Thermal Conductivity Gauge Assembly

Abstract

The present disclosure relates to a thermal conductivity vacuum gauge assembly. The assembly includes a body defining an internal chamber for receiving a working gas and a heating element disposed within the internal chamber. The body is defined by a wall having an outward-facing wall surface and an opposite inward-facing wall surface. A thermal compensation element is enclosed within the wall between the outward-facing wall surface and the inward-facing wall surface. The present disclosure also relates to a thermal conductivity vacuum gauge including the assembly.

Description

[Technical Field]

[0001] The present disclosure relates to a thermal conductivity vacuum gauge assembly, and also to a thermal conductivity vacuum gauge including the assembly. [Background technology]

[0002] Vacuum gauges are commonly used to measure pressure within vacuum systems. The pressure reading can be used to ensure that the system has a low enough vacuum for its intended purpose. If the reading indicates that the vacuum pressure within the system is low enough, this can be used to indicate and detect leaks or defects in the system and / or to provide feedback to aid in the control of the vacuum pump that evacuates the system.

[0003] A common type of gauge used for this purpose is a thermal conductivity gauge.

[0004] Thermal conductivity gauges use the heat conduction of gases to measure pressure and are sometimes known as heat loss gauges. Generally, these gauges use the relationship between the heat conduction of gases and pressure to obtain pressure measurements.

[0005] One such thermal conductivity gauge is the Pirani gauge.

[0006] In a Pirani gauge, a heating element (usually in the form of a filament or wire) is placed in contact with a working gas in a vacuum system and connected to an electrical circuit to allow the heating element to be heated with electrical energy. When gas molecules collide with the heating element, they transfer heat (i.e., conduct) away from the heating element. The higher the gas pressure, the more molecules collide with the heating element and the more heat is transferred away from the heating element (i.e., the higher the thermal conductivity of the gas).

[0007] If the heating element is held at a constant current or voltage, changes in the amount of heat transferred from the heating element due to changes in gas pressure will cause the temperature (and therefore resistance) of the heating element to change by a proportional amount. By measuring this change in resistance, changes in gas pressure can be measured. Alternatively, the heating element can be held at a constant temperature (and therefore resistance), and the change in voltage required to maintain this constant temperature can be measured as a function of gas pressure.

[0008] In this way, the pressure of the gas is measured as a function of the thermal conductivity of the gas.

[0009] As will be appreciated by those skilled in the art, a common way to accomplish this in a Pirani gauge is to include the heating element as an arm in a Wheatstone bridge circuit.

[0010] To obtain more accurate pressure measurements in thermal conductivity gauges, a thermal compensation element is generally required.

[0011] A thermal compensation element is an element or component that measures the ambient temperature of the thermal conductivity gauge itself, allowing pressure measurements to be corrected for ambient temperature.

[0012] This can be accomplished, for example, by using a thermal compensation element to provide a reference resistance or voltage according to the ambient temperature of the thermal conductivity gauge for comparison with the ambient temperature of the heating element, which can help minimize measurement inaccuracies or discrepancies related to the ambient temperature of the thermal conductivity gauge unintentionally affecting the resistance or voltage readings of the heating element.

[0013] As will be appreciated by those skilled in the art, one way to perform this thermal compensation in a Pirani gauge is to include a thermal compensation element (e.g., a temperature dependent resistor) as an arm in the same Wheatstone bridge circuit as the heating element.

[0014] Thermal compensation elements are known to be disposed on the surface of the body or tube of a thermal conductivity gauge assembly.

[0015] The inventors have found that such known arrangements can lead to potential inaccuracies and inconsistencies in thermal compensation measurements, and can also cause durability issues for the elements.

[0016] For example, it has been found that placing the element on the exterior surface of the thermal conductivity gauge assembly means that its measurements may be undesirably affected by the ambient temperature of the environment surrounding the thermal conductivity gauge assembly, and that the element may be easily damaged. It has also been found that placing the element on the interior surface of the thermal conductivity gauge assembly means that the element may be undesirably affected by the working / process gases passing through the thermal conductivity gauge assembly, and that this may cause corrosion. Summary of the Invention [Problem to be solved by the invention]

[0017] Therefore, a need exists to provide a thermal conductivity gauge assembly that improves upon these aspects of the thermal compensation elements used therein. There is also a general need to provide improved modularity and interchangeability of thermal conductivity gauges that include such assemblies.

[0018] Although Pirani gauge assemblies are generally illustrated herein, it should be understood that any other suitable type of thermal conductivity gauge assembly (using a heating element and requiring a temperature compensating element) can also benefit from the present disclosure and is within its scope, as appropriate. Such other thermal conductivity gauges may include, for example, a thermistor thermal conductivity gauge assembly or a thermocouple thermal conductivity gauge assembly. [Means for solving the problem]

[0019] In one aspect, the present disclosure provides a thermal conductivity vacuum gauge assembly including a body defining an interior chamber for receiving a working gas, the body being defined by a wall having an outward-facing wall surface and an opposite inward-facing wall surface, a heating element disposed within the interior chamber, and a thermal compensation element enclosed within the wall between the outward-facing and inward-facing wall surfaces.

[0020] Encapsulating the thermal compensating element within the wall of the body increases the contact area between the thermal compensating element and the body. This improves the durability and lifespan of a thermal compensating element secured within the body, and makes its temperature measurements more representative and accurate of the body. This arrangement also means that the thermal compensating element is protected within the wall itself (i.e., between the outer and inner wall surfaces) and is less adversely affected by the external and internal environments around and within the body 110.

[0021] Generally, this placement of the thermal compensation element increases the accuracy of the gas pressure measurements made possible by the assembly 100 and increases the durability of the assembly 100 .

[0022] In one embodiment of the above aspect, the thermal compensation element is a resistance temperature detector (RTD). In another embodiment, the thermal compensation element is a thermistor. The thermistor can be a positive temperature coefficient (PTC) thermistor or a negative temperature coefficient (NTC) thermistor. In another alternative embodiment, the thermal compensation element is a semiconductor temperature sensor.

[0023] These types of thermal compensation elements offer certain durability, cost and accuracy advantages over others.

[0024] In a further embodiment of any of the above, a cavity is enclosed within the wall between the outwardly facing wall surface and the inwardly facing wall surface, and the thermal compensation element is disposed within the cavity.

[0025] The cavity provides a convenient manufacturing route (eg, by machining) for placing a thermal compensation element within the wall between the outward-facing wall surface and the opposing inward-facing wall surface.

[0026] In a further embodiment of any of the above, an electrical connection member is attached to the thermal compensation element. A first portion of the electrical connection member is enclosed within the wall between the outward-facing wall surface and the inward-facing wall surface, and a second portion of the electrical connection member protrudes from the wall. In a further embodiment, the second portion includes an electrical connector for connection to a control circuit.

[0027] The electrical connection member provides a convenient means for mounting and supporting the thermal compensating element to a wall and for providing electrical communication between other components, and the second portion and electrical connector facilitate more modular / removable electrical connections between the thermal compensating element and other components.

[0028] In a further embodiment of the above, the electrical connection member is a printed circuit board (PCB) and the thermal compensation element is surface mounted thereon.

[0029] The PCB combined with the surface mounting of the thermal compensation element provides an integral component that improves the durability of the connection to the thermal compensation element.

[0030] In a further embodiment of any of the above, the body extends longitudinally between a base and a top, and has a sidewall extending between the base and the top, and the thermal compensation element is encapsulated within the sidewall.

[0031] In a further embodiment of any of the above, the cavity in which the thermal compensation element is disposed extends axially through the sidewall to an opening at the top.

[0032] In a further embodiment of any of the above, a first portion of the electrical connection member is disposed within the cavity and a second portion of the electrical connection member protrudes axially from the top.

[0033] These configurations provide an orientation of the assembly components that facilitates interchangeable electrical connections (eg, via the top) and allows for convenient installation thereof.

[0034] In a further embodiment of any of the above, the base includes a radially extending flange that defines an inlet passage in fluid communication with the chamber and can optionally include a recess therein for accommodating a seal (such as an O-ring seal or a metal seal).

[0035] The flange allows for a more secure fit of the assembly to the vacuum system, and the recess provides a better seal between the assembly and the vacuum system in use.

[0036] In a further embodiment of any of the above, the base includes a filter element positioned across the inlet passage for filtering the working gas.

[0037] The filter element can help keep contaminants from entering the chamber, which could damage the assembly or interfere with pressure measurements.

[0038] In a further embodiment of any of the above, the heating element is a filament for heating by a power source. In examples, the filament may be made of platinum or tungsten. Such an assembly may be commonly known as a Pirani gauge assembly.

[0039] In another aspect, the present disclosure provides a thermal conductivity vacuum gauge comprising an assembly according to any embodiment of the above aspects and a housing that receives and at least partially surrounds the body.

[0040] The housing and connections to the housing facilitated by the assembly embodiments allow for increased modularity and interchangeability of thermal conductivity gauges.

[0041] In one such embodiment, the housing contains control circuitry for providing electrical control of the heating element and the thermal compensation element.

[0042] The control circuitry may enable the housing to function as an interchangeable modular add-on to the assembly, allowing for interrogation of the pressure measurements of the assembly.

[0043] Although certain advantages are described above in connection with particular features, other advantages of the particular features will become apparent to those skilled in the art following this disclosure. One or more non-limiting embodiments will now be described, by way of example only, with reference to the accompanying figures. [Brief explanation of the drawings]

[0044] [Figure 1] 1 illustrates an exterior isometric view of a thermal conductivity vacuum gauge assembly according to one embodiment of the present disclosure. [Figure 2A] 2 shows a cross section of the assembly of FIG. 1 along line AA. [Figure 2B] 2 shows a cross section of the assembly of FIG. 1 taken along line BB. DETAILED DESCRIPTION OF THE INVENTION

[0045] 1, there is shown a thermal conductivity vacuum gauge assembly 100. The assembly 100 includes a body 110 having a sidewall 112 extending axially along a longitudinal axis X between a base 114 and a top 116.

[0046] In the illustrated embodiment, the body 110 is generally annular, but has a chamfer 111 around a portion of its circumference which, as will be described below, can aid in the mounting of the assembly with other components of the thermal conductivity gauge, such as a housing or cover (not shown).

[0047] Although a particular shape of body 110 is shown, it should be understood that any other suitable shape of body 110 (e.g., square or rectangular cross section) may be used within the scope of the present disclosure.

[0048] Base 114 includes a flange 115 extending radially therefrom about longitudinal axis X. In one embodiment, flange 115 has a nominal inner diameter specification of 1.6 mm.

[0049] The top portion 116 includes an end cap 118 through which protrudes and is secured, the end cap 118, through which the electrical connector 132 and support features 136 for the heating element 130 (described in detail below with reference to Figures 2A and 2B). An end cap 118 is secured within an opening 117 defined in the top portion 116 .

[0050] In some embodiments, the end cap 118 can be fixedly attached to the top 116, for example, by welding or press-fitting into the opening 117. In other embodiments, the end cap 118 can be removably secured to the top 116 by threaded engagement. Such a removable securing method can facilitate repair and replacement of the heating element 130 and the connections and support features. In yet another embodiment, the end cap 118 can be omitted, and the wall 122 of the body 110 extends radially across the top 116 without the opening 117 therein. In such an embodiment, the connections and support features would extend through the top 116 itself.

[0051] In the illustrated embodiment, end cap 118 includes marking area 119, which provides an area for marking various numbers or codes associated with the manufacture of the assembly (e.g., part number / bar code, batch number, etc.) It should be understood that within the scope of the present disclosure, such marking area 119 may alternatively be present in some other suitable portion of assembly 100 or may be omitted altogether.

[0052] Figure 2A shows a cross section of assembly 100 along longitudinal axis X (along the line defined by arrow AA) and looking in the direction of arrow AA. Figure 2B shows a cross section of assembly 100 along longitudinal axis X (along the line defined by arrow BB) and looking in the direction of arrow BB. 2A and 2B show the internal structure and components within the body 110, as will be described below.

[0053] The body 110 defines an internal chamber 120 configured to receive a working or process gas (e.g., from a vacuum system) during use of the assembly 100. By "working or process gas" is meant the gas(es) whose pressure the assembly seeks to measure. A "working gas" is typically the gas(es) that is / are being worked on (e.g., pumped) by the vacuum system. The pressure of this gas can provide an indication of the general vacuum pressure within the system.

[0054] In the illustrated embodiment, the body 110 is generally tubular and may also be understood as a “body tube.” Accordingly, the interior chamber 120 is generally cylindrical about the longitudinal axis X within the body 110.

[0055] Body 110 is defined or formed by wall 122. Wall 122 is defined between an outward-facing wall surface 122a and an opposing inward-facing wall surface 122b. Walls 122a and 122b are generally annular in accordance with the illustrated shape of body 110. Outward-facing wall surface 122a is radially outward of inward-facing wall surface 122b and faces toward the exterior of assembly 100. Inward-facing wall surface 122b faces toward the interior of assembly 100 and defines (or surrounds) interior chamber 120.

[0056] Body 110 can be made of any suitable material, such as stainless steel or aluminum alloy, or a plastic material (if operating conditions and temperature permit), and can be made by any suitable manufacturing method, such as molding / casting, machining from a solid block, 3D printing, etc. The base 114 defines an inlet passage 124 for the chamber 120 .

[0057] An inlet passage 124 extends axially from the base 114 into the chamber 120. The inlet passage 124 is in fluid communication with the chamber 120, allowing a working gas (e.g., from a vacuum system) to enter and exit the chamber 120 during use.

[0058] A filter element 126 is disposed across the inlet passage 124 to filter the working gas before it enters the chamber 120. The filter element 126 passes across the inlet passage 124 radially relative to the longitudinal axis X. The filter element 126 is used to ensure that contaminants do not enter the chamber 120. Such contaminants may damage the assembly 100 (e.g., by corroding or depositing on the heating element 130, the wall 122b, or electrical connections within the chamber 120) and / or may interfere with the pressure measurement process, causing inaccuracies therein. In one embodiment, the filter element 126 is a stainless steel mesh, although any other suitable type (e.g., membrane) or material for the filter element 126 may be used within the scope of the present disclosure.

[0059] The flange 115 of the base 114 includes a recess or groove 128 formed therein. The recess 128 is annular about the longitudinal axis X and allows a seal to be seated therein. This allows for a better seal to be formed between the assembly 100 and a vacuum system in use, with the seal being secured in place on the base 114 via the flange 115. The seal may be any suitable type of seal, such as an O-ring seal or a metal seal. In other embodiments, a gasket arrangement (e.g., made of metal) may instead be used between the flange 115 and the system.

[0060] A heating element 130 is disposed within the chamber 120. In the illustrated embodiment, the heating element 130 extends generally axially within the chamber 120 from the top portion 116 toward the base portion 114.

[0061] The heating element 130 in the illustrated embodiment is a filament that is heated by a power source. The filament can be made of any suitable material, such as tungsten or platinum. Platinum, in particular, can be used in vacuum system environments or applications known to contain more corrosive chemicals and / or working gases.

[0062] Electrical connectors or pins 132a, 132b, 132c protrude through and are secured within end cap 118. Heat generating element 130 is connected to a particular one of electrical connectors 132a, 132b, 132c to enable electrical communication therebetween for controlling heat generating element 130. In the illustrated embodiment, connectors 132a, 132c are connected to two opposite ends of heat generating assembly 130, while connector 132b is used for grounding purposes. Connectors 132a, 132b, 132c can then be connected to a separate control circuit (not shown) that can provide power to heat and control heat generating assembly 130 when assembly 100 is in use.

[0063] Heating element 130 may be connected to connectors 132a, 132c in any suitable manner, such as by wrapping around the base of the connector or by welding or soldering to the connector.

[0064] The heating element 130 is supported within the chamber 120 by a support structure which, in the illustrated embodiment, is in the form of a spring arm 134 and a bar 136.

[0065] A bar 136 projects through and is secured to the end cap 118. The bar 136 extends axially into the chamber 120 from the top 116 toward the base 114, substantially parallel to the heating element 130. In the illustrated embodiment, the bar 136 is a cylindrical rod.

[0066] Spring arms 134 are fixed to the ends of the bars 136 nearest the base 114 and extend radially (with respect to the longitudinal axis X) to support the heating element 130 .

[0067] The spring arms 134 feature hooks 135 around which the heating element 130 passes. The spring arms 134 and bar 136 are used to provide tension that holds the heating element 130 taut between the connectors 132a, 132c during use.

[0068] As can be seen, in the illustrated embodiment, the heat generating assembly 130 defines a substantially V- or U-shape when suspended between the connectors 132a, 132c via the hooks 135.

[0069] While one particular configuration of heating elements 130, electrical connectors 132a, 132b, 132c, and their support structures is shown, it should be understood that any other suitable configuration may be used within the scope of this disclosure. For example, different numbers and types of electrical connectors 132a, 132b, 132c, different types of heating elements 130 (e.g., thermistors), and different numbers or types of components for bar 136 and spring arms 134 may be used.

[0070] The thermal compensation element 140 is encapsulated within the wall 122 of the body 110. More specifically, the thermal compensation element 140 is encapsulated within the wall 122 between the outward-facing wall surface 122a and the inward-facing wall surface 122b. In this manner, the thermal compensation element 140 is encapsulated within the thickness of the wall 122 itself and is spaced apart from the outward-facing wall surface 122a and the inward-facing wall surface 122b by the wall thickness.

[0071] It should be understood that such an arrangement is different from simply placing the thermal compensation element 140 in a recess or depression provided in the wall 122 (i.e., a recess or depression provided in one of the outward-facing wall surface 122a and the inward-facing wall surface 122b), so that the thermal compensation element 140 is still located on one of the outward-facing wall surface 122a or the inward-facing wall surface 122b.

[0072] Thermal compensating element 140 may be of any suitable type capable of providing, for example, a resistance and / or a voltage indicative of the ambient temperature of wall 122 within which thermal compensating element 140 is disposed. In one embodiment, thermal compensating element 140 is a resistance temperature detector (RTD), such as a molybdenum or platinum RTD. In another embodiment, thermal compensating element 140 is a thermistor, such as a positive temperature coefficient thermistor (PTC) or a negative temperature coefficient thermistor (NTC) made of powdered metal oxide or polymer. In another embodiment, thermal compensating element 140 may be a solid-state temperature sensor.

[0073] While other types of thermal compensation element 140 fall within the scope of this disclosure, the above are believed to have certain advantages in terms of durability, cost, and accuracy over others.

[0074] It should be appreciated that encapsulating the thermal compensation element 140 within the wall 122 of the body 110 as shown is believed to offer certain advantages over prior art arrangements.

[0075] For example, this allows for a more sturdy and durable fixation of the thermal compensating element 140 in the assembly 100, which can improve its service life. Also, the amount of physical contact between the thermal compensating element 140 and the body 110 can be increased, resulting in more representative temperature measurements and providing more accurate compensation. The thermal compensation element 140 being enclosed within the wall 122 means that it is less susceptible to the external or internal environment around the assembly 100, which in turn helps make the temperature measurement of the body 110 more representative and accurate.

[0076] In this manner, encapsulating the thermal compensation element 140 within the wall 122 may result in a more accurate overall pressure measurement of the working gas in the chamber 120 provided by the assembly 100. It may also result in the assembly 100 being generally more durable.

[0077] An electrical connection member 142 is attached to the thermal compensation element 140. The electrical connection member 142 allows electrical communication between the thermal compensation element 140 and control circuitry (not shown) connectable to the element.

[0078] In the illustrated embodiment, the electrical connection member 142 is a FR-4 specification printed circuit board (PCB), although any suitable type of electrical connection member 142 (e.g., wire) or any other suitable specification PCB could be used instead. By using a PCB in the illustrated embodiment, the electrical connection member 142 also provides a durable / rigid substrate that provides some mechanical support for the thermal compensation element 140 to hold it against the wall surface 122a.

[0079] A first portion of the electrical connection member 142 is enclosed within the wall 122 (between the walls 122a, 122b). A second portion protrudes axially out of the wall 122 from the top 116.

[0080] The second portion includes an electrical connector 143 suitable for providing an electrical connection between the electrical connection member 142 and a control circuit (not shown) and for enabling electrical communication between such control circuit and the thermal compensation element 140 for reporting pressure measurements obtained by the assembly 100.

[0081] In the illustrated embodiment, the thermal compensation element 140 is surface mounted to an electrical connection member 142 .

[0082] This allows the thermal compensation element 140 to be fabricated integrally with the electrical connection member 142 as a one-piece component, which has advantages in cost, installation, and durability.

[0083] Nevertheless, any other suitable method of attaching the thermal compensation element 140 to the member 142 may be used within the scope of the present disclosure, such as through-hole or soldering techniques.

[0084] In the illustrated embodiment, a cavity 144 is defined in wall 122. Cavity 144 has an opening 146 through wall 122 at top 116 and extends axially through wall 122 toward base 114. Cavity 144 is enclosed within wall 122 between wall surfaces 122a, 122b.

[0085] The electrical connection member 142 and the thermal compensation element 140 are disposed within and axially inserted into the cavity 144. The electrical connection member 142 may be secured within the cavity 144 using any suitable means, such as an adhesive, or may be loosely held in place within the cavity 144 (e.g., by its own weight) without a securing means.

[0086] Locating the thermal compensation element 140 and the electrical connection member 142 within the cavity 144 may improve accessibility for inspection, repair, and / or replacement of the thermal compensation element 140 / electrical connection member 142.

[0087] In other embodiments (not shown), cavity 144 can be omitted. Instead, thermal compensating element 140 and electrical connection member 142 are integrally encapsulated (e.g., by insert molding / casting / additive manufacturing) within wall 122 without defining cavity 144 therearound. This can improve the life / durability of thermal compensating element 140 and electrical connection member 142 within wall 122, as well as the amount of contact between thermal compensating element 140 and wall 122 (for improved temperature compensation), at the expense of easy replaceability.

[0088] Although the illustrated embodiment shows the thermal compensation element 140, electrical connection member 142, and cavity 144 generally disposed on the side wall 112 of the body 110, it should be understood that they may be disposed on any other suitable part or portion of the body defined by the body wall 122 (e.g., the base 114 or the top 116) as may be suitable for a particular application or vacuum system.

[0089] In one embodiment, a thermal conductivity gauge (not shown) is formed using assembly 100, which may be contained within a housing or cover (not shown) that at least partially surrounds body 110. The housing may generally include control and / or electronic circuitry (e.g., the remainder of a Wheatstone bridge circuit) that may be connected to assembly 100 to control and operate heating element 130 in combination with thermal compensation element 140.

[0090] The electrical connectors 132a, 132b, 132c, 143 protruding from the assembly 100 can facilitate ease of integration with the housing because the connectors can be simply connected and disconnected to ports within the housing as the housing receives the assembly 100. This can also aid in the modularity and interchangeability of the housing and assembly 100.

[0091] The housing may feature unique electrical connections / connectors that may allow for powering and interrogating the control circuitry / electronics and assembly 100, if desired.

[0092] The housing may also feature a screen / readout thereon that may display / indicate pressure measurements or other parameters (resistance, temperature, voltage, etc.) related to the thermal conductivity gauge / assembly 100 and the vacuum system it is measuring.

[0093] As briefly mentioned above, the shape of the body 110, including the chamfered portion 111, can be used to aid in the installation of the housing. For example, the chamfered portion 111 provides a flat axial surface that aids in the insertion and installation of the housing onto the body 110. This can also provide an easy visual reference to ensure that the housing is inserted in the correct orientation over the element 200 and body 110. [Explanation of symbols]

[0094] 100 Thermal Conductivity Vacuum Gauge Assembly 110 Main Unit 111 Chamfered part 112 Side wall 114 Base 115 flange 116 Top 117 (top 116) opening 118 End Cap 119 Marking Area 120 Inner Chamber 122 Wall 122a Outward facing wall 122b Inward wall 124 Entrance Passage 126 filter elements 128 Recess (or groove) 130 Heating element (or filament) 132a Electrical connectors (or pins) 132b Electrical connectors (or pins) 132c electrical connector (or pin) 134 Spring Arm 135 Hook 136 Bar 140 Thermal compensation element 142 Electrical connection parts 143 Electrical Connectors 144 Cavity 146 (of cavity 144) opening X Longitudinal Axis A cross-sectional line of sight B Sectional line of sight

Claims

1. A thermal conductivity gauge assembly (100) comprising: a body (110) defined by a wall (122) having an outwardly facing wall surface (122a) and an opposite inwardly facing wall surface (122b) that defines an internal chamber (120) for receiving a working gas; a heating element (130) disposed within the interior chamber (120); a thermal compensation element (140) enclosed within the wall (122) between the outward-facing wall surface and the inward-facing wall surface (122a, 122b); an electrical connection member (142) attached to the thermal compensation element (140), wherein a first portion of the electrical connection member (142) is enclosed within the wall (122) between the outward-facing wall surface (122a) and the inward-facing wall surface (122b), and a second portion of the electrical connection member protrudes from the wall (122); The electrical connection member (142) is a printed circuit board, and the thermal compensation element (140) is attached to the printed circuit board. Thermal conductivity gauge assembly.

2. The assembly (100) of any preceding claim, wherein the thermal compensation element (140) is a resistance temperature detector (RTD).

3. The assembly (100) of claim 1, wherein the thermal compensation element (140) is a thermistor, such as a positive temperature coefficient (PTC) thermistor or a negative temperature coefficient (NTC) thermistor.

4. 4. The assembly (100) of claim 1, 2, or 3, wherein a cavity (144) is enclosed in the wall (122) between the outward-facing wall surface and the inward-facing wall surface (122a, 122b), and the thermal compensation element (140) is disposed in the cavity (144).

5. 5. An assembly (100) according to any of claims 1 to 4, wherein the second portion includes an electrical connector (143) for connection to a control circuit.

6. The body (100) extends in a longitudinal direction (X) between a base (114) and a top (116), and has a sidewall (112) extending between the base (114) and the top (116); The assembly (100) of any of claims 1 to 5, wherein the thermal compensation element (140) is encapsulated within the sidewall (112).

7. 7. The assembly (100) of claim 6, wherein a cavity (144) within which the thermal compensation element (140) is disposed extends axially through the sidewall (112) to an opening (146) in the top portion (116).

8. 8. The assembly (100) of claim 7, wherein a first portion of the electrical connection member (142) is enclosed within the cavity (144) and a second portion of the electrical connection member (142) protrudes axially from the top portion (116).

9. 9. The assembly (100) of claim 6, 7, or 8, wherein the base (114) defines an inlet passage (124) in fluid communication with the chamber (120) and includes a radially extending flange (115) having a recess (128) therein for accommodating a seal.

10. 10. The assembly (100) of claim 9, wherein the base (114) includes a filter element (126) disposed across the inlet passage (124) for filtering the working gas.

11. 11. The assembly (100) of any of claims 1 to 10, wherein the heating element (130) is a filament for heating by an electrical source.

12. An assembly (100) according to any one of claims 1 to 11; a housing that receives and at least partially surrounds the body (110); A thermal conductivity vacuum gauge comprising:

13. 13. The vacuum gauge of claim 12, wherein the housing includes a control circuit for electrical control of the heating element (130) and the thermal compensation element (140).

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