JPS6231853Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an electromagnetic flowmeter, and in particular, is provided between flanges on the upstream and downstream sides of a mating pipe that sends a fluid to be measured, and an exciting current is supplied to adjust the flow rate of the fluid to be measured. The present invention relates to an integrated electromagnetic flowmeter in which a transmitter section that outputs a corresponding flow rate signal and a converter section that has a converter circuit that processes and outputs the flow rate signal from the transmitter section are integrally formed.

FIG. 1 shows the configuration of a conventional integrated electromagnetic flowmeter of this type. FIG. 1a is a plan view showing the converter storage box with the cover and the printed board inside thereof omitted, and FIG. 1b is a front view in this case.

The transmitter section 1 has fixed therein a measuring pipe through which a measuring fluid flows, an excitation coil that applies a magnetic field to the measuring fluid, and an electrode that detects a signal voltage corresponding to the measuring fluid. A converter storage box 2 is fixed to the top of the transmitter section 1, and this converter storage box is composed of a bottom casting 2a and a lid 2b.

Heat-generating components such as an excitation power transistor 3 are directly attached to the bottom casting 2a itself. Further, the printed boards 4 and 5 of the converter circuit are screwed to the bottom casting 2a via the supports, and the signal line 6a from the transmitter section 1, the excitation electric wire 6b, or the comparison signal line 6c is connected to the relay terminal 7. Once screwed, it is connected to the terminal boards 4a, 5a of the printed boards 4, 5, and lead wires (not shown) are directly drawn out from the printed boards 4, 5 as external wiring via the bottom casting 2a. It is. Further, a resistor 8 for detecting a comparison signal is directly fixed to the bottom casting 2a.

The transducer storage box 2 is fixed to the transmitter section 1 by screws 9 at the bottom of its bottom casting 2a. In addition,
FL indicates the flow direction of the measured fluid.

A lid 2b is removably fixed onto the bottom casting 2a, and when the lid 2b is removed, the entire transducer circuit can be seen.

Historically, electromagnetic flowmeters have been separated into a transmitter that detects a flow rate signal and a converter that processes and outputs the flow rate signal detected by this transmitter. It was connected by a cable. On the other hand, the conventional integrated electromagnetic flowmeter shown in FIG. 1 has a compact structure in which the transmitter section is sandwiched and fixed in a sandwich-like manner between the flanges of the mating piping. However, the configuration of the electrical circuit that accompanies the coupling of the transmitter section and the converter section is such that the conventional separate converter is simply placed on top of the transmitter. No consideration is given to the problems that arise from carrying vehicles.

The present inventor focused on this point and found that the integrated electromagnetic flowmeter shown in FIG. 1 has the following problems.

(b) Since the integrated electromagnetic flowmeter is fixed together with the converter on top of the piping at the installation site where the atmosphere is poor, for example, when changing the span of the converter, the lid 2
When b is opened, the printed circuit board 4 and the like are exposed, making it easy for moisture and dirt to adhere to the electric circuit, and for the exposed parts to be easily damaged.

(b) Heat-generating components such as power transistors are fixed to the bottom casting 2a below the printed boards 4 and 5, and therefore the electrical circuits disposed above are easily affected by heat, resulting in reliability problems.

(c) External wiring is connected to printed boards 4 and 5 as lead wires.
Since the lead wire comes out directly from the lead wire, the user must provide a relay terminal on the lead wire, which is an extra burden.

(d) The power transistor 3 is attached to the bottom casting 2a, and the various wirings from the transmitter section 1 are screwed to the relay terminal board 7, so electronic components that are prone to failure are mounted on the transmitter section. It is difficult to attach and detach the converter section, which is difficult to assemble and maintain.

In view of the above-mentioned prior art, and in order to solve these problems, the present invention is designed to provide an excitation current between flanges on the upstream and downstream sides of the mating piping that sends the fluid to be measured. An integrated electromagnetic flowmeter in which a transmitter unit that outputs a flow rate signal corresponding to the flow rate and a converter unit that has a converter circuit that processes and outputs the flow rate signal from the transmitter unit are integrally formed, The converter unit is housed in a converter storage box provided above the transmitter unit, and the converter storage box includes a housing and a lid that covers the housing, and the housing is airtight between the lid side and the transmitter unit side. It has a cover that separates the
Furthermore, heat-generating parts such as power transistors are directly fixed to the transmitter side of this cover, and other circuit parts of the converter circuit are fixed to the bottom of these parts, and wiring is passed through the casing to the lid side of the cover. The terminal board that connects the power supply line and the output line is fixed airtight, and the signal line from the transmitter is connected to the bottom of the housing, and a signal correction circuit that removes noise contained in the flow rate signal and fluctuations in excitation current are installed. The comparison signal correction circuit and the comparison signal correction circuit for removing the noise are fixed and separated from each other, and these signal correction circuits, the comparison signal correction circuit, and the converter circuit are made detachable.

Hereinafter, the present invention will be explained with reference to FIGS. 2 to 6. Figures 2a to 2c show an embodiment of the present invention, a
Figure 2 is a plan view with the cover of the converter storage box removed, b is a plan view with the converter unit further removed from a, and c is a plan view of the inside from the front with the cover of the converter storage box and converter unit removed. It is a diagram. FIG. 3 is an exploded perspective view of the converter storage box, FIG. 4 is an exploded perspective view of the converter unit, and FIG. 5 is an overall block configuration diagram.
FIG. 6 is a circuit diagram of the adjustment unit.

In these figures, the converter storage box 10 has a housing 10a that is circularly recessed in the center of the bottom and has a lead wire extraction hole in the center of the recess;
It consists of a lid 10b which is screwed to the lid 10a for waterproofing through a sealing member 11 such as a gasket or an O-ring. The top of the transmitter section 1 is cylindrical, and this cylindrical top is fitted into the recess of the housing 10a through an O-ring seal 12, and is inserted through a seal 13 into the recess of the housing 10a.
The upper ends are fixed at equal intervals with screws 14, and the unit is waterproof and the mounting direction can be changed in 90 degree increments (see FIGS. 2 and 3).

As shown in FIG. 2b, the bottom of the housing 10a except for the center is equipped with a printed circuit board 15 for a signal correction circuit for canceling out the induced noise on the signal from the electrodes, and a printed board 15 for eliminating measurement errors due to fluctuations in the excitation current. Printed boards 16 of a comparison signal correction circuit for the purpose of further matching the comparison signal to the waveform of the applied magnetic field are mounted apart from each other. By separating both printed boards 15 and 16, interference is eliminated. The printed board 15 includes a terminal group TM ₁ for signal line connection consisting of TM _1-1 to TM _1-4 in FIG. 5, a signal correction circuit 17, and CN _1-1 to
Equipped with connector CN ₁ consisting of CN _1-4 ,
Two signal lines from each electrode 18a, 18b are connected to each terminal. In the correction circuit 17, the induced voltage generated when the loop connected to the electrode 18b cuts the magnetic flux is adjusted with the potentiometer VR ₁ , and the outputs of the buffer amplifiers 19 and 20 are differentially amplified by the differential amplifier 21 to remove the induced voltage. The signal is corrected to optimally cancel out the noise. In addition, 17
a and 17b are shields. The other printed board 16 has a terminal group TM ₂ for connecting exciting current lines consisting of TM _2-1 to _{TM 2-4} , a current detection resistor R ₁ , a comparison signal correction circuit 22 and CN _2-1 to CN A connector CN ₂ consisting of _2-4 is mounted, and an excitation current line from an excitation coil 23 is connected to each terminal. In the correction circuit 22, the excitation current proportional voltage generated across the resistor _R1 is made to match the magnetic flux waveform by the CR circuit.
The comparison signal is corrected to the correct waveform. In addition, 24 in FIG. 5 is a measurement conduit, and generally the flow direction of the fluid, the mounting direction of the electrodes, and the direction of the magnetic field are orthogonal to each other.

Inside the converter storage box 10, both printed boards 15,
Connector that connects with 16 connectors CN ₁ and CN ₂
Converter unit 2 with CN' ₁ and CN' ₂ at the bottom
5 are connected by connector coupling and stored.

This converter section unit 25 is covered with a metal cover 2.
6 is used as a support and the necessary parts are mounted on it, and a terminal board 27 for external connection is mounted on the cover 2.
6 via a gasket 28, heavy components such as a power transformer 29 and a power transistor 31 in an excitation current generating circuit 30
A printed board 32 and a buffer amplifier 19 are mounted on the bottom surface of the cover 26, and are equipped with power supply-related, excitation-related, and output-related components.
Amplifiers such as 20 and differential amplifier 21, signal processing related parts such as division loops, and the connectors mentioned above.
The printed board 33 with CN′ ₁ and CN′ ₂ mounted on the support 3
4 and 35 to the lower surface of the cover 26 (see FIGS. 2 and 4). Connectors CN ₃ , CN' ₃ and CN ₄ are connected between the two printed boards 32 and 33.
Bonded at CN′ ₄ . The periphery of the cover 26 is
When the converter unit 25 is stored in the converter storage box 10, the stepped portion 1 provided on the inner surface of the housing 10a
It is attached to 0c via a gasket 36, and has a waterproof structure.

By making the converter section into such a unit structure, even if the lid 10b is opened, the converter circuit is covered by the cover 26 and is not exposed, so moisture, dust, etc. do not adhere to it. Also, since there is a terminal board 27 on the top surface of the cover 26, in the case of an external connection, external wiring (not shown) that has passed through the ground is passed through each wiring port for the output signal and the power supply, and each terminal 27a to 27b of the terminal board 27 is connected to the terminal board 27.
In FIG. 3, the wiring ports are closed with plugs 37 and 38.
Reference numeral 9 denotes an air purge port, through which pressurized gas is introduced to prevent the intrusion of outside air. Furthermore, the converter unit 25 is connected to the correction circuits 17 and 22 by connectors, so it can be easily attached and detached, facilitating the assembly and maintenance of the electromagnetic flowmeter, and the maintenance and replacement of the converter unit. In addition, the power transformer and heat-generating components are attached to the metal cover 26, which provides good heat dissipation, and other electrical components are located below this, so they are not affected by heat and reliability is improved.

By the way, in the converter unit 25 of this embodiment, the span adjustment circuit 41, the zero point adjustment potentiometer VR ₂ , and the output damping adjustment potentiometer VR ₃ are mounted on another printed board 42, and this printed board 42 is connected to a printed circuit board 33 for an amplifier by a connector (see FIGS. 4 to 6). Therefore, an edge card connector is attached to the printed board 42, and a corresponding connector CN ₅ is attached to the upper surface of the printed board 33.
An insertion slot 26a is provided in the cover 26 so that the printed board 42 can be attached and removed with the cover 26 attached, but for waterproofing, the printed board 42 is housed inside a shield cover 43 with a top plate 43a attached. The insertion opening 26a is closed with a plate 43a.
By making the adjusting section into a unit and making it removable in this way, if the specifications or adjustment range changes, it can be easily replaced with a suitable unit. here,
The span adjustment circuit 41 can easily adjust the span.
Moreover, after adjustment, the sixth
As shown in the figure, two potentiometers VR ₄ ,
The circuit network consists of VR ₅ , a large number of resistors, and connecting lines such as short circuits, and the circuit configuration can be selected by cutting the connecting lines at any point indicated by the V mark. This span adjustment circuit 41 is connected between an amplifier 44 at the next stage of the differential amplifier 21 and a deviation amplifier 45 in the division loop to adjust the gain. Further, the zero point adjustment potentiometer _VR2 adjusts the zero point by supplying a part of the comparison signal to the deviation amplifier 45. The potentiometer VR ₃ for output damping adjustment adjusts the voltage in the divider loop -
It is connected to a smoothing circuit 48 for smoothing a signal obtained by amplifying the duty cycle signal f from a frequency converter (V/F) 46 by an amplifier 47, and adjusts output damping by changing the time constant. 49 is a circuit that outputs a current signal proportional to the flow rate as a final output.

In the division loop shown in FIG. 5, reference numeral 50 denotes a sample/synchronous rectifier circuit consisting of sampling switches SW ₁ and SW ₂ and a differential amplifier 52 operated by a timing signal from a timing signal generator 51;
54 is a smoothing amplifier circuit, and 54 is an amplified comparison signal e _re
This is a multiplication switch that takes in _f for a time proportional to the output f of the V/F converter 46. switch 54
By supplying the product signal f·e _ref from , to the deviation amplifier 45, a voltage V proportional to the ratio of the flow rate signal e _s passed through the span adjustment circuit 41 and the comparison signal e _ref is obtained from the smoothing amplifier circuit 53. This voltage V is not affected by fluctuations in the excitation current and is proportional to the flow rate. Further, in FIG. 5, the power supply section is shown as only one set of the power transformer 29 and the rectifier 55, but it goes without saying that there may be a plurality of power supply sections as required.

In addition, in Fig. 4, 56 is a fuse holder, and 57 is a fuse holder.
and 58 are the top plates 43a for the movable axes of VR ₂ and VR ₃
59 is a shield cover for the amplifier section.

As specifically explained above in conjunction with the embodiments, the present invention has the following effects.

(b) A cover is provided between the housing and the lid of the converter storage box to airtightly partition the converter storage box, and the terminal board is placed on top of this cover, so even if the lid is removed for external wiring, the converter section remains intact. Electronic circuit components are not exposed to the outside, and high reliability can be maintained even when integrated with a transmitter section fixed on piping at a site with a poor atmosphere.

(b) Since the heat-generating components are directly fixed under the cover and the electronic circuit components of the converter section are arranged under this, there is little thermal influence on the electronic circuit components.

(c) A signal correction circuit and a comparison signal correction circuit, to which the signal line from the transmitter section is connected, are fixed and separated from each other at the bottom of the housing, and these signal correction circuits, comparison signal correction circuits, and converter circuits are fixed. Since the converter section is made detachable, it is possible to easily replace the converter section, and furthermore, it is possible to prevent induction from the comparison signal correction circuit side to the signal correction circuit. Therefore, maintenance and workability are improved.

(d) Since the terminal board provided on the top of the cover can be connected to external wiring by screwing, there is no need to place an unnecessary burden on the user by providing a relay terminal.

[Brief explanation of the drawing]

FIG. 1a is a plan view of a conventional integrated electromagnetic flowmeter with the lid and printed board removed, and FIG. 1b is a front view of the conventional integrated electromagnetic flowmeter with the lid removed. Figures 2 to 6 relate to an embodiment of the present invention, in which Figure 2a is a plan view with the lid removed, Figure 2b is a plan view with the converter unit removed, and Figure 2c is a plan view of the converter. Figure 3 is an exploded perspective view of the converter storage box, Figure 4 is an exploded perspective view of the converter unit, Figure 5 is a block diagram, and Figure 6 is a diagram showing the inside of the converter storage box. FIG. 3 is a circuit diagram of the adjustment unit. In the drawing, 1 is a transmitter section, 10 is a converter storage box,
10a and 10b are the casings and lids, 11 to 13 and 28, 36 are sealing members, 15 is a printed board for the signal correction circuit, 16 is a printed board for the comparison signal correction circuit, 25 is a converter unit, 26 is a cover, 2
7 is a terminal board, 29 is a power transformer, 31 is an excitation power transistor, 32 and 33 are printed boards,
34 and 35 are pillars, 42 is a printed board of the adjustment unit, and CN ₁ , CN' ₁ , CN ₂ , CN' ₂ and CN ₅ are connectors.

Claims (1)

[Scope of utility model registration request] A transmitter section is provided between each flange on the upstream side and the downstream side of the mating piping for sending the measurement fluid, and is supplied with an exciting current and outputs a flow rate signal corresponding to the flow rate of the measurement fluid; In an integrated electromagnetic flowmeter formed integrally with a converter section having a converter circuit that processes and outputs a flow rate signal, the converter section includes a converter storage box provided above the transmitter section. The converter storage box includes a housing and a lid that covers the housing, the housing has a cover that airtightly partitions the lid side and the transmitter side, and the transmitter of the cover Heat-generating components such as power transistors are directly fixed to the side, and other circuit components of the converter circuit are fixed to the bottom of these components, and wiring is connected to the lid side of the cover through the housing. A terminal board connecting the power supply line and the output line is fixed airtightly, and a signal line from the transmitter section is connected to the bottom of the housing, and a signal correction circuit for removing noise included in the flow rate signal and the excitation current are connected. A comparison signal correction circuit for removing fluctuations in the signal correction circuit and a comparison signal correction circuit are separated from each other and fixed, and these signal correction circuits and comparison signal correction circuits and the converter circuit are made detachable. Electromagnetic flowmeter.