阅读说明：本技术 用于高温环境的电容压力计 (Capacitance manometer for high-temperature environment ) 是由 斯科特·维德曼 于 2019-08-20 设计创作，主要内容包括：本公开的差分电容压力计可以包括在一端处固定并且在另一端处自由的石墨挡板,使得所述挡板在存在压差的情况下朝向和远离一对电极弯曲。因为所述电极中的一个设置得更靠近所述挡板的自由端,所以所述挡板和每个电极之间的电容存在差值,并且该差值根据挡板的位移而变化。(The differential capacitance manometer of the present disclosure can include a graphite baffle fixed at one end and free at the other end such that the baffle bends toward and away from a pair of electrodes in the presence of a pressure differential. Because one of the electrodes is disposed closer to the free end of the baffle, there is a difference in capacitance between the baffle and each electrode, and the difference varies according to the displacement of the baffle.)

1. A capacitance manometer, comprising:

a flexible conductive baffle comprising an extension fixed at a proximal end and free at a distal end, the extension having a first face and a second face; and

a first electrode and a second electrode, the first electrode spaced apart from the second electrode adjacent the second face of the baffle;

wherein the first electrode is closer to the proximal end of the baffle than the second electrode; and is

Wherein the proximal end of the baffle is fixed relative to the first and second electrodes such that the expanded portion is configured to bend toward and away from the first and second electrodes with a magnitude corresponding to a pressure differential across the baffle.

2. The capacitance manometer of claim 1, further comprising:

an Alternating Current (AC) voltage source coupled to the baffle such that the baffle in combination with the first electrode forms a first capacitor and in combination with the second electrode forms a second capacitor; and

a circuit configured to receive a first current measured on the first electrode and a second current measured on the second electrode and convert a difference between the first current and the second current into a measure of a pressure differential across the first face and the second face of the baffle.

3. The capacitance manometer of claim 1, further comprising:

a tab extending from the proximal end of the baffle; and

a fastener that secures the tab of the baffle such that the proximal end of the baffle is fixed relative to the first and second electrodes and the distal end of the baffle is free to move toward and away from the first and second electrodes.

4. The capacitance manometer of claim 1, wherein the baffle contains graphite.

5. The capacitance manometer of claim 1, wherein the first and second electrodes are housed in a graphite block and the proximal end of the baffle is clamped to the block.

6. The capacitance manometer of claim 5, further comprising a plurality of insulating separators electrically isolating the first and second electrodes from each other and from the graphite block.

7. The capacitance manometer of claim 6, wherein each insulating separator includes a ceramic tube having an open end adjacent the second face of the baffle.

8. The capacitance manometer of claim 1, further comprising an integral heating element.

9. A system for measuring a vacuum differential pressure, the system comprising:

a capacitance manometer comprising first and second electrodes adjacent a flexible conductive baffle fixed at a proximal end and free at a distal end such that the distal end of the baffle is configured to bend toward and away from the first and second electrodes with a magnitude of bending corresponding to a pressure differential across the baffle;

a time-varying voltage source coupled to the baffle such that the baffle in combination with the first electrode forms a first capacitor and in combination with the second electrode forms a second capacitor; and

a measurement circuit configured to receive a first current measured on the first electrode and a second current measured on the second electrode and convert a difference between the first current and the second current into a measurement of a pressure differential across the first and second faces of the baffle.

10. The system of claim 9, further comprising:

a tab extending from the proximal end of the baffle; and

a fastener that secures the tab of the baffle such that the proximal end of the baffle is fixed relative to the first and second electrodes.

11. The system of claim 9, wherein the baffle comprises graphite.

12. The system of claim 9, wherein the first and second electrodes are housed in a graphite block and the proximal end of the baffle is clamped to the graphite block.

13. The system of claim 12, wherein the proximal end of the baffle includes an extension, and the extension is clamped to the graphite block between a pair of insulator plates.

14. The system of claim 12, further comprising a plurality of insulating separators electrically isolating the first and second electrodes from each other and from the graphite block.

15. The system of claim 14, wherein each insulating separator comprises a ceramic tube having an open end adjacent the second face of the baffle.

16. The system of claim 9, wherein each of the first and second electrodes has a respective end adjacent the baffle, and the respective ends are coplanar.

17. A method for measuring a vacuum pressure differential between two compartments, the method comprising:

sensing a pressure differential between a first compartment and a second compartment using a capacitance manometer, wherein the capacitance manometer comprises a first electrode and a second electrode, the first electrode and the second electrode being adjacent to a flexible conductive baffle, the baffle being fixed at a proximal end and free at a distal end, such that the distal end of the baffle is configured to bend toward and away from the first electrode and the second electrode, and a magnitude of bending corresponds to the pressure differential;

generating a first current in the first electrode and a second current in the second electrode by applying a time-varying voltage source to the baffle of the capacitance manometer such that the baffle in combination with the first electrode forms a first capacitor and in combination with the second electrode forms a second capacitor; and

converting a difference between the first current and the second current to a measure of differential pressure.

18. The method of claim 17, wherein the capacitance manometer further comprises:

a tab extending from the proximal end of the baffle; and

a fastener that secures the tab of the baffle such that the proximal end of the baffle is fixed relative to the first and second electrodes.

19. The method of claim 17, wherein the baffle comprises graphite.

20. The method of claim 17, further comprising:

receiving the first and second electrodes in a graphite block; and

clamping the proximal end of the baffle to the graphite block.

Technical Field

The present disclosure relates to systems and methods for sensing pressure in a vacuum environment. More particularly, the disclosed embodiments relate to capacitance manometers.

Background

For many vacuum deposition processes, the vapor pressure of a component in a vacuum chamber must be measured or controlled. There are various meters for this purpose, including ionization gauges (based on thermionic generation), Pirani gauges (Pirani gauges) (based on thermal conduction), Penning gauges (Penning gauges) (based on plasma ionization) and capacitance manometer types. However, ion meters are only used in a limited low pressure range and are susceptible to contamination. Thermal conductivity meters are often inaccurate. Penning meters have the same disadvantages as ionic meters. Known capacitance manometers are not suitable for operation in extreme environments (e.g., at high temperatures or in the presence of harsh corrosive reactants).

Some existing capacitance manometers are intended for "high temperature" use. However, these meters rarely operate above 125 ℃ - > 150 ℃ and they may be "baked" at higher temperatures. Furthermore, none of the known commercial capacitance manometers are intended for use in harsh chemical environments, such as those requiring corrosive condensed selenium and the like.

Disclosure of Invention

The present disclosure provides systems, devices, and methods involving capacitance manometers configured to operate in a range up to 1000 ℃ or higher and/or in corrosive environments.

In some embodiments, a capacitance manometer can include: a flexible conductive baffle including an extension (expansion) fixed at a proximal end and free at a distal end, the extension having a first face and a second face; and a first electrode and a second electrode, the first electrode spaced apart from the second electrode adjacent the second face of the baffle; wherein the first electrode is closer to the proximal end of the baffle than the second electrode; and wherein the proximal end of the baffle is fixed relative to the first and second electrodes such that the flared portion is configured to bend toward and away from the first and second electrodes by an amount corresponding to a pressure differential across the first and second faces of the baffle.

In some embodiments, a system for measuring a vacuum differential pressure may comprise: a capacitance manometer comprising first and second electrodes adjacent to a flexible conductive baffle, the baffle fixed at a proximal end and free at a distal end such that the distal end of the baffle is configured to bend toward and away from the first and second electrodes, and a magnitude of the bending corresponds to a pressure differential across the baffle; a time varying voltage source coupled to the baffle such that the baffle in combination with the first electrode forms a first capacitor and in combination with the second electrode forms a second capacitor; and a measurement circuit configured to receive a first current measured on the first electrode and a second current measured on the second electrode, and convert a difference between the first current and the second current into a measurement of a differential pressure across the baffle.

In some embodiments, a method for measuring a vacuum pressure differential between two compartments may comprise: sensing a pressure differential between the first compartment and the second compartment using a capacitance manometer, wherein the capacitance manometer comprises a first electrode and a second electrode, the first electrode and the second electrode being adjacent to a flexible conductive baffle fixed at a proximal end and free at a distal end, such that the distal end of the baffle is configured to bend toward and away from the first electrode and the second electrode, and a magnitude of the bending corresponds to the pressure differential; generating a first current in the first electrode and a second current in the second electrode by applying a time-varying voltage source to a baffle of the capacitance manometer such that the baffle in combination with the first electrode forms a first capacitor and in combination with the second electrode forms a second capacitor; and converting the difference between the first current and the second current into a measure of the voltage difference.

The features, functions, and advantages can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings.

Drawings

FIG. 1 is a schematic diagram of an exemplary multi-chamber process including sensors according to the present teachings.

FIG. 2 is an isometric view of an example differential capacitance manometer in accordance with aspects of the present disclosure.

Figure 3 is another isometric view of the differential capacitance manometer of figure 2.

Figure 4 is an isometric view of a cover portion of the housing of the differential capacitance manometer of figure 2.

Figure 5 is an isometric view of the differential capacitance manometer of figure 2 with the cover portion removed.

Figure 6 is an isometric exploded view showing various components of the differential capacitance manometer of figure 2.

Figure 7 is an isometric view of selected operational components of the differential capacitance manometer of figure 2.

FIG. 8 is a block diagram of an exemplary system including the differential capacitance manometer of FIG. 2.

FIG. 9 is a flow chart depicting steps of an exemplary method for measuring vacuum pressure according to the present teachings.

Detailed Description

Various aspects and examples of capacitance manometers and associated systems and methods configured to reliably operate in high temperature and/or highly corrosive environments are described below and illustrated in the associated drawings. Unless otherwise indicated, a capacitance manometer and/or various components thereof in accordance with the present teachings can include at least one of the structures, components, functions, and/or variations described, illustrated, and/or incorporated herein. Moreover, unless expressly excluded, process steps, structures, components, functions, and/or variations described, illustrated, and/or incorporated herein in connection with the present teachings can be included in other similar apparatus and methods, including interchangeable between disclosed embodiments. The following description of various examples is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. Additionally, the advantages provided by the examples and embodiments described below are exemplary in nature, and not all examples and embodiments provide the same advantages or the same degree of advantages.

This detailed description includes the following sections immediately following: (1) defining; (2) for review; (3) examples, components, and alternatives; (4) advantages, features and benefits; and (5) a conclusion. The examples, components and alternatives section is further divided into subsection a and subsection B, each subsection labeled accordingly.

Definition of

The following definitions apply herein unless otherwise indicated.

"substantially" means more or less conforming to a particular size, range, shape, concept, or other aspect modified by the term such that the features or components do not need to be precisely conformed. For example, an object that is "substantially cylindrical" means that the object resembles a cylinder, but may have one or more deviations from a true cylinder.

The terms "comprising" and "having" (and variants thereof) are used interchangeably to mean including, but not necessarily limited to, and are open-ended terms that are not intended to exclude additional, unrecited elements or method steps.

Terms such as "first," "second," and "third" are used to distinguish or identify members of a group or the like, and are not intended to illustrate sequential or numerical limitations.

"AKA" means "also called" and may be used to denote alternative or corresponding terms for a given element or elements.

"coupled" means permanently or releasably connected, whether directly or indirectly through intervening components.

"elastic" describes a material or structure that is configured to elastically deform under normal operating loads (e.g., upon compression) and return to an original shape or position upon unloading.

"rigid" describes a material or structure that is configured to be rigid, non-deformable, or substantially lack flexibility under normal operating conditions.

"processing logic" may include any suitable device or hardware configured to process data by performing one or more logical and/or arithmetic operations (e.g., executing coded instructions). For example, processing logic may include one or more processors (e.g., a Central Processing Unit (CPU) and/or a Graphics Processing Unit (GPU)), microprocessors, processing core clusters, FPGAs (field-programmable gate arrays), Artificial Intelligence (AI) accelerators, Digital Signal Processors (DSPs), and/or any other suitable combination of logic hardware.

Overview

A capacitance manometer according to the present disclosure solves the problem of operating a differential pressure gauge in a harsh, high temperature environment. This is achieved by using mechanically and chemically stable building materials with high sensitivity. The differential capacitance manometer taught herein is particularly suitable when there are sufficient distinct measurements, for example when a low vacuum pressure within the chamber is to be measured relative to another low or negligible vacuum pressure outside the chamber (e.g., the reaction region). The pressure gauge may be interchangeably referred to herein as a pressure measurement device, a pressure gauge, and/or a pressure sensor.

In general, the pressure measurement device of the present disclosure includes a differential capacitive sensor having a thin conductive (e.g., graphite) plate or baffle disposed on one side of a pair of stationary electrodes (stationary electrodes). The baffle is fixed at one end and free at the other end and positioned adjacent to the electrode. Thus, the baffle is configured to flex toward and away from the electrode in accordance with the sensed pressure. Each electrode is effectively combined with a baffle to form a separate capacitor. When the baffle bends, the distance between the baffle and the two electrodes is modulated, thereby differentially changing the capacitance of the two capacitors. By measuring the relative change in capacitance between the two capacitors, the movement of the flapper in response to the differential pressure can be accurately monitored. Since the blade (paddle) is bent more at the free side than at the fixed side, the capacitance of one capacitor will vary more than the capacitance of the other capacitor.

The pressure measurement device is mounted in a housing that exposes one side of the graphite baffle to the higher pressure to be measured and the other side of the baffle to a reference pressure (typically a low or negligible amount of pressure). As described above, the graphite baffle is formed as a blade and is mechanically retained (e.g., to the housing) by clamping onto a tab or protrusion extending from one edge of the baffle. Thus, the baffle is allowed to easily bend in response to a pressure differential across the baffle.

By constructing the sensor primarily from graphite materials, operation can be performed under harsh, high temperature, and/or corrosive conditions. Graphite is unreactive with most harsh chemical components, such as selenium. It can also withstand very high temperature environments (e.g., up to 1000 ℃ or higher). Unlike metals, graphite is not subject to internal stresses that cause deformation when exposed to temperature. Graphite is mechanically and chemically stable, has a high yield stress at high temperatures, and has an advantageous elastic modulus that provides reproducible bending behavior due to pressure changes. In some cases (e.g., in a selenium environment), contamination on the gauge components may be avoided by actively heating the gauge components to prevent condensation of the material.

Although graphite components are described herein, other materials may alternatively or additionally be used in some embodiments. Examples of suitable materials may include crystalline silicon, silicon carbide, aluminum (aluminum oxide), aluminum nitride, and/or boron nitride. These materials are subjected to high temperatures and are chemically quite inert. However, some have insulation properties. This presents a potential problem because, for example, the baffle is intended to be electrically conductive. This disadvantage can be solved, for example, by coating at least one side of the baffle (e.g. the disc portion) with a thin metal layer. For example, an inert high temperature metal (e.g., molybdenum, tungsten, iridium, rhenium, niobium, tantalum, gold, etc.) may be sputtered or evaporated onto one or more components. In some examples, the metal coating may comprise a conductive oxide, such as indium tin oxide.

The differential pressure gauge or manometer of the present disclosure includes a baffle having a fixed proximal end and a free distal end such that the baffle flexes in the presence of a differential pressure. This results in a differential change in capacitance between the curved baffle and two separate electrodes disposed nearby, as the baffle is bent at an angle relative to its attachment point. In some embodiments, the capacitance manometer can operate at temperatures up to 1000 ℃ and/or in harsh corrosive chemical environments.

In many applications (e.g., absolute pressure gauges), a constant reference pressure is required on one side of the diaphragm. This may include an evacuated volume in which a reactive material (called a "getter") intended to complete and maintain a vacuum is deposited. In these examples, the actual pressure obtained may be an absolute value. However, in these examples, the diaphragm separating the volume to be measured and the reference volume must provide a perfect hermetic seal. In other words, the edge of the diaphragm is rigidly held by the sealing surface, so the movement of the diaphragm is limited to a slight bending of the material near the center of the diaphragm. This movement (and thus sensitivity) is therefore much lower than that of the present disclosure, where the entire diaphragm is free to deflect over a narrow cantilever, rather than only in the central portion where the edges are fixed.

In the present disclosure, it is assumed that the reference vacuum pressure is actively provided, present and/or maintained at the back side of the sensor and communicated to the back side of the blade through an open channel through the device. A differential pressure, i.e., a pressure differential of the front side pressure relative to the back side pressure, is measured. The CIGS chamber, described briefly below, operates in this case.

Without a complete edge seal, there is some gas leakage from the volume to be measured to the reference volume. However, a small amount of leakage is not important in case both volumes are actively pumped and controlled, or in case at least a reference volume pressure can be maintained.

The system of the present disclosure may be particularly useful at low pressures (e.g., <10 mTorr). The gas density at these pressures is about 100,000 times less than atmospheric pressure and many of the effects (e.g., bernoulli effect) of viscous moving fluids with significant mass and momentum are absent. The gas becomes an aggregate of particles. The mean free path (in cm) can be approximated as 5/P using "rule of thumb," where P is the pressure in mTorr. Thus, the mean free path longer than about 5mm is longer than the leakage path behind the vane-like baffle. Gas molecules generally do not interact with each other to produce a directed flow having mass and momentum.

Nonetheless, the apparatus of the present disclosure may also be suitable for applications where near atmospheric pressure, requiring measurement of extremely small pressure differentials. At small pressure differentials measurable with these devices, the pressure differential between the front and back is small enough that there is no significant flow around the baffle and therefore no practical effect due to the flow.

Examples, Components and alternatives

The following sections describe selected aspects of exemplary differential capacitance manometers and related systems and/or methods. The examples in these sections are intended to be illustrative and should not be construed as limiting the scope of the disclosure. Each portion may include one or more different embodiments or examples, and/or context or related information, functionality, and/or structure.

A.Exemplary differential capacitance manometer

As shown in fig. 1-8, this section describes an exemplary robust differential capacitance manometer 10 suitable for measuring selenium vapor pressure in high temperature vacuum environments. Manometer 10, also referred to as a sensor, is an example of a differential capacitance manometer described in the overview above.

FIG. 1 is a schematic illustration of an exemplary environment in which a pressure gauge 10 may be used. Figures 2 and 3 are isometric views of the pressure gauge 10 from different vantages. FIG. 4 shows the pressure gauge with a portion of the housing removed, showing the relationship between the various components. Figure 5 is an isometric view of the differential capacitance manometer 10 of figure 2 with the cover portion removed. . Figure 6 is an isometric exploded view showing various components of the differential capacitance manometer of figure 2. Figure 7 is an isometric view of selected operational components of pressure gauge 10. Fig. 8 is a schematic block diagram describing the overall function of the pressure gauge 10.

Fig. 1 depicts a portion of a manufacturing system for a flexible photovoltaic device in which a flexible substrate 12, also referred to as a web, travels through a series of deposition areas or zones, all contained within a common chamber. Specifically, the evaporation zone has a first zone 14 and a Cu/In/Ga deposition zone 16, the first zone 14 comprising NaF deposition using thermal evaporation, the Cu/In/Ga deposition zone 16 comprising vapor transport of copper, gallium and indium. Deposition zones 14 and/or 16 include a heated effusion source 18 for generating a vapor stream (plume of vapor) from these materials. Each of these sources of seepage may include any suitable device configured to generate a vapor stream. Cu, In and Ga are typically deposited using a vacuum reactive co-evaporation process, In which a significant overpressure or overpressure of selenium (Se) is maintained on the grown film on the web.

Although there is a vacuum throughout the system, an internal vacuum isolation wall 20 is included to isolate the chambers so that different levels of vacuum and/or temperature, or different gas species, can be maintained in different sub-chambers. At locations where the substrate 12 needs to pass through each of the internal vacuum isolation walls, conductive slots (i.e., conductive slots 22A, 22B, and 22C) may be included to allow the substrate 12 to be transferred from one portion of the chamber to another. The conductive slots 22A, 22B, 22C (also referred to as conductive limiters) are configured to limit the effective movement of gas atoms from one side to the other.

As shown in fig. 1, the pressure gauge 10 may be provided in such a system, for example in the wall 20, such that one side of the device is exposed to the pressure P1 in the first chamber (i.e., region 14) and the other side of the device is exposed to the pressure P2 in the second chamber (i.e., region 16). Thus, the pressure difference between the two chambers can be measured. If the pressure in one chamber is known (or indeed known or assumed to be known), this also helps to determine the pressure in the other chamber.

With continued reference to fig. 2-8, the pressure gauge 10 includes a housing 30, the housing 30 having a housing body 32 (also referred to as a sensor body) and a housing cover 34 and a stress bridge portion 36. The housing 30 may include any suitable structure or structures that are stable under the expected operating conditions and configured to securely hold and protect the internal components of the sensor in its desired orientation and position while more or less exposing both sides of the baffle (described below) to the ambient environment. In this example, the components of the housing are made primarily or entirely of graphite to withstand high temperatures and chemical corrosion while remaining mechanically stable.

The housing body 32 is a block (e.g., a cube-shaped block) having a first face 38 (also referred to as a front face) and a second face 40 (also referred to as a back face), and the interior compartment 42 is formed by a void in the block. The compartment 42 is open at both face 38 and face 40, defining a large aperture through the block. As depicted in fig. 3 and 5, the peripheral wall 44 of the compartment generally defines a square shape with rounded corners, and semicircular channels 46, 48, 50, 52 are formed in each otherwise flat side of the square. Although the compartment 42 has a rounded square perimeter in this example, any suitable shape may be used. Similarly, although there is a semi-circular channel in this example, the channel may have any suitable shape or cross-section corresponding to the components (see below) held within the channel. In some examples, there may be more or fewer channels.

A plurality of through holes 54 are formed in the body 32 with corresponding through holes 56 in the cover 34. Thus, when the housing 30 is fully assembled, the apertures 54 and 56 are aligned with one another to provide limited fluid communication around the central compartment. Other fastener holes and various mounting structures may also be present to facilitate attachment of portions of the device.

As best shown in fig. 2 and 4, the cover 34 is coupled to the first face 38 of the body 32 and has a plurality (six in this example) of openings 60, the openings 60 providing fluid communication through the cover and into (or out of) the body 32. In this example, the openings 60 are circular holes formed in the cover 34 and are arranged in a circular pattern generally aligned with the compartments 42. Any suitable shape and/or number of openings 60 may be used. In general, the cover 34 may include any suitable structure configured to allow fluid communication with the internal components of the sensor while also providing mechanical protection to the internal components.

Turning to fig. 5-7, the internal components of the pressure gauge 10 are housed in a housing 30 and include a baffle 70, a first electrode block 72, a second electrode block 74, and insulating separators 76, 78, 80, 82 (also referred to as spacers). The electrode block 72 and the electrode block 74 are arranged adjacent to each other within the compartment 42. The electrode block may comprise any suitable material that is mechanically stable and electrically conductive while being able to withstand high temperatures and chemically corrosive environments. In this example, each electrode block is made of graphite.

The two electrodes are physically and electrically separated from each other by separators 78 and 80. The two electrodes are also physically and electrically separated from the peripheral wall 44 of the body 32 by separators 76 and 82. In this example, all of the separate pieces are tubes or cylinders having a circular cross-section. However, the separator may comprise any suitable insulating material, having any suitable shape. The tubular structure in this example is a multi-stage alumina ceramic tube. Alumina ceramics can withstand high temperatures, are inexpensive, are mechanically stable, and provide an insulating support to securely hold the graphite electrode. Each tube is oriented with the open end adjacent the baffle to reduce interference throughout the compartment.

In some examples, more or fewer separate pieces may be used. Here, the separators 76 and 82 are received in the passages 46 and 50 of the housing, respectively, and in the corresponding passages 84 and 86 in the electrode blocks 72 and 74, respectively. Similar channels 88 and 90 are formed in the electrode block for receiving the separators 78 and 80. Thus, when assembled, electrode block 72 and electrode block 74 remain electrically isolated and in a fixed position relative to each other and relative to housing 30. In this example, the planar face 92 of the electrode block 72 is substantially aligned with the planar face 94 of the electrode block 74 such that the face 92 and the face 94 are coplanar. The faces 92 and 94 are oriented such that they are associated with the first face 38 of the housing body 32. In some examples, the faces may be offset by a selected amount, i.e., not coplanar.

As shown in fig. 5-7, a baffle 70 is disposed adjacent the electrodes, covering (but spaced from) the opening of the compartment 42 at the first face 38. The baffle 70 is a flat, blade-like sheet or plate that is oriented parallel to the first face 38 and the faces 92 and 94 of the electrodes. Further, the baffle 70 is a unitary structure including tabs 96 extending from a circular extension 98 (also referred to as a disc) having a front face and a back face. The baffle 70 may include any suitable extension of electrically conductive material configured to elastically bend in the presence of a pressure differential, and may have any suitable size and/or shape. Here, the baffle 70 is made of graphite, and the tabs 96 are fastened to the housing by fasteners. Here, the fastener includes a clamping mechanism in which the tabs are held between a pair of insulating (e.g., ceramic) plates 100, the plates 100 being held in place by stress bridge portions 36. Thus, the remainder of the baffle 70 is free to flex toward and away from the electrode block 70 and the electrode block 72 (e.g., due to a pressure gradient). Due to the clamping described above, the flapper 70 will experience more movement near the distal end 104 of the flapper than near the proximal end 102. In general, the flap may be said to pivot or bend at the proximal end, although the actual movement need not be about a separate pivot.

FIG. 8 is a schematic diagram of an exemplary sensor system 110 for measuring differential pressure using pressure gauge 10. As shown in fig. 8, system 110 includes a circuit 112 (e.g., including processing logic), which circuit 112 is configured to convert the capacitance difference measured by pressure gauge 10 into a differential pressure. The circuitry 112 may include any suitable combination of hardware and software, or may be entirely hardware or entirely software.

In this example, the system 110 includes a voltage source 114, which is labeled V in FIG. 8_ACBy means of an Alternating Current (AC) voltage, e.g. metal foilContacts (not shown) are applied to tabs 96 of shutter 70. Although an AC voltage is applied in this example, any suitable excitation signal may be applied. As shown throughout the figures, the baffle 70 is positioned adjacent to the electrodes 72 and 74 with a small gap between the baffle and the electrode faces. This effectively creates a pair of capacitors, with a first capacitor CAP1 formed by baffle 70 and electrode 72 and a second capacitor CAP2 formed by baffle 70 and electrode 74. The gap is variable as the distal end 104 of the baffle moves toward and away from the electrode (see arrow 115), thereby changing the capacitance of the CAP1 and CAP 2. However, the change in capacitance is different. By fixing the proximal end 102 and creating a cantilever effect, the flapper 70 can only move at an angle rather than translate back and forth as a whole. Thus, for any given movement of the shutter, the capacitance of the two capacitors will change by different amounts. For the purposes of this description, it is assumed that the shutter moves due to a pressure differential across the shutter (i.e., the difference between P1 and P2), where a higher P2 causes the shutter to move toward the electrode and a higher P1 causes the shutter to move away from the electrode.

As V_ACAnd capacitive effects, a first AC current 116 is detected at electrode 72 and a second AC current 118 is detected at electrode 74. Specifically, a small AC voltage from an oscillator is applied (modulated) to the baffle (e.g., about 2 to 5V)_AC40kHz) which forms an AC current across both capacitors CAP1 and CAP2 at that frequency. The small AC currents 116 and 118 are amplified (e.g., by solid state circuitry) and bandpass filtered to reduce noise. This operation is represented by block 120 of fig. 8. The filtered and amplified signals corresponding to current 116 and current 118 are then input to a differential amplifier 122 so that only the difference between the two signals is amplified.

A signal proportional to the pressure differential is then generated so that a pressure related value can be calculated at block 124. In some examples, the differential signal is input into a synchronous amplifier and the weak differential signal is amplified by a positive factor during one half of the period of the oscillator waveform and by an equal negative factor during the other half of the period of the waveform. It is then integrated into a DC value and amplified again.

This method helps to recover the extremely small signal buried in the noise. The sensor itself generates a differential signal in response to very small pressures on the blade, since the blade away from the cantilevered mount naturally deflects more than the blade closest to the mount. The capacitance can be approximated as epsilon a/D, where epsilon is the dielectric constant of the material (vacuum) in the capacitive gap, a is the area of the rectangular electrodes, and D is the separation distance between the baffle and each electrode. Thus, the capacitance change of the farther electrode is greater than the capacitance of the closer electrode, and a difference signal proportional to the pressure change is generated. The difference signal may be isolated from common mode noise using the techniques described above.

In operation, the baffle responds to a pressure differential in either direction (i.e., from high to low on either side of the baffle). Thus, the sensor may be mounted in any orientation with respect to the two chambers or regions in question. However, it may be advantageous to orient the sensor with the high voltage on the exposed side of the baffle (i.e., away from the electrodes). This is because the entire blade-like area is then exposed to the pressure to be measured, without being restricted to the gas flow around the electrodes, etc. Furthermore, in transient conditions with very high pressures (e.g., outside the measurement range), such an oriented baffle will simply "bottom out" when the baffle hits the electrode. Little or no damage is present. Although the capacitor is expected to be shorted in this case, the small AC signal is also shorted and the circuit is configured to detect the short and display an error. When the low pressure is on the exposed side of the flapper (i.e., the sensor faces the other direction), the sudden pressure applied to the back side of the flapper can deflect it beyond its breaking point.

As described above, the pressure gauge 10 and system 110 may operate in harsh environments, including those that typically cause solids to condense onto the sensor. In some cases, such as in the presence of selenium or other condensing compounds, a heat source 130 (e.g., a heater or cartridge heater) (see fig. 3) may be incorporated or added to the system to heat the various components that are subject to selenium condensation. For example, a cartridge heater may be inserted into a hole somewhere in the sensor body, or a heating device may be incorporated into the cover. Heat source 130 may include any suitable heating device or mechanism configured to raise the temperature of exposed components of the pressure gauge. In some examples, an integral heating element is included, for example, in a housing of the pressure gauge. In some examples, the integrated heating element may be configured to raise the temperature of the pressure gauge above ambient temperature.

Based on the foregoing description and taken together, other aspects and features of the capacitance manometer and related systems are set forth in the following series of paragraphs, which are designated by alphanumeric form, for clarity and efficiency reasons, and not by way of limitation. Each of these paragraphs may be combined with one or more other paragraphs in any suitable manner, and/or with the disclosure of other sections of this application. Some of the following paragraphs explicitly refer to and further limit other paragraphs, providing examples of some suitable combinations, but not by way of limitation.

A0. A capacitance manometer (e.g., manometer 10) comprising:

a flexible conductive baffle (e.g., baffle 70) including an extension (e.g., extension 98) fixed at a proximal end and free at a distal end, the extension having a first face and a second face; and

a first electrode and a second electrode, the first electrode being spaced apart from the second electrode (e.g., electrode blocks 72, 74) adjacent the second face of the baffle;

wherein the first electrode is closer to the proximal end of the baffle than the second electrode; and is

Wherein the proximal end of the baffle is fixed relative to the first and second electrodes such that the flared portion is configured to bend toward and away from the first and second electrodes by an amount corresponding to a pressure differential across the first and second faces of the baffle.

A1. The capacitance manometer of a0, further comprising:

a time-varying (e.g., alternating current) voltage source coupled to the baffle such that the baffle in combination with the first electrode forms a first capacitor (e.g., CAP1) and in combination with the second electrode forms a second capacitor (e.g., CAP 2); and

a circuit (e.g., circuit 112) configured to receive a first current measured on the first electrode and a second current measured on the second electrode and convert a difference between the first current and the second current into a measure of a pressure differential across the first face and the second face of the baffle.

A2. The capacitance manometer of a1, wherein for a given extension bend amplitude, the second capacitance of the second capacitor varies by a greater amount than the first capacitance of the first capacitor.

A3. The capacitance manometer of any of paragraphs a 0-a 2, further comprising:

a tab extending from a proximal end of the baffle; and

a fastener that secures the tab of the baffle such that the proximal end of the baffle is fixed relative to the first and second electrodes and the distal end of the baffle is free to move toward and away from the first and second electrodes.

A4. The capacitance manometer of any of paragraphs a 0-A3, wherein the baffle comprises graphite.

A5a. the capacitance manometer of a4, wherein the baffle consists essentially of graphite.

A5b. the capacitance manometer of a4, wherein the baffle consists of graphite.

A6. The capacitance manometer of any of paragraphs a 0-A5B, wherein the first and second electrodes are housed in a graphite block (e.g., the body 32) and the proximal end of the baffle is clamped to the block.

A7. The capacitance manometer of a6, wherein the proximal end of the baffle includes an extension (e.g., tab 96), and the extension is clamped to the housing between a pair of insulating plates (e.g., plates 100).

A8. The capacitance manometer of a6, further comprising a plurality of insulating separators (e.g., separators 76, 78, 80, 82) electrically isolating the first and second electrodes from each other and from the graphite block.

A9. The capacitance manometer of A8, wherein each insulating separator comprises a ceramic tube having an open end adjacent the second face of the baffle.

A10. The capacitance manometer of a6, wherein the first and second electrodes are housed in open compartments through the block.

A11. The capacitance manometer of any of paragraphs a 0-a 10, wherein the first and second electrodes have respective ends (e.g., faces 92, 94) adjacent the baffle, and the respective ends are coplanar.

B0. A system for measuring a vacuum differential pressure, the system comprising:

a capacitance manometer comprising first and second electrodes adjacent to a flexible conductive baffle fixed at a proximal end and free at a distal end such that the distal end of the baffle is configured to bend toward and away from the first and second electrodes with a magnitude of the bend corresponding to a pressure differential across the baffle;

a time-varying voltage source coupled to the baffle such that the baffle in combination with the first electrode forms a first capacitor and in combination with the second electrode forms a second capacitor; and

a measurement circuit configured to receive a first current measured on the first electrode and a second current measured on the second electrode and convert a difference between the first current and the second current into a measurement of a differential pressure across the first face and the second face of the baffle.

B1. The system of B0, wherein the measurement circuit comprises a solid state circuit.

B2. The system of any of paragraphs B0-B1, wherein the measurement circuit comprises processing logic configured to convert a difference signal corresponding to a difference between the first current and the second current into a differential pressure measurement.

B3. The system of any of paragraphs B0-B2, further comprising:

a tab extending from a proximal end of the baffle; and

a fastener that secures the tab of the baffle such that the proximal end of the baffle is fixed relative to the first electrode and the second electrode.

B4. The system of any of paragraphs B0-B3, wherein the baffle comprises graphite.

B5. The system of B4, wherein the baffle is comprised of graphite.

B6. The system of any of paragraphs B0 to B5, wherein the first and second electrodes are housed in a graphite block and the proximal end of the baffle is clamped to the graphite block.

B7. The system of B6, wherein the proximal end of the baffle includes an extension, and the extension is clamped to the housing between a pair of insulation plates.

B8. The system of B6, further comprising a plurality of insulating separators electrically isolating the first and second electrodes from each other and from the graphite block.

B9. The system of B8, wherein each insulating separator comprises a ceramic tube having an open end adjacent the second face of the baffle.

B10. The system of B6, wherein the first electrode and the second electrode are housed in an open compartment through the block.

B11. The system of any of paragraphs B0-B10, wherein each of the first and second electrodes has a respective end adjacent the baffle, and the respective ends are coplanar.

In summary, the pivoting, bending or buckling of the baffle is caused by a pressure differential across the baffle, and this displacement results in a change in the capacitance of the two capacitors formed by the baffle and the pair of electrodes. The variation in the two capacitors is not the same because the gap between the baffle and each capacitor varies differently as the baffle moves. This is due to one of the capacitors being closer to the (free) distal end of the baffle, which will move a larger amount than the (fixed) proximal end. This difference in capacitance change can be measured by applying a time-varying voltage to the baffle and measuring the resulting current at each electrode. The difference between the currents is proportional to the difference in capacitance, which is proportional to the deflection of the baffle, which is proportional to the difference in pressure. Accordingly, any suitable electronics and/or software may be used to calculate the pressure differential. The use of graphite (or the like) to construct the housing and the baffle for the capacitance manometer facilitates proper operation in high temperature and highly corrosive environments. Heating the device prevents condensation of solids (e.g., selenium).

B. Exemplary method

This section describes the steps of an exemplary method 200 for measuring differential pressure (e.g., between two compartments) in a high temperature or other harsh environment, see fig. 9. Aspects of the differential capacitance manometer described above may be used in the method steps described below. Where appropriate, reference may be made to components and systems which may be used to perform each step. These references are for illustration only and are not intended to limit the possible ways of performing any particular step of the method.

Fig. 9 is a flow diagram illustrating steps performed in an exemplary method, and may not describe a complete process or all of the steps of the method. Although various steps of method 200 are described below and depicted in fig. 9, the steps do not necessarily all have to be performed, and in some cases may be performed simultaneously or in a different order than shown.

Step 202 comprises sensing a pressure differential (e.g., between a first compartment and a second compartment) by deflecting a baffle of the pressure gauge using a capacitance manometer of the present disclosure. As described above, the capacitance manometer includes a first electrode and a second electrode adjacent to the flexible conductive barrier. The baffle is fixed at the proximal end and free at the distal end such that the distal end of the baffle is configured to bend toward and away from the first and second electrodes. The magnitude of the bending corresponds to the pressure difference.

In some examples, the capacitance manometer has a tab extending from a proximal end of the baffle. The fastener is configured to secure the tab of the baffle such that the proximal end of the baffle is fixed relative to the first electrode and the second electrode. In some examples, the method 200 further includes housing the first and second electrodes in a graphite block and clamping the proximal end of the baffle to the graphite block. For example, the proximal end of the baffle may include an extension, and the extension may be clamped to the graphite block between a pair of insulator plates.

In some examples, the baffle comprises graphite. In some examples, the baffle is made entirely of graphite or consists essentially of graphite. Each of the first and second electrodes may have a respective end adjacent the baffle, and the respective ends are coplanar. In some examples, the pressure gauge further includes a plurality of insulating separators that electrically isolate the first and second electrodes from each other and from the graphite block. The separating members may be ceramic tubes, each ceramic tube having an open end adjacent the baffle. The first and second electrodes may be housed in open compartments through the block.

Step 204 includes generating a first current in the first electrode and a second current in the second electrode by applying a time-varying voltage source to a baffle of the capacitance manometer. For example, an Alternating Current (AC) voltage may be applied to the tabs or other portions of the baffle, e.g., via foil contacts sandwiched by the ceramic plates and the tabs. The baffle combines with the first electrode to form a first capacitor and combines with the second electrode to form a second capacitor. See, for example, CAP1 and CAP2 in fig. 8.

Step 206 includes converting the difference between the first current and the second current to a measure of the differential pressure. In some examples, this may be performed by solid state electronic circuitry and/or processing logic configured to receive the first current and the second current (signals corresponding to those currents). The circuitry and/or logic may also be configured to filter, amplify, and determine a difference between the two signals. The circuitry and/or logic may also be configured to calculate a differential pressure corresponding to the difference. In some examples, the reference pressure of one of the compartments being measured is known so that the differential pressure can be converted to an absolute pressure of the other compartment.

The method 200 may also include preventing condensation (e.g., selenium condensation) on the capacitance manometer by heating the device. This may include heating the housing of the device, for example by inserting a heating element into a cavity of the manometer housing.

Advantages, features and benefits

The various embodiments and examples of capacitance manometers described herein provide numerous advantages over known solutions. For example, the exemplary embodiments and examples described herein allow for pressure measurements at temperatures up to 1000 ℃ or higher, e.g., due to their graphite construction.

Additionally, the exemplary embodiments and examples described herein are constructed using graphite that is mechanically and chemically stable, resistant to high temperatures, not subject to internal stresses that cause deformation upon temperature exposure, has high yield stress at high temperatures, and has a good elastic modulus, among other benefits. These features allow the disclosed differential pressure gauge to operate under harsh, corrosive, and high temperature conditions.

Additionally, the exemplary embodiments and examples described herein provide, among other benefits, reproducible bending behavior in response to pressure changes.

Additionally, the exemplary embodiments and examples described herein prevent or reduce condensation (e.g., selenium) by actively heating the device, among other benefits.

There are no known systems or devices that can perform these functions, particularly in high temperature and/or corrosive environments. However, all embodiments and examples described herein may not provide the same advantages or the same degree of advantages.

Conclusion

The disclosure set forth above may encompass a number of different examples having independent utility. While each of these examples has been disclosed in its preferred form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. As to the section headings used in this disclosure, these headings are for organizational purposes only. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various elements, features, functions, and/or properties disclosed herein. The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. Other combinations and subcombinations of features, functions, elements, and/or properties may be claimed in applications claiming priority from this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.