuing the excitation becomes low, and the excitation continuous power supply 27 is switched. As a result, in order to supply a high voltage at start-up and a constant voltage at stable operation, a dedicated power supply can be prepared, so that an increase in power supply or an increase in power loss can be avoided. Prevents heat generation.

  Further, the output of the excitation polarity switching circuit 28 is input to the control unit 40 on the display unit 50 side. The display unit 50 includes an A / D converter 38, a control unit 40, a display unit 51, a setting unit 80, an input unit 70, and an output unit 60. The control unit 40 is constituted by a microcomputer or the like, and drives and controls the excitation circuit 24 and the detection circuit 34 in synchronization. The setting unit 80 is a switch or console for performing various settings and operations. The display unit 51 includes a 7-segment display and the like, and switches or simultaneously displays the detected instantaneous flow rate, integrated flow rate, or set value. The input unit 70 is an input circuit that inputs an external signal. The output unit 60 includes an external output circuit 61 and an analog current output circuit 62 for outputting a control signal and the like.

  It should be noted that the classification of the display unit, the main body case, the excitation circuit, the detection circuit, and the like is an example, and it goes without saying that the same function can be realized by appropriately changing the unit or circuit to which each constituent member belongs. Moreover, as long as a function is implement | achieved, it is also possible to integrate arbitrary members.

The operation principle of the capacitive electromagnetic flow meter 100 will be described with reference to FIG. The measurement tube 10 that guides the fluid to be detected is generated by a pair of exciting coils 22 disposed on the left and right sides of the measurement tube 10 and is disposed so as to be orthogonal to the substantially parallel magnetic field guided to the pole piece 178. The pair of electrodes 30 arranged to face the upper and lower surfaces of the measuring tube 10 are arranged so as to detect the electromotive force generated in the direction perpendicular to the magnetic field generated by the exciting coil 22 and the direction of passage of the fluid to be detected. Has been. In this configuration, when the fluid to be detected flows in the measuring tube 10, that is, when the conductive fluid moves in a direction orthogonal to the magnetic field, the moving speed (flow velocity) of the fluid to be detected is increased according to Faraday's law of electromagnetic induction. Proportional electromotive force is generated. At this time, the electromotive force is proportional to the product of the magnetic flux density, the flow velocity, and the measurement tube diameter according to Faraday's law. The electrode 30 faces the fluid to be detected through the tube wall of the measuring tube 10 made of a derivative and is capacitively coupled, and functions to electrically extract an electromotive force generated in the fluid. The extracted electromotive force is transmitted to the control unit 40, converted into a flow rate signal, displayed on the display unit 51, or output as an electrical signal.
(Excitation circuit)

  FIG. 21 shows an example of an excitation circuit for a capacitive electromagnetic flow meter. The excitation circuit 24C for a capacitive electromagnetic flow meter shown in this figure includes a constant voltage power supply 27B, an excitation coil 22, a constant current circuit 29, an excitation polarity switching circuit 28, and a residual voltage detection circuit 180. The constant voltage power source 27 </ b> B, the excitation coil 22, and the constant current circuit 29 are connected in series via the excitation polarity switching circuit 28. Residual voltage detection circuit 180 is connected between constant current circuit 29 and constant voltage power supply 27B.

  The constant voltage power supply 27B constitutes an exciting power supply, and a variable voltage DC / DC converter can be used. The DC / DC converter is a step-down converter that performs a switching operation. Since the power loss is small when voltage conversion is performed, an efficient operation can be obtained.

  The excitation polarity switching circuit 28 is a switching circuit that converts DC power into AC power by switching. In the example of FIG. 21, the polarity changeover switches SW1 to SW4 are connected in a bridge shape, and by switching these ON / OFF, a constant voltage supplied from the constant voltage power supply 27B is converted to AC, and an AC electric field is applied to the excitation coil 22. Apply.

  The constant current circuit 29 defines a current required for generating a uniform magnetic flux in the exciting coil 22. The constant current circuit 29 in FIG. 21 includes a transistor Q, a resistor, a Zener diode, and the like. In the transistor Q, the emitter side is grounded via a resistor, the base side is connected to the collector side via a resistor, and the base side is grounded via a Zener diode.

In the constant current circuit 29, a residual voltage is generated due to a voltage drop between the transistor Q and the resistor. In particular, the voltage drop of the transistor Q becomes a power loss and causes heat generation. This residual voltage is detected by the residual voltage detection circuit 180 and controlled so that the residual voltage becomes small.
(Residual voltage detection circuit 180)

  The residual voltage detection circuit 180 is a feedback circuit composed of an operational amplifier 181. The + side input of the operational amplifier 181 is connected to a predetermined reference voltage, and the − side input is connected to the collector side of the constant current circuit 29 via a resistor. The output side of the operational amplifier 181 is input to the input terminal of the constant voltage power supply 27B, and is further connected to the negative input through a capacitor. The residual voltage detection circuit 180 detects the residual voltage of the constant current circuit 29, compares it with the reference voltage, and controls the excitation power supply voltage of the constant voltage power supply 27B so that the comparison result is minimized. Therefore, the excitation power supply voltage is not unnecessarily high, and the residual voltage of the constant current circuit 29 can be extremely reduced by suppressing the excitation power supply voltage to the minimum necessary voltage.

  The excitation circuit 24C converts the constant voltage obtained by the constant voltage power supply 27B into a constant current by the constant current circuit 29, converts the constant voltage into an alternating current by the excitation polarity switching circuit 28, and supplies it to the excitation coil 22. Further, the residual voltage of the constant current circuit 29 is detected by the residual voltage detection circuit 180 and fed back to the constant voltage power supply 27B, thereby exciting the constant voltage power supply 27B so that the residual voltage of the constant current circuit 29 has a low value. The power supply voltage can be automatically controlled. For this reason, it is possible to suppress the power loss of the transistors of the constant current circuit, reduce heat generation, and contribute to the adoption of small parts and the miniaturization of the housing.

The excitation circuit 24C can be controlled so as to automatically adjust the excitation power supply voltage value required for each excitation coil 22. In other words, the voltage can be adjusted to an appropriate voltage value and applied to the excitation coil regardless of the type and characteristics of the excitation coil connected to the excitation circuit. For this reason, it is not necessary to design a dedicated excitation circuit for each excitation coil, and the labor can be saved and the cost can be reduced by sharing the members.
(Modification of excitation circuit)

  In the above excitation circuit, an example in which one constant voltage power supply is used as the excitation power supply has been described. On the other hand, the excitation circuit can have a plurality of power supplies. In the example of FIG. 3, two excitation power sources 27 and an initial excitation power source 26 are used as the excitation power source 25. Thereby, reduction of flow noise can be aimed at.

  In a capacitive electromagnetic flow meter, since the detected signal level is generally low, it is preferable to reduce the influence of noise (flow noise) as much as possible. In particular, the influence of flow noise becomes significant when the conductivity of the fluid to be detected is low. For such a flow noise reduction measure, it is effective to excite the exciting coil at a high frequency. However, in order to increase the excitation frequency, the rise of excitation must also be accelerated. In order to speed up the excitation rise, it is useful to apply a high voltage at the initial stage of excitation. In this case, the residual voltage of the constant current circuit increases in the final phase of the high voltage application period. At this stage, in the control for detecting the residual voltage, the high residual voltage becomes an unnecessary signal. Therefore, the switching circuit 190 is used to shut off the residual voltage detection circuit 180 at this stage, and in a stable steady state operation, the selection of connecting the residual voltage detection circuit 180 causes a power loss during stable operation. It is possible to achieve both suppression and flow noise reduction.

An example of such an excitation circuit 24D is shown in FIG. In this figure, the same members as those in FIG. 21 described above are denoted by the same reference numerals, and detailed description thereof is omitted. The excitation circuit 24D of FIG. 22 includes two constant voltage power sources 27B constituting an excitation continuous power source and an initial excitation power source 26 as excitation power sources, and these can be switched by a power source switch 192. The initial excitation power source 26 is a high voltage power source for applying a high voltage in the initial stage of excitation.
(Switching circuit 190)

Further, a switching circuit 190 is connected between the residual voltage detection circuit 180 and the constant voltage power supply 27B. As the switching circuit 190, a double throw switch such as an analog switch that can be switched bidirectionally can be used. The analog switch performs ON / OFF switching of the control electric signal circuit in accordance with the state of the input signal. Here, when the initial excitation power supply 26 is selected by the power supply switch 192 and a high voltage is applied to the excitation coil 22, the analog switch is turned off and the residual voltage detection circuit 180 is disconnected from the constant current circuit 29. At this stage, since the constant voltage power supply 27B is not connected by the power supply changeover switch 192, the control signal of the residual voltage detection circuit 180 becomes unnecessary. On the other hand, since the magnetic flux stabilizes in a short time after the high voltage is applied, in this state, the power source switch 192 is switched from the initial excitation power source 26 side to the constant voltage power source 27B, and the analog switch is turned on to turn on the constant current circuit 29 and the residual voltage. The detection circuit 180 is connected. In this state, as described above, the constant voltage power supply 27B is controlled to minimize the residual voltage detection. Thus, when the high voltage is applied and the residual voltage of the constant current circuit 29 is increased, the feedback control of the constant voltage power supply 27B is interrupted, and in the steady state, the residual voltage is controlled by the feedback control of the constant voltage power supply 27B. Can be suppressed, and efficient operation becomes possible.
(Main body case 110)

  Next, details of each member of the capacitive electromagnetic flow meter will be described with reference to the drawings. A capacitive electromagnetic flow meter 100 shown in FIGS. 4 and 5 includes a main body case 110 constituting a capacitive electromagnetic flow meter main body and a display unit 50. This capacitive electromagnetic flow meter allows the fluid to be detected to pass through the flow passage openings 111 opened at both end faces of the main body case 110, detects the flow rate, and displays it on the display unit 50.

  PPS resin or the like can be used for the main body case 110. In particular, by forming the main body case 110 from a resin instead of a metal, it is possible to obtain an advantage that the weight can be reduced and a complicated shape can be easily formed and the structure can be made at low cost. As shown in FIG. 5, the display unit 50 is fixed to the upper surface of the main body case 110. Further, as shown in FIG. 6, side covers 130 are fixed to the side surfaces of the main body case 110 before and after the housing 120 that houses the measurement tube 10. Each side cover 130 is provided with a channel port 111 through which the fluid to be detected flows in and out.

  Further, the upper surface of the side cover 130 is closed with a yoke lid 140 and the lower surface is closed with a reinforcing plate 142. Furthermore, the reinforcing plate 142 is covered with a body cover 150 having a U-shaped cross section, and the side cover 130 is fixed and reinforced at both ends of the body cover 150. A state in which the main body case 110 is covered with the main body cover 150 and the side covers 130 are fixed to each other with the main body cover 150 is shown in FIG. As shown in this figure, a step is formed so that the side plate 155 of the main body cover 150 can be inserted in a state where the side cover 130 is fixed before and after the housing 120. Further, with the main body cover 150 covering the main body case 110, screws are inserted into screw holes 156 opened in the side plate 155, and the side covers 130 are screwed and fixed at both ends of the main body cover 150. Furthermore, the screw hole 156 can also be used for the connection between the housing 120 and the side cover 130, thereby improving the assembly work efficiency.

  The main body cover 150 is made of a rigid member such as a sheet metal, and the casing of the capacitive electromagnetic flowmeter is given strength by being screwed with the side cover 130 and screws at both ends. Thereby, when piping a capacity type electromagnetic flow meter, even if stress is applied to the piping fixing mechanism provided on both sides of the capacity type electromagnetic flow meter, it is possible to give strength that can sufficiently resist. For example, when the screw groove 112 provided on the inner surface of the flow path port 111 is screwed, torque in the opposite direction is applied from both ends. However, the main body cover 150 reinforces the main body case 110 from being damaged by such twisting stress.

  In addition, the entire casing of the capacitive electromagnetic flow meter is not made of metal, but the weight can be reduced by using the main body case 110 as a resin member. Although the main body cover 150 is made of a metal but relatively light metal plate, the overall weight can be reduced. Furthermore, even if the main body case 110 has a complicated shape, it can be formed at a lower cost than the case of metal, which is advantageous in terms of cost. In particular, metal parts can be made inexpensive by using a simple sheet metal shape. Furthermore, by covering the surface of the main body case 110 of the capacitive electromagnetic flow meter with a main body cover 150 such as a sheet metal, an effect of protecting the housing surface can be obtained. In addition, by connecting the side covers 130 at both ends with the metal main body cover 150, a secondary effect that the both end surfaces are made conductive and the ground potential can be made common can be obtained. On the other hand, the main body case 110 is provided with a liquid earth terminal 144, and the potential of the fluid to be detected is set to the ground potential of the side cover 130.

In the above example, the main body cover 150 is configured to cover the entire housing 120 with a single U-shaped main body cover 150 as shown in FIG. In particular, the bending strength can be further increased by bending the sheet metal into a U-shaped cross section. Further, since the side covers 130 can be connected to each other with a single body cover 150, the number of parts can be minimized and the assembly workability is excellent. However, the main body cover is not limited to the above configuration, and may be configured by a plurality of sheets. For example, as shown in FIG. 8B, two main body covers 151 each having a U-shaped cross section may be formed so as to cover them from above and below the housing 120. Alternatively, as shown in FIG. 8C, a main body cover 152 having an L-shaped cross section may be used, and these may be sandwiched from the diagonal direction of the housing 120. Further, as shown in FIG. 8D, a configuration may be used in which the side covers are bridged by using two flat plate-like body covers 153.
(Side cover 130)

The side cover 130 opens the flow path port 111. The channel port 111 constitutes a channel with the measurement tube 10 built in the main body case 110. The diameter of the flow path is set to substantially the same diameter from one end to the other end of the flow path port 111 to reduce loss when the detected fluid flows in one direction in the flow path. A thread groove 112 is formed on the inner surface of the channel port 111 at the channel port 111 as a piping fixing mechanism for connecting to an external piping (not shown) of a factory or the like where a capacitive electromagnetic flow meter is installed. . In order to ensure mechanical strength when piping by screwing, the side cover 130 is preferably formed integrally with metal. As another connection method between the external pipe and the flow path, a bolt is planted on the open end face of the main body case, and on the other hand, a flange is provided at the end of the external pipe, and the nut is passed through the bolt through the flange insertion hole. The main body case and the external pipe may be connected by screwing.
(Measurement tube 10)

  The measurement tube 10 is an insulating lining that allows a fluid to be detected to pass through the inside of the tube. The measuring tube 10 is required to have excellent chemical resistance as a pipe through which a fluid to be detected passes and electrical characteristics for constituting a capacitor. From the viewpoint of mechanical characteristics, the measuring tube 10 is a strength matrix that bears the force of tension or compression based on the expansion and contraction of the pipe due to pressure and temperature changes of the fluid to be detected, and the required inner diameter, thickness, and length to withstand it. A rigid structural member having On the other hand, from the viewpoint of electrical characteristics, the measuring tube 10 is desirably a dielectric material as a nonmagnetic insulating member. In particular, the electrode 30 is made of a material having a high dielectric constant in order to enhance the capacitive coupling between the electrode 30 attached around the measuring tube 10 and the fluid to be detected and to improve the S / N ratio. Ceramics, plastics, etc. can be used as such materials. In general, ceramics are used. However, when a protrusion 12 and a step 14 for positioning, which will be described later, are integrally formed on the outer peripheral surface of the measuring tube, the positioning accuracy is reduced due to thermal shrinkage during molding, or post-processing is performed. If such protrusions and steps are formed, the cost may increase. For this reason, in the present embodiment, a PPS resin mixed with ceramics that has relatively high strength and can ensure molding accuracy and high dielectric property is employed. PPS resin is excellent in oil resistance and chemical resistance. In the present embodiment, Flexis (registered trademark) manufactured by Polyplastics Co., Ltd. was used. A lining is applied to the inner surface of the measuring tube 10 as necessary.

  The fluid to be detected is water or a non-corrosive liquid, and is a liquid having a predetermined conductivity. Unlike the liquid contact type electromagnetic flow meter, the capacity type electromagnetic flow meter does not directly contact the electrode 30 with the fluid to be detected. Therefore, even a liquid that corrodes an electrode that could not be used conventionally can be measured. Moreover, it can respond to various to-be-detected fluids by selecting the material of the measuring tube 10. FIG. In particular, the material of the measuring tube 10 can be selected according to the dielectric constant required in accordance with the measurement accuracy and the resistance to the fluid to be detected. In particular, since the capacitive electromagnetic flow meter according to the present embodiment uses the measurement tube 10 as a separate member from the main body case 110, only the measurement tube 10 is changed, and other component parts are used in common, so that the capacitance type has various specifications. An electromagnetic flow meter can be configured, which is advantageous for product preparation.

  Further, the measurement tube 10 is provided with a rotation blocking mechanism for blocking the rotation of the columnar measurement tube 10. That is, since it is necessary to make the electrode 30 and the exciting coil 22 orthogonal to each other around the measurement tube 10, if the cylindrical measurement tube 10 is rotated and misaligned, accurate detection may be hindered. . For this reason, as shown in FIG. 9A, a projection 12 is provided on the outer periphery of the measuring tube 10. By forming a hole for supporting the protrusion 12 in the preamplifier module 160, the main body case 110, and the like, the measuring tube 10 is positioned in a predetermined posture and rotation is prevented.

The measurement tube 10 is a separate member from the main body case 110. Thereby, the material suitable for a capacitor | condenser can be selected for the member which comprises the measurement pipe | tube 10. FIG. On the other hand, a resin that can be easily molded into a complicated shape can be used for the main body case 110. Thus, by making the measuring tube 10 a separate member from the main body case 110, it can be configured by a member suitable for each. In particular, since the high dielectric material constituting the measuring tube is generally expensive, only necessary portions are made of expensive members, and the other members can be made of less expensive materials to reduce the overall cost. Moreover, the measuring tube 10 made of an appropriate material can be selected according to the accuracy required for the capacity type electromagnetic flow meter. Furthermore, it can be replaced with a measuring tube having a different diameter. Thus, a measuring tube made of an appropriate material can be selected according to the detection purpose and application of the capacity type electromagnetic flow meter, the required specifications and cost. In addition, by making it possible to set a plurality of measurement tubes in one capacity type electromagnetic flow meter, the members of various types of capacity type electromagnetic flow meters can be shared and provided at low cost.
(Electrode 30)

  An electrode 30 is disposed around the measurement tube 10. As the electrode 30, an insulating tape such as polyimide coated with a copper foil can be used. As shown in FIG. 9B, the electrode 30 is a planar conductor that is curved along the outer periphery of the cylindrical measurement tube 10, and the pair of electrodes 30 are opposed to each other with the measurement tube 10 interposed therebetween. Arrange to do. Thus, by electrostatic coupling between the pair of electrodes 30 and the fluid to be detected, the electromotive force generated in the fluid can be taken out from the measuring tube 10 and the flow rate can be detected. Each electrode 30 is affixed to the outer periphery of the measuring tube 10 without a gap. Tape or adhesive can be used for pasting. The electrode 30 is preferably made of a flexible member and can be fixed to the outer surface of the measuring tube 10 without a gap.

  In order to prevent conduction between the pair of electrodes due to corrosion or condensation of the electrode which is a planar conductor, the conductor is preferably covered with an insulating layer. In the example of FIG. 9, the insulating layer is formed and bonded simultaneously by bonding to the outer periphery of the measuring tube 10 via an insulating adhesive such as silicone resin. As another configuration, a polyimide resin tape may be used as the insulating layer, and an electrode 30 in which a copper foil planar conductor is previously provided on the polyimide resin tape may be disposed on the measuring tube 10. Around the measurement tube 10, a step 14 is formed at the position and size where the electrode 30 is disposed, and the positioning of the electrode 30 is realized. The step 14 is formed by reducing the thickness of the outer circumference of the measuring tube 10.

  Further, the electrode 30 is provided with leads for electrical connection with the preamplifier module 160. In the example of FIG. 9, a lead piece 32 is formed by cutting a part of a sheet conductor of copper foil, and this is pulled out. This configuration eliminates the need for lead wiring or the like, and enables wiring of the electrode 30 to be performed very inexpensively and easily.

Although a pair of electrodes is used in this example, two or more sets of electrodes can be used. When a plurality of sets of electrodes are used, the positions of the electrodes are adjusted so that the electric field detected by each electrode is orthogonal to the magnetic field.
(Housing 120)

Next, members housed in the housing 120 will be described based on the exploded perspective view of FIG. As shown in this figure, the housing 120 includes a measuring tube 10, a pair of preamplifiers, and an excitation module 170. A through-hole 121 is opened before and after the housing 120, and the measuring tube 10 is inserted therein. Preamplifiers are arranged above and below the measurement tube 10 held inside the housing 120. As shown in FIG. 11, the preamplifier module 160 holds the electrode 30 from above and below with the electrode 30 attached.
(Preamplifier)

The preamplifier module 160 constitutes a preamplifier for signal amplification. In the capacitive electromagnetic flow meter, since the capacitive coupling between the electrode 30 and the fluid to be detected is generally as small as several tens of pF, the impedance of the resistance when providing a filter for passing an electrical signal is extremely high. . For this reason, a preamplifier is connected to each electrode 30 as a detection circuit 34 to lower the impedance. The preamplifier shown in FIG. 10 is electrically connected to a pair of electrodes 30 arranged in the measurement tube 10, amplifies the detected electrical signal, and sends it to the control unit 40. In this preamplifier, the preamplifier module 160 is housed in a shield case 161 and is further closed by a shield cover 162, so that the preamplifier including the electrode 30 is reliably shielded to protect the electrical signal from noise.
(Preamplifier module 160)

An appearance of the preamplifier module 160 is shown in FIG. 11A is a perspective view of a pair of preamplifier modules 160, and FIG. 11B is an exploded perspective view of the preamplifier module 160. Each preamplifier module 160 includes a preamplifier substrate 164, a preamplifier substrate holder 165, and an electrode protection sheet 166, as shown in FIG. The preamplifier substrate 164 is mounted with an electronic component for amplifying the electric signal detected by the electrode 30. The preamplifier substrate 164 is held by a preamplifier substrate holder 165. The preamplifier substrate holder 165 shown in FIG. 11B has an opening for holding the preamplifier substrate 164 on the upper surface. The preamplifier substrate holder 165 has a lower surface curved in an arch shape along the side surface of the measurement tube 10, and the electrode protection sheet 166 is fixed to the curved surface. The electrode protection sheet 166 is made of an elastic body such as rubber and is pressed by the curved surface of the preamplifier substrate holder 165 to press the electrode 30 around the measuring tube 10 without a gap. In particular, in order to increase the capacitive coupling by the electrode 30, it is necessary to fix the electrode 30 and the measuring tube 10 so that no gap is generated. By using the electrode protection sheet 166 for this work, when the preamplifier module 160 is set on the measurement tube 10, the electrode 30 can be reliably pressed around the measurement tube 10 and fixed without any gap, thereby improving reliability. At the same time, the configuration is simplified to improve the work efficiency.
(Excitation module 170)

  Furthermore, the excitation module 170 is arrange | positioned so that the housing 120 shown in FIG. The excitation module 170 includes an excitation coil 22 and applies a magnetic field from the left and right of the measurement tube 10. Therefore, the arrangement positions of the excitation module 170 and the preamplifier are set so that the electric field and magnetic field detected by the electrode 30 are orthogonal to each other.

A perspective view of the excitation module 170 is shown in FIG. FIG. 12A shows a perspective view of the excitation module 170 as viewed obliquely from above, and FIG. 12B shows a perspective view as seen from obliquely below. The excitation module 170 shown in this figure includes a coil case 172 that holds the excitation coil 22, an excitation plate 174 that fixes the coil case 172 as a pair so as to face each other, and a relay substrate 176.
(Excitation plate 174)

  A perspective view of the excitation plate 174 is shown in FIGS. The excitation plate 174 holds the pair of coil cases 172 apart from each other, and generates a magnetic field between the pole pieces 178 of the coil case 172. The excitation plate 174 is formed in a substantially U-shaped cross-section in which opposed pieces 174a that are separated from each other in parallel are connected at both ends of the connecting piece 174b. And keep them apart. Further, yoke pieces 174c for fixing the yoke lid are formed at both ends of the upper surface of the excitation plate 174, respectively.

The excitation plate 174 is made of a ferromagnetic material because it forms a magnetic circuit with the magnetic field generated by the excitation coil 22. The excitation plate 174 is integrally formed of metal or the like. In other words, the magnetic flux generated from the pole piece 178 reduces the leakage magnetic flux toward the downward connecting piece 174b so that the magnetic field is efficiently generated between the opposing pole pieces 178. Is partially open. In particular, a magnetic circuit is prevented from being short-circuited by forming an opening 174d by greatly opening a joint portion between the connecting piece 174b and the opposing piece 174a. By using the excitation plate 174 having such a shape, the leakage magnetic field can be reduced and the efficiency of the magnetic circuit can be increased.
(Relay board 176)

As shown in FIG. 12B, a relay substrate 176 is fixed to the back surface of the connecting piece 174b of the excitation plate 174. The relay board 176 constitutes an initial excitation power supply 26, an excitation continuation power supply 27, an excitation polarity switching circuit 28, and a constant current circuit 29 shown in FIG. 3 as the excitation circuit 24 for exciting the excitation coil 22. A necessary electric circuit is mounted on the relay substrate 176 so that the exciting circuit 24 generates an alternating magnetic field between the pole pieces 178. The excitation module 170 generates an alternating magnetic field at a frequency different from the commercial frequency. Preferably, the excitation frequency is higher than the commercial frequency, for example, 75 kHz. Thereby, the noise which arises in a commercial frequency can be avoided.
(Coil case 172)

The coil case 172 has a configuration in which a core is inserted and the exciting coil 22 is wound around the core. An exploded perspective view of the coil case 172 is shown in FIG. As shown in this figure, the coil case 172 has a shape in which flat plates 172a and 172b are connected by a hollow shaft, and a coil winding space 172c for winding the exciting coil 22 is formed between the flat plates 172a and 172b. One flat plate 172a has a pole piece insertion opening 172d into which a pole piece 178 is inserted as a core. The pole piece insertion port 172d has a hollow shaft shape and penetrates the coil winding space 172c. Further, the other flat plate 172b has a rectangular shape and is fixed to the opposing piece 174a of the excitation plate 174 as shown in FIG.
(Pole piece 178)

  The exciting coil 22 is wound around the pole piece core 178a. The pole piece 178 has a rectangular flat plate 178b fixed to one end of an iron core forming the pole piece core 178a, and magnetic flux enters and exits through the flat plate 178b. A conductive magnetic material such as a laminated iron core can be suitably used for the pole piece core 178a. Moreover, it is good also as a structure which reduces the magnetic circuit delay which arises in this part, without using a pole piece core.

  In this excitation module 170, a pair of built-in excitation coils 22 are arranged apart from each other, and the excitation coil 22 is excited by the relay substrate 176 to generate a magnetic field between the pole pieces 178. As a result, when a liquid having conductivity as the fluid to be detected flows through the measuring tube 10 installed between the pole pieces 178, an electromotive force is generated in a direction orthogonal to the moving direction of the liquid.

  In the example of FIG. 1, two exciting coils 22 are used and are provided on the left and right of the measuring tube 10, but the number of coils may be one. For example, as shown in FIG. 20, if the measurement tube 10B is sandwiched between both ends of the core 178B, the exciting coil 22B wound around the core 178B can be integrated. Similarly to FIG. 1 and the like, the capacitive electromagnetic flow meter shown in this figure excites the exciting coil 22B with the exciting circuit 24B, and the detection circuit 34B detects the electromotive force generated by the fluid to be detected passing through the measuring tube 10B with the electrode 30B. It is detected, sent to the control unit 40B, and displayed on the display unit 51B.

Further, returning to FIG. 5, the capacitive electromagnetic flow meter has the display unit 50 fixed to the upper surface of the main body case 110. Screw holes 122 for fixing the display unit 50 are formed at the four corners of the housing 120 on the upper surface of the main body case 110. In addition, a recessed step space is formed at the upper end of the side cover 130 so as to be flush with the surface of the display unit 50 fixed to the upper surface of the main body case 110. This step space is formed to be approximately equal to or slightly larger than the outer shape and size of the display unit 50.
(Display unit 50)

  The display unit 50 is a member for displaying information such as the flow rate of the fluid to be detected, and includes a display screen 52 as the display unit 51 as shown in FIG. In the example of FIG. 4, a 7-segment display is used as a numerical display area for displaying numerical values on the display screen 52, and the flow rate and the like are displayed numerically. The 7-segment display displays numerical values such as instantaneous flow rate and integrated flow rate for the detected flow rate. The display screen 52 shown in this figure includes two stages of 7-segment displays, and can display the integrated flow rate and the set value simultaneously. However, it is needless to say that the display of the integrated flow rate, the instantaneous flow rate, the set value, etc. can be switched by providing only one screen with a 7-segment display.

  The display screen 52 includes a fluid display lamp 53 that indicates the flow velocity and the flow direction of the fluid to be detected. The fluid indicator lamp 53 is composed of LEDs arranged in a bar shape. The fluid indicator 53 can light up the LEDs sequentially in the flow direction at a speed corresponding to the flow rate, for example, and can express the flow velocity and the flow direction sensuously. Moreover, instead of the bar-shaped LED, an arrow-shaped indicator lamp or the like can be used. Furthermore, instead of the segment-type display screen 52 using LEDs or the like, a display screen using liquid crystal or organic EL can be used. In this way, the display screen 52 can display not only numerical values such as flow rate but also figures and images such as arrows or alternatively, and can easily display the detected flow rate information to the user. Can be displayed.

  The display unit 50 also includes an operation panel 54 as a setting unit 80 for performing various settings. The operation panel 54 includes keys and buttons for performing various settings. In the example of FIG. 4 and the like, a 4-digit 7-segment display is arranged in two stages on the display screen 52, an operation panel 54 is provided in the lower right, and keys are arranged in the cross direction. The setting unit 80 functions as a reset setting unit for setting an initial value of an integrated flow rate, which will be described later, or a predetermined reset value.

In this example, the display circuit that displays the display screen 52 incorporates a control unit 40 that is connected to the detection circuit 34 and the excitation circuit 24 and controls them. However, it goes without saying that the control circuit can be formed of individual members and incorporated in the main body case 110. It is also possible to integrate a control circuit, a detection circuit, an excitation circuit, and the like.
(Output unit 60)

  Further, the display unit 50 includes an output unit 60. In this example, the output unit 60 includes a control output, an analog output, and a timeout output, and includes an external output terminal corresponding to each output. The control output can be used as an ON / OFF output for directly controlling the ON / OFF operation of an external device with a capacitive electromagnetic flow meter. In this case, it functions as a switch that outputs in two states of HIGH / LOW so that the ON / OFF output is switched when the detected instantaneous flow rate reaches a predetermined value. The switch function may be either normally open or normally closed. Alternatively, a pulse voltage corresponding to the detected integrated flow rate can be output as the control output. In this case, the external voltage input device can be used for controlling the integrated flow rate. Further, a reset signal input terminal for resetting the integrated flow rate may be provided.

  On the other hand, the analog output can output an analog current according to the measured instantaneous flow rate or integrated flow rate. In this example, when the instantaneous flow rate changes in the range of 0 to the rated value, an analog current is output in the range of 4 to 20 mA. For this reason, the output unit 60 includes an analog current output circuit 62. The analog current has better noise immunity than the voltage signal, and can be used for data recording and analysis by outputting it to the outside. Further, the timeout output outputs a timeout signal at the time of timeout as will be described later.

Thus, the output unit 60 can function as an integrated value output unit or an instantaneous value output unit. Note that the output unit may omit any of the control output, analog output, and timeout output, or may include another output terminal. Furthermore, you may provide the output indicator lamp which shows the output state of each output terminal.
(Input unit 70)

Further, the display unit 50 can include an input unit 70. The input unit 70 is an interface for inputting an input signal from an external device such as a temperature sensor, a reset signal for resetting the integrated value, and various setting information. As the input unit, a communication unit capable of data communication, an I / O terminal, a memory card, or the like can be used.
(Display unit 50)

On the other hand, as the display unit 50, an integrated display unit 50 in which the display unit 50 is provided in the main body case 110 and a separate display unit 50B in which the display unit is disposed at a position different from the main body case 110 can be used. FIG. 15 is an exploded perspective view of the integrated display unit 50.
(Integrated display unit 50)

The integrated display unit 50 shown in this figure includes a front case 55, a power cable 56, a display substrate 57, and a power substrate 58. The front case 55 is a housing of the display unit 50 and holds the display substrate 57 inside, and is positioned so that a 7-segment display provided on the display substrate 57 is exposed to the outside through an opening window. And fix. Further, a power supply substrate 58 is disposed on the back surface of the display substrate 57 so as to be separated. The power cable 56 is connected to an external power source for driving the capacitive electromagnetic flow meter, and supplies power to the capacitive electromagnetic flow meter. The display board 57 is mounted with a drive circuit for a display element such as a LED constituting a 7-segment display and various indicators, an electronic component including a switch of the operation panel 54, and a control component such as a CPU. Further, a power supply board 58 is prepared separately from the display board 57, and power supply circuit components are mounted on the power supply board 58. By separating the display substrate 57 on which the display drive circuit is mounted from the power supply substrate 58 on which the power supply circuit is mounted, the heat generated in the power supply circuit can be separated from the electronic components of the display circuit.
(Alternative fixing mechanism)

  The display unit 50 can change the mounting direction of the display unit 50 so that the user can easily view the display screen 52 according to the mounting position and posture of the capacitive electromagnetic flow meter. FIG. 16 shows how the display unit 50 is fixed to the main body case 110 of the capacitive electromagnetic flow meter. 16A shows a separation type display unit 50B, FIG. 16B shows a state in which the integrated display unit 50 is fixed, a state in which the display unit 50 is fixed horizontally with the flow direction of the non-detection fluid, and FIG. The state where the same integrated display unit 50 as in (b) is fixed in a posture perpendicular to the flow direction of the non-detection fluid is shown.

  Specifically, the step space on the upper surface of the display unit 50 and the main body case 110 is substantially square, and the display unit 50 can be fixed even when the attachment angle of the display unit 50 is rotated by 90 °. For this reason, the screw holes 122 for fixing the display unit 50 to the upper surface of the main body case 110 are precisely drilled at the four corners. Accordingly, the display unit 50 can be fixed to the main body case 110 even when the display unit 50 is rotated by 90 °, and the display direction of the display screen 52 can be changed. That is, while the measuring tube 10 is fixed in a posture along the flow direction (for example, up and down or left and right) of the fluid to be detected, the posture of the display unit 50 fixed to the capacitive electromagnetic flow meter is determined by the user viewing the display screen 52. Can be fixed in an easy direction.

  Conventionally, when a capacitive electromagnetic flow meter is fixed to a pipe or the like, the capacitive electromagnetic flow meter is sometimes fixed not only in a horizontal posture but also in a vertical posture. In this case, since the display device is arranged in the vertical direction, there is a problem that it is difficult to read numerical values displayed in horizontal writing. On the other hand, as shown in Patent Document 2 described above, there has been a flow meter provided with a mechanism for rotating the display unit 50 with the main body case 110 so that the display screen 52 can be visually recognized in both the vertical and horizontal directions, but a rotation mechanism is necessary. As a result, the structure is complicated, and there are problems such as an increase in cost and an increase in size. On the other hand, the above configuration is an extremely simple configuration in which the mounting posture is changed and screwed, so that the number of parts is not increased and the display screen 52 is made horizontal while achieving downsizing. In other words, it can be fixed to a posture that the user can see from an upright posture, and the visibility is improved.

  Note that the method of fixing the display unit 50 is not limited to screwing at the four corners. For example, a screw hole may be drilled in the middle of each side of the square, or engagement or fitting with a hook or the like.

  In addition, it is not necessarily limited to the configuration in which the mounting angle of one display unit is changed. For example, a display unit for horizontal display and a display unit for vertical display are prepared separately, and an appropriate display unit is selected according to the application. And may be configured to be fixed. This configuration eliminates the need for a 90 ° rotatable configuration, so there is no need to make the upper surface of the main body case substantially square, and the main body case can have various shapes such as a rectangular shape. Is obtained.

Furthermore, the display unit 50 fixed to the main body case 110 can be replaced. As a result, the main body case 110 can be used in common for both the integral type and the separated type display unit 50, and the advantage that the members can be shared is obtained.
(Separate display unit 50B)

  FIG. 16A shows an example of a separate display unit 50B. As shown in FIG. 17, the separation type display unit 50 </ b> B separates the display screen 52 from the main body case 110, arranges the display panel 50 </ b> C in the main body case 110, and exchanges electric signals with cables or the like. Information such as the flow rate is displayed on the display screen 52 at a position distant from. The display panel 50C can have the same configuration as the integrated display unit 50 described above.

  FIG. 18 shows a block diagram of an electromagnetic flow meter 200 using a separate display unit. The electromagnetic flow meter 200 shown in this figure can use the same main body case as the main body case 110 of the electromagnetic flow meter using the integrated display unit according to FIG. 3 described above, and detailed description thereof will be omitted. In the block diagram of FIG. 18, the display unit 50B includes an A / D converter 38B, a control unit 40C, an operation display screen 52B as a display unit, an analog current output circuit 62B as an output unit, and a serial communication circuit as a communication unit. 63. The serial communication circuit 63 performs data communication with the display panel 50C and transmits necessary data to be displayed on the display panel 50C.

  In the example of FIG. 16A, an indicator 53B indicating the passage of the fluid to be detected is provided as an operation display screen 52B on the upper surface of the main body case 110 instead of the 7-segment display. The operation display screen 52B can indicate the movement direction of the fluid to be detected in addition to the operation state of the capacitive electromagnetic flow meter, such as detecting the flow rate. In the example of FIG. 16A, as the indicator 53B, four arrow-shaped indicator lamps are arranged horizontally along the detection direction of the measuring tube 10, and the indicator lamps are turned on by LEDs or the like. The indicator 53B visually displays the flow direction by blinking the indicator 53B in the direction of passage of the fluid to be detected and lighting it so as to move the light.

  For example, when the fluid to be detected is flowing along the detection direction, the indicator lamp is lit in blue, while when the fluid to be detected is flowing in the reverse direction, it is displayed in red. Further, by dynamically changing the blinking pattern of the indicator lamp to display the movement direction of the fluid to be detected, the movement of the fluid can be more easily recognized visually.

  FIG. 19 shows an exploded perspective view of the operation display screen 52B constituting the separation type display unit 50B. The separation type display unit 50B shown in this figure includes a front case 55B, a display substrate 57B, a power supply substrate 58B, a power supply cable 56B, and a temperature sensor cable 59B. The front case 55B is insert-molded with the indicator 53B. The display board 57B and the power supply board 58B can be configured by mounting the same components as the integrated display unit 50 described above. Further, in this example, an input signal from a temperature sensor that detects the temperature of the fluid to be detected is input to the input unit 70 via the temperature sensor cable 59B, and the temperature of the fluid to be detected is arranged on the side of the display panel 50C that is spaced apart. Can be sent to and displayed.

  In addition, omitting the indicator from the operation display screen on the top surface of the main body case, or conversely providing a display screen for displaying the flow rate etc. on the main body case side even if it is a separate display unit. Needless to say, it can also be provided at two positions.

  In addition, although the example applied to the capacity | capacitance type electromagnetic flowmeter was demonstrated above, it is not restricted to this, The liquid contact type electromagnetic flowmeter and other flow detection means with which the to-be-detected fluid and electrode inside a measuring tube contact are provided. Various known sensors such as an electromagnetic flow meter, for example, a turbine type, a Karman vortex type, a diaphragm type, a paddle type, and an ultrasonic type can be appropriately employed.

The electromagnetic flow meter of the present invention can be suitably applied as a capacitive electromagnetic flow meter that detects the flow rate of a conductive liquid.

It is a block diagram which shows the structure of an electromagnetic flowmeter. It is sectional drawing of a main body case. It is a detailed block diagram of a capacitive electromagnetic flow meter. It is a perspective view which shows the electromagnetic flowmeter which concerns on one embodiment of this invention. It is the disassembled perspective view which removed the display unit of the electromagnetic flowmeter shown in FIG. It is a disassembled perspective view which removed the nozzle | cap | die and the reinforcement board from the main body case of FIG. It is a disassembled perspective view which shows the state which fixes a side cover with a main body cover. It is sectional drawing which shows the state holding a housing with a main body cover. The It is the perspective view of a measurement tube, and the exploded perspective view which removed the electrode. It is a disassembled perspective view of the main body case of FIG. It is a disassembled perspective view of a preamplifier module. It is a perspective view of an excitation module. It is a perspective view of an excitation plate. It is a disassembled perspective view of an exciting coil. It is a disassembled perspective view of an integrated display unit. It is a perspective view which shows a mode that a display unit is fixed to the main body case of an electromagnetic flowmeter. It is a perspective view which shows the electromagnetic flowmeter which uses a separation type display unit. It is a block diagram which shows the electromagnetic flowmeter which uses a separation type display unit. It is a disassembled perspective view of a separation type display unit. It is a block diagram which shows the other structure of an electromagnetic flowmeter. It is a circuit diagram which shows an example of the excitation circuit for capacitive electromagnetic flowmeters. It is a circuit diagram which shows the modification of the excitation circuit for capacitive electromagnetic flowmeters. It is a block diagram which shows an example of a capacity | capacitance type electromagnetic flowmeter. It is a circuit diagram which shows an example of the excitation circuit of a capacity | capacitance type electromagnetic flowmeter. It is a graph which shows the voltage waveform applied from the excitation initial state of an exciting coil to a steady state. It is a block diagram which shows the structure of a liquid-contact type electromagnetic flowmeter.

DESCRIPTION OF SYMBOLS 100, 200 ... Electromagnetic flowmeter 10, 10B ... Measuring tube; 12 ... Protrusion; 14 ... Level difference 22, 22B ... Excitation coil; 24, 24B, 24C, 24D ... Excitation circuit 25 ... Excitation power source; ... excitation continuous power supply; 27B ... constant voltage power supply 28 ... excitation polarity switching circuit; 29 ... constant current circuit 30, 30B ... electrode; 32 ... lead piece; 34, 34B ... detection circuit 35 ... differential amplifier; ... periodic reset circuits 38, 38B ... A / D converters 40, 40B, 40C ... control unit 50 ... display unit; 50B ... separate display unit; 50C ... display panel 51, 51B ... display unit; 52 ... display screen; 52B ... operation display screen 53 ... fluid indicator lamp; 53B ... indicator 54 ... operation panel; 55, 55B ... front case 56, 56B ... power cable; 57, 57B ... 58, 58B ... power supply board 59B ... temperature sensor cable 60 ... output unit; 61 ... external output circuit; 62, 62B ... analog current output circuit 63 ... serial communication circuit 70 ... input unit; 80 ... setting unit 110 ... main body 111: channel opening; 112 ... screw groove 120 ... housing; 121 ... through hole; 122 ... screw hole 130 ... side cover; 140 ... yoke lid; 142 ... reinforcing plate; 144 ... liquid earth terminals 150, 151, 152, 153 ... Main body cover; 155 ... Side plate; 156 ... Screw hole 160 ... Preamplifier module; 161 ... Shield case; 162 ... Shield cover 163 ... Preamplifier; 164 ... Preamplifier substrate; 165 ... Preamplifier substrate holder 166 ... Electrode protection sheet 170 ... Excitation module 172 ... Coil cases 172a, 172b ... Flat plate; 172 172d: Pole piece insertion port 174 ... Excitation plate 174a ... Opposing piece; 174b ... Connection piece; 174c ... Yoke piece; 174d ... Opening 176 ... Relay board 178 ... Pole piece; 178a ... Pole piece core; 178b ... Flat plate 178B ... Core 180 ... Residual voltage detection circuit; 181 ... Operational amplifier 190 ... Switching circuit; 192 ... Power supply switch 800 ... Liquid contact type electromagnetic flow meter; 801 ... Flow rate detection means; 802 ... AC amplifier; ... Synchronous rectification circuit; 805 ... Timing pulse generation circuit; 806 ... A / D converter 808 ... Output unit; 810 ... AC power supply; 811 ... Measuring tube 822 ... Excitation coil; 824 ... Excitation circuit; Display unit 910 ... Measuring tube; 922 ... Excitation coil; 924 ... Excitation circuit; 927 ... Constant voltage power supply 92 8 ... Excitation polarity switching circuit; 929 ... Constant current circuit; 930 ... Electrodes SW1 to SW4 ... Polarity switching switch Q ... Transistor

Claims (4)

An electromagnetic flow meter for detecting a flow rate of a fluid to be detected,
A measuring tube constituting a flow path through which the fluid to be detected passes,
At least a pair of exciting coils arranged to be orthogonal to the flow path of the measuring tube;
An excitation circuit for exciting the excitation coil;
At least a pair of electrodes arranged to be orthogonal to a straight line connecting the flow path of the measurement tube and the pair of electrodes;
A detection circuit capable of detecting a voltage signal detected by the electrode;
Based on the voltage signal detected by the detection circuit, calculation means for calculating the flow rate of the fluid to be detected that passes through the flow path of the measurement tube;
With
The excitation circuit further includes
A constant voltage power supply connected in series with the excitation coil and capable of adjusting and supplying an output voltage value for exciting the excitation coil;
A constant current circuit connected in series with the excitation coil to regulate a current flowing through the excitation coil to a predetermined value;
An excitation polarity switching circuit interposed between the excitation coil and a constant voltage power source and a constant current circuit for switching the polarity of excitation;
A residual voltage detection circuit connected to the constant current circuit for detecting a residual voltage of the constant current circuit;
With
The constant voltage power supply compares the residual voltage detected by the residual voltage detection circuit with a predetermined reference voltage, and controls the output voltage so that the comparison result is minimized ,
The constant voltage power source includes a variable voltage DC / DC converter;
The variable voltage DC / DC converter applies a high voltage so that the current can easily flow when the excitation coil is turned on, and after the current starts flowing, the voltage is decreased and a constant low voltage is applied. electromagnetic flowmeter characterized by comprising Te. A capacitive electromagnetic flow meter for detecting the flow rate of a fluid to be detected,
A measuring tube constituting a flow path through which the fluid to be detected passes,
At least a pair of exciting coils arranged to be orthogonal to the flow path of the measuring tube;
An excitation circuit for exciting the excitation coil;
At least a pair of electrodes, which are arranged so as to be orthogonal to a straight line connecting the flow path of the measurement tube and the pair of electrodes, and coupled to the measurement tube in a non-contact state with a fluid to be detected;
A detection circuit capable of detecting a voltage signal detected by the electrode;
Based on the voltage signal detected by the detection circuit, calculation means for calculating the flow rate of the fluid to be detected that passes through the flow path of the measurement tube;
With
The excitation circuit further includes
A constant voltage power supply connected in series with the excitation coil and capable of adjusting and supplying an output voltage value for exciting the excitation coil;
A constant current circuit connected in series with the excitation coil to regulate a current flowing through the excitation coil to a predetermined value;
An excitation polarity switching circuit interposed between the excitation coil and a constant voltage power source and a constant current circuit for switching the polarity of excitation;
A residual voltage detection circuit connected to the constant current circuit for detecting a residual voltage of the constant current circuit;
With
The constant voltage power supply compares the residual voltage detected by the residual voltage detection circuit with a predetermined reference voltage, and controls the output voltage so that the comparison result is minimized ,
The constant voltage power source includes a variable voltage DC / DC converter;
The variable voltage DC / DC converter applies a high voltage so that the current can easily flow when the excitation coil is turned on, and after the current starts flowing, the voltage is decreased and a constant low voltage is applied. capacitive electromagnetic flowmeter characterized by comprising Te. The capacitive electromagnetic flow meter according to claim 2,
The constant voltage power source includes an input terminal for inputting a signal from the residual voltage detection circuit;
The residual voltage detection circuit is configured by a feedback circuit, and connects the output side and the input side of the feedback circuit via a capacitor, and the difference between the residual voltage of the constant current circuit and a predetermined reference voltage on the input side. Is input, and the output side is connected to the input terminal of the constant voltage power source. The capacitive electromagnetic flow meter according to claim 3, wherein the excitation circuit further includes:
A capacitive electromagnetic flow meter comprising a switching circuit connected between an input terminal of the constant voltage power source and a residual voltage detection circuit.

Images