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 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 and a thermal uniformizing element are in thermal communication with the body. The body is made of a material having a first thermal conductivity, and the thermal uniformizing element is made of a material having a second thermal conductivity higher than the first thermal conductivity. 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. The present disclosure also relates to a thermal conductivity vacuum gauge including the assembly. [Background technology]

[0002] Vacuum gauges are commonly used to measure the pressure in vacuum systems. The pressure measurement can be used to ensure that the system has a low enough vacuum for its intended purpose. If the measurement indicates that the vacuum pressure in 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] Heat conduction gauges use the heat conduction of gases to measure pressure and are sometimes known as heat loss gauges. In general, these gauges use the relationship between 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 by electrical energy. When gas molecules collide with the heating element, they transfer (i.e., conduct) heat away from the heating element. The higher the pressure of the gas, the more molecules that collide with the heating element and the more heat that is transferred away from the heating element (i.e., the higher the thermal conductivity of the gas).

[0007] When the heating element is maintained at a constant current or voltage, the temperature (and thus the resistance value) of the heating element will change in proportion to the change in the amount of heat transferred from the heating element due to the change in gas pressure. By measuring this change in resistance value, the change in gas pressure can be measured. Alternatively, the heating element can be maintained at a constant temperature (and thus a constant resistance value), and the change in voltage required to maintain this constant temperature can be measured according to the gas pressure.

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

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

[0010] In order to obtain a more accurate pressure measurement value in a thermal conductivity vacuum gauge, a thermal compensation element is generally required.

[0011] The thermal compensation element is an element or component that measures the ambient temperature of the thermal conductivity vacuum gauge itself. Thereby, the pressure measurement value can be corrected with respect to the ambient temperature.

[0012] This can be achieved, for example, by using a thermal compensation element that provides a reference resistance or voltage according to the ambient temperature of the thermal conductivity vacuum gauge for comparison with the ambient temperature of the heating element. This can help minimize measurement inaccuracies or inconsistencies related to the ambient temperature of the thermal conductivity vacuum gauge that unintentionally affect the resistance value or voltage reading of the heating element.

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

[0014] The thermal compensation element is typically disposed on a surface of the body or tube of the thermal conduction gauge assembly and relies on heat conduction through the body to determine the ambient temperature of the thermal conduction gauge assembly for comparison to the heating element.

[0015] A thermal conduction gauge body will often develop a temperature gradient over its length because one end of the body typically contains active electronics that can function to heat the tube (powering the thermal conduction gauge to measure and display the pressure therein), while the opposite end, which can act as a heat sink, is attached to the vacuum system.

[0016] Process gases used in vacuum systems are often corrosive, and thermal conductivity gauge assembly bodies are typically made of stainless steel (or other suitable corrosion-resistant materials). While such materials provide acceptable corrosion characteristics for the thermal conductivity gauge assembly, they have relatively low thermal conductivity. For example, stainless steel has a thermal conductivity on the order of about 15 W / mK.

[0017] The relatively low thermal conductivity of the thermal conduction gauge assembly body means that temperature gradients can be relatively slow to propagate and equalize across the thermal conduction gauge body, which can lead to fluctuating and inaccurate temperature compensated measurements during use of the thermal conduction gauge assembly, which can result in potential inaccuracies and inconsistencies in the resulting pressure measurements.

[0018] Traditionally, to attempt to reduce such inaccuracies and inconsistencies in pressure measurements, a thermal compensation element has been positioned at a particular location along the length of the thermal conduction gauge body (e.g., halfway along the body) that represents the best "average" temperature of the body.

[0019] Unfortunately, this solution has some limitations because the most accurate temperature location will change if, for example, heat dissipation from the electronics, ambient air temperature, or vacuum system temperature changes, as occurs periodically during different stages of vacuum system operation, and therefore these changes will again introduce error into the pressure measurement.

[0020] When measuring lower vacuum pressures and using more compact Pirani gauges (with smaller filaments and therefore lower sensitivity), discrepancies and errors found in temperature compensation due to temperature gradients across and changes therein can be large enough to mask any pressure-related changes in the process gas measured within the heat conduction gauge. This problem can therefore impose limitations on the size and pressure measurement sensitivity of heat conduction gauges that can be practically implemented. Summary of the Invention [Problem to be solved by the invention]

[0021] Therefore, there is a need to provide a thermal conductivity gauge assembly that improves on the above situation, which can lead to thermal conductivity gauges with high accuracy and sensitivity, as well as enable a more compact gauge to be realized.

[0022] Although a Pirani gauge assembly is generally illustrated herein, it should be understood that any other suitable type of heat conduction gauge assembly (heating element with temperature compensation element) may likewise benefit from the present disclosure and is within its scope as appropriate, such other heat conduction gauges may include, for example, a thermistor heat conduction gauge assembly or a thermocouple heat conduction gauge assembly. [Means for solving the problem]

[0023] In one aspect, the present disclosure provides a thermal conduction gauge assembly including a body defining an interior chamber for receiving a working gas, a heating element disposed within the chamber, a thermal compensation element in thermal communication with the body, and a thermal uniforming element in thermal communication with the body, the body being defined by a wall having an outwardly facing wall surface and an opposing inwardly facing wall surface, the body being made of a material having a first thermal conductivity, and the thermal uniforming element being made of a material having a second thermal conductivity greater than the first thermal conductivity.

[0024] The thermal equalization element helps to conduct heat throughout the body, which can help reduce temperature gradients between different portions of the body and reduce variations and inaccuracies in the ambient body temperature transmitted to the thermal compensation element, which can result in more accurate pressure measurements.

[0025] The thermal compensation element is an element that provides a measurement indicative of the ambient temperature of a body. In one embodiment, the thermal compensation element is a resistance temperature detector (RTD). In another example, the thermal compensation element is a thermistor (such as a positive temperature coefficient (PTC) thermistor or a negative temperature coefficient (NTC) thermistor).

[0026] In the above embodiments, the thermal uniformity element at least partially surrounds the interior chamber and is in thermal contact with the body.

[0027] In further embodiments of the above, the thermal uniformity element at least partially surrounds the outwardly facing wall surface, and in further embodiments, the thermal uniformity element forms an outer sleeve around the body, in such embodiments, the thermal uniformity element completely surrounds the periphery of the body.

[0028] In another embodiment, the thermal uniformity element comprises at least one strip extending along the body.

[0029] In another embodiment, the thermal uniformity element is enclosed within the wall between the inwardly facing and outwardly facing wall surfaces. In a further embodiment, the thermal uniformity element disposed within the wall is at least one strip or sleeve disposed within the wall.

[0030] These embodiments provide configurations of thermal equalization elements that provide good thermal contact with the body to reduce the magnitude of temperature gradients between different portions of the body, and it will be recognized from the following description that certain of these configurations have manufacturing and assembly advantages over others.

[0031] In further embodiments of any of the above, the second thermal conductivity is at least 10 times (ie, an order of magnitude) greater than the first thermal conductivity.

[0032] This provides the thermal equalization element with sufficient thermal conductivity to conduct heat quickly enough to reduce the magnitude of temperature gradients between different portions of the body to help reduce variations or inaccuracies in the ambient body temperature transmitted to the thermal compensation element compared to the body.

[0033] In certain preferred embodiments, the thermal uniformity element is made of a material having a thermal conductivity of 100 W / mK or greater, 150 W / mK or greater, or 200 W / mK or greater.

[0034] In a further embodiment of any of the above, the body is made of stainless steel and the thermal uniformity element is made of aluminum, hi another embodiment, the thermal uniformity element is made of copper.

[0035] In a further embodiment of any of the above, the thermal compensation element is located within a cavity defined in the wall.

[0036] In a further embodiment of any of the above, the assembly further includes an electrical connection member attached to the thermal compensation element, wherein at least a portion of a first portion of the electrical connection member is surrounded by the thermal equalization element and a second portion of the electrical connection member protrudes from the body.

[0037] Placing the thermal compensation element within the cavity and / or using electrical connections can help support the thermal compensation element in better thermal contact with the body to improve accuracy of temperature measurements of the body.

[0038] In a further embodiment of any of the above, the body extends along the longitudinal axis between a base and a top, has a sidewall extending between the base and the top, and the thermal uniformity element at least partially surrounds the sidewall and extends axially along the longitudinal axis.

[0039] The enclosing sidewall encloses a larger surface area of ​​the body for improved heat transfer.

[0040] In a further embodiment of the above, the body includes a radially extending shoulder that abuts the thermal uniformity element.

[0041] The shoulders can help support the thermal uniformity element in place, for example, without the need for additional bonds or adhesives, which can facilitate assembly and replacement of the thermal uniformity element on the body.

[0042] In a further embodiment of the above, the base defines an inlet passage in fluid communication with the chamber and includes a radially extending flange having a recess that accommodates the seal.

[0043] The flanges allow for a more secure mounting of the assembly to the vacuum system, and the recesses (allowing for an internal O-ring seal) result in a better seal being formed between the assembly and the vacuum system during use.

[0044] In further embodiments of any of the above, the heating element is a filament for heating by a power source. In embodiments, the filament may be made of platinum or tungsten. Such an assembly may be generally referred to as a Pirani gauge assembly.

[0045] In another aspect, the present disclosure provides a thermal conduction gauge comprising an assembly according to any of the embodiments of the above aspects, and a housing that receives and at least partially surrounds the body and the thermal uniformity element.

[0046] The housing and connections to the housing facilitated by the assembly embodiments allow for increased modularity and interchangeability of thermal conduction gauges.

[0047] In the above embodiment, the housing contains control circuitry that provides electrical control of the heating element and the thermal compensation element.

[0048] The control circuitry can enable the housing to function as a replaceable modular add-on to the assembly, allowing interrogation of the pressure measurement of the assembly.

[0049] 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.

[0050] One or more non-limiting embodiments will now be described, by way of example only, with reference to the accompanying figures. [Brief description of the drawings]

[0051] [Figure 1] 1 illustrates an exterior isometric view of a thermal conductivity vacuum gauge assembly according to one embodiment of the present disclosure. [Diagram 2] 2 shows a cross section of the assembly of FIG. 1 along line AA. [Diagram 3] 2 shows the assembly of FIG. 1 with the thermal equalization element removed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0052] 1, there is shown a thermal conduction 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. The body 110 includes a shoulder 113 that projects radially outward from the sidewall 112 at the base 114.

[0053] In the illustrated embodiment, the body 110 is generally annular, but has a chamfer 111 about a portion of its circumference that can aid in mounting and orienting the assembly with other components of the thermal conductivity gauge, such as a housing or cover (not shown), as described below.

[0054] Although a particular shape of body 110 is shown, it should be understood that any other suitable shape of body 110 (eg, square or rectangular cross-section) may be used within the scope of the present disclosure.

[0055] The inlet passage 124 extends axially from the base 114 and includes a flange 115 extending radially therefrom. In one embodiment, the flange 115 has a nominal inside diameter specification of 16 mm. In another embodiment, the flange 115 has a nominal inside diameter specification of 10 mm. However, any suitable type and size of flange 115 may be used within the scope of the present disclosure.

[0056] The top portion 116 includes an end cap 118 through which protrudes and is secured to an electrical connector 132 and support features 136 for the heating element 130 (described in more detail below with reference to FIG. 2).

[0057] An end cap 118 is secured within an opening 117 formed in the top 116 .

[0058] In some embodiments, the end cap 118 can be fixedly attached to the top 116, for example, by welding into the opening 117 or by press fitting therein. 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 further embodiments, the end cap 118 can be omitted and the top 116 extends radially across the top 116 without having an opening 117 therein. In such an embodiment, the connections and support features would extend through the top 116 itself.

[0059] In the illustrated embodiment, end cap 118 includes a 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 any other suitable portion of assembly 100 or may be omitted entirely.

[0060] Figure 2 shows a cross-section of assembly 100 along longitudinal axis X (along the line defined by arrow AA) looking in the direction of arrow AA. Figure 2 shows the internal structure and components within body 110, as described below.

[0061] 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 gas" or "process gas" is meant the gas(es) for which the assembly seeks to measure the pressure. A "working gas" is typically the gas(es) that is being worked on (e.g., pumped) by the vacuum system. The pressure of this gas can provide an indication of the general vacuum pressure in the system.

[0062] In the illustrated embodiment, the body 110 is generally tubular and may also be referred to as a “body tube.” The interior chamber 120 is thus generally cylindrical about the longitudinal axis X within the body 110.

[0063] Body 110 is defined or formed by a wall 122. Wall 122 is defined between an outwardly facing wall surface 122a and an opposing inwardly facing wall surface 122b. Walls 122a and 122b are generally annular in accordance with the illustrated shape of body 110. Outwardly facing wall surface 122a is radially outward of inwardly facing wall surface 122b and faces toward the exterior of assembly 100. Inwardly facing wall surface 122b faces toward the interior of assembly 100 and defines (or surrounds) an interior chamber 120.

[0064] As mentioned above, the body 110 is typically made from a corrosion-resistant metal with a relatively low thermal conductivity, such as stainless steel, which enables the body 110 to withstand the potentially corrosive effects of the process gases.

[0065] The body 110 may be made by any suitable manufacturing method, such as molding / casting, machining from a solid block, or 3D printing.

[0066] 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 to allow a working gas (e.g., from a vacuum system) to enter and exit the chamber 120 during use.

[0067] A filter element 126, which filters the working gas before it enters the chamber 120, is disposed across the inlet passage 124. The filter element 126 passes across the inlet passage 124 in a radial direction relative to the longitudinal axis X and, in the illustrated embodiment, is secured in place with a retaining ring 127 positioned within the inlet passage 124.

[0068] 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 walls 122b, or electrical connections within the chamber 120) and / or may interfere with the pressure measurement process, causing inaccuracies therein.

[0069] In one embodiment, the filter element 126 is stainless steel mesh, although any other suitable type (eg, membrane) or material for the filter element 126 may be used within the scope of the present disclosure.

[0070] The flange 115 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, which is secured in place 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 (e.g., metallic) gasket arrangement may instead be used between the flange 115 and the system.

[0071] A heating element 130 is disposed within the chamber 120. In the illustrated embodiment, the heating element 130 extends generally axially into the chamber 120 from the top 116 towards the base 114.

[0072] The heating element 130 in the illustrated embodiment is a filament that is heated by a power source. The filament may be made of any suitable material, such as tungsten or platinum. Platinum in particular may be used in vacuum system environments or applications known to contain more corrosive chemicals and / or working gases.

[0073] Electrical connectors or pins 132a, 132b, 132c protrude through and are secured within end cap 118. Heat generating elements 130 are connected to particular ones of the electrical connectors 132a, 132b, 132c to enable electrical communication therebetween for controlling the heating elements 130.

[0074] In the illustrated embodiment, connectors 132a, 132c are connected to two opposite ends of heating 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 for heating and controlling heating assembly 130 when assembly 100 is in use.

[0075] The heating element 130 may be connected to the connectors 132a, 132c in any suitable manner, such as, for example, by wrapping it around the base of the connector or by welding or soldering it to the connector.

[0076] The heating element 130 is supported within the chamber 120 by a support structure. In the illustrated embodiment, the support structure is in the form of a spring arm 134 and a bar 136.

[0077] The bar 136 projects through and is secured to the end cap 118. The bar 136 extends axially from the top 116 towards the base 114 and into the chamber 120 substantially parallel to the heating element 130. In the illustrated embodiment, the bar 136 is a cylindrical rod.

[0078] A spring arm 134 is secured to the end of the bar 136 closest to the base 114 and extends radially (with respect to the longitudinal axis X) to support the heating element 130 .

[0079] 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.

[0080] As can be seen, in the illustrated embodiment, the heating assembly 130 defines a substantially V- or U-shape when suspended between the connectors 132a, 132c via the hooks 135.

[0081] Although one particular configuration of heating elements 130, electrical connectors 132a, 132b, 132c, and their supporting structures is shown, it should be understood that any other suitable configurations 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.

[0082] The thermal compensation element 140 is held in a cavity 144 defined within the body 110 against the outer surface 122a of the wall 122 of the body 110. In this manner, the thermal compensation element 140 is held in thermal communication with the body 110. This enables the thermal compensation element 140 to provide a reference reading of the ambient temperature of the body 110 to help calibrate pressure measurements due to thermal conduction through the body 110 to the thermal compensation element 140.

[0083] For ease of assembly, it is desirable to maintain the thermal compensation element 140 in contact with the exterior surface 122a without any additional bonding or adhesion, however, in certain embodiments, a thermal paste may be applied between the surface 122a in the recess 144 and the thermal compensation element 140 in contact therewith to improve the thermal contact therebetween.

[0084] The 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 the wall 122 in which the thermal compensating element 140 is disposed. In one embodiment, the thermal compensating element 140 is a resistance temperature detector (RTD), such as a molybdenum or platinum RTD. In another embodiment, the thermal compensating element 140 is a thermistor, such as a positive temperature coefficient thermistor (PTC) or a negative temperature coefficient thermistor (NTC) made of a powdered metal oxide or a polymer. In another embodiment, the thermal compensating element 140 may be a solid-state temperature sensor.

[0085] While other types of thermal compensation element 140 are within the scope of this disclosure, the above are believed to have certain advantages in terms of durability, cost, and accuracy over others.

[0086] The electrical connection member 142 is attached to the thermal compensation element 140 and is used to hold the thermal compensation element 140 in a predetermined position relative to the body 110. The electrical connection member 142 also allows electrical communication between the thermal compensation element 140 and control circuitry (not shown) that is connectable to the thermal compensation element 140.

[0087] In the illustrated embodiment, the electrical connection 142 is a FR-4 specification printed circuit board (PCB), although any suitable type of electrical connection 142 or any other suitable specification PCB could be used instead. By using a PCB in the illustrated embodiment, the electrical connection 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.

[0088] A first portion of the electrical connection member 142 is retained within the recess 144. A second portion protrudes axially out of the wall 122 from the top 116.

[0089] The first portion of the electrical connection member 142 and the recess 144 are sized and shaped such that the first portion can be pressed and held securely within the recess 144 to hold the thermal compensation element 140 in place and maintain good thermal communication / contact with the wall surface 122a of the body 110. However, the electrical connection member 142 with the element 140 thereon can be held relative to the body 110 in other suitable manners, for example, by having the first portion of the electrical connection member 142 adhesively secured within the cavity 144.

[0090] A second portion of the electrical connection member 142 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 to communicate pressure measurements obtained by the assembly 100.

[0091] In the illustrated embodiment, the thermal compensation element 140 is surface mounted to an electrical connection member 142 .

[0092] 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.

[0093] Nonetheless, any other suitable method of attaching thermal compensation element 140 to member 142 may be used within the scope of this disclosure, such as through-hole or soldering techniques.

[0094] In other embodiments (not shown), the thermal compensation element 140 can be held against the exterior surface 122a without the cavity 144 in the exterior surface 122a.

[0095] In another embodiment (also not shown), the thermal compensation element 140 and the first portion of the electrical connection member 142 can be enclosed within the wall 122 (i.e., between the surfaces 122a and 122b) instead of being held against the outer surface 122a. This can be accomplished by disposing a cavity 144 in the wall 122 between the surfaces 122a and 122b, and fastening the thermal compensation element 140 and the first portion of the electrical connection member 142 within the cavity 144. Such an embodiment can improve the useful life / durability of the thermal compensation element 140 and the member 142, and can also provide a greater amount of thermal contact between the thermal compensation element 140 and the wall 122 (for improved temperature compensation accuracy).

[0096] Although the illustrated embodiment shows the thermal compensation element 140, electrical connection member 142, and cavity 144 generally disposed on the sidewall 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.

[0097] 1 and 2, the sidewall 112 of the body 110 is surrounded (or surrounded) by a thermal uniformity element 200. FIG.

[0098] Thermal uniformity element 200 includes a cylindrical portion 202 and a chamfered portion 204 that correspond to the contours of sidewall 112 and chamfered portion 111 of body 110, respectively.

[0099] As shown in FIG. 3, the thermal uniformity element 200 (i.e., having portions 202 and 204) forms an outer sleeve that allows the thermal uniformity element 200 to slide axially over the body 110 and is sized and shaped to abut (or rest against) the shoulder 113 in use.

[0100] The thermal uniformity element 200 is sized and shaped such that the thermal uniformity element 200 can be pressed onto the body 110 and held in place by the pressing (i.e., by slight interference between the sidewalls 112 and the thermal uniformity element 200). This allows the thermal uniformity element 200 to make good thermal contact with the sidewalls 112 of the body 110.

[0101] Pressing provides for simple assembly and facilitates removal and replacement of element 200, as compared, for example, to gluing or bonding element 200 to body 110 instead. That being said, however, any other suitable method of retaining element 200 to body 110 (such as welding or brazing, or using an adhesive) is contemplated within the scope of this disclosure. In certain embodiments, thermal paste can also be applied between element 200 and surface 122a / sidewall 112 of body 110 to improve retention and thermal contact therebetween.

[0102] The thermal uniformity element 200 is made of a material that has a relatively high thermal conductivity compared to that of the body 110. In the illustrated embodiment, the thermal uniformity element 200 is made of aluminum (or an alloy thereof). Aluminum has a thermal conductivity on the order of approximately 230 W / mK, which is significantly greater than the thermal conductivity of approximately 15 W / mK of the exemplary stainless steel that is commonly used to make the body 110.

[0103] It should be appreciated that the thermal uniformity element 200 in thermal communication with the body 110 helps to conduct heat generated at different points within the body 110 more quickly across the body 110. This can help reduce problematic temperature gradients between different portions of the body 110 (e.g., resulting from heat from the electronics at or near the top 116 and the relatively cooler heat sink at or near the base 114 / flange 115), which can help reduce variations and inaccuracies in the ambient body temperature transmitted to the thermal compensation element 140. This results in more accurate pressure measurements.

[0104] Although aluminum is illustrated, any other suitable material having sufficient thermal conductivity may be used within the scope of the present disclosure, for example copper, which has a thermal conductivity of about 400 W / mK.

[0105] In some embodiments, a suitable thermal uniformity element 200 is made from a material having a thermal conductivity of 100 W / mK or greater, 150 W / mK or greater, or 200 W / mK or greater.

[0106] In a further embodiment, the thermal uniformity element 200 is made of a material whose thermal conductivity is at least ten times (ie, an order of magnitude) greater than the thermal conductivity of the material of the body 100 .

[0107] The thermal uniformity element 200 defines a wall thickness T (i.e., in the radial direction) that may be any suitable thickness. In some embodiments, the wall thickness may be between 1 mm and 5 mm, or narrower, between 2 mm and 3 mm.

[0108] In the illustrated embodiment, the thermal uniformity element 200 is fabricated by extrusion, which is a relatively low-cost manufacturing process that results in a consistently sized element 200. That being said, the thermal uniformity element 200 may be manufactured by any other suitable method within the scope of this disclosure, such as by machining or additive manufacturing / 3D printing.

[0109] The thermal uniformizing element 200 extends axially along a longitudinal axis X for a majority of its length L in the axial direction of the body 110 (i.e., defined between its top 116 and base 114). The thermal uniformizing element 200 can be of any suitable axial length relative to the body 110, so long as the thermal uniformizing element 200 has a sufficient length to be in sufficient thermal contact with the body 110 to effectively uniform a temperature gradient across the body. It should be appreciated that such a sufficient length allows the element 200 to extend a sufficient axial length across the heating element 130 (e.g., across the entire axial length or a majority of the axial length of the heating element 130).

[0110] In some preferred embodiments, the thermal uniformity element 200 extends between 50 and 100%, between 60 and 100%, between 70 and 100%, between 75 and 100%, between 80 and 100%, between 75 and 95%, between 75 and 90%, between 75 and 85%, or between 75 and 80% of the axial length L of the body 110.

[0111] Although the illustrated thermal uniformity element 200 completely (i.e., around the circumference) surrounds the sidewall 112 of the body 110, it should be understood that in alternative embodiments, the thermal uniformity element 200 need only partially surround the sidewall 112 of the body 110 instead.

[0112] In such an embodiment, the thermal uniformity element 200 may have a slit or split along its axial length, such that its axial cross section is substantially C- or U-shaped. Such an embodiment may be conveniently clipped around a body, rather than being forced axially onto the body.

[0113] In other such embodiments, the thermal uniformity element 200 may be an axially extending strip(s) of material secured to the sidewall 112 .

[0114] Furthermore, within the scope of the present disclosure, the thermal uniformity element 200 need not be limited to at least partially surrounding the exterior of the body 110 (i.e., the outer wall 122a of the body 110) as shown. The thermal uniformity element 200 can instead be disposed within the wall 122 of the body 110 itself (i.e., within the radial thickness of the wall 122 between the outer wall surface 122a and the inner wall surface 122b).

[0115] In such an embodiment, the thermal uniformity element 200 would still at least partially surround the chamber 120 (and the interior wall surface 122b of the body 100), as in the illustrated embodiment.

[0116] In such an embodiment, the thermal uniformity element 200 may be incorporated into an axially extending cavity within the wall 122 of the body 110 (between surfaces 122a and 122b) and may be in thermal contact with the body 110 within the cavity. Alternatively, the element 200 may be integrally formed within the wall 122 during formation of the body 110 (e.g., using additive manufacturing / 3D printing).

[0117] As shown in the illustrated embodiment, the thermal uniformizing element 200 covers the recess 144 in which the thermal compensation element 140 is located. Such positioning is advantageous because it provides for uniformization of the temperature gradient in the immediate vicinity of the thermal compensation element 140, which further aids in providing more accurate temperature measurements. Thus, in some embodiments, the thermal uniformizing element 200 surrounds the body 110 at least in the area in which the thermal compensation element 140 is located (i.e., covers the radial cross-sectional area in which the thermal compensation element 140 is positioned).

[0118] For example, in an alternative to the illustrated embodiment, the thermal uniformity element 200 is a flat axial strip along the sidewall 112 that covers the recess 144 containing the thermal compensation element 140 .

[0119] In one embodiment, a thermal conductivity gauge (not shown) may be formed using the assembly 100, whereby the thermal uniformity element 200 and the body 110 may be housed within an additional housing or cover (not shown) that at least partially surrounds and traverses thereover.

[0120] The housing may generally contain control circuitry and / or electronic circuitry (e.g., remnants of a Wheatstone bridge circuit) that may be connected to the assembly 100 to control and operate the heating element 130 in combination with the thermal compensation element 140.

[0121] 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 modularity and replaceability of the housing and assembly 100.

[0122] The housing may feature unique electrical connections / connectors that may allow for powering and interrogating the control circuitry / electronics and assembly 100, if desired.

[0123] 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.

[0124] As briefly mentioned above, the shape of the body 110 and thermal uniformity element 200, including the chamfered portions 111 and 204, can be used to aid in mounting of the housing. For example, the chamfered portions 111, 204 provide flat axial surfaces that aid in the insertion and mounting of the housing onto the element 200 and body 110. The chamfered portions 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]

[0125] 100 Thermal Conductivity Vacuum Gauge Assembly 110 Main unit 111 Chamfered part 112 Side wall 113 Shoulder 114 Base 115 Flange 116 Top 117 Opening 118 End Cap 119 Marking Area 120 Inner Chamber 122 Wall 122a Outer wall 122b Inward wall 124 Entrance Passage 126 Filter Element 127 Filter Retaining Ring 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 200 Heat equalization elements 202 Cylindrical part 204 Chamfered part X Longitudinal Axis L is the axial length of the body 110 (defined between the base 114 and the top 116) T (radial) wall thickness (of thermal uniformity element 200) A cross-sectional line of sight

Claims

1. A thermal conductivity gauge assembly (100), comprising: a body (110) defining an internal chamber (120) for receiving a working gas, the body being defined by a wall (122) having an outwardly facing wall surface (122a) and an opposite inwardly facing wall surface (122b); a heating element (130) disposed within the interior chamber (120); a thermal compensation element (140) in thermal communication with the body (110) and located within a cavity (144) defined in the wall (110); a thermal equalization element (200) in thermal communication with said body (110); Equipped with the body (110) is made of a material having a first thermal conductivity and the thermal uniformity element (200) is made of a material having a second thermal conductivity higher than the first thermal conductivity; A thermal conductivity gauge assembly, wherein the body (110) is made of stainless steel and the thermal uniformity element (200) is made of aluminum.

2. The assembly of claim 1 , wherein the thermal uniformity element (200) at least partially surrounds the interior chamber (120) and is in thermal contact with the body (110).

3. The assembly of claim 2 , wherein the thermal uniformity element (200) at least partially surrounds the outwardly facing wall surface (122a).

4. The assembly of claim 3 , wherein the thermal uniformity element (200) forms an outer sleeve around the body (110).

5. The assembly of claim 3 , wherein the thermal uniformity element (200) comprises at least one strip extending along the body (110).

6. The assembly of claim 1 , wherein the second thermal conductivity is at least 10 times greater than the first thermal conductivity.

7. 7. The assembly of claim 1, further comprising an electrical connection member (142) attached to the thermal compensation element (140), wherein at least a portion of a first portion of the electrical connection member (142) is surrounded by the thermal uniformity element (200) and a second portion of the electrical connection member (142) protrudes from the body (110).

8. The body (110) extends along a longitudinal axis (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 of any of claims 1 to 7, wherein the thermal uniformity element (200) at least partially surrounds the sidewall (112) and extends axially along the longitudinal axis (X).

9. The assembly of claim 8, wherein the body (110) includes a radially extending shoulder (113) that abuts the thermal uniformity element (200).

10. 10. The assembly of claim 8 or 9, wherein the base (114) defines an inlet passage (124) in fluid communication with the interior chamber and includes a radially extending flange (115) having a recess for receiving a seal.

11. The assembly of any of claims 1 to 10, wherein the heating element (130) is a filament for heating by an electrical power 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) and the thermal uniformity element (200); A thermal conductivity vacuum gauge comprising:

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

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