Intrinsic safety explosion proof level gage

Abstract

To provide an intrinsic safety explosion proof level gage which can be simplified in design.SOLUTION: An intrinsic safety explosion proof level gage 100 includes a level gage body 1 and a power supply path 5 so as to measure a level of a stored object L stored in a container V. The level gage body 1 has a transmission circuit 2, a reception circuit 3, a level determination section 4, an operation switch 21, and a display section 20. The transmission circuit 2 transmits a measurement signal S. The reception circuit 3 receives the measurement signal S reflected by the stored object L. The level determination section 4 determines the level on the basis of the measurement signal S received by the reception circuit 3 and information on the container V. The operation switch 21 receives an input operation of set information. The display section 20 displays the determined level. The power supply path 5 supplies power to the level gage body 1. The power supply path 5 has an intrinsic safety explosion proof barrier 6 for preventing the level gage body 1 from becoming an ignition source and a proof pressure explosion proof box 7 for storing the intrinsic safety explosion proof barrier 6.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an intrinsically safe level meter. [Background technology]

[0002] A level meter is disclosed in Patent Document 1. The level meter described in Patent Document 1 can easily identify the actual amount of a contained object (medium) contained in a container. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-002091 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when the level meter described in Patent Document 1 is placed in an explosion-proof hazardous location, it is considered to have a pressure-resistant explosion-proof structure. In the pressure-resistant explosion-proof structure, it is necessary to cover the level meter described in Patent Document 1 with a pressure-resistant explosion-proof casing. With such a level meter, the pressure-resistant explosion-proof casing gets in the way, making the display less visible or making it less easy to operate.

[0005] Therefore, it is considered that the level meter described in Patent Document 1 has an intrinsically safe explosion-proof structure instead of a pressure-resistant explosion-proof structure. An intrinsically safe structure is a structure that uses an intrinsically safe electric circuit (intrinsically safe circuit) that does not become an ignition source in normal conditions and in specific fault conditions. Intrinsically safe equipment is divided into intrinsically safe equipment whose entire circuit is composed of intrinsically safe circuits and can be used in hazardous locations, and intrinsically safe-related equipment whose circuit is partially composed of intrinsically safe circuits and is installed in safe locations and connected to intrinsically safe equipment. In an intrinsically safe explosion-proof structure, an intrinsically safe explosion-proof barrier, which is an intrinsically safe-related device, is connected to a level meter that is an intrinsically safe device. Since a level meter connected to an intrinsically safe explosion-proof barrier does not become an ignition source, it does not need to be covered with a pressure-resistant explosion-proof housing.

[0006] However, in an intrinsically safe explosion-proof structure, the level meter and the intrinsically safe explosion-proof barrier must be connected with intrinsically safe dedicated wiring. Existing wiring cannot be used for the intrinsically safe dedicated wiring in order to prevent electromagnetic induction, electrostatic induction, and contact from other circuits. Furthermore, since the level meter is placed in a dangerous location and the intrinsically safe explosion-proof barrier is placed in a safe location, the intrinsically safe dedicated wiring is inevitably long. Therefore, if the level meter described in Patent Document 1 is made into an intrinsically safe explosion-proof structure, the design becomes complicated.

[0007] The present invention has been made in consideration of the above problems, and has an object to provide a level meter that has an explosion-proof structure, simplifies installation and wiring, and has high visibility and operability. [Means for solving the problem]

[0008] According to one aspect of the present invention, an intrinsically safe explosion-proof level meter measures the level of an object contained in a container. The intrinsically safe explosion-proof level meter includes a level meter body and a power supply path. The level meter body includes a transmission circuit, a reception circuit, a level determination unit, an operation switch, and a display unit. The transmission circuit transmits a measurement signal for measuring the level of the object. The reception circuit receives the measurement signal reflected by the object. The level determination unit determines the level based on the measurement signal received by the reception circuit and information about the container. The operation switch accepts an input operation of setting information. The display unit displays the level determined by the level determination unit. The setting information includes information about the container and a threshold value for the level determined by the level determination unit. The power supply path supplies power to the level meter body. The power supply path includes an intrinsically safe explosion-proof barrier and a pressure-resistant explosion-proof box. The intrinsically safe explosion-proof barrier prevents the level meter body from becoming an ignition source. The pressure-resistant explosion-proof box houses the intrinsically safe explosion-proof barrier. Effect of the Invention

[0009] The intrinsically safe explosion-proof level meter of the present invention can have a simplified design. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic perspective view of an intrinsically safe explosion-proof level meter. [Diagram 2] 11 is a front view of the display unit of the level meter body displaying a bottom distance setting screen. FIG. [Diagram 3] FIG. 2 is an exploded perspective view of a pressure-resistant explosion-proof box and an intrinsically safe explosion-proof barrier. [Figure 4] This is a circuit diagram when a 2-wire / 2-wire insulating barrier is used as an intrinsically safe explosion-proof barrier. [Diagram 5] This is a circuit diagram when a 4-wire / 2-wire insulating type barrier is used as an intrinsically safe explosion-proof barrier. [Figure 6] This is a circuit diagram when a 2-wire / 2-wire non-insulated barrier is used as an intrinsically safe explosion-proof barrier. [Figure 7] FIG. 7 is a circuit diagram showing a modification of FIG. 6. [Figure 8] FIG. 2 is a perspective view of the level meter body immediately before it is used as a whole. [Figure 9] FIG. 2 is a perspective view of the level meter body in a separated state for use. [Figure 10] FIG. [Figure 11] 13 is a display screen of a display for displaying the determined level. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference symbols and will not be described repeatedly. In the following description, terms meaning a position or direction may be used. These terms are used for convenience to facilitate understanding of the embodiment, and are not limited to a position or direction in the strict sense unless otherwise clearly stated.

[0012] Hereinafter, an intrinsically safe explosion-proof level meter 100 according to an embodiment of the present invention will be described with reference to Figs.

[0013] First, an overview of an intrinsically safe explosion-proof level meter 100 will be described with reference to Fig. 1. Fig. 1 is a schematic perspective view of the intrinsically safe explosion-proof level meter 100.

[0014] 1, an intrinsically safe explosion-proof level meter 100 measures the level of an object L contained in a container V. The intrinsically safe explosion-proof level meter 100 includes a level meter main body 1 and a power supply path 5.

[0015] The level meter main body 1 has a transmitting circuit 2, a receiving circuit 3, a level determining section 4, an operating switch 21, and a display section 20.

[0016] The transmitting circuit 2 transmits a measurement signal S for measuring the level of the contained item L. The receiving circuit 3 receives the measurement signal S reflected by the contained item L. The level determining unit 4 determines the level based on the measurement signal S received by the receiving circuit 3 and information about the container V.

[0017] The operation switch 21 accepts an input operation of setting information. The display unit 20 displays the level determined by the level determination unit 4. The setting information includes information on the container V. The setting information may also include a threshold value for the level determined by the level determination unit 4.

[0018] When the information of the container V is set, as shown in FIG. 2, the display unit 20 displays a bottom distance setting screen 23. In the bottom distance setting screen 23, the distance from the measurement reference surface 132 of the level meter main body 1 to the bottom 133 of the container V is set. In the bottom distance setting field 131, candidates for the distance to the bottom 133 are displayed as numerical values. When the user operates the operation switch 21 indicating increase / decrease in the bottom distance setting screen 23, the numerical value displayed in the bottom distance setting field 131 decreases and increases. Then, when the user operates the operation switch 21 indicating determination, the numerical value displayed in the bottom distance setting field 131 (for example, 5000 mm) is set in the level meter main body 1. The level determination unit 4 determines the level of the contained item L based on the distance to the contained item L based on the measurement signal S received by the receiving circuit 3 and the distance to the bottom of the container V as the information of the container V. For example, the level determination unit 4 determines the value obtained by subtracting the distance to the contained item L from the distance to the bottom of the container V as the level of the contained item L.

[0019] The level meter body 1 outputs information indicating the level of the contained contents L determined by the level determination unit 4 to an external device via the power supply path 5. The level meter body 1 may output an analog signal indicating the level as the information indicating the level, or may output the information indicating the level via communication. The level meter body 1 may also output a comparison result between the level of the contained contents L determined by the level determination unit 4 and one or more threshold values ​​set as information indicating the level to an external device. When the operation switch 21 is operated by a user, a threshold value is set for the level of the contained contents L. The level meter body 1 has an indicator light 19 that displays the state of the level based on the comparison result between the level of the contained contents L determined by the level determination unit 4 and the set threshold value. The level meter main body 1 may be of a two-wire type that outputs an analog signal indicating the level of the contained contents L determined by the level determination unit 4 and communication information indicating the level by superimposing them on a power line.

[0020] The bottom distance setting screen 23 and the like are displayed on the display unit 20 by the display 23, which will be described in detail later. The display 23 is, for example, an LCD (Liquid Crystal Display). Since the display 23 is an LCD display, it has high expressive power and therefore improves visibility for the user.

[0021] The display 3 is capable of displaying a level graph and a color display, so that the level status can be displayed in a color gauge 170 (see FIG. 11). By displaying the level status in the color gauge 170 (see FIG. 11), visibility for the user is improved.

[0022] The indicator light 19 may be a ring indicator light arranged in a circular shape so as to surround the axis of the level meter main body 1. The indicator light 19 is a ring indicator light, and thus the display is notified over a wide area, improving the visibility of the user. The indicator light 19 may be arranged between the display unit 20 and the mounting unit 13 (described later), but may also be arranged in another part, such as the upper end of the display unit 20. The indicator light 19 lights up or goes out in different colors according to the level determined by the level determination unit 4. The color that the indicator light 19 lights up is not particularly limited, but may be, for example, green, yellow, or red. Specifically, when the determined level is within a standard range, the indicator light 19 lights up green. When the determined level is within a range requiring a warning, the indicator light 19 lights up yellow. When the determined level is within a dangerous range, the indicator light 19 lights up red.

[0023] 1, a power supply path 5 supplies power to a level meter main body 1. The power supply path 5 has an intrinsically safe explosion-proof barrier 6 and a pressure-resistant explosion-proof box 7.

[0024] The intrinsically safe explosion-proof barrier 6 prevents the level meter body 1 from becoming an ignition source. The pressure-resistant explosion-proof box 7 houses the intrinsically safe explosion-proof barrier 6 therein.

[0025] The intrinsically safe explosion-proof barrier 6 limits the electrical energy supplied to the level meter body 1 under both normal and fault conditions, thereby preventing the level meter body 1 from becoming an ignition source.

[0026] The level meter body 1 does not need to be pressure-resistant and explosion-proof because the intrinsically safe explosion-proof barrier 6 provides an intrinsically safe explosion-proof structure. Furthermore, the intrinsically safe explosion-proof barrier 6 is housed in a pressure-resistant explosion-proof box 7, so it can be placed in a hazardous location together with the level meter body 1. Therefore, the intrinsically safe dedicated wiring 50 connecting the intrinsically safe explosion-proof barrier 6 and the level meter body 1 need only be short. As a result, the intrinsically safe explosion-proof level meter 100 can simplify the design of wiring, installation, and the like.

[0027] The intrinsically safe explosion-proof level meter 100 will now be described in detail.

[0028] The level meter main body 1 is supplied with power from a DC power source P via a power supply path 5. The DC power source P is arranged in a safe location, unlike the level meter main body 1 and the power supply path 5. The supply of power from the DC power source P is controlled by a control panel C arranged in the safe location. A large number of wires (not shown) are provided from the control panel C arranged in the safe location to the hazardous location.

[0029] The numerous wirings from the control panel C are configured as normal wiring in safe locations and as explosion-proof wiring in dangerous locations. Normal wiring is wiring for which explosion-proofing is not ensured. Explosion-proofing is explosion-proof performance that meets explosion-proof standards or criteria. Explosion-proof wiring is wiring for which explosion-proofing is ensured. Explosion-proof wiring is, for example, wiring whose periphery is protected by a steel pipe (not shown). The inside of the joint connected to the steel pipe is sealed around the wiring with cement or a pressure-resistant packing is placed therein. A power supply path 5 is connected to explosion-proof wiring E, one of the numerous wirings from the control panel C.

[0030] The power supply path 5 further includes the aforementioned intrinsically safe wiring 50. The intrinsically safe wiring 50 connects the intrinsically safe explosion-proof barrier 6 and the level meter main body 1. The intrinsically safe wiring 50 is wiring that meets certain standards for preventing electromagnetic induction from other circuits, electrostatic induction, and contact.

[0031] The pressure-resistant explosion-proof box 7 further includes an upstream cable gland 8 and a downstream cable gland 9. The upstream cable gland 8 fixes the explosion-proof wiring E connecting the control panel C and the intrinsically safe barrier 6 to the pressure-resistant explosion-proof box 7. That is, the explosion-proof wiring E passes through the pressure-resistant explosion-proof box 7 and is fixed to the pressure-resistant explosion-proof box 7 by the upstream cable gland 8. The downstream cable gland 9 fixes the intrinsically safe dedicated wiring 50 connecting to the intrinsically safe barrier 6 to the pressure-resistant explosion-proof box 7. That is, the intrinsically safe dedicated wiring 50 passes through the pressure-resistant explosion-proof box 7 and is fixed to the pressure-resistant explosion-proof box 7 by the downstream cable gland 9. The upstream cable gland 8 and the downstream cable gland 9 (hereinafter, sometimes collectively referred to as cable gland 89) are both pressure-resistant explosion-proof and waterproof between the pressure-resistant explosion-proof box 7 and the wiring.

[0032] The flameproof box 7 will be described in detail below with reference to Fig. 3. Fig. 3 is an exploded perspective view of the flameproof box 7 and the intrinsically safe barrier 6.

[0033] The pressure-resistant explosion-proof box 7 further includes a box body 70 and a lid 78. The box body 70 has a flange portion 71 that protrudes outward at a portion where the box body 70 contacts the lid 78.

[0034] In the flange portion 71, the portion that comes into contact with the lid 78 has a width necessary to ensure explosion-proof performance. Therefore, the box body 70 is thinner than the flange portion 71 in areas other than the flange portion 71. As a result, the level meter for the intrinsically safe explosion-proof barrier 6 can reduce the size of the pressure-resistant explosion-proof box 7.

[0035] The portions of the flange portion 71 and the lid 78 that come into contact with each other are both flat surfaces. Therefore, the pressure-resistant explosion-proof box 7 closes the lid 78 to the box body 70 through flat surface contact. As a result, the intrinsically safe explosion-proof level meter 100 allows the pressure-resistant explosion-proof box 7 to be made smaller, unlike a structure in which the lid is closed by screwing.

[0036] The box body 70 has two wiring ports 72. The two wiring ports 72 each have a cable gland 89 fixed thereto by screwing. Each of the two wiring ports 72 is formed with a female thread (not shown) for fixing the cable gland 89. Each of the female threads of the two wiring ports 72 has the number of threads required to ensure explosion-proof performance.

[0037] The explosion-proof box 7 has a fixing screw 81. The fixing screw 81 fixes the lid 78 to the box body 70 by screwing it. Therefore, the lid 78 has a through hole 79 through which the fixing screw 81 passes. On the other hand, the box body 70 has a screw hole 73 into which the fixing screw 81 is screwed.

[0038] The flameproof box 7 further has an accommodation space 74. The accommodation space 74 accommodates the intrinsically safe barrier 6. The accommodation space 74 is a substantially rectangular parallelepiped having a length 75, a width 76, and a height 77. The length 75 of the accommodation space 74 is shorter than the height 77, and the height 77 is shorter than the width 76.

[0039] The accommodation space 74, which is short in length 75, height 77, and width 76, has a thin shape that matches the intrinsically safe explosion-proof barrier 6 made of a circuit board. Therefore, the intrinsically safe explosion-proof level meter 100 can reduce the size of the pressure-resistant explosion-proof box 7.

[0040] The direction in which flange portion 71 protrudes outward is the direction of vertical 75. Therefore, box body 70 is thin in the length of horizontal 76. As a result, the level meter having intrinsically safe explosion-proof barrier 6, which is an intrinsically safe related device, can have a pressure-resistant explosion-proof box 7 that is compact.

[0041] The accommodation space 74 extends not only to the inside of the box body 70 but also to the inside of the lid 78. Therefore, the intrinsically safe barrier 6 accommodated in the accommodation space 74 is protected by the box body 70 and the lid 78. The inside of the lid 78 not only accommodates the upper part of the intrinsically safe barrier 6, but also accommodates wiring.

[0042] The intrinsically safe explosion-proof barrier 6 is fixed to the bottom of the box body 70 in the accommodation space 74 with small screws 69. By fixing the intrinsically safe explosion-proof barrier 6 to the bottom of the box body 70, electrical grounding is possible via the box body 70. Therefore, a non-insulated type barrier that requires electrical grounding may be adopted as the intrinsically safe explosion-proof barrier 6. When electrical grounding is performed, a ground wire is connected to the box body 70, although not shown. The ground wire is explosion-proof wiring in a dangerous area, and electrical grounding is performed in a safe area. Note that the intrinsically safe explosion-proof barrier 6 is not limited to a non-insulated type barrier, and may be any barrier that prevents the level meter body 1 from becoming an ignition source.

[0043] Hereinafter, the types of intrinsically safe explosion-proof barrier 6 will be described in detail with reference to Figs. 4 to 7. Fig. 4 is a circuit diagram in which an insulated type barrier with a 2-wire / 2-wire system in which the wiring on the safe area side is 2 wires and the wiring on the hazardous area side is 2 wires is used as the intrinsically safe explosion-proof barrier 6. Fig. 5 is a circuit diagram in which an insulated type barrier with a 4-wire / 2-wire system in which the wiring on the safe area side is 4 wires and the wiring on the hazardous area side is 2 wires is used as the intrinsically safe explosion-proof barrier 6. Fig. 6 is a circuit diagram in which a non-insulated type barrier with a 2-wire / 2-wire system in which the wiring on the safe area side is 2 wires and the wiring on the hazardous area side is 2 wires is used as the intrinsically safe explosion-proof barrier 6. Fig. 7 is a circuit diagram in which Fig. 6 is modified.

[0044] As shown in Figs. 4, 6 and 7, the intrinsically safe explosion-proof barrier 6 is a two-wire barrier. Here, the explosion-proof wiring E from the control panel C is also a two-wire type. Therefore, since the intrinsically safe explosion-proof barrier 6 is also a two-wire type like the explosion-proof wiring E from the control panel C, the internal configuration of the pressure-resistant explosion-proof box 7 is simplified. Specifically, inside the pressure-resistant explosion-proof box 7, only a total of four connections are required for the number of connections of the terminal blocks used, and the wiring is simplified. As a result, the intrinsically safe explosion-proof level meter 100 can simplify the configuration of the power supply path 5.

[0045] 4 and 5, the intrinsically safe explosion-proof barrier 6 is an insulating type barrier. Therefore, the intrinsically safe explosion-proof barrier 6 does not require electrical grounding. As a result, the intrinsically safe explosion-proof level meter 100 can simplify the configuration of the power supply path 5.

[0046] As shown in FIG. 4, the intrinsically safe explosion-proof barrier 6 is an insulating type since it has a 2-wire / 2-wire insulating circuit 62. The 2-wire / 2-wire insulating circuit 62 supplies power from a DC power source P to a 2-wire level meter body 1, and transmits a measurement value signal m superimposed on the power line by the 2-wire level meter body 1 to the DC power source P side. The 2-wire / 2-wire insulating circuit 62 has, for example, an insulating transformer and an insulating amplifier. Power from the DC power source P is supplied to the 2-wire level meter body 1 by the insulating transformer. The measurement value signal m superimposed on the power line is superimposed on the power line on the DC power source P side via the insulating amplifier. As a result, the 2-wire / 2-wire insulating circuit 62 is a circuit that insulates the power supplied from the DC power source P to the 2-wire level meter body 1 and the communication information and analog signals superimposed by the 2-wire level meter body 1, but generates an output as if they were transmitted through the 2-wire / 2-wire insulating circuit 62. An external resistor R is disposed between the intrinsically safe explosion-proof barrier 6 and the DC power supply P. The external resistor R extracts the measurement value signal m from the level meter main body 1 as a voltage signal.

[0047] As shown in Fig. 5, the intrinsically safe barrier 6 is an insulating type since it has a 4-wire / 2-wire insulating circuit 64. The 4-wire / 2-wire insulating circuit 64 functions as a distributor that supplies power from a DC power source P to a 2-wire level meter main body 1 and separates a measurement signal m, such as analog information and communication information, from the 2-wire level meter main body 1 from the power line and transmits it to the external resistor R. The path from the intrinsically safe barrier 6 to the DC power source P is separate from the path from the intrinsically safe barrier 6 to the external resistor R. In other words, the 4-wire / 2-wire insulating circuit 64 also functions as a distributor that separates the supply of power and the transmission of the measurement signal m.

[0048] 6 and 7, the intrinsically safe explosion-proof barrier 6 is a Zener barrier. By using the Zener barrier, the intrinsically safe explosion-proof barrier 6 can be simplified in configuration. Therefore, the intrinsically safe explosion-proof level meter 100 can simplify the configuration of the power supply path 5.

[0049] As shown in FIG. 6, the intrinsically safe barrier 6 is a Zener barrier because it has a Zener diode 66. The intrinsically safe barrier 6 is configured so that power and signals are transmitted through without being insulated between the two wires on the safe location side and the two wires on the hazardous location side. The intrinsically safe barrier 6 further has an internal resistor 65 and a first fuse 51. The internal resistor 65 and the first fuse 51 are provided on one wire 61 of the two-wire system. The Zener diode 66 is provided on a connection path 67 that connects the one wire 61 and the other wire 63. The connection path 67 is connected between the internal resistor 65 and the first fuse 51 on the one wire 61. The intrinsically safe barrier 6 is electrically grounded 68 from the other wire 63 via a ground wire. The electrical ground 68 is a type A ground. The electrical ground 68 is provided in the safe location. The safety location where the electrical grounding 68 is performed does not have to be a remote safety location where the control panel C is located, but may be any safety location close to the intrinsic safety explosion-proof barrier 6 as long as it is a safety location.

[0050] As shown in FIG. 7, the intrinsically safe barrier 6 is a Zener barrier since it has a Zener diode 66. The intrinsically safe barrier 6 further has a general-purpose diode 56 and a second fuse 52. The general-purpose diode 56 and the second fuse 52 are provided on the other line 63. A connection path 67 is connected between the general-purpose diode 56 and the second fuse 52. There are two connection paths 67 and four Zener diodes 66. Two Zener diodes 66 are provided in each connection path 67. An electrical ground 68 is provided from a path 57 that connects the two connection paths 67 to each other. The path 57 connects between the two Zener diodes 66 of each connection path 67.

[0051] The level gauge body 1 will be described in detail below with reference to Fig. 8 and Fig. 9. Fig. 8 is a perspective view of the level gauge body 1 immediately before it is used as a whole. Fig. 9 is a perspective view of the level gauge body 1 when it is separated and used.

[0052] 8 and 9, the level meter main body 1 further includes a sensor housing 10. The sensor housing 10 houses a transmitting circuit 2 and a receiving circuit 3. The display unit 20 is detachably connected to the sensor housing 10.

[0053] By detachably connecting the display unit 20 to the sensor housing 10, the intrinsically safe explosion-proof level meter 100 can be used in a hazardous location either integrally with the level meter main body 1 or separated therefrom.

[0054] Between the display unit 20 and the sensor housing 10, "attached" or "detached" means a physical state, that is, physical attachment and detachment. Also, between the display unit 20 and the sensor housing 10, "connected" means an electrical connection. Therefore, a state in which the display unit 20 and the sensor housing 10 are detachably connected means a state in which they are electrically connected while being physically attached or detached.

[0055] The display unit 20 further includes a detachable portion 24, a first connection portion 31, and a second connection portion 32. The detachable portion 24 is attached to and detached from the sensor housing 10. The first connection portion 31 is for fixing the intrinsically safe dedicated wiring 50 penetrating the display unit 20 to the display unit 20, and is, for example, a cable gland. The second connection portion 32 is for fixing the wiring connecting the display unit 20 and the sensor housing 10 to the display unit 20 when the display unit 20 and the sensor housing 10 are used separately, and is closed with a plug when the display unit 20 and the sensor housing 10 are directly connected since it is not used. The second connection portion 32 is, for example, a cable gland, and fixes the wiring connecting the display unit 20 and the sensor housing 10 in a waterproof manner.

[0056] The sensor housing 10 also houses the level determination unit 4. The sensor housing 10 is located closer to the contained object L than the display unit 20. The sensor housing 10 has, in order from the side closer to the contained object L, a transmission window 11, a mounting screw portion 12, a mounting portion 13, a third connection portion 33, and a detachable portion 14. The mounting screw portion 12 is male-threaded. Therefore, the mounting screw portion 12 is attached by screwing into a through hole (not shown) in the container V in which a female thread is formed. The mounting portion 13 is a nut-shaped member protruding radially outward. The third connection portion 33 is used to fix the wiring connecting the display unit 20 and the sensor housing 10 to the sensor housing 10 when the display unit 20 and the sensor housing 10 are used separately, and is not used when the display unit 20 and the sensor housing 10 are directly connected, and is closed with a plug. The third connection portion 33 is, for example, a cable gland, and fixes the wiring connecting the display unit 20 and the sensor housing 10 in a waterproof manner. The detachable portion 24 is attached to and detached from the detachable portion 14.

[0057] As shown in Fig. 8, when the level meter main body 1 is used as an integrated unit, the display unit 20 and the sensor housing 10 are supplied with power and transmit signals via the detachable part 24 and the detachable part 14. On the other hand, as shown in Fig. 9, when the level meter main body 1 is used separately, the display unit 20 and the sensor housing 10 are supplied with power and transmit signals via an intrinsically explosion-proof wiring cable 34 fixed by a second connecting part 32 and a third connecting part 33.

[0058] The measurement signal S is a signal that is transmitted from the transmission circuit 2, reflected by the contained object L through the transmission window 11, and then received by the receiving circuit 3 through the transmission window 11. The measurement signal S is not particularly limited as long as it is such a signal, but may be, for example, a radio wave.

[0059] The configurations of the transmitting circuit 2, the receiving circuit 3, and the level determining unit 4 are not particularly limited, but may be, for example, a sensor. The sensor has one or more ICs (Integrated Circuits) and, if necessary, a microcomputer. The IC may be an MMIC (Monolithic Microwave Integrated Circuit) or an MMIC with an integrated antenna.

[0060] The sensor is set according to a method for measuring the level of the contained goods L. The method for measuring the level of the contained goods L is a TOF (Time of Flight) method, a radar method, etc. In the radar method, FMWC (Frequency Modulated Continuous Wave) or the like is used.

[0061] The level determination unit 4 calculates the distance from the transmitting circuit 2 and the receiving circuit 3 to the upper surface of the contained item L. The level determination unit 4 determines the level, which is the position of the upper surface of the contained item L, from the calculated distance and the information of the container V.

[0062] The content L is not particularly limited as long as it is an object that can be contained in the container V, and is, for example, a liquid or a powder. The level of the content L refers to the position of the upper surface of the content L.

[0063] Hereinafter, a configuration for operation and display by the level meter main body 1 will be described with reference to Fig. 10. Fig. 10 is a front view of the display unit 20 and the operation switch 21.

[0064] As shown in FIG. 10, the display unit 20 further has a display unit housing 22 exposed to the outside. The operation switch 21 has push buttons 40-45 provided on the display unit housing 22. Providing the push buttons 40-45 on the display unit housing 22 exposed to the outside allows the push buttons 40-45 to be directly pressed from the outside. Therefore, unlike a pressure-resistant explosion-proof structure, the operation switch 21 is not covered by a pressure-resistant explosion-proof housing, and is therefore easy to operate. As a result, the intrinsically safe explosion-proof level meter 100 can improve operability by the user.

[0065] The display unit 20 further has a display 23 provided in the display unit housing 22. By providing the display 23 in the display unit housing 22 that is exposed to the outside, the display 23 can be directly viewed from the outside. Therefore, unlike a pressure-resistant explosion-proof structure, the display 23 is not covered by a pressure-resistant explosion-proof housing, and is therefore easily visible. As a result, the intrinsically safe explosion-proof level meter 100 can improve visibility for the user.

[0066] The push buttons 40 to 45 include a menu key 41, direction keys 42 to 45, and a decision key 40. When the menu key 41 is pressed, a menu for operation is displayed on the display 23. When the direction keys 42 to 45 are pressed, an input is made according to the direction in which they are pressed. The direction keys 42 to 45 consist of an up key 42, a down key 43, a left key 44, and a right key 45. When the decision key 40 is pressed, it decides the input content.

[0067] Hereinafter, examples of operation and display by the level meter main body 1 will be described with reference to Figures 10 and 11. Figure 11 shows the display screen of the display 23 for displaying the determined level.

[0068] As shown in FIG. 10, the display 23 displays, as an operation screen, items that have already been set and items to be set.

[0069] The already set items are the container height 110 as information about the container V, and one of the thresholds for the level to be determined (hereinafter, the first threshold) 111. The already set container height 110 is 4800 mm. The already set first threshold 111 is 4000 (mm).

[0070] If the user wishes to modify an item that has already been set, the user can press the left key 44 to return to the operation screen (not shown) for setting the first threshold value 111. By pressing the left key 44 again, the user can return to the operation screen (not shown) for setting the container height 110.

[0071] As shown in FIG. 10, the item to be set is another one of the thresholds for the level to be determined (hereinafter, the second threshold) 112. 3000 mm is displayed in the selection field 130 as the second threshold 112 to be set. By pressing the up key 42 or the down key 43, the value in the selection field 130 increases or decreases. In response to the increase and decrease of the value in the selection field 130, the horizontal line 122 inside the container 120 displayed as an image moves up and down. After the value to be set as the second threshold 112 is displayed in the selection field 130, the decision key 40 is pressed to set the value in the selection field 130 as the second threshold 112.

[0072] In the same manner, the thresholds that have not been set among the thresholds for the level to be determined are sequentially set by operating the operation switch 21. The information on the container V and the thresholds that have been set constitute the setting information. After all settings have been completed, the level of the contained item L is measured.

[0073] As shown in Fig. 11, the determined level of 1500 mm is displayed on the auxiliary display section 150 of the display 23. A bar display 162 overlapping a container 160 displayed as an image moves up and down in response to the determined level. The bar display 162 points to a color gauge 170 adjacent to the container 160 displayed as an image. The color gauge 170 is divided into level ranges 171 to 175 of different colors by a set threshold value. One of the level ranges 171 to 175 (level range 174 in the example of Fig. 11) is indicated by the bar display 162.

[0074] However, the above embodiment is illustrative in all respects and is not restrictive. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. Among the configurations described in the above embodiment, those other than those described as one aspect of the present invention in the "Means for solving the problem" are optional configurations and can be deleted or modified as appropriate. [Industrial Applicability]

[0075] INDUSTRIAL APPLICABILITY The present invention provides an intrinsically safe explosion-proof level meter and has industrial applicability. [Explanation of symbols]

[0076] V container L Contents 1 Level meter body 2. Transmitting circuit 3. Receiving circuit 4 Level determination section 5 Power supply path 6 Intrinsically safe explosion-proof barrier 7 Explosion-proof box 10 Sensor housing 20 Display section 21 Operation switch 23 Display 40~45 Push button 50 Intrinsically safe dedicated wiring 51 First Fuse 52 Second Fuse 65 Internal resistor 66 Zener Diode 68 Electrical Grounding 70 Box body 71 Flange 74 Containment Space 75 vertical 76 horizontal 77 Height 78 Lid 89 Cable Gland 100 Level Gauge 111 First Threshold 112 Second Threshold

Claims

1. An intrinsically safe explosion-proof level meter for measuring the level of a substance contained in a container, comprising: A level meter body, a power supply path for supplying power to the level meter body and transmitting a signal indicating a level from the level meter body; Equipped with The level meter body includes: a transmitter circuit for transmitting a measurement signal for measuring the level of the content; a receiving circuit for receiving the measurement signal reflected by the object; a level determination unit that determines the level based on the measurement signal received by the receiving circuit and information about the container; an operation switch for receiving an input operation of setting information related to the container information; a display unit that displays the level determined by the level determination unit; having The power supply path is an intrinsically safe explosion-proof barrier that prevents the level meter body from becoming an ignition source; a pressure-resistant explosion-proof box for accommodating the intrinsically safe explosion-proof barrier; This is an intrinsically safe explosion-proof level meter.

2. The pressure-resistant explosion-proof box has a box body and a lid, 2. The intrinsically safe explosion-proof level meter according to claim 1, wherein the box body has a flange portion that protrudes outward at a portion that contacts the lid.

3. The pressure-resistant explosion-proof box further has an accommodation space for accommodating the intrinsically safe explosion-proof barrier, The storage space is a substantially rectangular parallelepiped having a length, a width and a height, 3. The intrinsically safe explosion-proof level meter according to claim 1, wherein the length of the accommodation space is shorter than the height, and the height of the accommodation space is shorter than the width.

4. The pressure-resistant explosion-proof box has a box body and a lid, 2. The intrinsically safe explosion-proof level meter according to claim 1, wherein the box body has a threaded portion that is screw-fitted with the lid at a portion that contacts the lid.

5. the level meter body is of a two-wire type that outputs information indicating the level determined by the level determination unit by superimposing it on a power line, 2. The intrinsically safe explosion-proof level meter according to claim 1, wherein the intrinsically safe explosion-proof barrier is a two-wire / two-wire barrier having two wires on the safe location side and two wires on the hazardous location side.

6. 6. The intrinsically safe explosion-proof level meter according to claim 1, wherein the intrinsically safe explosion-proof barrier is an insulating type through-transmission barrier.

7. 6. The intrinsically safe explosion-proof level meter according to claim 5, wherein the intrinsically safe explosion-proof barrier comprises a Zener diode for limiting voltage, a fuse for limiting current, and a ground wire, the ground wire being installed in a safe location.

8. The level meter body further includes a sensor housing that houses the transmitting circuit and the receiving circuit, 3. The intrinsically safe explosion-proof level meter according to claim 1, wherein the display unit is detachably connected to the sensor housing.

9. The display unit has a display housing exposed to the outside and a display provided in the display housing, the intrinsically safe explosion-proof barrier and the level meter body are connected by an intrinsically safe dedicated wiring that penetrates the display unit housing and the pressure-resistant explosion-proof box; the intrinsically safe dedicated wiring is fixed to the display unit housing and the flameproof box via cable glands, 3. The intrinsically safe explosion-proof level meter according to claim 1, wherein the operation switch has a push button provided on the display housing.

10. the operation switch accepts an operation for setting a threshold value for the level determined by the level determination unit, 2. The intrinsically safe explosion-proof level meter according to claim 1, wherein the level meter body further comprises an indicator light for indicating a state of the level based on the level determined by the level determination unit and a set threshold value.

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