Adjustable pressure gauge and electric contact signal connection device

Abstract

The present invention relates to the technical field of electric contact pressure gauges, and discloses an adjustable pressure gauge and an electric contact signal connection device. The pressure gauge is arranged with the center position of the cavity of an outer shell at the center point of a C-type Bourdon tube as the center of a circle. One end of the C-type Bourdon tube is fixedly connected to an external connector, and the other end is connected to a pointer adjustment mechanism. The pointer adjustment mechanism is connected to a pointer assembly, and the pointer assembly can be adjusted by fine-tuning the pointer adjustment mechanism. The external connector is provided with a cavity adjustment nut, which is used to adjust the pressure in the pressure gauge by controlling the size of the volume inside the external connector. The pressure adjustment of the pressure gauge by the pressure generating system can be effectively controlled. At the same time, an electric contact circuit device is provided on the outer shell of the pressure gauge, and a digital multimeter or a speaker battery pack is connected through the electric contact circuit device, which effectively simplifies the electric contact signal connection and facilitates detection by the user.

Description

Technical Field

[0001] The present invention relates to the technical field of electric contact pressure gauges, in particular to an adjustable pressure gauge and an electric contact signal connection device. Background Art

[0002] As a precision measuring tool, pressure gauges have undergone numerous improvements and innovations, driven by the increasing demands for pressure measurement accuracy and range as industrial technology advances. Common pressure gauges can experience pressures exceeding the maximum pressure indicated on the scale. The lack of protective devices can cause the Bourdon tube of a pressure gauge to deform excessively or even damage, leading to false readings. Furthermore, the switching differential detection of electric contact pressure gauges requires connecting the lower limit signal output terminal to the common signal output terminal, and the upper limit signal output terminal to the common signal output terminal, respectively. This requires multiple switching cycles for an electric contact pressure gauge, which is cumbersome, inefficient, and unscientific. Summary of the Invention

[0003] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide an adjustable pressure gauge and an electric contact signal connection device to solve the technical problems in the prior art that the pressure gauge pointer cannot be fine-tuned and the electric contact signal connection is cumbersome.

[0004] The present invention is achieved through the following technical solutions:

[0005] In a first aspect, the present invention provides an adjustable pressure gauge, comprising a pressure gauge body;

[0006] The pressure gauge body includes an outer shell, a C-type Bourdon tube, a pointer assembly, an external connector, a pointer adjustment mechanism, and an electrical contact circuit device;

[0007] The outer shell has a hollow structure, and the C-shaped Bourdon tube, the pointer assembly, and the pointer adjustment mechanism are arranged in the cavity of the outer shell;

[0008] The external connector is provided with an air inlet passage connected to the C-type Bourdon tube, wherein one end of the external connector extends into the outer shell and the other end is connected to the pressure generating system;

[0009] The pointer assembly is arranged at the center of the cavity of the outer shell and performs a circular motion with the center as the center point;

[0010] The center point of the C-shaped Bourdon tube is set with the center position of the cavity of the outer shell as the center of the circle. One end of the C-shaped Bourdon tube is fixedly connected to the external connector, and the other end is connected to the pointer adjustment mechanism; the pointer adjustment mechanism is connected to the pointer assembly;

[0011] The external joint is provided with a cavity adjustment bolt for adjusting the pressure in the pressure gauge by controlling the size of the volume inside the external joint;

[0012] The electric contact circuit device is arranged on the outer shell and is used for controlling the pointer assembly through the outer shell.

[0013] Preferably, a threaded hole is provided on the external joint, and the cavity adjusting bolt is threadedly connected and arranged in the threaded hole. The cavity adjusting bolt is used in the external joint to adjust the gas pressure of the external joint and the total volume of the C-type Bourdon tube.

[0014] Furthermore, the length of the cavity adjusting bolt is smaller than the thickness of the external joint, that is, the cavity adjusting bolt can seal the external joint so that only the lower end interface of the pressure gauge is connected to the outside world.

[0015] Furthermore, the cavity adjustment bolt includes a stud and a nut integrally connected;

[0016] The stud is a hollow structure, the nut is arranged at the end of the stud, and an inner hexagonal space is provided on the nut. A thin wall is formed between the inner hexagonal space and the end of the stud, and the thickness of the thin wall is less than the thickness of the C-type Bourdon tube.

[0017] Furthermore, a column is provided at the end of the external joint inside the outer shell, the end of the column is located at the center of the cavity of the outer shell, and the pointer assembly is arranged at the end of the column.

[0018] Furthermore, the pointer assembly includes a central rotating shaft, a pressure gauge pointer, a lower limit signal position pointer, an upper limit signal position pointer, and a circular spring;

[0019] The central rotating shaft is set at the end of the column, the circular spring is sleeved on the central rotating shaft, the rotating shafts of the pressure gauge pointer, the lower limit signal pointer and the upper limit signal pointer are all rotatably set on the central rotating shaft, and the pressure gauge pointer, the lower limit signal pointer and the upper limit signal pointer are all connected to the electric contact circuit device.

[0020] Furthermore, the electric contact circuit device includes upper and lower limit signal output terminals and a common signal output terminal, the upper and lower limit signal output terminals are respectively connected to the lower limit signal position pointer and the upper limit signal position pointer with soft wires, the common signal output terminal is connected to the pressure gauge pointer through a soft wire, and the signal terminals of the upper and lower limit signal output terminals and the common signal output terminal are both connected to a digital multimeter or a speaker battery pack.

[0021] In a second aspect, the present invention further provides an electric contact signal connection device, comprising a standard pressure gauge, a pressure-generating system, a digital multimeter, and the above-mentioned adjustable pressure gauge;

[0022] The adjustable pressure gauge includes a pressure gauge body, the standard pressure gauge and the pressure gauge body are connected by electrical contact signals, and the lower interface input ends of the standard pressure gauge and the pressure gauge body are connected to the pressure generation system; the pressure gauge body is provided with upper and lower limit signal output ends and a common signal output end, and the upper and lower limit signal output ends and the common signal output end are respectively connected to the connection ends of the digital multimeter.

[0023] In a third aspect, the present invention further provides an electrical contact signal connection device, comprising a standard pressure gauge, a pressure-generating system, a speaker battery pack, and the adjustable pressure gauge described above;

[0024] The adjustable pressure gauge includes a pressure gauge body, the standard pressure gauge and the pressure gauge body are connected by electrical contact signals, and the input ends of the standard pressure gauge and the pressure gauge body are connected to the pressure generation system; the pressure gauge body is provided with upper and lower limit signal output ends and a common signal output end, and the upper and lower limit signal output ends and the common signal output end are respectively connected to the connection ends of the speaker battery pack.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] The present invention provides an adjustable pressure gauge, which is arranged with the center position of the cavity of an outer shell at the center point of a C-type Bourdon tube as the center of a circle. One end of the C-type Bourdon tube is fixedly connected to an external connector, and the other end is connected to a pointer adjustment mechanism; the pointer adjustment mechanism is connected to a pointer assembly, and the pointer assembly can be adjusted by fine-tuning the pointer adjustment mechanism. The external connector is provided with a cavity adjustment nut, which is used to adjust the pressure in the pressure gauge by controlling the size of the volume inside the external connector, and can effectively control the pressure adjustment of the pressure gauge by the pressure generating system. At the same time, an electric contact circuit device is provided on the outer shell of the pressure gauge, and is connected to a digital multimeter or a speaker battery pack through the electric contact circuit device, effectively simplifying the electric contact signal connection and facilitating detection by the user.

[0027] Furthermore, the cavity adjusting nut is threadedly connected and arranged in the threaded hole. The cavity adjusting nut is used in the external joint to adjust the size of the inner cavity volume of the gas pressure in the external joint. The cavity adjusting nut can play a blocking role in the cavity of the external joint. Pushing or pushing the cavity adjusting nut back and forth can control the size of the cavity volume of the external joint, thereby controlling the pressure entering the pressure gauge.

[0028] Furthermore, the length of the cavity adjustment nut is less than the thickness of the external connector, meaning the cavity adjustment bolt can seal the external connector, leaving only the lower end of the pressure gauge connected to the outside world. When the end of the cavity adjustment nut abuts the inner wall of the external connector, the volume of gas passing through the internal cavity of the external connector decreases, reducing the amount of gas entering the C-type Bourdon tube and thereby increasing gas pressure. Conversely, when the end of the cavity adjustment nut slowly moves outward toward the external connector, the volume of gas passing through the internal cavity of the external connector increases, increasing the amount of gas entering the C-type Bourdon tube and thereby decreasing gas pressure, thereby fine-tuning the pressure gauge needle.

[0029] Furthermore, the cavity adjusting bolt includes a stud and a nut that are integrally connected; the stud is a hollow structure, and the nut is arranged at the end of the stud. An inner hexagonal space is provided on the nut, and a thin wall is formed between the inner hexagonal space and the end of the stud. The thickness of the thin wall is less than the thickness of the C-type Bourdon tube. When the cavity adjusting nut is used in conjunction with the external joint for sealing, if the pressure gauge is subjected to a pressure exceeding the maximum pressure, the elastic thin sheet structure will be deformed and ruptured, thereby protecting the C-type Bourdon tube of the pressure gauge from excessive deformation, inaccurate indication, or even unusable phenomenon.

[0030] Furthermore, the electric contact circuit device includes upper and lower limit signal output terminals and a common signal output terminal, and both the upper and lower limit signal output terminals and the common signal output terminal can be connected to a digital multimeter or a speaker battery pack. When the pressure gauge is an electric contact pressure gauge, the upper limit signal lead and the lower limit signal lead are connected with a connecting wire to form an output terminal, forming a loop with the common terminal, so that the electric contact pressure gauge only works in alarm and non-alarm modes, simplifying the wiring method and making it convenient for users to use and for measurement personnel to detect. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the structure of a pressure gauge in an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the external connector assembly structure in an embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the cavity adjustment nut structure in an embodiment of the present invention;

[0034] Figure 4 This is a structural diagram of an electric contact signal connection device according to an embodiment of the present invention;

[0035] Figure 5 This is a structural diagram of another electrical contact signal connection device according to an embodiment of the present invention;

[0036] In the figure: 1-pressure gauge body; 2-outer shell; 3-C-type Bourdon tube; 4-external connector; 5-pointer adjustment mechanism; 6-cavity adjustment bolt; 7-electric contact circuit device; 8-column; 9-pressure gauge pointer; 10-lower limit signal pointer; 11-upper limit signal pointer; 12-circular spring; 13-standard pressure gauge; 14-pressure building system; 15-digital multimeter; 16-speaker battery pack; 61-stud; 62-nut; 63-thin wall; 71-upper and lower limit signal output terminals; 72-common signal output terminal. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0038] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0039] The present invention is described in further detail below with reference to the accompanying drawings:

[0040] The purpose of the present invention is to provide an adjustable pressure gauge and an electric contact signal connection device to solve the technical problems in the prior art that the pressure gauge pointer cannot be fine-tuned and the electric contact signal connection is cumbersome.

[0041] Example 1

[0042] See also Figure 1 ,In one embodiment of the present invention, an adjustable pressure gauge is provided, comprising a pressure gauge body 1;

[0043] The pressure gauge body 1 includes an outer shell 2, a C-type Bourdon tube 3, a pointer assembly, an external connector 4, a pointer adjustment mechanism 5 and an electrical contact circuit device 7;

[0044] The outer shell 2 has a hollow structure, and the C-shaped Bourdon tube 3, the pointer assembly and the pointer adjustment mechanism 5 are arranged in the cavity of the outer shell 2;

[0045] The external connector 4 is provided with an air inlet passage connected to the C-type Bourdon tube 3, wherein one end of the external connector 4 extends into the outer shell 2, and the other end is connected to the pressure generating system 14;

[0046] The pointer assembly is arranged at the center of the cavity of the outer shell 2 and performs a circular motion with the center as the center point;

[0047] The center point of the C-shaped Bourdon tube 3 is set with the center position of the cavity of the outer shell 2 as the center of the circle. One end of the C-shaped Bourdon tube 3 is fixedly connected to the external connector 4, and the other end is connected to the pointer adjustment mechanism 5; the pointer adjustment mechanism 5 is connected to the pointer assembly;

[0048] The external connector 4 is provided with a cavity adjustment bolt 6, which is used to adjust the pressure in the pressure gauge by controlling the size of the volume inside the external connector 4;

[0049] The electrical contact circuit device 7 is disposed on the outer housing 4 and is used for controlling the pointer assembly via the outer housing 4 .

[0050] Specifically, according to Figure 2 As shown, a threaded hole is provided on the external joint 4 , and the cavity adjusting bolt 6 is threadedly connected and arranged in the threaded hole. The cavity adjusting bolt 6 is used in the external joint 4 to adjust the gas pressure in the external joint 4 .

[0051] The length of the cavity adjusting bolt 6 is smaller than the thickness of the external joint 4 , that is, the cavity adjusting bolt 6 can cooperate with the external joint 4 to perform a sealing function.

[0052] In this embodiment, the cavity adjusting nut can play a blocking role in the cavity of the external joint. The cavity adjusting nut can be rotated in or out to control the size of the cavity volume of the external joint, thereby controlling the pressure entering the pressure gauge. When the end of the cavity adjusting nut is screwed into the inner wall of the external joint, the volume of the inner cavity of the external joint becomes smaller, and the volume of gas entering the C-type Bourdon tube is correspondingly reduced, thereby increasing the gas pressure. Conversely, when the cavity adjusting nut is screwed out of the external joint, the volume of gas passing through the inner cavity of the external joint becomes larger, and the volume of gas entering the C-type Bourdon tube is also correspondingly increased, thereby reducing the gas pressure, thereby fine-tuning the pressure gauge pointer.

[0053] Among them, according to Figure 3 As shown, the cavity adjustment bolt 6 includes a stud 61 and a nut 62 that are integrally connected;

[0054] The stud 61 is a hollow structure, and the nut 62 is arranged at the end of the stud 61. The nut 62 is provided with an inner hexagonal space, and a thin wall 63 is formed between the inner hexagonal space and the end of the stud 61. The thickness of the thin wall 63 is less than the thickness of the C-type Bourdon tube 3.

[0055] The cavity adjustment bolt 6 is in the form of a hollow circular flat-head bolt, one side of which is a cylinder with an inner hexagonal space, and the other side is a hollow cylinder with a thread on the outside. When in use, it cooperates with the inner thread of the circular adjustment hole on the rectangular surface on the rear side of the external joint 4 to seal so that the C-type Bourdon tube 3 and the external joint 4 are connected to the external atmospheric pressure only through the lower air inlet channel. The inner hexagon of the corresponding size is inserted into the inner hexagonal space and rotated. When the lower end of the pressure gauge is sealed and pressurized, the size of the internal cavity can be adjusted so that the pressure gauge pointer 9 moves clockwise or counterclockwise around the central shaft.

[0056] In this embodiment, when the cavity adjusting nut and the external joint are used in conjunction with sealing, if the pressure gauge is subjected to a pressure exceeding the maximum pressure, the elastic sheet structure will deform and rupture, thereby protecting the pressure gauge C-type Bourdon tube from excessive deformation, inaccurate indication, or even unusable phenomenon.

[0057] Specifically, a column 8 is provided at the end of the external joint 4 inside the outer shell 2 , the end of the column 8 is located at the center of the cavity of the outer shell 2 , and the pointer assembly is arranged at the end of the column 8 .

[0058] The pointer assembly includes a central rotating shaft, a pressure gauge pointer 9, a lower limit signal pointer 10, an upper limit signal pointer 11 and a circular spring 12;

[0059] The central rotating shaft is set at the end of the column 8, the circular spring 12 is sleeved on the central rotating shaft, the rotating shafts of the pressure gauge pointer 9, the lower limit signal pointer 10 and the upper limit signal pointer 11 are all rotatably set on the central rotating shaft, and the pressure gauge pointer 9, the lower limit signal pointer 10 and the upper limit signal pointer 11 are all connected to the electric contact circuit device 7.

[0060] Specifically, the electric contact circuit device 7 includes upper and lower limit signal output terminals 71 and a common signal output terminal 72. The upper and lower limit signal output terminals 71 are respectively connected to the lower limit signal position pointer 10 and the upper limit signal position pointer 11 with soft wires, and the common signal output terminal 72 is connected to the pressure gauge pointer 9 through a soft wire. The signal ends of the upper and lower limit signal output terminals 71 and the common signal output terminal 72 are both connected to the digital multimeter 15 or the speaker battery pack 16.

[0061] In this embodiment, when the pressure gauge is an electric contact pressure gauge, the upper limit signal lead and the lower limit signal lead are connected by a connecting wire to form an output terminal, forming a closed loop with the common terminal, so that the electric contact pressure gauge only works in alarm and non-alarm modes, simplifying the wiring method and facilitating use by users and inspection by measurement personnel.

[0062] When the electrical contacts of the pressure gauge body 1 in this embodiment are closed, the electrical contact signal output terminal and the buzzer of the digital multimeter form a closed loop, and the pressure value indicated by the standard digital pressure gauge or precision pressure gauge is read at this time;

[0063] The adjustable pressure gauge provided in this embodiment is used:

[0064] When the pressure gauge body 1 exceeds the upper limit and an elastic sheet in the cavity adjusting bolt 6 breaks, the cavity adjusting bolt 6 can be replaced with the same specification and the pressure indication can be calibrated on site. If it passes the test, it can continue to be used. When the indication error of the pressure gauge body 1 exceeds the verification procedure or calibration specification requirements, the metrology verification department can make the following adjustments:

[0065] First, connect the air inlet channel at the lower end of the pressure gauge to the atmosphere. If the pressure gauge pointer is not at the zero stop pin, you can rotate the dial to adjust the zero position. After the pointer indicates the zero scale position on the dial, connect the pressure gauge to the pressure standard and set the pressure to the upper limit of the pressure gauge scale. If the pointer does not indicate the upper limit scale, you can use an adjustment tool such as a small bottle screwdriver to insert it into the corresponding wire groove on the first adjusting nut through the thin hole in the case and rotate to adjust the pointer position. You can also insert it into the corresponding wire groove on the second adjusting nut and rotate to adjust the pointer position. If the pointer has not reached the qualified position after both adjustments, you can also adjust the cavity adjusting nut. By inserting the tool into the hexagonal space on the cavity adjusting bolt 6 and rotating the cavity adjusting nut, the total volume of the C-type Bourdon tube and the built-in cavity can be increased or decreased. After the pointer indicates the qualified position, the pressure gauge can be verified or calibrated.

[0066] When the C-type Bourdon tube 5 expands beyond a set value, the cavity adjusting bolt on the sealed cavity formed by the C-type Bourdon tube 3 and the external joint 4 has an elastic thin sheet structure at the connection between the inner hole and the outer cylinder, which will preferentially rupture and release pressure, thereby protecting the C-type Bourdon tube 3 from excessive deformation or even permanent rupture.

[0067] In summary, an adjustable pressure gauge is provided in this embodiment. The center position of the cavity of the outer shell is concentrically arranged with the center point of the C-type Bourdon tube as the center of a circle. One end of the C-type Bourdon tube is fixedly connected to the external connector, and the other end is connected to the pointer adjustment mechanism. The pointer adjustment mechanism is connected to the pointer assembly, and the pointer assembly can be adjusted by fine-tuning the pointer adjustment mechanism. The external connector is provided with a cavity adjustment bolt, which is used to adjust the pressure in the pressure gauge by controlling the size of the volume inside the external connector. The pressure-generating system can effectively control the adjustment of the pressure in the pressure gauge. At the same time, an electric contact circuit device is provided on the outer shell of the pressure gauge. The digital multimeter or speaker battery pack is connected through the electric contact circuit device, which effectively simplifies the electric contact signal connection and facilitates detection by the user.

[0068] Example 2

[0069] according to Figure 4 As shown, this embodiment provides an electric contact signal connection device, including a standard pressure gauge 13, a pressure generating system 14, a digital multimeter 15 and the above-mentioned adjustable pressure gauge;

[0070] The adjustable pressure gauge includes a pressure gauge body 1, the standard pressure gauge 13 and the pressure gauge body 1 are connected to the electrical contact signal, and the input ends of the standard pressure gauge 13 and the pressure gauge body 1 are connected to the pressure generation system 14; the pressure gauge body 1 is provided with upper and lower limit signal output ends 71 ​​and a common signal output end 72, and the upper and lower limit signal output ends 71 ​​and the common signal output end 72 are respectively connected to the connection ends of the digital multimeter 15.

[0071] Example 3

[0072] according to Figure 5 As shown, this embodiment provides an electric contact signal connection device, including a standard pressure gauge 13, a pressure-generating system 14, a speaker battery pack 16, and the above-mentioned adjustable pressure gauge;

[0073] The adjustable pressure gauge includes a pressure gauge body 1, the standard pressure gauge 13 and the pressure gauge body 1 are connected by electrical contact signals, and the input ends of the standard pressure gauge 13 and the pressure gauge body 1 are connected to the pressure generating system 14; the pressure gauge body 1 is provided with upper and lower limit signal output ends 71 ​​and a common signal output end 72, and the upper and lower limit signal output ends 71 ​​and the common signal output end 72 are respectively connected to the connection ends of the speaker battery pack 16.

[0074] In Example 2 and Example 3, the upper limit pointer lead and the lower limit pointer lead are connected by a soft wire, and a two-wire connection mode is formed with the needle connection wire to simplify the wiring method, and the electric contact pressure gauge is also enabled to operate in alarm and non-alarm modes; the pressure gauge includes a general pressure gauge, a pressure vacuum gauge, a vacuum gauge and a precision pressure gauge.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. An adjustable pressure gauge, characterized in that: including a pressure gauge body (1); The pressure gauge body (1) comprises an outer shell (2), a C-type Bourdon tube (3), a pointer assembly, an external connector (4), a pointer adjustment mechanism (5), and an electrical contact circuit device (7); The outer shell (2) has a cavity structure, and the C-shaped Bourdon tube (3), the pointer assembly, and the pointer adjustment mechanism (5) are arranged in the cavity of the outer shell (2); An air inlet passage communicating with the C-type Bourdon tube (3) is provided in the external connector (4), wherein one end of the external connector (4) extends into the outer shell (2) and the other end is connected to the pressure generating system (14); The pointer assembly is arranged at the center of the cavity of the outer shell (2) and performs circular motion with the center as the center point; The center point of the C-shaped Bourdon tube (3) is set with the center position of the cavity of the outer shell (2) as the center of the circle, one end of the C-shaped Bourdon tube (3) is fixedly connected to the external joint (4), and the other end is connected to the pointer adjustment mechanism (5); the pointer adjustment mechanism (5) is connected to the pointer assembly; The external joint (4) is provided with a cavity adjustment bolt (6) for adjusting the pressure in the pressure gauge by controlling the size of the internal volume of the external joint (4); The electric contact circuit device (7) is arranged on the outer shell (4) and is used to control the pointer assembly through the outer shell (4); The cavity adjustment bolt (6) comprises a stud (61) and a nut (62) connected integrally; The stud (61) is a hollow structure, and the nut (62) is arranged at the end of the stud (61). The nut (62) is provided with an inner hexagonal space, and a thin wall (63) is formed between the inner hexagonal space and the end of the stud (61). The thickness of the thin wall (63) is less than the thickness of the C-type Bourdon tube (3).

2. An adjustable pressure gauge according to claim 1, characterized in that: The external joint (4) is provided with a threaded hole, and the cavity adjustment bolt (6) is threadedly connected and arranged in the threaded hole. The cavity adjustment bolt (6) is used in the external joint (4) to adjust the gas pressure of the external joint (4) and the total volume of the C-type Bourdon tube (3).

3. An adjustable pressure gauge according to claim 2, characterized in that: The length of the cavity adjusting bolt (6) is less than the thickness of the external joint (4), that is, the cavity adjusting bolt (6) can seal the external joint (4) so ​​that only the lower end interface of the pressure gauge is connected to the outside world.

4. The adjustable pressure gauge according to claim 1, characterized in that: The end of the external joint (4) inside the outer shell (2) is provided with a column (8), the end of the column (8) is located at the center of the cavity of the outer shell (2), and the pointer assembly is arranged at the end of the column (8).

5. The adjustable pressure gauge according to claim 4, characterized in that: The pointer assembly includes a central rotating shaft, a pressure gauge pointer (9), a lower limit signal position pointer (10), an upper limit signal position pointer (11), and a circular spring (12); The central rotating shaft is arranged at the end of the column (8), the circular spring (12) is sleeved on the central rotating shaft, the rotating shafts of the pressure gauge pointer (9), the lower limit signal pointer (10) and the upper limit signal pointer (11) are all rotatably arranged on the central rotating shaft, and the pressure gauge pointer (9), the lower limit signal pointer (10) and the upper limit signal pointer (11) are all connected to the electric contact circuit device (7).

6. The adjustable pressure gauge according to claim 5, characterized in that: The electric contact circuit device (7) includes upper and lower limit signal output terminals (71) and a common signal output terminal (72), wherein the upper and lower limit signal output terminals (71) are respectively connected to the lower limit signal position pointer (10) and the upper limit signal position pointer (11) by soft wires, and the common signal output terminal (72) is connected to the pressure gauge pointer (9) by soft wires, and the signal terminals of the upper and lower limit signal output terminals (71) and the common signal output terminal (72) are both connected to a digital multimeter (15) or a speaker battery pack (16).

7. An electrical contact signal connection device, characterized in that: It comprises a standard pressure gauge (13), a pressure-generating system (14), a digital multimeter (15), and an adjustable pressure gauge according to any one of claims 1 to 6; The adjustable pressure gauge comprises a pressure gauge body (1), the standard pressure gauge (13) and the pressure gauge body (1) are connected by electrical contact signals, and the lower interface input ends of the standard pressure gauge (13) and the pressure gauge body (1) are connected to a pressure generating system (14); the pressure gauge body (1) is provided with upper and lower limit signal output ends (71) and a common signal output end (72), and the upper and lower limit signal output ends (71) and the common signal output end (72) are respectively connected to the connection ends of a digital multimeter (15).

8. An electrical contact signal connection device, characterized in that: It comprises a standard pressure gauge (13), a pressure-generating system (14), a speaker battery pack (16), and an adjustable pressure gauge according to any one of claims 1 to 6; The adjustable pressure gauge comprises a pressure gauge body (1), the standard pressure gauge (13) and the pressure gauge body (1) are connected by electrical contact signals, and the input ends of the standard pressure gauge (13) and the pressure gauge body (1) are connected to a pressure generating system (14); the pressure gauge body (1) is provided with upper and lower limit signal output ends (71) and a common signal output end (72), and the upper and lower limit signal output ends (71) and the common signal output end (72) are respectively connected to the connection ends of the speaker battery pack (16).

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