Pirani gauge

Abstract

The invention relates to the technical field of detection devices, and provides a Pirani gauge which comprises a Pirani gauge body and a protective cover, the Pirani gauge body comprises a gauge tube and a resistance wire, the gauge tube is of a cylindrical structure with one open end, and the resistance wire is arranged in the gauge tube; the protective cover is arranged in the gauge tube and at least covers the resistance wire, and a communicating hole is formed in the end, away from the open end of the gauge tube, of the protective cover so as to communicate the inner space of the protective cover with the inner space of the gauge tube. Thus, the protective cover physically isolates the resistance wire, can weaken or block the direct impact of the air flow of the environment to be detected on the resistance wire, and avoids the problem of unstable heat dissipation of the resistance wire caused by air flow. The communicating hole can ensure that the gas pressure in the protective cover is consistent with the gas pressure in the gauge tube slowly, and accurate measurement is realized. In addition, the communication hole can also buffer and damp the gas flow and stabilize the gas environment around the resistance wire, so that the problem of poor measurement precision of the Pirani gauge under the gas flow condition in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of detection device technology, and in particular to a Pirani gauge. Background Technology

[0002] A Pirani gauge is a sensor used to measure gas pressure. It typically consists of a gauge tube and a hot wire inside the tube. The hot wire is heated by an electric current. At higher gas pressures, there is more gas around the hot wire, and gas molecules frequently collide with the wire, causing heat to be rapidly dissipated. To maintain a constant temperature in the hot wire, a relatively large current is required. Conversely, at lower gas pressures, there is less gas around the wire, and gas molecules are less densely packed, resulting in slower heat dissipation. Therefore, the current required to maintain a constant temperature in the hot wire is relatively smaller. Thus, the current in the gas pressure can be calculated by measuring the electrical power required to maintain the wire temperature or by measuring the change in the wire's resistance.

[0003] In practical applications, the gauge tube needs to be connected to the target environment, and the internal space of the gauge tube must be consistent with the target environment. For target environments with significant gas flow, the measurement accuracy of the Pirani gauge deteriorates drastically, limiting the application of existing Pirani gauges under gas flow conditions. Although Pirani gauges can be calibrated, different levels of gas flow have varying effects on their detection accuracy, making the same Pirani gauge unsuitable for environments with varying degrees of gas flow.

[0004] Therefore, how to solve the problem of poor measurement accuracy of Pirani gauges under gas flow conditions has become an important technical problem for those skilled in the art to solve. Summary of the Invention

[0005] This invention provides a Pirani gauge to address the shortcomings of related technologies in terms of poor measurement accuracy under gas flow conditions.

[0006] This invention provides a Pirani gauge, comprising: The Pirani gauge body includes a gauge tube and a resistance wire. The gauge tube has a cylindrical structure with one end open, and the resistance wire is disposed inside the gauge tube. A protective cover is disposed inside the gauge tube, and the protective cover covers at least the outside of the resistance wire. A connecting hole is provided at one end of the protective cover away from the open end of the gauge tube, and the connecting hole connects the internal space of the protective cover with the internal space of the gauge tube.

[0007] According to a Pirani gauge provided by the present invention, the Pirani gauge body further includes: The first electrode rod and the second electrode rod pass through the opposite ends of the open end of the gauge tube. The first end of the first electrode rod and the first end of the second electrode rod are both located outside the gauge tube, and the second end of the first electrode rod and the second end of the second electrode rod are both located inside the gauge tube. The two ends of the resistance wire are respectively electrically connected to the second end of the first electrode rod and the second end of the second electrode rod.

[0008] According to a Pirani gauge provided by the present invention, the protective cover includes: A protective cylinder is fixed relative to the gauge tube. The protective cylinder has a cylindrical structure with one end open. The protective cylinder is sleeved on a portion of the first electrode rod and the second electrode rod, as well as the outside of the resistance wire. A cap is provided at the open end of the protective cylinder, and the cap is sealed to the open end of the protective cylinder. The first electrode rod and the second electrode rod both penetrate the cap, and the first electrode rod and the second electrode rod are insulated from the cap.

[0009] According to a Pirani gauge provided by the present invention, the connecting hole is a circular hole with a diameter of 1 mm to 2 mm.

[0010] According to a Pirani gauge provided by the present invention, the connecting hole is provided on the cover, and at least two connecting holes are provided, with each connecting hole being evenly distributed on the cover.

[0011] According to a Pirani gauge provided by the present invention, the protective cylinder is fixedly connected to the cap, and one of the protective cylinder and the cap is connected to the gauge tube by a rigid connection structure; Alternatively, both the protective cylinder and the cap are rigidly connected to the gauge tube via a connection structure.

[0012] According to a Pirani gauge provided by the present invention, the rigid connection structure includes: A set of first connectors, one end of which is fixed to the inner wall of the gauge tube, and the other end of which extends away from the inner wall of the gauge tube. The set of first connectors are distributed circumferentially along the gauge tube. A set of second connectors, one end of which is fixed to the outer wall of the protective cylinder or the cover, and the other end of which extends away from the outer wall of the protective cylinder or the cover. A set of second connectors are distributed circumferentially along the protective cylinder or the cover. The first connector and the second connector correspond one-to-one and are overlapped and fixed.

[0013] According to a Pirani gauge provided by the present invention, the cap is provided with a first clearance hole and a second clearance hole; The first clearance hole is used to avoid the first electrode rod, and there is a gap between the first electrode rod and the side wall of the first clearance hole; The second clearance hole is used to avoid the second electrode rod, and there is a gap between the second electrode rod and the side wall of the second clearance hole.

[0014] According to a Pirani gauge provided by the present invention, the central axis of the resistance wire coincides with the central axis of the protective cylinder, and both the central axis of the resistance wire and the central axis of the protective cylinder are parallel to the axis of the gauge tube.

[0015] According to a Pirani gauge provided by the present invention, the first electrode rod and the second electrode rod are arranged symmetrically about the central axis of the protective cylinder; The second end of the first electrode rod is provided with a first connecting part, which extends toward the second electrode rod. The second end of the second electrode rod is provided with a second connecting part, which extends toward the first electrode rod. The two ends of the resistance wire are electrically connected to the first connecting part and the second connecting part.

[0016] The Pirani gauge provided by this invention includes a gauge body and a protective cover. The gauge body includes a gauge tube and a resistance wire. The gauge tube has a cylindrical structure with one open end, and the resistance wire is disposed inside the gauge tube. When measuring the pressure of the environment to be measured, the gauge tube needs to be connected to the environment. The gas in the environment to be measured can enter the interior of the gauge tube through the open end, making the gas pressure inside the gauge tube consistent with the gas pressure in the environment to be measured. The protective cover is disposed inside the gauge tube and covers at least the outside of the resistance wire. By physically isolating the resistance wire with the protective cover, the direct impact of airflow from the environment to the resistance wire can be effectively reduced or blocked, avoiding the problem of unstable heat dissipation of the resistance wire caused by gas flow, which helps to reduce measurement errors. A connecting hole is provided at the open end of the protective cover away from the gauge tube, connecting the interior space of the protective cover with the interior space of the gauge tube. The connecting hole ensures that the gas pressure inside the protective cover and the gas pressure inside the gauge tube slowly equalize, achieving accurate measurement. Furthermore, the connecting hole effectively buffers and dampens gas flow, stabilizing the gas environment around the resistance wire, thus solving the problem of poor measurement accuracy of Pirani gauges in related technologies under gas flow conditions. The measurement accuracy of the Pirani gauge provided by this invention is not affected by the gas flow in the test environment. Therefore, the Pirani gauge provided by this invention can adapt to the detection of environments with different levels of gas flow, and the consistency of detection accuracy is high. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a cross-sectional view of the Pirani gauge provided by the present invention.

[0019] Figure 2 These are the pressure effect curves of the Pirani gauge provided by this invention and a traditional Pirani gauge without a protective cover under the same environment.

[0020] Figure label: 1. Gauge tube; 2. Resistance wire; 3. Communicating hole; 4. First electrode rod; 5. Second electrode rod; 6. Protective cylinder; 7. Cover; 8. First connecting part; 9. Second connecting part; 10. First connecting piece; 11. Second connecting piece. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0022] The following is combined Figures 1 to 2 The Pirani gauge of the present invention is described.

[0023] like Figures 1 to 2 As shown, the Pirani gauge provided in this embodiment of the invention includes a Pirani gauge body and a protective cover.

[0024] Specifically, the Pirani gauge body includes a gauge tube 1 and a resistance wire 2. The gauge tube 1 is a cylindrical structure with one open end, and the resistance wire 2 is located inside the gauge tube 1. When measuring the pressure of the environment to be measured, the gauge tube 1 needs to be connected to the environment to be measured. The gas in the environment to be measured can enter the interior of the gauge tube 1 through the open end, so that the gas pressure inside the gauge tube 1 is consistent with the gas pressure of the environment to be measured.

[0025] The protective cover is installed inside the gauge tube 1 and covers at least the outside of the resistance wire 2. By physically isolating the resistance wire 2 through the protective cover, the direct impact of airflow from the test environment on the resistance wire 2 can be effectively weakened or blocked, avoiding the problem of unstable heat dissipation of the resistance wire 2 caused by gas flow, which is conducive to reducing measurement error.

[0026] A connecting hole 3 is provided at the open end of the protective cover away from the gauge tube 1, connecting the internal space of the protective cover with the internal space of the gauge tube 1. The connecting hole 3 ensures that the gas pressure inside the protective cover and the gas pressure inside the gauge tube 1 gradually reach consistency, achieving accurate measurement. Moreover, the connecting hole 3 effectively buffers and dampens the gas flow, stabilizing the gas environment around the resistance wire 2, thereby solving the problem of poor measurement accuracy of Pirani gauges under gas flow conditions in related technologies.

[0027] The measurement accuracy of the Pirani gauge provided in this embodiment of the invention is not affected by the gas flow in the test environment. Therefore, the Pirani gauge provided in this embodiment of the invention can be adapted to the detection of environments with different levels of gas flow, and the consistency of detection accuracy is high.

[0028] In this embodiment, the Pirani gauge body also includes a first electrode rod 4 and a second electrode rod 5.

[0029] The first electrode rod 4 and the second electrode rod 5 pass through the opposite ends of the open end of the gauge tube 1, with the first end of the first electrode rod 4 and the first end of the second electrode rod 5 both located outside the gauge tube 1. The opposite ends of the open end of the gauge tube 1 provide reliable mechanical fixation for the resistance wire 2, ensuring the stability of the resistance wire 2's position inside the gauge tube 1. Simultaneously, the first end of the first electrode rod 4 and the first end of the second electrode rod 5 being located outside the gauge tube 1 allows for convenient connection to the measuring circuit.

[0030] The second ends of the first electrode rod 4 and the second ends of the second electrode rod 5 are both located inside the gauge tube 1. The two ends of the resistance wire 2 are electrically connected to the second ends of the first electrode rod 4 and the second electrode rod 5, respectively. With this configuration, the resistance wire 2 is effectively suspended in the internal space of the gauge tube 1, and the resistance wire 2 can be completely surrounded by the gas in the environment to be measured. This provides the necessary physical conditions and a stable electrical path for pressure measurement based on the thermal conduction effect of gas molecules, which is the foundation for achieving accurate measurement.

[0031] In this embodiment of the invention, the protective cover includes a protective cylinder 6 and a cap 7.

[0032] The protective cylinder 6 is fixed relative to the gauge tube 1. The protective cylinder 6 has a cylindrical structure with one end open. The open end of the protective cylinder 6 allows the first electrode rod 4 and the second electrode rod 5 to extend into it. The protective cylinder 6 is sleeved on a portion of the first electrode rod 4 and the second electrode rod 5, as well as the outside of the resistance wire 2.

[0033] The protective sleeve 6 can effectively shield the resistance wire 2. When there is gas flow inside the gauge tube 1, it can effectively reduce or even block the impact of gas flow on the heat dissipation of the resistance wire 2, thereby ensuring that the heat change of the resistance wire 2 is mainly determined by the gas pressure, which greatly improves the measurement accuracy and stability of the Pirani gauge in a gas flow environment.

[0034] The cap 7 is located at the open end of the protective cylinder 6, and the cap 7 and the open end of the protective cylinder 6 are sealed together. This further enhances the airtightness of the shielding space formed by the protective cylinder 6, ensuring that gas exchange can only occur through the preset connecting hole 3, thereby providing a relatively static and stable internal measurement environment for the resistance wire 2.

[0035] Specifically, a sealing ring can be installed between the cap 7 and the protective cylinder 6 to ensure the sealing of the open ends of the cap 7 and the protective cylinder 6.

[0036] Both the first electrode rod 4 and the second electrode rod 5 penetrate the cover 7, and both are insulated from the cover 7. This effectively prevents short circuits between the first electrode rod 4, the second electrode rod 5, and the cover 7, ensuring the normal and safe operation of the Pirani gauge and its connected measuring circuit.

[0037] In a further embodiment, a connecting hole 3 is provided on the cover 7, and at least two connecting holes 3 are provided, with each connecting hole 3 being evenly distributed on the cover 7.

[0038] Multiple connecting holes 3 increase the total connecting area between the inner and outer spaces of the protective cover, accelerating the pressure balance between the inner space of the protective cover and the inner space of the gauge tube 1, and improving the response sensitivity of the Pirani gauge to pressure changes. Furthermore, the uniformly distributed connecting holes 3 allow gas in the test environment to enter or exit the protective cover evenly from different directions, preventing directional airflow or localized eddies caused by gas exchange inside the protective cover from impacting the resistance wire 2, thus ensuring the stability of the gas environment around the resistance wire 2.

[0039] The size and number of connecting holes 3 can be designed according to specific circumstances, as long as the response sensitivity, measurement accuracy and stability are guaranteed.

[0040] In a specific embodiment, the connecting hole 3 can be set as a circular hole for easy processing.

[0041] By controlling the diameter of the connecting hole 3 within the range of 1 mm to 2 mm, the influence of gas flow in the target environment on the internal space of the protective cover can be effectively reduced. By limiting the direct impact of airflow on the resistance wire 2, excessive heat loss from the resistance wire 2 due to gas flow is avoided, thus ensuring the measurement accuracy of the Pirani gauge under gas flow conditions. In addition, the connecting hole 3 within this size range ensures a sufficient gas exchange rate between the internal space of the protective cover and the internal space of the gauge tube 1, enabling the Pirani gauge to respond quickly to pressure changes in the target environment, ensuring measurement response speed, and achieving a good balance between measurement accuracy and response speed.

[0042] Specifically, the diameter of the connecting hole 3 is 1.5 mm.

[0043] In some embodiments, the protective cylinder 6 and the cover 7 are fixedly connected together, and one of the protective cylinder 6 and the cover 7 is connected to the gauge 1 through a rigid connection structure.

[0044] In other embodiments, both the protective cylinder 6 and the cap 7 are rigidly connected to the gauge tube 1 via a rigid connection structure.

[0045] This ensures the relative stability of the cap 7 and the protective cylinder 6, as well as their positional stability inside the gauge tube 1. It prevents the protective cover from shifting or shaking due to external impact vibration or internal gas flow, ensuring that the protective cover can still effectively isolate the resistance wire 2 under strong airflow impact, thereby ensuring the stability of the measurement environment around the resistance wire 2.

[0046] In this embodiment, the rigid connection structure includes a set of first connectors 10 and a set of second connectors 11.

[0047] One end of the first connector 10 is fixed to the inner wall of the gauge tube 1, and the other end of the first connector 10 extends away from the inner wall of the gauge tube 1. A group of first connectors 10 are distributed circumferentially along the gauge tube 1.

[0048] One end of the second connector 11 is fixed to the outer wall of the protective cylinder 6 or the cover 7, and the other end of the second connector 11 extends away from the outer wall of the protective cylinder 6 or the cover 7. A group of second connectors 11 are distributed circumferentially along the protective cylinder 6 or the cover 7.

[0049] The first connector 10 and the second connector 11 correspond one-to-one, and the first connector 10 and the second connector 11 are overlapped and fixed.

[0050] A set of first connectors 10 on the gauge tube 1 provides multiple stable support points for fixing the protective cylinder 6 or the cover 7, improving the stability and load-bearing capacity of the rigid connection structure. Moreover, it enables the force on the protective cover to be evenly transmitted to the gauge tube 1, preventing deformation or damage caused by stress concentration, and ensuring the installation accuracy and long-term reliability of the protective cover.

[0051] The overlapping and fixing method of the first connector 10 and the second connector 11 increases the contact area and bonding strength between them, forming a robust overall structure regardless of whether welding, bolting, or bonding is used. This ensures that the protective sleeve 6 or the cap 7 is reliably fixed inside the gauge tube 1, effectively resisting external influences such as vibration and impact, thereby guaranteeing the safety and durability of the Pirani gauge.

[0052] In this embodiment, for the insulating fit structure between the first electrode rod 4 and the cover 7 and the insulating fit structure between the second electrode rod 5 and the cover 7, a first clearance hole and a second clearance hole are provided on the cover 7.

[0053] The first clearance hole is used to allow passage for the first electrode rod 4, and there is a gap between the first electrode rod 4 and the side wall of the first clearance hole. This ensures reliable electrical insulation between the first electrode rod 4 and the cover 7, preventing short circuits or leakage due to accidental contact, thereby guaranteeing the accuracy and stability of the electrical characteristic measurement of the resistance wire 2. Moreover, the existence of this gap also provides the necessary assembly tolerance for the installation process of the first electrode rod 4 on the cover 7, reducing the assembly difficulty.

[0054] The second clearance hole is used to allow passage for the second electrode rod 5, and there is a gap between the second electrode rod 5 and the side wall of the second clearance hole. Similarly, this ensures reliable electrical insulation between the second electrode rod 5 and the cover 7, preventing short circuits or leakage due to accidental contact, thereby ensuring the accuracy and stability of the electrical characteristic measurement of the resistance wire 2. Moreover, the existence of this gap also provides the necessary assembly tolerance for the installation process of the second electrode rod 5 on the cover 7, reducing the assembly difficulty.

[0055] In addition, the gap between the first clearance hole and the first electrode rod 4 and the gap between the second clearance hole and the second electrode rod 5 can also serve as auxiliary gas channels outside the connecting hole 3, which helps to accelerate the pressure balance between the internal space of the protective cover and the internal space of the gauge tube 1, thereby effectively isolating external airflow interference and improving the measurement response speed of the Pirani gauge.

[0056] In this embodiment, the central axis of the resistance wire 2 coincides with the central axis of the protective cylinder 6, and both the central axes of the resistance wire 2 and the protective cylinder 6 are parallel to the axis of the gauge tube 1. This ensures that the distance between the resistance wire 2 and the inner wall of the protective cylinder 6 in the radial direction is equal everywhere, thereby forming a uniform and symmetrical heat dissipation environment around the resistance wire 2 and ensuring the uniformity of heat exchange between the resistance wire 2 and the gas inside the protective cover. This together ensures that the heat loss state of the resistance wire 2 is mainly affected by gas pressure, eliminating the interference of structural position deviations on the measurement results.

[0057] In this embodiment, the first electrode rod 4 and the second electrode rod 5 are arranged symmetrically about the central axis of the protective cylinder 6.

[0058] The second end of the first electrode rod 4 is provided with a first connecting portion 8, which extends toward the second electrode rod 5. The second end of the second electrode rod 5 is provided with a second connecting portion 9, which extends toward the first electrode rod 4. The two ends of the resistance wire 2 are electrically connected to the first connecting portion 8 and the second connecting portion 9.

[0059] This configuration facilitates the installation and fixation of the resistance wire 2, and effectively ensures that the resistance wire 2 remains taut during use, thereby avoiding measurement errors caused by the slackness or positional shift of the resistance wire 2, and further improving the reliability of the measurement.

[0060] Comparative tests were conducted using the Pirani gauge provided in this embodiment of the invention and a traditional Pirani gauge without a protective cover, under the same temperature, humidity, vacuum environment, test platform, and data processing method. The resulting pressure effect curves are shown below. Figure 2 As shown. The results demonstrate that the protective cover of the Pirani gauge provided in this embodiment of the invention can significantly suppress the upward tilting of the response curve caused by gas convection in the high-pressure range, effectively solving the problems of poor accuracy of traditional Pirani gauges in the high-pressure range and poor measurement repeatability in different application scenarios.

[0061] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A Pirani gauge characterized in that, The application relates to a Pirani gauge body, which comprises a gauge tube (1) in a cylindrical structure with an open end and a resistance wire (2) arranged in the interior of the gauge tube (1). A protective cover is arranged in the interior of the gauge tube (1) and covers at least the exterior of the resistance wire (2), and one end of the protective cover away from the open end of the gauge tube (1) is provided with a communication hole (3) which communicates the interior space of the protective cover with the interior space of the gauge tube (1). The Pirani gauge body further comprises:

2. The Pirani gauge of claim 1, wherein, a first electrode rod (4) and a second electrode rod (5) which penetrate through the opposite ends of the open end of the gauge tube (1), the first ends of the first electrode rod (4) and the second electrode rod (5) are located outside the gauge tube (1), the second ends of the first electrode rod (4) and the second electrode rod (5) are located inside the gauge tube (1), and the two ends of the resistance wire (2) are electrically connected to the second ends of the first electrode rod (4) and the second electrode rod (5) respectively. The protective cover comprises:

3. The Pirani gauge of claim 2, wherein, a protective cylinder (6) which is fixed opposite to the gauge tube (1), the protective cylinder (6) is in a cylindrical structure with an open end, the protective cylinder (6) is sleeved outside the partial segments of the first electrode rod (4) and the second electrode rod (5) and the resistance wire (2); a cover (7) arranged at the open end of the protective cylinder (6), the cover (7) is in sealing cooperation with the open end of the protective cylinder (6), the first electrode rod (4) and the second electrode rod (5) penetrate through the cover (7), and the first electrode rod (4) and the second electrode rod (5) are in insulating cooperation with the cover (7). The communication hole (3) is a circular hole, and the diameter of the communication hole (3) is 1-2 mm.

4. The Pirani gauge of claim 3, wherein, The communication hole (3) is arranged on the cover (7), and at least two communication holes (3) are arranged, and the communication holes (3) are uniformly distributed on the cover (7).

5. The Pirani gauge of claim 3, wherein, The protective cylinder (6) and the cover (7) are fixedly connected, one of the protective cylinder (6) and the cover (7) is connected to the gauge tube (1) through a rigid connecting structure; 6. The Pirani gauge of claim 3, wherein, Alternatively, the protective cylinder (6) and the cover (7) are both connected to the gauge tube (1) through a rigid connecting structure. The rigid connecting structure comprises:

7. The Pirani gauge of claim 6, wherein, a group of first connecting members (10), one end of the first connecting member (10) is fixed to the inner wall of the gauge tube (1), the other end of the first connecting member (10) extends away from the inner wall of the gauge tube (1), and a group of the first connecting members (10) are spaced apart along the circumference of the gauge tube (1). ​ A second connecting piece (11) is fixed to the outer wall of the protective cylinder (6) or the cover (7) at one end, and extends away from the outer wall of the protective cylinder (6) or the cover (7) at the other end. A plurality of the second connecting pieces (11) are distributed along the circumference of the protective cylinder (6) or the cover (7) at intervals. The first connecting piece (10) corresponds to the second connecting piece (11) one by one, and the first connecting piece (10) and the second connecting piece (11) are fixed by overlapping.

8. The Pirani gauge of claim 3 wherein, The cover (7) is provided with a first avoiding hole and a second avoiding hole; The first avoiding hole is used for avoiding the first electrode rod (4), and a gap is formed between the first electrode rod (4) and the side wall of the first avoiding hole; The second avoiding hole is used for avoiding the second electrode rod (5), and a gap is formed between the second electrode rod (5) and the side wall of the second avoiding hole.

9. The Pirani gauge of claim 3 wherein, The central axis of the resistance wire (2) coincides with the central axis of the protective cylinder (6), and both the central axis of the resistance wire (2) and the central axis of the protective cylinder (6) are parallel to the axis of the gauge tube (1).

10. Pirani gauge according to claim 9, characterized in that The first electrode rod (4) and the second electrode rod (5) are symmetrically arranged about the central axis of the protective cylinder (6); The second end of the first electrode rod (4) is provided with a first connecting part (8) extending towards the second electrode rod (5), and the second end of the second electrode rod (5) is provided with a second connecting part (9) extending towards the first electrode rod (4). The two ends of the resistance wire (2) are electrically connected to the first connecting part (8) and the second connecting part (9).

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