KR20000001874A - Differential pressure gauge - Google Patents

Abstract

PURPOSE: A differential pressure gauge is described, which converts straight displacement of a diaphragm resulting form pressure difference into a rotation displacement by a noncontact method to precisely measure differential pressure of a pneumatic apparatus. CONSTITUTION: The gauge comprises a casing(1) of which a front is covered with a cover(11); a dashboard(2) supported in the cover; a diaphragm(5) dividing a back space of the dashboard into a high pressure room(14) and a low pressure room(15); a high compression port(16) leading to the high pressure room; a low compression port(17) leading to the low pressure room; a driving plate(6) of which one end is supported to an upper end of the high pressure room, a middle end is coupled to the diaphragm by a spring(62), and a free end has a magnet(64); a screw axis(3) rotated by a magnetism according to movement of the magnetic; and an indication needle adhered to the screw axis to be circulated. The dashboard is mounted in an internal space of the casing, is coupled to a support arm(22) located in both sides of an upper end of a base plate(21) rotatably supported on a back of the low end. A null adjustment bolt(27), which is coupled to a null adjustment axis(13) rotatably inserted into the cover(11), is coupled to a low end of the base plate(21). An auxiliary compression port(18) coupled to the high compression port may further be mounted upon one side of the back of the casing, and an auxiliary low compression port(19) coupled to a low pressure room(15) may further be mounted in the middle of the back thereof.

Description

Differential pressure gauge

The present invention relates to a differential pressure gauge connected to the inlet and outlet ends of a pneumatic mechanism such as a valve, a filter, or a strainer installed in a pneumatic line or a gas line, for example, to measure the pressure difference between both ends. The present invention relates to a differential pressure gauge capable of precisely measuring differential pressure by reducing mechanical operating error by causing a linear displacement to be converted into a rotational displacement in which an indicator hand rotates by a magnetic force of a magnet.

Various pneumatic mechanisms are widely used in fluid lines such as pneumatic lines or gas lines, and representative ones of these include valves, filters or strainers (hereinafter referred to as "pneumatic mechanisms").

The fluid flowing along the fluid line contains moisture or foreign matter, and the scale is created inside the pipeline, and when the seal passes, water, foreign matter or scale (hereinafter referred to as "foreign substance") is the pneumatic mechanism. Blocking the internal flow path may cause the fluid to flow smoothly. In this case, if the fluid flow is not smooth, for example, in the case of a production line, a result of failing to obtain a predetermined pressure and a flow rate required at each driving part of a mechanical device is frequently caused by a heavy production line operation. do.

If there is no foreign matter inside the pneumatic mechanism, the pressure difference between the outlet end and the inlet end of the pneumatic mechanism is hardly different. However, if there is foreign matter, the pressure at the outlet end is higher than the pressure at the inlet end due to the flow resistance. When the pressure difference between the stage and the inlet is more than the predetermined value, it is possible to obtain the predetermined pressure and flow rate required in the fluid line by periodically cleaning or replacing the pneumatic mechanism to prevent the production line from stopping or the sudden increase in power loss. .

Therefore, in order to measure the pressure difference between the outlet end and the inlet end of the pneumatic mechanism so that the cleaning time or the replacement time of the pneumatic mechanism can be clearly understood, a pressure gauge is usually provided at both the outlet end and the inlet end of the pneumatic mechanism. The differential pressure at both ends was measured by comparing the results.

In this method, however, both pressures have to be compared and two pressure gauges are required for each of the many installed pneumatic devices, resulting in an increase in pressure gauge installation costs and securing installation space for pressure gauges. Differential pressure gauges have been proposed to measure differential pressures with only the measuring instrument of.

Conventional differential pressure gauges, the front of the instrument panel is protected by a cover is installed and the casing is installed rotatably on the surface of the instrument panel; A diaphragm dividing the inside of the casing into a high pressure chamber and a low pressure chamber; A low pressure side port installed in the casing to communicate with the low pressure chamber of the diaphragm and connected to an outlet end of the pneumatic mechanism; A high pressure side port installed in the casing to communicate with the high pressure chamber of the diaphragm and connected to an inlet end of the pneumatic mechanism; A shaft connected to an approximately central portion of the diaphragm and protruding toward the high pressure chamber; A link mechanism interlocked with the shaft in front and rear directions; A rack connected to the link mechanism and linearly moving according to the operation of the link mechanism; And a pinion for rotating the indicator hand by engaging the rack and rotating.

According to the conventional differential pressure gauge configured as described above, the pressure of the inlet end of the pneumatic mechanism acts on the high pressure chamber of the diaphragm through the high pressure side port in the process of passing the fluid along the fluid line through the pneumatic mechanism, the outlet end of the pneumatic mechanism Is applied to the low pressure chamber of the diaphragm through the low pressure side port. Therefore, when foreign matter is blocking the flow path of the pneumatic mechanism, the pressure at the inlet end of the pneumatic mechanism is higher than the pressure at the outlet end, so that the diaphragm expands from the neutral state to the low pressure chamber, and the shaft moves along with the link mechanism and rack. And by the sequential interlocking of the pinion, the indicator needle is rotated, and by checking the scale indicated by the indicator needle it is possible to determine whether to repair or replace the pneumatic mechanism by recognizing the differential pressure between the inlet end and the outlet end of the pneumatic mechanism.

However, there are the following problems in the differential pressure gauge as described above.

First, it is difficult to accurately measure the differential pressure because the indicator needle is rotated by the linkage of the shaft, link mechanism, rack and pinion, so that not only the power transmission loss of the mechanical elements but also the mechanical error such as the backlash of the rack and pinion is large. Do.

Second, due to the large mechanical operating error, the state where the indicator needle returns to zero at low or high pressure is also inaccurate. As such, if the zero return state of the indicator hand is bad, it is difficult to maintain the differential pressure gauge because of frequent zero adjustments, and it is difficult to perform zero adjustment from the outside, causing inconvenience to use the differential pressure gauge.

Third, precise differential pressure measurement is more difficult due to the vibration of mechanical components when subjected to vibration or shock.

Fourth, when the mechanical elements operate in contact with each other, the wear between each other is large and durability is lowered, which causes further deterioration of precision.

Fifth, when the low pressure side port and the high pressure side port are formed in the casing, respectively, it is difficult to install the differential pressure gauge when the pneumatic mechanism is installed in a place where it is difficult to check the differential pressure gauge.

The present invention has been made to solve the conventional problems as described above, it is possible to accurately measure the differential pressure of the pneumatic mechanism by converting the linear displacement of the diaphragm due to the pressure difference to the rotational displacement through a non-contact method and the zero point of the indicator needle The return is also aimed at providing an accurate differential pressure gauge.

Another object of the present invention is to provide a differential pressure gauge which can be improved in durability by being subjected to non-contact differential pressure measurement, and is not affected by vibration or shock.

It is an additional object of the present invention to provide a differential pressure gauge that can be easily zeroed externally when zeroing is required for the indicator hand.

1 is a perspective view showing a differential pressure gauge according to the present invention.

Figure 2 is a rear view showing a differential pressure gauge according to the present invention.

3 is a cross-sectional view showing a differential pressure gauge according to the present invention.

Figure 4 is an exploded perspective view showing the main portion of the differential pressure gauge according to the present invention.

<Explanation of symbols for main parts of the drawings>

1: casing 2: instrument panel

3: screw right 4: indicator hand

5: Diaphragm 6: Drive Plate

11 cover 12 fastening ring

13: zero adjustment axis 21: base plate

27: zero adjustment bolt 62: spring

64: magnet

In order to achieve the above object, the differential pressure gauge according to the present invention comprises: a casing in which an open front is covered with a cover and sealed and an inner space is formed; An instrument panel installed in the inner space of the cover so as to be moved forward and backward and having a lower end supported by a lower end of the cover; A diaphragm for dividing an inner space behind the instrument panel into a front high pressure chamber and a rear low pressure chamber; A high pressure side port installed at one side of an outer circumferential surface of the casing to communicate with the high pressure chamber and connected to an inlet end of the pneumatic mechanism; A low pressure side port installed at one side of an outer circumferential surface of the casing to communicate with the low pressure chamber and connected to an outlet end of the pneumatic mechanism; A driving plate having one end supported on an upper end portion of an inner wall surface of the high pressure chamber, a stop portion connected to a center portion of the diaphragm by a spring, and a magnet installed at a free end thereof, the free end of which rotates forward and backward along the expansion direction of the diaphragm; A screw shaft which is rotatably supported on the rear surface of the lower end of the instrument panel so as to rotate by the magnetic force according to the movement of the magnet; In addition, the lower end portion is in contact with the screw right shaft is placed on the surface of the instrument panel so as to be rotated in accordance with the rotation of the screw shaft, characterized in that it comprises an indicator needle for indicating the scale of the instrument panel.

According to the present invention, the instrument panel is formed in a substantially semi-circular shape and is disposed in the upper half of the inner space of the case. In addition, the lower half of the inner space of the case is provided with a base plate which is supported by the lower end cover is connected to the instrument panel can be supported by the instrument panel.

The lower end of the base plate is fastened to a zero point adjustment bolt formed with a male thread on the front end portion, the zero adjustment bolt is fastened to the female screw formed on the rear end of the zero adjustment bolt is rotatably inserted into the lower end of the cover. Therefore, the forward and backward distance of the zero adjustment bolt is determined according to the amount of rotation of the zero adjustment shaft, and the base plate and the instrument panel connected thereto may be advanced together by the forward and backward movement of the zero adjustment bolt.

Further, according to the differential pressure gauge of the present invention, an auxiliary high pressure side port communicating with a high pressure side port is further provided on one side of the case to facilitate installation of the differential pressure gauge, and an auxiliary low pressure side port communicating with the low pressure chamber is further provided at the center of the case back. Can be installed.

According to the differential pressure gauge of the present invention configured as described above, the zero point adjustment is first performed so that the indicator hand points to zero for use in connection with a pneumatic mechanism. When the zero adjustment shaft is rotated, the base plate and the instrument panel connected thereto are moved back and forth together by the forward and backward movement of the zero adjustment bolt, and accordingly, the screw right shaft is also moved forward and backward. When the screw shaft moves back and forth, zero adjustment may be performed by turning the indicator needle with the lower end pivoted on the screw shaft as the screw shaft rotates due to the influence of the magnetic force of the magnet installed correspondingly.

Next, the high pressure side port or the auxiliary high pressure side port is connected to the inlet end of the pneumatic mechanism by a connecting pipe, and the low pressure side port or the auxiliary low pressure side port is connected to the outlet end of the pneumatic mechanism by the connecting pipe. Block ports not connected to the pneumatic line.

When the differential pressure gauge is installed as described above, the pressure at the inlet end of the pneumatic mechanism acts on the high pressure chamber, and the pressure at the outlet end of the pneumatic mechanism acts on the low pressure chamber. When the inside of the pneumatic mechanism is blocked and the pressure difference between the high pressure chamber and the low pressure chamber increases, the diaphragm expands toward the low pressure chamber, and the driving plate connected with the spring is pulled toward the diaphragm and pivoted. When the driving plate moves to the rear side, the magnet installed at the free end of the driving plate is also pivoted to the rear side together with the driving plate, so that the magnetic force of the magnet continuously acts along the threaded portion of the screw right shaft, and thus the screw right shaft is rotated, thus connected with the screw right shaft. By turning the indicator hand, the scale is indicated as much as the differential pressure between the high pressure chamber and the low pressure chamber. If this indication is above the prescribed value, repair or replace the pneumatic device to prevent line interruption or power loss.

Other features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings.

As shown in FIG. 1, reference numeral 1 is a casing which is formed in a substantially cylindrical shape, the front of which is opened and a space is formed therein as shown in FIG.

The front of the casing 1 is covered with a cover 11 to seal the inner space. 1 and 3, the cover 11 is preferably detachably coupled to the casing (1) by a fastening ring (12) fastened to the male screw portion formed along the front outer peripheral surface of the casing (1). Do.

As shown in FIGS. 1 and 3, an inside of the cover 11 is provided with an instrument panel 2 at a predetermined distance from the cover 11. According to the present invention, the instrument panel 2 is formed in a shape slightly larger than the semi-circle, and is arranged to be moved forward and backward in the upper half of the inner space of the casing 1, and the lower end of the instrument panel 2 is the lower half of the inner space of the casing 1. It is connected to the base plate 21 is arranged to be able to move forward and backward. That is, the inner space of the casing 1 inside the cover 11 is blocked by the instrument panel 2 and the base plate 21.

As shown in FIG. 4, the base plate 21 has two support arms 22 and 22 which are bent backwards from both upper ends and upwardly bent toward the rear surface of the instrument panel 2, and the support arms 22. Are fastened to the instrument panel 2 with the fastening means 23. Thus, the base plate 21 is positioned slightly ahead of the instrument panel 2 by the support arms 22, so that the upper end of the base plate 21 between the support arms 22 and the lower end of the instrument panel 2 and the base plate 21. Between the passages are formed passages 24 that run up and down.

In addition, the base plate 21 has a first support rib 25 which is bent from the rear end center to the rear side like the support arm 22 and slightly bent upwards again, so that the back plate and the first support of the base plate 21 are supported. A predetermined space is formed between the ribs 25. The screw shaft 3 is rotatably installed in this space. The screw right shaft 3 can be rotated by supporting the front end portion rotatably on the base plate 21 and the rear end portion rotatably on the first support rib 25.

The lower end of the indicator needle 4 is condensed to the screw right shaft 3. The indicator needle 4 has a passage 24 formed from the screw right side 3 along the rear surface of the base plate 21 between the upper end of the base plate 21 and the lower end of the instrument panel 2. By being rotatable in a state spaced slightly apart from the surface of the instrument panel (2) through the rotation of the screw right shaft (3) left and right.

In addition, the base plate 21 has a second support rib 26 extending downwardly from the first support rib 25, and the second support rib 26 has a zero adjustment bolt having a male thread at the front end portion thereof. 27) are condensed. The zero adjustment bolt 27 is fastened to the female screw formed at the rear end of the zero adjustment shaft 13 inserted into the lower end of the cover 11 so that the base plate 21 and the instrument panel 2 can be moved forward and backward. Can be supported. That is, when the zero adjustment shaft 13 is rotated, the zero adjustment bolt 27 moves forward and backward along the fastening length of the zero adjustment bolt 27, so that the base plate 21 and the instrument panel 2 connected thereto are also moved forward and backward together.

On the other hand, the inner space of the casing 1 at the position behind the instrument panel 2 is the diaphragm 5, the front of the diaphragm 5 to the high pressure chamber 14, the rear of the diaphragm 5 to the low pressure chamber 15. Compartment. In addition, a high pressure side port 16 connected to an inlet end of the pneumatic mechanism is installed at one side of the outer circumferential surface of the casing 1 so as to communicate with the high pressure chamber 14, and connected to an outlet end of the pneumatic mechanism so as to communicate with the low pressure chamber 15. The low pressure side port 17 is provided on one side of the outer circumferential surface of the casing 1. Here, as shown in FIG. 1, the high pressure side port 16 and the low pressure side port 17 are sequentially installed on the same side of the outer circumferential surface of the casing 1.

The diaphragm 5 has an edge portion fixed to the inner wall surface of the casing 1 by a disk-shaped bracket 51, so that the center portion of the diaphragm 5 is formed according to the pressure difference between the high pressure chamber 14 and the low pressure chamber 15. It is installed to expand toward 15). The front and rear sides of the diaphragm 5 is preferably reinforced by the high pressure cover 52 and the low pressure cover 53, and the diaphragm bolt 54 penetrates through the center of the high pressure cover 52 and the low pressure cover 53. A hole is formed in the center of the disk-shaped bracket 51 corresponding to the diaphragm bolt 54.

In addition, the driving plate 6 is provided in the high pressure chamber 14 formed by the diaphragm 5. The upper end of the drive plate 6 is fixed to the upper end of the inner wall surface of the casing 1, the connection bolt 61 is installed through the stop of the drive plate 6, the spring (on the rear end of the connection bolt 61) 62 is connected to the front end, and the rear end of the spring 62 is connected to the front end of the bolt of the diaphragm 5 through the hole of the disc-shaped bracket 51. The free end of the drive plate 6 is disposed at a predetermined interval at a position corresponding to one side (here, left) of the screw right shaft 3.

According to the invention, it is preferable that the free end of the screw right shaft 3 and the corresponding drive plate 6 bend in an arc shape, and a magnet 64 is inserted into the arc bend portion 63.

Therefore, when the diaphragm 5 expands according to the pressure difference between the low pressure chamber 15 and the high pressure chamber 14, the free end of the driving plate 6 is elastically rotated in the expansion direction of the diaphragm 5 by the spring 62. The screw shaft 3 is rotated by the magnetic force of the magnet 64 that continuously acts along the threaded portion of the screw shaft 3 by moving the magnet 64 along the one side of the screw shaft 3. As a result, the indicator needle 4, the lower end of which is condensed on the screw right shaft 3, turns left and right, so that the indicator needle 4 is scaled by the pressure difference between the high pressure chamber 14 and the low pressure chamber 15. Will be indicated.

Further, according to the differential pressure gauge of the present invention, in order to conveniently connect the differential pressure gauge to the pneumatic mechanism, for example, as shown in FIG. 2, the high pressure side port 16 or the high pressure chamber 14 is connected to one side of the back of the casing 1. An auxiliary high pressure side port 18 may be further installed, and an auxiliary low pressure side port 19 communicating with the low pressure chamber 15 or the low pressure side port 17 may be further installed in the center of the rear surface of the casing 1.

Reference numeral 29 denotes a stopper which protrudes forward on both sides of the instrument panel 2 to prevent the indicator needle 4 from moving out of the scale range of the instrument panel 2.

Next, the operation of the differential pressure gauge according to the present invention configured as described above will be described.

In order to use the differential pressure gauge according to the present invention to the pneumatic mechanism, it is checked whether the indicator needle 4 is zero, and if the indicator needle 4 is not zero, the zero point of the indicator needle 4 is adjusted.

When the zero adjusting shaft 13 inserted into the lower end of the cover 11 is rotated, the zero adjusting bolt 27 moves forward and backward as the fastening amount of the zero adjusting bolt 27 fastened thereto is changed, and accordingly, the base plate 21 is rotated. By moving forward and backward, the instrument panel 2 connected to the base plate 21 also moves forward and backward together. When the base plate 21 moves forward and backward, the screw right shaft 3 provided between the base plate 21 and the first support rib 25 moves forward and backward so that the magnetic force of the magnet 64 is in the longitudinal direction of the screw right shaft 3. In accordance with the continuous operation along the screw right shaft (3) is rotated, and thus the zero point adjustment can be carried out by turning the indicator needle (4) with the lower end is condensed on the screw right shaft (3). That is, the zero adjustment with respect to the indicator needle 4 can be performed according to the amount of rotation of the zero adjustment axis 13.

Next, the high pressure side port 16 or the auxiliary high pressure side port 18 is connected to the inlet end of the pneumatic mechanism by the connecting pipe, and the low pressure side port 17 or the auxiliary low pressure is connected to the outlet end of the pneumatic mechanism. Connect the side port (19). Here, for example, it is assumed that the high pressure side port 16 and the auxiliary low pressure side port 19 are sequentially connected to the inlet end and the outlet end of the pneumatic mechanism. The auxiliary high pressure side port 18 and the low pressure side port 17 which are not connected to the pneumatic line prevent the fluid flowing into the high pressure chamber 14 and the low pressure chamber 15 from leaking.

As described above, when the differential pressure gauge is installed and the valves of the connection pipes between the pneumatic line and the differential pressure gauge are opened, the fluid flowing through the inlet end of the pneumatic mechanism passes through the connection pipe and the high pressure side port 16 in order to the high pressure chamber 14. By flowing in, the fluid pressure at the inlet end of the pneumatic mechanism acts on the high pressure chamber 14. Then, the fluid flowing through the outlet end of the pneumatic mechanism passes through the connecting pipe and the auxiliary low pressure side port 19 in order to flow into the low pressure chamber 15, so that the fluid pressure at the outlet end of the pneumatic mechanism acts on the low pressure chamber 15.

As such, when the differential pressure gauge is connected to the pneumatic mechanism and the inside of the pneumatic mechanism is not blocked, the pressure acting on the high pressure chamber 14 and the pressure acting on the low pressure chamber 15 are almost the same. ) Maintains an equilibrium state, and there is no change in the turning amount of the indicator needle 4. However, when the seal is caused by moisture contained in the fluid as the seal passes, foreign matter or scale blocks the flow path inside the pneumatic mechanism, so that the fluid flows smoothly, and a large fluid pressure acts on the high pressure chamber 14. A small fluid pressure acts on the low pressure chamber 15 so that a large pressure difference occurs between the high pressure chamber 14 and the low pressure chamber 15.

As such, when the pressure difference between the high pressure chamber 14 and the low pressure chamber 15 increases, the diaphragm 5 is pushed toward the low pressure chamber 15 and expands, so that the driving plate 6 is rearward, that is, the diaphragm through the spring 62. It is towed to (5) and it turns. When the drive plate 6 pivots to the rear side, the magnet 64 installed in the arc-shaped bent portion 63 of the free end of the drive plate 6 also moves along with the drive plate 6 along the screw right side 3 at one side of the right side of the screw. By turning to the rear side, the magnetic force of the magnet 64 continuously acts on the threaded portion of the screw right shaft 3, and the screw needle 3 is rotated by this magnetic force change, so that the indicator needle 4 connected to the screw right shaft 3 is Turn around. Therefore, the differential pressure between the high pressure chamber 14 and the low pressure chamber 15 can be known through the scale indicated by the indicator needle 4. It can be seen that when the differential pressure is higher than a predetermined value, the flow path of the pneumatic mechanism is blocked so much that the flow of fluid is very deteriorated. In this way, if the fluid flow does not flow smoothly and the pressure loss is too great to obtain the required pressure and flow rate required for the fluid line, the operation cannot be performed and the line operation is stopped. Therefore, the operation cost of the pneumatic line increases, so to prevent this, periodically check the differential pressure of the differential pressure gauge and repair or replace the pneumatic mechanism having a large differential pressure.

On the other hand, the differential pressure does not need to be measured and the differential pressure gauge according to the present invention can be used as a general pressure gauge even when only the inlet pressure or the outlet pressure of the pneumatic mechanism is measured. That is, when the high pressure side port 16 or the auxiliary high pressure side port 18 is connected to the inlet end or the outlet end of the pneumatic mechanism and all the remaining ports are blocked, the inlet pressure or the outlet pressure of the pneumatic mechanism acts on the high pressure chamber 14. Thus, the diaphragm 5 expands toward the low pressure chamber 15 so that the pressure acting on the high pressure chamber 14 can be measured by the above-described action. When the differential pressure gauge according to the present invention is used as a pressure gauge, since the mechanical operating error is small, the pressure can be measured more precisely than a general pressure gauge.

According to the differential pressure gauge according to the present invention configured as described above, the mechanical displacement by converting the linear displacement of the diaphragm (5) due to the pressure difference to the rotational displacement through the non-contact method by the magnetic force of the magnet 64, not the mechanical contact method. By eliminating the error, the pressure difference between the pressure at the inlet end and the outlet end of the pneumatic mechanism can be precisely measured.

In addition, by measuring the differential pressure by a non-contact method, the wear of the mechanical elements can be reduced and durability can be improved, and the differential pressure can be measured more precisely because it is not affected by vibration or impact.

In addition, zero adjustment can be performed very simply by rotating the zero adjustment shaft 13 externally without having to disassemble the differential pressure gauge.

In addition, by additionally installing the auxiliary ports 18 and 19, it is possible to conveniently install the differential pressure gauge even when the pneumatic mechanism is difficult to connect the differential pressure gauge.

In addition, even when the differential pressure gauge according to the present invention is used as a pressure gauge, since the pressure can be measured through a non-contact method, the pressure can be measured more precisely than a general pressure gauge, and the durability is also improved.

Claims (3)

A casing in which an opened front is covered with a cover and sealed and an inner space is formed; An instrument panel supported by an inner space inside the cover and having a lower end supported by a lower end of the cover; A diaphragm for dividing an inner space behind the instrument panel into a front high pressure chamber and a rear low pressure chamber; A high pressure side port installed at one side of an outer circumferential surface of the casing to communicate with the high pressure chamber and connected to an inlet end of the pneumatic mechanism; A low pressure side port installed at one side of an outer circumferential surface of the casing to communicate with the low pressure chamber and connected to an outlet end of the pneumatic mechanism; A driving plate having one end supported on an upper end portion of an inner wall surface of the high pressure chamber, a stop portion connected to a center portion of the diaphragm by a spring, and a magnet installed at a free end thereof, the free end of which rotates forward and backward along the expansion direction of the diaphragm; A screw shaft which is rotatably supported on the rear surface of the lower end of the instrument panel so as to rotate by the magnetic force according to the movement of the magnet; And, And the indicator hand which pivots in accordance with the rotation of the screw right by instructing the lower end of the screw right side to be pivotally placed on the surface of the instrument panel to indicate the scale of the instrument panel. The method of claim 1, The instrument panel is formed in a substantially semi-circular shape and is disposed in the upper half of the inner space of the casing, is installed in the lower half of the inner space of the casing, and is connected to both support arms of the upper end of the base plate on which the screw shaft is rotatably supported on the rear surface of the lower part. , The lower end of the base plate is fastened to the zero point adjustment bolt formed with a male thread in the front end, And the zero adjustment bolt is fastened to a zero adjustment shaft which is rotatably inserted into the lower end of the cover, so that the zero adjustment of the indicator needle is performed according to the rotation amount of the zero adjustment shaft. The method of claim 1, An auxiliary high pressure side port communicating with the high pressure side port or the high pressure chamber is further installed on one side of the rear side of the casing, A differential pressure gauge, further comprising a low pressure side port or an auxiliary low pressure side port communicating with the low pressure chamber in the center of the rear surface of the casing.