Vacuum Gauge Assembly with Directional Sensor

Abstract

The present disclosure relates to a vacuum gauge assembly 100 for measuring gas pressure in a vacuum system. The assembly includes a pressure sensing element 130, a directional sensor 160 capable of determining a direction of the pressure sensing element 130, and a microcontroller 155 configured to determine the gas pressure using data received from both the pressure sensing element 130 and the directional sensor 160. The present disclosure also relates to an associated method of correcting the gas pressure output value in the vacuum gauge assembly 100.

Description

[Technical field]

[0001] The present disclosure relates to a vacuum gauge assembly, a vacuum gauge including the assembly, and a method for correcting a gas pressure output value of the assembly. [Background technology]

[0002] Typically, a vacuum gauge is used to measure the pressure within a vacuum system. 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 system has a low enough vacuum pressure, this can be used to indicate and detect leaks or defects in the system and / or allow feedback to assist in the control of the vacuum pump that evacuates the system.

[0003] Typically, gauges use a pressure-sensing element that detects changes in the thermal or electrical properties of the gas within the gauge and can correlate this to the gas pressure.

[0004] One type of gauge used for this purpose is a thermal conductivity gauge.

[0005] Heat conduction gauges use the thermal conductivity of gases for pressure measurement purposes and are also known as heat loss gauges. In general, these gauges use the relationship between the thermal conductivity of gases and pressure to make pressure measurements.

[0006] One such thermal conductivity gauge is the Pirani gauge.

[0007] In a Pirani gauge, the pressure-sensing element is in the form of a heating element (usually a filament or wire) that is placed in contact with the working gas of the vacuum system and is further connected to an electrical circuit so that it can be heated using electrical energy. When gas molecules collide with the heating element, they will transfer (conduct) heat away from the heating element. The higher the gas pressure, the more molecules will collide with the heating element, which will transfer more heat away from the heating element (i.e. the gas has a higher thermal conductivity).

[0008] If a heating element is held at a constant current or voltage, any change in the amount of heat conducted from the heating element due to a change in gas pressure will cause a proportional change in the temperature (and therefore resistance) of the heating element. By measuring this change in resistance, one can measure the change in pressure of the gas. Alternatively, one can hold the heating element at a constant temperature (and therefore resistance) and measure the change in voltage required to maintain this constant temperature as a function of gas pressure.

[0009] In this way, the gas pressure is measured as a function of its thermal conductivity.

[0010] As will be appreciated by those skilled in the art, a common way to implement this in a Pirani gauge is to include a heating element as an arm of a Wheatstone bridge circuit.

[0011] Typically, a Pirani gauge measures vacuum pressure (e.g., about 10 -4 mbar-10 -3 mbar) and atmospheric pressure (e.g., about 10 3 The gauge is designed to operate between 100 and 2000 mbar. Unfortunately, at relatively high gauge pressures, for example between 100 mbar and atmospheric pressure, the accuracy of the gauge can be adversely affected by convection effects. Specifically, the heating element generates convective currents that can heat the gas therein and rise within the gauge. This causes cooler gas within the gauge to be drawn onto the heating element, which will adversely affect its temperature / resistance or the amount of voltage required to keep it at a constant temperature.

[0012] This convection effect therefore causes deviations from the expected gas pressure vs. thermal conductivity correlation for the gauge, resulting in inconsistencies and errors in the pressure output from the gauge.

[0013] Furthermore, the extent to which this convection effect affects the gauge depends on the orientation of the heating element within the gauge.

[0014] Although this specification generally illustrates a Pirani gauge assembly, it should be understood that any other suitable type of thermal conductivity gauge assembly (in which a heating element is used and a temperature compensation element is required) may also benefit from the present disclosure and is within its scope as appropriate. Such other thermal conductivity gauges may include, for example, a thermistor gauge assembly or a thermocouple gauge assembly.

[0015] Additionally, other types of vacuum gauges, such as capacitance diaphragm gauges, may also benefit from the present disclosure.

[0016] Such gauges typically determine gas pressure by measuring the relative capacitance in a gap between a plate and a movable diaphragm (the pressure-sensing element).

[0017] The position of the diaphragm relative to the plate can be adversely affected by the orientation of the gauge. For example, the diaphragm can flex under the influence of gravity and move towards or away from the plate to varying degrees depending on the orientation. This can introduce inaccuracies and errors in the measurement of capacitance for a particular gas pressure, similar to the convection effects discussed above in thermal conduction gauges. Summary of the Invention [Problem to be solved by the invention]

[0018] Thus, there is a general need to take into account the orientation of the pressure-sensing element within the gauge and to provide appropriate corrections to the gauge pressure output accordingly. [Means for solving the problem]

[0019] From one aspect, the present disclosure provides a vacuum gauge assembly according to claim 1.

[0020] It has been found that the pressure output accuracy of a vacuum gauge assembly can be adversely affected by the orientation of the pressure sensing element. By using a directional sensor to detect the orientation of the pressure sensing element and using this data when measuring the gas pressure, the true gas pressure within the vacuum gauge assembly can be more accurately determined.

[0021] In one embodiment of the above aspect, the microcontroller is configured to use the data received from the directional sensor to determine a correction to apply to the data received from the pressure sensing element and to apply the correction to the data received from the pressure sensing element to determine the gas pressure.

[0022] This allows the gas pressure value output by the vacuum gauge assembly to be corrected depending on whether a particular direction is detected, in one example, the correction takes the form of a correction factor applied to the pressure output value.

[0023] In a further embodiment of any of the above, the microcontroller is configured to normalize the data received from the pressure sensing element and apply a correction in the form of a correction factor to the normalized data.

[0024] In a further embodiment of the above, the microcontroller comprises a memory and a processor in electrical communication with the memory, the memory storing a look-up table of reference data and correction factors and instructing the processor to normalize data received from the pressure sensing element before applying the transfer function and the correction factors.

[0025] Normalizing the data allows the output pressure values ​​of the gauge assembly to be more accurately corrected to account for minor variations in the design of the same gauge assembly (such as accidental manufacturing / construction differences, contamination, external environmental differences, etc.) Applying a correction factor to the normalized data helps improve the accuracy of the gauge as it reduces the impact of undesirable directional effects on the gauge's normalized output data.

[0026] In a further embodiment of any of the above, the direction sensor is configured to determine whether the pressure sensing element is in one of a first direction or a second direction. The microcontroller is configured to store a correction factor according to the second direction and selectively apply the correction factor depending on whether the first direction or the second direction is determined by the direction sensor. In one example, the first direction corresponds to a vertical direction of the pressure sensing element and the second direction corresponds to a horizontal direction of the pressure sensing element. In another example, the first direction corresponds to a horizontal direction of the pressure sensing element and the second direction corresponds to a vertical direction of the pressure sensing element.

[0027] This allows a correction factor to be applied according to the different orientation of the pressure sensing element being detected compared to the orientation that is expected or was originally calibrated to when the gauge was manufactured.

[0028] In a further embodiment of any of the above, the correction factor is an average of multiple correction factors determined for different orientations of the pressure sensing element. In one example, the different orientations may be different horizontal orientations.

[0029] This provides a relatively simple method of calculating and applying correction factors that improve gauge output accuracy across multiple pressure sensing element orientations.

[0030] In any of the above alternative embodiments, the direction sensor is further configured to determine whether the pressure sensing element is in one of a third or fourth direction. The microcontroller is further configured to store first, second and third correction factors according to the second, third and fourth directions, respectively, and selectively apply the first, second or third correction factor, respectively, according to whether the first, second, third or fourth direction is determined by the direction sensor. In one example, the first direction is a vertical direction of the pressure sensing element, and the second, third and fourth directions are different horizontal directions of the pressure sensing element.

[0031] By storing and applying different correction factors for each different direction during detection, a more complete treatment of the gauge output error from each direction can be provided, thereby further improving the accuracy of the gauge assembly output data.

[0032] In a further embodiment of any of the above, the pressure sensing element is a heating element for a Pirani gauge.

[0033] In another aspect, the present disclosure provides a vacuum gauge including an assembly of any of the above aspects or any embodiment thereof.

[0034] In one embodiment, the vacuum gauge is a Pirani gauge.

[0035] In another aspect, the present disclosure provides a method for correcting a gas pressure output value in a vacuum gauge assembly according to claim 11.

[0036] By receiving and using directional data in determining the gas pressure, a more accurate determination of the gas pressure may be made.

[0037] In one embodiment of the above aspect, the method further includes determining a correction to apply to the data received from the pressure sensing element based on the data received from the direction sensor, and applying the correction to the data received from the pressure sensing element in response to the data received from the direction sensor.

[0038] In a further embodiment of any of the above, the data received from the direction sensor determines whether the pressure sensing element is in one of a first direction or a second direction, and the method further includes selectively applying a correction to the data received from the pressure sensing element according to whether the first direction or the second direction is determined by the data from the direction sensor.

[0039] These embodiments allow the gas pressure value output by the vacuum gauge assembly to be corrected depending on whether a particular direction is detected or not.

[0040] In a further embodiment of any of the above, the method further comprises normalizing the data received from the pressure sensing element and applying the transfer function using a look-up table of reference data prior to applying the correction, the correction being applied to the normalized data in the form of a correction factor.

[0041] Applying a correction factor to the normalized data helps to improve the accuracy of the gauge since it can reduce the impact of undesirable directional effects on the normalized output data of the gauge.

[0042] In a further embodiment of any of the above, the method is performed using a microcontroller.

[0043] The microcontroller includes a memory and a processor for storing the data and instructions necessary to apply a correction and / or normalization process to the gas pressure output data of the vacuum gauge assembly.

[0044] In an embodiment, the method utilises a vacuum gauge assembly including features of the assembly of any of the above aspects or embodiments thereof.

[0045] Although certain advantages have been 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.

[0046] One or more non-limiting embodiments will now be described, by way of example only, with reference to the accompanying drawings. [Brief description of the drawings]

[0047] [Figure 1] 1 illustrates an exterior isometric view of a vacuum gauge assembly according to one embodiment of the present disclosure. [Diagram 2] 2 shows a cross section of the assembly of FIG. 1 taken along line AA. [Figure 3A] 3 shows a pressure sensing element according to the embodiment of FIGS. 1 and 2 in a vertical orientation. [Figure 3B] The pressure-sensing element of the embodiment of Figures 1 and 2 is shown in a first horizontal orientation. [Figure 3C] 3 shows the pressure sensing element of the embodiment of FIGS. 1 and 2 in a second horizontal orientation. [Figure 3D] 1 and 2 in a third horizontal orientation. [Figure 4] 5A-5D show exemplary graphs of raw input voltage and pressure output values ​​for embodiments of a vacuum gauge having a pressure sensing element assembled in different orientations according to FIGS. 3A-3D. [Diagram 5] 5 shows an exemplary graph in which the raw data values ​​from FIG. 4 have been normalized according to a transfer function based on a lookup table of reference data at those data values. [Figure 6] 3B-3D show exemplary graphs of percentage error of normalized pressure output values ​​compared to true pressure values ​​for vacuum gauge embodiments according to the orientation of FIGS. [Figure 7] 7 shows an exemplary graph of correction factors calculated for embodiments of a vacuum gauge according to the orientations of FIGS. 3B-3D according to the percentage error shown in FIG. 6, and further includes a plot of the average correction factor. [Figure 8] 8 illustrates the effect on the percentage error in the gauge output data when the average correction factor of FIG. 7 is applied to normalized output data from a gauge having a direction BD. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] 1, there is shown a vacuum gauge assembly 100. The assembly 100 is a thermal conduction vacuum gauge and includes a body 110 having a sidewall 112 extending axially along a longitudinal axis X between a base 114 and a top 116.

[0049] In the illustrated embodiment, the body 110 is generally annular, but includes a chamfered section 111 about a portion of its circumference, which can aid in mounting the assembly with other components of the thermal conductivity gauge, such as a housing or cover (not shown), as described below.

[0050] Although a particular shape of body 110 is shown, it should be understood that any other suitable shape of body 110 may be used within the scope of the present disclosure (eg, square or rectangular cross-section).

[0051] The base 114 includes a flange 115 that extends radially from the base 114 about the longitudinal axis X. In one example, the flange 115 is a NW25 specification, although any suitable size and shape flange may be used within the scope of the present disclosure.

[0052] The top portion 116 includes an end cap 118 through which protrudes and is secured to the end cap 118 (described below with reference to FIG. 2) with support features 136 for the electrical connector 132 and the pressure sensing element 130 .

[0053] An end cap 118 is secured within an opening 117 defined in the top portion 116 .

[0054] In some embodiments, the end cap 118 can be fixedly attached to the top 116, for example, by welding or press-fitting into the opening 117. In other embodiments, the end cap 118 can be removably secured to the top 116 by threaded engagement. Such a removable fastening method can facilitate repair and replacement of the heating element 130 and the connections and support features. In yet another embodiment, the end cap 118 can be omitted and the wall 122 of the body 110 can extend radially across the top 116 without the opening 117 therein. In such an embodiment, the connections and support features can extend through the wall 122 of the top 116 itself.

[0055] 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, illustrating the internal structure and components within body 110, as described below.

[0056] The body 110 defines an internal chamber 120 that is configured to receive a working or process gas (e.g., from a vacuum system) during use of the assembly 100. By "working or process gas" is meant the gas or gases for which the assembly seeks to measure the pressure. A "working gas" is typically the gas or gases that are "worked" (i.e., pumped) by the vacuum system. The pressure of this gas can provide an indication of the general vacuum pressure in the system.

[0057] In the illustrated example, the body 110 is generally tubular, sometimes known as a “body tube.” Accordingly, the interior chamber 120 is generally cylindrical about a longitudinal axis X within the body 110.

[0058] Body 110 is defined or formed by 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 conformity with the depicted 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) interior chamber 120.

[0059] The body 110 can be made of any suitable material, such as stainless steel or aluminum alloy, or a plastic material (if the operating conditions and temperature permit), and can be made by any suitable manufacturing method, such as molding / casting, machining from a solid block, 3D printing, etc.

[0060] The base 114 defines an inlet passage 124 for the interior chamber 120 .

[0061] An inlet passage 124 extends axially from the base 114 and 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.

[0062] The filtration element 126 is disposed across the inlet passage 124 to filter the working gas before it enters the chamber 120. The filtration element 126 passes across the inlet passage 124 in a radial direction relative to the longitudinal axis X. The filtration element 126 is used to ensure that contaminants do not enter the chamber 120. Such contaminants may damage the assembly 100 (e.g., by corroding or depositing on the heating element 130, the wall surface 122b, or electrical connections within the chamber 120) and / or may interfere with the pressure measurement process, causing inaccuracies therein. In one embodiment, the filtration element 126 is stainless steel (e.g., 316L) 30-2 mesh, although any other suitable type (e.g., membrane), material, and specification of the filtration element 126 may be used within the scope of the present disclosure.

[0063] The flange 115 of the base 114 includes a recess or groove 128 defined therein. The recess 128 is annular about the longitudinal axis X and allows an O-ring seal to be seated therein. This can provide a better seal between the assembly 100 and a vacuum system during use, and can be further secured in place on the base 114 via the flange 115.

[0064] In the illustrated embodiment, which is a thermal conductivity vacuum gauge, the pressure sensing element 130 is a heating element 130 disposed within the chamber 120. In the illustrated example, the heating element 130 extends generally axially into the chamber 120 from the top 116 toward the base 114.

[0065] 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. In particular, platinum may be used in vacuum system environments or applications known to contain more corrosive chemicals and / or working gases.

[0066] 3A-3D, electrical connectors or pins 132a, 132b, 132c protrude through and are secured to the end cap 118. The heating elements 130 are connected to particular electrical connectors 132a, 132b, 132c to enable electrical communication for control of the heating elements 130.

[0067] In the illustrated example, connectors 132a, 132c are connected to two opposite ends of the heating assembly 130, while connector 132b is used for grounding purposes.

[0068] The connectors 132a, 132b, 132c are then connected to electrical control circuitry (not shown) within an electronics module 150 (described in more detail below) which can provide power for heating and controlling the heating assembly 130 when the assembly 100 is in use.

[0069] The heating element 130 may be connected to the connectors 132a, 132c in any suitable manner, for example by wrapping it around the base of the connector or by welding or soldering thereto.

[0070] The heating element 130 is supported within the chamber 120 by a support structure. In the illustrated example, the support structure is in the form of a spring arm 134 and a spring bar 136.

[0071] The bar 136 protrudes through and is secured to the end cap 118. The bar 136 extends axially within the chamber 120 from the top 116 toward the base 114, substantially parallel to the heating element 130. In the illustrated embodiment, the bar 136 is a cylindrical rod.

[0072] A spring arm 134 is fixed 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 .

[0073] 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 keeps the heating element 130 anchored and supported between the connectors 132a, 132c during use.

[0074] As can be appreciated, in the illustrated embodiment, the heating assembly 130, when hung between the connectors 132a, 132c via the hooks 135, provides a substantially V- or U-shape.

[0075] Although one particular arrangement of heating elements 130, electrical connectors 132a, 132b, 132c, and their support structures is shown, it should be understood that any other suitable arrangement 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.

[0076] In the illustrated embodiment, the electronics module 150 is mounted to the end cap 118 and receives the electrical connectors 132a, 132b, 132c and support features 136 of the pressure sensing element 130. The electronics module 150 may be attached to the end cap 118 in any suitable removable or non-removable manner, for example, using fasteners, threaded engagement, or adhesive.

[0077] The electronics module 150 is shown in very schematic form and may have any suitable shape and be mounted in any other suitable location on the vacuum gauge 100 .

[0078] The electronic module 150 is a housing that contains a microcontroller 155 and other typical electronic circuitry and computing elements (not shown) in electrical communication with the electrical connectors 132a, 132b, 132c, which are configured to control the heating of the pressure sensing element 130 and calculate the resulting pressure output value.

[0079] The pressure sensing element 130 and the electronics module 150 (including the microcontroller 155 and associated circuitry and computing elements) may be powered in any suitable manner.

[0080] For example, they may be connectable to an external power source via an interface connector (not shown) (e.g. a D-sub, RJ45 or USB connector) provided through the body 110. The external power source may be a mains supply, or the vacuum gauge 100 may be connected to receive power from a wider vacuum system (e.g. a vacuum pump) whose pressure it is measuring.

[0081] In another example, alternatively / additionally, the vacuum gauge 100 can include an internal power source, such as a battery (not shown). The battery can be removable and replaceable from the body 110, and can be a rechargeable battery, such as a lithium-ion battery.

[0082] The vacuum gauge 100 also includes a direction sensor 160 (shown only diagrammatically in FIG. 2) in electrical communication with the microcontroller 155 .

[0083] The directional sensor 160 is configured to output a data signal to the microcontroller 155 that is indicative of a particular orientation of the pressure sensing element 130. As will be described in more detail below, this enables the microcontroller 155 to take the orientation of the pressure sensing element 130 into account when calculating a pressure output value from the pressure sensing element 130.

[0084] Although the direction sensor 160 is shown diagrammatically as being included within the electronics module 150 of the vacuum gauge 100, the scope of this disclosure is not limited to such an arrangement.

[0085] For example, the directional sensor 160 may be located somewhere else within the vacuum gauge 100 that can effectively recognize the relative orientation of the pressure sensing element 130 (i.e., distinguish between various orientations of the pressure sensing element 130) and communicate with the microcontroller 155.

[0086] In one such example, the direction sensor 160 may be fixed to the pressure element 130. In another such example, the direction sensor 160 may be fixed to or integrated into the body 110 of the vacuum gauge 100.

[0087] The directional sensor 160 can be any sensor or combination of sensors capable of providing a signal indicative of the orientation of the various pressure-sensing elements. For example, the directional sensor 160 can be one or a combination of an accelerometer, a gyroscope, a magnetometer, and a tilt switch.

[0088] 3A-3D show various possible orientations of the pressure sensing element 130 that have been found to cause fluctuations in the pressure output from the gauge 100 (i.e., due to convection effects at higher gauge pressures (100 mbar to 1,000 mbar)).

[0089] In FIG. 3A, the pressure sensing elements 130 are vertically aligned.

[0090] In FIG. 3B, the pressure sensing element 130 is aligned horizontally, while the V-shaped filament is aligned in the vertical plane (ie, vertically aligned with the support bar 136).

[0091] In FIG. 3C, the pressure sensing element 130 is aligned horizontally, while the V-shaped filament is aligned downward in the horizontal plane (i.e., vertically below the support bar 136).

[0092] In FIG. 3D, the pressure sensing element 130 is aligned horizontally, while the V-shaped filament is aligned upward in the horizontal plane (i.e., vertically above the support bar 136).

[0093] Although not shown in Figures 3A-3D for clarity, it should be understood that in use, the pressure sensing element 130 will be surrounded by the remaining vacuum gauge components (e.g., vacuum gauge body 110, end cap 118, electronics module 150, and sensor 160) as shown in Figures 1 and 2.

[0094] As one skilled in the art can appreciate, to accommodate different vacuum pump designs and spatial arrangements, the vacuum gauge 100 and pressure sensing element 130 may need to be positioned in different orientations, and therefore a vacuum gauge 100 that can account for these (or more) different orientations would be advantageous.

[0095] 4 is a graph showing the variation in vacuum gauge output seen from the pressure sensing element 130 when the pressure sensing element 130 is used in different orientations according to Figures 3A-3D. The graphs are schematic and for illustrative purposes only.

[0096] The lines of each gauge output are labeled AD according to the respective orientation of the pressure sensing element 130 shown in Figures 3A-3D. Direction A=pressure sensing element 130 is vertically aligned. Orientation B=pressure sensing element 130 is aligned horizontally in a vertical plane. Orientation C=pressure sensing element 130 is aligned horizontally facing downward in a horizontal plane. Orientation D = pressure sensing element 130 aligned horizontally facing upwards in a horizontal plane.

[0097] In the illustrated example, the pressure sensing element 130 is a heating element that operates to maintain a constant temperature.

[0098] Thus, the X-axis represents the pressure indicated by the vacuum gauge 100, and the Y-axis represents the relative voltage required to maintain the heating element at a constant temperature for that pressure output value.

[0099] Particular values ​​of P are specified in mbar along the x-axis and particular values ​​of V are specified in volts along the y-axis of a particular exemplary vacuum gauge 100 that will be used to provide a better understanding of the present invention.

[0100] It should be understood that within the scope of this disclosure, the vacuum gauge 100 may operate at higher or lower ranges of pressure output values ​​that may correlate with different voltage values ​​than those shown. Indeed, different vacuum gauge implementations, applications, and control circuits will exhibit different voltage vs. pressure output value characteristics (e.g., due to lower / higher inherent electrical resistances).

[0101] As shown in FIG. 4, the majority of the operating range of the vacuum gauge 100 (i.e., 10 -4 mbar to 10 2 At 10 mbar, the applied voltage and the corresponding pressure output value are substantially the same in the direction AD of the different pressure sensing elements 130. However, at higher pressures (i.e., 10 2 mbar to 10 3 It can be seen that in mbar), different directions AD result in variations in the voltage applied to the pressure sensing element 130 to result in the same pressure output value.

[0102] As discussed above, for the thermal conductivity gauge 100, this variation is caused by convection effects due to heating of the pressure sensing element 130. For example, some directions produce greater convection effects than other directions and therefore are likely to require more voltage to maintain the temperature of the pressure sensing element 130 for a particular output pressure value than other directions.

[0103] For example, as shown in FIG. 4, it has been found that the voltage output for a given pressure value in direction B is higher than the voltage output in direction C, which is higher than the voltage output in direction D, which is higher than the voltage output in direction A.

[0104] Unlike the illustrated embodiment, known gauges do not include a direction sensor 160 and a microcontroller 155 configured to account for the effect that the orientation of the pressure sensing element has on the gauge output data. Thus, known gauges are unable to determine the relative orientation of the pressure sensing element 130 and are unable to account for the variations in voltage and pressure output data due to different orientations of the pressure sensing element 130. In so doing, known gauges ignore the impact of convection effects and their relationship across different pressure sensing element 130 orientations. The illustrated embodiment addresses this issue.

[0105] As will be appreciated by those skilled in the art, known vacuum gauges 100 and microcontrollers 155 are programmed to allow the vacuum gauge 100 to account for variations in voltage vs. pressure output values ​​found in different instances of the same vacuum gauge design (e.g., due to slight manufacturing or construction variations in the pressure sensing element 130 / vacuum gauge 100, different degrees of contamination on the pressure sensing element 130 / vacuum gauge 100, and variations in the local environment (e.g., outside temperature)). To accomplish this, it is commonly known that the microcontroller 155 is configured to normalize the data received from the pressure sensing element 130 and apply a transfer function to provide a corrected pressure output value that accounts for these variations.

[0106] In an exemplary normalization process, the microcontroller 155 comprises a processor and a memory in communication therewith. The memory includes a look-up table of reference data values ​​and instructions that cause the processor to normalize the raw output data received from the pressure sensing element 130 according to preset offset and span adjustments (e.g., in the x-axis and y-axis output values) and perform a transfer function thereon according to a comparison with the reference data values. This process results in the microcontroller 155 shifting and remapping the raw output data values ​​to provide a more consistent and accurate set of output values ​​for the vacuum gauge.

[0107] This known normalization process fails to take into account the fluctuations in the gauge output values ​​due to the above-mentioned direction-dependent convection effects at high pressure values. Thus, the direction-dependent output data fluctuations shown in Figure 4 will result in deviations in the normalized output values, which leads to inaccuracies and inconsistencies in the gauge output.

[0108] FIG. 5 shows the results of performing such normalization processing on the output data results for different directions AD in FIG.

[0109] As shown in Figure 5, this result was obtained at relatively high pressure (~10 2 From ~10 3 mbar) (where convective effects are more pronounced), there is a large variation in the normalized power values ​​between the different directions A-D, as well as at low pressures (~10 -3 From ~10 2 mbar) also adversely affects the normalized output values ​​for each direction AD (although to a lesser extent). Therefore, it is also necessary to take the above-mentioned directional fluctuations into account after the normalization process.

[0110] In Fig. 6, the output data in the direction BD from Fig. 4 has been normalized according to reference data collected for a pressure sensing element 130 having a vertical direction A. The true pressure P true Compared to the vacuum gauge P indicated The percent error of the resulting normalized pressure output value, denoted by , is shown.

[0111] The percentage error is Percent error = 100 × ((P indicated -P true )) / P true It is calculated as follows.

[0112] The power variation in the horizontal direction BD compared to the vertical direction A results in a lower operating pressure (~10 -3 From ~10 2 At high operating pressures (~10 mbar), the vacuum gauge pressure output value has an error of about -5%. 1 From ~10 3It can be seen that the -% error increases at higher inputs (between 500 and 600 mbar) and peaks at around -55% error and around -75% error (between 500 and 600 mbar) depending on the particular direction BD.

[0113] It will thus be appreciated that if a user were to use such a gauge in a horizontal orientation (such as direction BD) rather than a vertical orientation (i.e., direction A), these errors would cause the gauge to give inaccurate pressure measurements. As noted above, a user may need to use such different orientations of pressure element 130 to suit the application and spatial requirements of a particular gauge.

[0114] To solve this problem, the present invention utilizes a correction factor CF that is applied to the normalized gauge output data when the direction sensor 160 indicates that the gauge 100 is in a different orientation than the orientation for which the reference data was taken and the normalization process was performed.

[0115] The correction factor CF is calculated before the vacuum gauge 100 is used according to the percentage error mentioned above, according to the following formula: CF=100 / ((Percentage Error + 100))

[0116] The calculated correction factor CF is stored in the memory of the microcontroller 155 and is used by the microcontroller 155 to correct the normalized output data P when the direction sensor 160 indicates that this is necessary. indicated applies to.

[0117] FIG. 7 shows examples of correction factors CF calculated for each of the different horizontal directions BD to take into account the different percentage errors that occur after the normalization of FIG.

[0118] As can be seen from FIG. 7, the correction factor CF is set to 0.01 for the primary intended operating pressure range of the gauge assembly where the percent error between the horizontal direction BD and the vertical direction A is relatively constant (~10 -3 From ~10 1The correction factor CF is relatively constant in the higher pressure range (~10 mbar), where convective effects and the directional variations caused by them become more prevalent. 1 From ~10 3 mbar) becomes more substantial and changes.

[0119] In one embodiment, as shown in FIG. 7, the normalization and lookup reference data is calculated according to a vertical direction A, and a single average correction factor CF corresponding to the average of the correction factors for each of three different horizontal directions BD is used. avg is calculated.

[0120] The correction factor CF is applied during use of the vacuum gauge 100 by the microcontroller 155 according to the following general formula: P true =P indicated ×CF

[0121] Figure 8 shows the average correction factor CF avg 4 shows the comparative reduction in percentage error found when applying to the gauge output data in each of the directions BD normalized according to direction A.

[0122] As is clear from FIG. 8, this correction factor CF avg By applying this, the percentage error in the pressure output value is approximately 10% over the operating range of the vacuum gauge 100, and in particular the primary operating pressure range of the vacuum gauge assembly. -3 From ~10 1 It decreases over the mbar range.

[0123] Although some error still exists, the results nevertheless provide a simple means of more accurately accounting for variations in convection effects on the normalized gauge output. For example, only one correction factor needs to be calculated and stored before using the gauge, and the orientation sensor 160 need only be able to distinguish between vertical and generally horizontal orientations in order to correctly apply the correction factor.

[0124] In another embodiment, the direction sensor 160 is configured to distinguish between different horizontal directions BD, and a separate correction factor CF for each direction BD is stored by the microcontroller 155. The separate correction factor CF for each direction BD can then be applied by the microcontroller 155 to the normalized gauge output data when a particular direction BD is detected and indicated by the direction sensor 160.

[0125] Although the present invention has been described with reference to vertical and horizontal orientations, it should be understood that within the scope of the present disclosure, the correction factor CF for any number of pressure sensing element 130 orientations (e.g., between vertical and horizontal) can be calculated, stored, and applied by the microcontroller 155 in the same manner, provided, of course, that the direction sensor 160 is configured to effectively distinguish between the different orientations.

[0126] As will be appreciated, such an embodiment may be implemented using the CF avg This may require the use of multiple / more sophisticated directional sensors, and the calculation, storage, and application of more reference data and correction factors C than the embodiments utilizing , however, these embodiments may provide a more "complete" treatment of the errors from each individual direction, thereby further improving the accuracy of the vacuum gauge output.

[0127] Furthermore, while in the described embodiment the normalization process is applied according to reference data for the vertical direction A, in other embodiments the normalization process can instead be applied according to reference data for some other direction (e.g., any of the horizontal directions BD) and the percentage error and correction coefficients can be calculated with reference thereto.

[0128] As noted above, it should be appreciated that the present disclosure may also be applied to other types of gauges (e.g., other than the illustrated Pirani or thermal conduction gauges) in which convection effects are not present / relevant, but in which the output pressure value may nevertheless be adversely affected by the orientation of the pressure sensing element therein.

[0129] It will be appreciated that in such alternative gauge applications it may not be necessary to apply the same normalization process and correction factors described above, but an appropriate correction can still be calculated and applied to the gauge output value depending on the direction detected by the direction sensor.

[0130] One such example is a capacitance diaphragm gauge (mentioned above), where the indicated gauge pressure output value generated depends on the spacing between the diaphragm and the plate: changing the orientation of the gauge changes the geometry of the diaphragm, which changes the spacing even though the pressure does not change, and this can result in inaccuracies in the pressure output value.

[0131] In applying the present disclosure to such an example, a correction to the pressure output value can be calculated and applied according to the change in spacing found for a particular orientation of the diaphragm. Once the directional sensor indicates a particular direction, the appropriate correction can be applied. Thus, the correction can take the form of a correction offset to the indicated output value, the magnitude of which depends on the amount of known or expected change in spacing for the particular orientation determined.

[0132] A list of symbols used in accompanying Figures 1 to 3 is provided below for ease of reference. [Explanation of symbols]

[0133] 100 Vacuum gauge assembly 110 Main unit 111 Chamfer Section 112 Side wall 114 Base 115 Flange 116 Top 117 (top 116) opening 118 End Cap 119 Marking Area 120 Inner Chamber 122 Wall 122a Outer wall 122b Inward facing wall 124 Entrance Passage 126 Filtration element 128 Recess (or groove) 130 Pressure Sensing Element (Heating Element / Filament) 132a Electrical connectors (or pins) 132b Electrical connectors (or pins) 132c Electrical Connector (or Pin) 134 Spring Arm 135 Hook 136 Bar 150 Electronic Module 155 Microcontrollers 160 Direction Sensor X Longitudinal Axis A cross-sectional line of sight

Claims

1. A vacuum gauge assembly for measuring the gas pressure within a vacuum system, comprising: a pressure sensing element; a direction sensor configured to determine the direction of the pressure sensing element; a microcontroller configured to determine the gas pressure using data received from both the pressure sensing element and the direction sensor; The vacuum gauge assembly comprising the above components.

2. The vacuum gauge assembly according to claim 1, wherein the microcontroller is configured to use data received from the direction sensor to determine a correction to be applied to the data received from the pressure sensing element, and to apply the correction to the data received from the pressure sensing element to determine the gas pressure.

3. The vacuum gauge assembly according to claim 2, wherein the microcontroller is configured to normalize the data received from the pressure sensing element and to apply the correction in the form of a correction factor to the normalized data.

4. The vacuum gauge assembly according to claim 3, wherein the microcontroller comprises a memory and a processor for electrical communication with the memory, the memory storing reference data and a look-up table of the correction factors, and the processor being instructed to normalize the data received from the pressure sensing element before applying the transfer function and the correction factor.

5. The vacuum gauge assembly according to claim 2, wherein the direction sensor is configured to determine whether the pressure sensing element is in one of a first direction or a second direction, the microcontroller storing a correction factor corresponding to the second direction and being configured to selectively apply the correction factor according to which of the first direction or the second direction is determined by the direction sensor.

6. The vacuum gauge assembly according to claim 5, wherein the first direction corresponds to a direction perpendicular to the pressure sensing element, the second direction corresponds to a direction horizontal to the pressure sensing element, or vice versa.

7. The vacuum gauge assembly according to claim 5, wherein the correction factor is an average of a plurality of correction factors determined for different directions of the pressure sensing element.

8. The direction sensor is further configured to determine whether the pressure sensing element is in one of a third or fourth direction, and the microcontroller stores first, second, and third correction factors respectively according to the second, third, and fourth directions, and is further configured to selectively apply the first, second, or third correction factor respectively according to whether any one of the first, second, third, or fourth directions is determined by the direction sensor. The vacuum gauge assembly according to claim 5.

9. The first direction is a direction perpendicular to the pressure sensing element, and the second, third, and fourth directions are different horizontal directions of the pressure sensing element. The vacuum gauge assembly according to claim 8.

10. The pressure sensing element is a heating element for a Pirani vacuum gauge. The vacuum gauge assembly according to any one of claims 1 to 9.

11. A method for correcting the gas pressure output value of a vacuum gauge assembly, comprising: receiving data indicating gas pressure from a pressure sensing element; receiving data indicating the direction of the pressure sensing element from a direction sensor; using the data received from both the pressure sensing element and the direction sensor to determine a corrected gas pressure output value; A method comprising.

12. determining a correction to be applied to the data received from the pressure sensing element based on the data received from the direction sensor; applying the correction to the data received from the pressure sensing element in response to the data received from the direction sensor; The method according to claim 11, further comprising.

13. The data received from the direction sensor determines whether the pressure sensing element is in one of a first direction or a second direction, and the method further comprises selectively applying the correction to the data received from the pressure sensing element according to the determination of either the first direction or the second direction by the data from the direction sensor. The method according to claim 11.

14. normalizing the data received from the pressure sensing element before applying the correction and applying a transfer function using a look-up table of reference data; applying a correction in the form of a correction factor to the normalized data; The method according to claim 11, further comprising.

15. The method is the method according to any one of claims 11 to 14, which is executed using a microcontroller.

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