Pressure sensor with improved drift compensation

Abstract

A disclosed example pressure sensor includes a first body defining a reference pressure chamber; a second body defining a test pressure chamber and having an inlet configured to receive a fluid; a diaphragm between the reference pressure chamber and the test pressure chamber; an electrode separated from the diaphragm by a gap to form a capacitance between the electrode and the diaphragm; measurement circuitry configured to determine a pressure in the test pressure chamber based on the capacitance; and a contaminant shield configured to reduce contaminant on the first face of the septum, the contaminant shield comprising: a first portion configured to obstruct a direct path between the inlet and the septum; and a second portion configured to occupy a volume within the test pressure chamber.

Description

[0001] Related Applications

[0002] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 618,635, filed on January 8, 2024, entitled "PRESSURE SENSORS HAVING IMPROVED DRIFT COMPENSATION". The entire content of U.S. Provisional Patent Application Serial No. 63 / 618,635 is hereby incorporated by reference in its entirety. Technical Field

[0003] The present disclosure generally relates to pressure sensors, and more particularly to pressure transducers having improved drift compensation. Background Art

[0004] A pressure sensor or pressure transducer measures the pressure of a fluid input to the sensor relative to a reference pressure. A pressure sensor can be configured to compare the input pressure to a fixed reference pressure or a variable reference pressure. Summary of the Invention

[0005] Disclosed are pressure sensors having improved drift compensation, substantially as shown by and described in connection with at least one of the figures, and more fully set forth in the claims. Brief Description of the Drawings

[0006] These and other features, aspects, and advantages of the present disclosure will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like reference numerals represent like parts throughout the drawings:

[0007] Figure 1A is a block diagram of an example process control system including a pressure transducer having a fixed reference pressure, according to aspects of the present disclosure.

[0008] Figure 1B is a block diagram of an example process control system including a pressure transducer coupled to a variable reference pressure source, according to aspects of the present disclosure.

[0009] Figure 2 is a schematic diagram of an example pressure sensor, according to aspects of the present disclosure, which can be used to implement Figure 1A and / or Figure 1B the pressure sensors of.

[0010] Figure 3 is a plot showing an example current drift rate calculation that can be implemented by the Figure 2 pressure sensors of.

[0011] Figure 4 is a flowchart showing example machine-readable instructions that can be executed by a Figure 2 pressure sensor to compensate pressure measurement results for sensor drift.

[0012] Figure 5A is Figure 2 a first perspective view of an example contaminant shield.

[0013] Figure 5B is Figure 2 a second perspective view of the example contaminant shield.

[0014] Figure 6 a schematic diagram of an example pressure sensor that can be used to implement the Figure 1A and / or Figure 1B pressure sensor, and wherein the second body is configured to reduce the wetting volume of the test pressure chamber.

[0015] Figure 7 is a schematic diagram of another example pressure sensor according to aspects of the present disclosure that can be used to implement the Figure 1A and / or Figure 1B pressure sensor.

[0016] Figure 8A and Figure 8B are other views of the example contaminant shield coupled to the pressure sensor. Figure 7 The drawings are not necessarily to scale. Where appropriate, like or identical reference numerals are used to indicate like or identical parts.

[0017] DETAILED DESCRIPTION In order to facilitate an understanding of the principles of the claimed technology and to present its currently understood best mode of operation, reference will now be made to the embodiments shown in the drawings and specific language will be used to describe these embodiments. However, it should be understood that this is not intended to limit the scope of the claimed technology, as any changes and further modifications of the apparatus shown and the further applications of the principles of the claimed technology shown herein are generally contemplated by those skilled in the art to which the claimed technology pertains.

[0018]

[0019] ​Over time, conventional pressure sensors are exposed to contaminants that can accumulate and cause the measured capacitance to change for the same input pressure. This change in the measured capacitance over time (due to particulate accumulation and / or other reasons) is referred to as "drift" of the pressure sensor. After sufficient time has elapsed, the drift can cause significant errors in the output of the pressure sensor such that the pressure sensor needs to be replaced. Drift is unpredictable for different devices and can be significantly affected depending on the application, making it impossible to reliably predict drift during manufacturing.

[0020] The disclosed example pressure sensors and methods reduce contamination on the diaphragm, thereby reducing drift in the pressure sensor. In some examples, the pressure sensor includes a contaminant blocker that reduces the amount of contaminants present in the test pressure chamber and increases the amount of contaminants captured or blocked before reaching the diaphragm. The disclosed example pressure sensors and methods provide enhanced contaminant blocking capabilities and reduce the wetting volume to extend the life of the pressure sensor.

[0021] The disclosed example pressure sensors and methods further compensate for drift occurring in the pressure sensor by measuring the drift rate over a period of time and using the determined drift rate to predict drift in subsequent time periods. In some examples, the pressure sensor is calibrated at a fixed reference pressure at which the drift rate for subsequent time periods can be measured and predicted. The disclosed example pressure sensors and methods exclude temperature-based errors to determine the drift rate such that errors due to temperature do not affect the determination of the current drift rate. The pressure sensor and method then use the drift rate to compensate the pressure measurement result. Accordingly, the disclosed pressure sensors and methods have reduced measurement errors over time.

[0022] As used herein, the term "fluid" includes substances in both liquid and gaseous states.

[0023] The disclosed example pressure sensor includes: a first body that defines a reference pressure chamber; a second body that defines a test pressure chamber and has an inlet configured to receive fluid; a diaphragm disposed between the reference pressure chamber and the test pressure chamber; an electrode separated from the diaphragm by a gap to form a capacitance between the electrode and the diaphragm; a measurement circuitry configured to determine the pressure in the test pressure chamber based on the capacitance; and a contaminant blocker configured to reduce contaminants on a first surface of the diaphragm, the contaminant blocker including: a first portion configured to block a direct path between the inlet and the diaphragm; and a second portion configured to occupy a volume within the test pressure chamber.

[0024] In some example pressure sensors, the first portion includes a first face facing the inlet, and the first face is configured to provide a tortuous path for the fluid between the inlet and the diaphragm. Some example pressure sensors further include a housing external to the first body and the second body, wherein the first portion is configured to provide the tortuous path together with the housing.

[0025] In some example pressure sensors, the second portion of the contaminant shield is sized to provide a gap between the second portion of the contaminant shield and the second body to allow the fluid to flow. In some example pressure sensors, around the circumference of the second portion of the contaminant shield, the gap is less than 0.05 inches.

[0026] Some example pressure sensors further include a housing that is external to the housing configured to provide a tortuous path for the fluid between the inlet and the diaphragm. In some example pressure sensors, the second body provides a tortuous path for the fluid between the inlet and the diaphragm. Some example pressure sensors further include a temperature sensor and measurement circuitry configured to: in response to a first calibration trigger, record a first pressure measured via the electrodes, a first timestamp, and a first temperature measurement measured via the temperature sensor; in response to a second calibration trigger, record a second pressure measured via the electrodes, a second timestamp, and a second temperature measurement measured via the temperature sensor; calculate a first sensor drift rate by: determining a temperature-compensated second measured pressure by removing a first thermal shift from the second pressure; and determining the first sensor drift rate as a first curve between the first measured pressure and the temperature-compensated second measured pressure; and compensate pressure measurements after the second timestamp based on the calculated first sensor drift rate.

[0027] In some example pressure sensors, the temperature sensor is configured to measure the ambient temperature. In some example pressure sensors, the measurement circuitry is configured to compensate pressure measurements after the second timestamp based on the calculated first sensor drift rate. In some example pressure sensors, the measurement circuitry is further configured to: in response to a third calibration trigger, record a third pressure measured via the electrodes, a third timestamp, and a third temperature measurement measured via the temperature sensor; and calculate a second sensor drift rate by: determining a temperature-compensated third measured pressure by removing a second thermal shift from the third pressure; and determining the second sensor drift rate as a second curve between the temperature-compensated third measured pressure and at least one pressure before the third timestamp.

[0028] In some example pressure sensors, the measurement circuitry is configured to compensate pressure measurements after a third timestamp based on a calculated second sensor drift rate. In some example pressure sensors, the measurement circuitry is configured to determine a curve as a linear slope from a temperature-compensated second measured pressure and a temperature-compensated third measured pressure, and is configured to compensate pressure measurements after a third timestamp based on the slope. In some example pressure sensors, the measurement circuitry is further configured to calculate an additional sensor drift rate based on a corresponding calibration trigger, and to compensate subsequent pressure measurements based on the most recent sensor drift rate.

[0029] In some example pressure sensors, the first calibration trigger signal and the second calibration trigger signal are received via an operator input device. In some example pressure sensors, the first calibration trigger signal and the second calibration trigger signal are generated by an external controller based on an external measurement sensor determining that an input pressure is a predetermined reference pressure.

[0030] In some example pressure sensors, a first thermal shift is based on a difference between a first temperature measurement and a second temperature measurement. In some example pressure sensors, the measurement circuitry is configured to determine a temperature-compensated second measured pressure based on a stored thermal model of the pressure sensor.

[0031] In some example pressure sensors, the measurement circuitry is configured to determine a drift rate as a linear slope. In some example pressure sensors, the measurement circuitry is configured to determine a drift rate as a polynomial curve. In some example pressure sensors, the pressure measurement component includes at least one of a capacitance diaphragm gauge (CDG), a piezoresistive pressure sensor, a magnetic pressure sensor, a resonant frequency pressure sensor, an optical pressure sensor, or a piezoelectric pressure sensor.

[0032] Some example pressure sensors further include measurement circuitry configured to: record a first pressure measured via the electrode and a first timestamp in response to a first calibration trigger; record a second pressure measured via the electrode and a second timestamp in response to a second calibration trigger; calculate a first sensor drift rate as a first curve between the first measured pressure and the temperature-compensated second measured pressure; and compensate pressure measurements after the second timestamp based on the calculated first sensor drift rate.

[0033] In some example pressure sensors, the contaminant shield includes one or more circumferentially disposed passages and one or more direct passages. In some examples, each of the one or more circumferentially disposed passages provides a longer flow path and a larger flow area than the direct passage. In some examples, the contaminant shield includes a body and a plurality of fins extending from the body to capture contaminants.

[0034] Figure 1A is a block diagram of an example process control system 100 that includes a pressure sensor 102. The example process control system 100 of FIG. 1 includes a processing chamber 104, and the pressure sensor 102 is fluidly coupled to the processing chamber via a fluid input line 106 to measure the pressure in the processing chamber 104.

[0035] The example processing chamber 104 may receive one or more inputs, such as process feed materials, via a corresponding number of feed lines 108a, 108b, and these feed lines may be controlled via mass flow controllers 110a, 110b.

[0036] The example system 100 may include: a vacuum pump 112 or other pressure control pump; and a valve 114 to control the flow between the vacuum pump 112 and the processing chamber 104. The valve 114 may be controlled by a controller 116, a computing device, and / or any other control technique to maintain the pressure in the processing chamber 104 within a desired range. The example pressure sensor 102 is communicatively coupled to the controller 116 to provide pressure feedback (e.g., for a pressure control loop) to the controller 116. For example, when the pressure in the processing chamber 104 increases, the pressure sensor 102 measures the pressure and provides a signal representative of the pressure to the controller 116, and then the controller controls the valve 114 to increase the flow from the processing chamber 104 to the vacuum pump 112. The vacuum pump 112 may have an output to any suitable location based on the nature of the process.

[0037] In Figure 1A example, the pressure sensor 102 is configured to have a fixed pressure 118 and compare the input pressure of the fluid received via the fluid input line 106 with the fixed pressure to output a pressure signal. For example, as discussed in more detail below, the pressure sensor 102 may be provided with a sealable evacuation port that can be sealed when a desired pressure is provided within the pressure sensor 102, and / or the pressure sensor 102 may be assembled and sealed within a volume having a desired reference pressure. The fixed pressure 118 may be a vacuum pressure or another predetermined fixed reference pressure, and the another predetermined fixed reference pressure may be lower than, equal to, or higher than the nominal atmospheric pressure. In Figure 1A this configuration, the pressure sensor 102 may function as an absolute pressure sensor.

[0038] Figure 1B is a block diagram of another example process control system 150. The example process control system 150 includes Figure 1A example pressure sensor 102, process chamber 104, fluid input line 106, feed lines 108a, 108b, mass flow controllers 110a, 110b, vacuum pump 112, valve 114, and controller 116. In Figure 1B the example, the pressure sensor 102 is coupled to a variable reference pressure source 152 external to the pressure sensor 102. For example, the pressure sensor 102 may have a port (e.g., a selectively sealed evacuation port) that is connected to the reference pressure source to operate as a pressure sensor with a variable reference, and / or the port is in communication with the ambient pressure to operate as a pressure gauge.

[0039] Figure 2 is a schematic diagram of an example pressure sensor 200 that may be used to implement Figure 1A and / or Figure 1B the pressure sensor 102. The example pressure sensor 200 includes a pressure measurement assembly 202, an inner housing 204, and an outer housing 206. The pressure sensor 200 receives fluid via a fluid input line 208 (e.g., the fluid input line 106 of FIG. 1), measures the absolute pressure of the received fluid, and outputs one or more signals representative of the measured pressure.

[0040] The pressure measurement assembly 202 is a capacitance diaphragm gauge (CDG) sensor attached to the fluid input line 208. The pressure measurement assembly 202 may also be referred to as a “sensor core,” where the pressure measurement assembly 202 performs the measurement and the measurement result is converted into an output signal. The pressure measurement assembly 202 is at least partially surrounded by the inner housing 204. The inner housing 204 may provide thermal insulation and / or physical protection to the pressure measurement assembly 202. Both the pressure measurement assembly 202 and the inner housing 204 are at least partially surrounded by the outer housing 206. The outer housing 206 may provide thermal insulation and / or physical protection to the pressure measurement assembly 202.

[0041] In the example shown, the pressure measurement assembly 202 is a capacitance pressure sensor where a flexible diaphragm 210 is separated from an electrode 212 by a gap 214. The pressure measurement assembly 202 includes a first body 216 that defines a reference pressure chamber 218 and a second body 220 that defines a test pressure chamber 222. The second body 220 is coupled to the fluid input line 208 such that the test pressure chamber 222 has the same pressure as the fluid in the fluid input line 208. For example, the second body 220 may be welded, brazed, or otherwise sealed relative to the fluid input line 208 to provide an airtight seal.

[0042] As the pressure at the fluid input line 208 changes relative to the reference pressure in the reference pressure chamber 218 (e.g., vacuum pressure), the diaphragm 210 moves or flexes, thereby changing the capacitance at the measurement electrode 212, and the amount of change corresponds to the pressure at the fluid input line 208 and / or in the test pressure chamber 222.

[0043] In Figure 2 an example, the pressure measurement assembly 202 further includes a reference electrode 226 that also measures capacitance when the diaphragm 210 moves in response to pressure. Electrodes 212, 226 are metallized to form two capacitances with the flexible diaphragm 210. The signals generated by the two electrodes 212, 226 vary with pressure but at different rates. The signal from the reference electrode 226 is output via the signal port 228 and can be used to measure and cancel common-mode errors (e.g., temperature-induced errors).

[0044] The capacitance signal is output from the pressure measurement assembly 202 via the signal port 228, which is coupled to the measurement circuitry 238 that converts the capacitance into a measurement signal and / or outputs the capacitance signal to an external signal conversion device. The measurement circuitry 238 can correct the measurement signal. The measurement signal (representing the measured pressure in the pressure measurement assembly 202) can then be transmitted by the measurement circuitry 238 via the communication circuitry 240 (e.g., a connector) (e.g., transmitted to Figure 1A or Figure 1B the controller 116 of Figure 2 or another control and / or data collection device, etc.). In

[0045] To perform the measurement and processing, the measurement circuitry 238 can be implemented using at least one controller or processor that controls the operation of the pressure sensor 200. The measurement circuitry 238 receives and processes multiple inputs. The measurement circuitry 238 can include one or more microprocessors (e.g., one or more "general-purpose" microprocessors, one or more dedicated microprocessors, and / or ASICs) and / or any other type of processing device. For example, the measurement circuitry 238 can include one or more digital signal processors (DSPs). The measurement circuitry 238 can further include a memory device and / or a data storage device.

[0046] The pressure sensor 200 can include a contaminant shield 230 positioned between the fluid input line 208 and the diaphragm 210 to block contaminants, thereby reducing the accumulation of contaminants on the diaphragm 210. Figure 5A is a first perspective view of an example contaminant shield 230, Figure 5Bis a second perspective view of an example contaminant blocker 230.

[0047] Figure 2 , Figure 5A and Figure 5B The example contaminant blocker 230 of ,

[0047] , Figure 2 , Figure 5A , and Figure 5B includes a first portion 232 and a second portion 234. The first portion 232 obstructs a direct path between the fluid input line 208 and the diaphragm 210. For example, the first portion 232 has a first face 236 facing the fluid input line 208 and extends to the periphery of the inner housing 204.

[0048] The example first face 236 forms a tortuous path 246 (depicted in Figure 5A ) for fluid to pass between the fluid input line 208 and the diaphragm 210. The tortuous path 246 provides additional surface area and causes contaminants in the input fluid to deposit on the surface of the first face 236, thereby reducing the deposition of contaminants on the face of the diaphragm 210 and reducing drift of the pressure sensor 200.

[0049] The second portion 234 of the contaminant blocker 230 occupies most of the remaining volume of the test pressure chamber 222. By reducing the wetted volume of the test pressure chamber 222 that contains the input fluid, the second portion 234 reduces the amount of contaminants to which the diaphragm is exposed while still allowing the pressure at the fluid input line 208 to be applied to the diaphragm 210.

[0050] The dimensions of the first portion 232 and the second portion 234 are sized to provide one or more gaps 248 between the first portion 232 and the inner housing 204 and / or between the second portion 234 and the second body 220 to allow fluid to reach the diaphragm 210. The total surface area of the gaps 248 can affect the response time of the pressure sensor 200 to pressure changes at the fluid input line 208. In some examples, the width of the gaps 248 around the circumference of the contaminant blocker 230 is less than 0.05 inches.

[0051] In some other examples, the second body 220 can be configured to reduce the volume occupied by the second portion 234 of the contaminant blocker 230 in Figure 2 the example of ,

[0047] , Figure 2 , Figure 5A , and Figure 5B . Figure 6 is a schematic diagram of an example pressure sensor 600 that can be used to implement Figure 1A and / or Figure 1B the pressure sensor 102 of ,

[0047] , Figure 2 , Figure 5A , and Figure 5B , and wherein the second body 620 is configured to reduce the wetted volume of the test pressure chamber 222.

[0052] The pressure sensor 600 is similar to Figure 2The pressure sensor 200, wherein the second body 620 reduces the wetting volume of the test pressure chamber 222. For example, the second body 620 can be a continuous piece of material having holes 650, orifices, or other passageways disposed therethrough to allow an input fluid to follow a tortuous path 246 and / or a gap 248 between a first portion 232 of the contaminant shield 230 and the inner housing 204 to reach the diaphragm 210.

[0053] In some examples, the tortuous path 246 can be implemented by the inner housing 204 and / or by the second housing 220.

[0054] Example materials that can be used to construct the first body 216, the second body 220, and / or the contaminant shield 230 include corrosion-resistant alloys such as nickel alloys (e.g., alloys) and / or superalloys, cobalt superalloys, iron superalloys, aluminum, copper alloys, titanium, and / or stainless steel.

[0055] To set a fixed reference pressure, the first body 216 can include an evacuation port 242 (e.g., a pinch or break-off tube). The evacuation port 242 is in fluid communication with the reference pressure chamber 218. During the manufacture of the pressure measurement assembly 202 and after sealing, the pressure (e.g., a vacuum or other set pressure) within the reference pressure chamber 218 is drawn via the evacuation port 242, and when the desired pressure level is reached, the evacuation port is clamped to seal the reference pressure chamber 218. In some other examples, the pressure measurement assembly 202 can be constructed and sealed in a volume in which a desired reference pressure exists, and when the evacuation port 242 is sealed in a fixed pressure chamber via welding or break-off cold welding, the volume fixes the desired reference pressure within the reference pressure chamber 218.

[0056] In some examples in which a fixed reference pressure is set, an aspirator can be installed within the reference pressure chamber 218 and activated during manufacture, such as when establishing the fixed reference pressure but before the reference pressure chamber 218 is sealed. Additionally or alternatively, the inner surface of the reference pressure chamber 218 (e.g., the first body 216, the electrode 212 adjacent to the reference pressure chamber 218) is coated with a material that reduces or prevents outgassing. An example coating that can be used is parylene-C.

[0057] In some other examples, the evacuation port 242 can remain open to the ambient surroundings and / or be connected to a variable reference pressure source.

[0058] The inner housing 204 is attached to the second body 220 (e.g., using glue, welding, press fitting, etc.). The outer housing 206 is secured to the measurement circuitry 238 and / or the inner housing 204 (e.g., via fasteners, adhesives, welding, etc.).

[0059] The pressure sensor 200 further includes a temperature sensor 244 coupled to the measurement circuitry 238. The temperature sensor 244 measures the ambient temperature or other environmental temperature that may affect the measurement results of the electrodes 212, 226. For example, a temperature change can change the size of the gap 214 and / or the tension of the diaphragm 210.

[0060] As described above, the example measurement circuitry 238 can compensate for drift that occurs over time in the pressure sensor 200. To compensate for drift, the measurement circuitry 238 can be calibrated at regular or irregular time intervals to determine the measured output at a predetermined input pressure, as described in more detail below. The example measurement circuitry 238 can use sequential calibration to determine the drift rate and compensate the measurement results based on the determined drift rate.

[0061] Because in addition to drift, the temperature of the pressure sensor 200 can affect the measurement error, the example measurement circuitry 238 compensates the calibration of the pressure sensor 200 to reduce or remove temperature-based errors from the determination of the drift rate.

[0062] The measurement circuitry 238 records a timestamp, a pressure output voltage, and the ambient temperature T at a predetermined fixed pressure P0, which can be any arbitrarily selected pressure. The measurement circuitry 238 can record data in response to a trigger input, which can be an automatic trigger or an operator-accessible input device (e.g., a calibration button).

[0063] Figure 3 is a plot 300 showing an example current drift rate calculation that can be implemented by Figure 2 the pressure sensor 200. The plot 300 shows a set of calibration measurement results 302, 304, 306 obtained at different times (t1, t2, t3) at the same predetermined pressure. The predetermined pressure can be determined based on a pressure sensor that is separate from the pressure sensor 200 and fluidly coupled to the input line 208.

[0064] At a first time t1 and at a predetermined pressure P0, the measurement circuitry 238 records the timestamp t1, the output V1 of the electrode 212, and the temperature T1 measured by the temperature sensor 244 as the calibration measurement result 302. V1 and T1 are stored as base or reference measurement results.

[0065] At a second time t2 and at a predetermined pressure P0, measurement circuitry 238 records the time stamp t2, the output V2 of electrode 212, and the temperature T2 measured by temperature sensor 244 as calibration measurement result 304. Using the stored temperature coefficients at multiple temperatures (e.g., % of full sensitivity per degree Celsius) (e.g., the temperature coefficient at zero output is TZS and the temperature coefficient at full sensitivity is TSS) and the full sensitivity output (VFS), measurement circuitry 238 calculates the thermal shift VT2 between the first time t1 and the second time t2 using Equation 1:

[0066] VT2 = TZS * VFS * (T2 - T1) + TSS * V1 * (T2 - T1) (Equation 1)

[0067] To compensate subsequent measurement results, measurement circuitry 238 determines the planned drift rate (S12) from t1 to t2 using Equation 2:

[0068] S12 = (V2' - V1) / (t2 - t1) (Equation 2)

[0069] In Equation 2, V2' is the temperature-compensated output, calculated as V2' = V2 - VT2. Measurement circuitry 238 uses the planned drift rate S12 from after t2 until before t3 to compensate the pressure measurement results. To compensate the pressure measurement results, measurement circuitry 238 removes the planned drift amount from the measurement results after t2, which increases over time starting from t2 according to the planned drift rate S12. Measurement circuitry 238 uses Equation 3 to compensate the pressure measurement results that occur after t2 to determine the compensated output V':

[0070] V' = V – (V2' - V1) – S12 * (t - t2) – VT (Equation 3)

[0071] In Equation 3, V is the measured pressure output from electrode 212, t is the time of the measured pressure output, and the thermal shift VT is determined according to Equation 4:

[0072] VT = TZS * VFS * (T - T1) + TSS * V * (T - T1) (Equation 4)

[0073] At a third time t3 and at a predetermined pressure P0, measurement circuitry 238 records the time stamp t3, the output V3 of electrode 212, and the temperature T3 measured by temperature sensor 244 as calibration measurement result 306. Using the stored temperature coefficients TZS, TSS, and the full sensitivity output VFS, measurement circuitry 238 uses Equation 5 to calculate the thermal shift VT3 between the first time t1 and the third time t3:

[0074] VT3 = TZS * VFS * (T3 - T1) + TSS * V1 * (T3 - T1) (Equation 5)

[0075] The measurement circuitry 238 again configures the output value of the pressure P0 to be equal to V1 to calibrate the output signal from the electrode 212. To compensate for subsequent measurement results after time t3, the measurement circuitry 238 uses Equation 6 to determine the planned drift rate (S23) from t2 to t3 (which may be different from the drift rate from t1 to t2 and / or from t1 to t3):

[0076] S23 = (V3' - V2') / (t3 - t2) (Equation 6)

[0077] In Equation 6, V3' is calculated as V3 - VT3. The measurement circuitry 238 continues to use Equation 3 above to compensate for the pressure measurement results that occur after t3 to determine the compensated output V', substituting the current drift rate S23 and the most recent compensated output and time t3 into the equation.

[0078] The measurement circuitry 238 can repeat calibration, drift rate calculation, and compensation at additional times after t3 to reduce the output error caused by drift during the operating life of the pressure sensor 200 of the pressure sensor 200.

[0079] The plot 300 shows the total drift 310 from t1 to t2, the planned drift 312 from t2 to t3, the total compensated drift 314 at t3, and the remaining uncompensated drift 316 at t3.

[0080] Instead of Figure 3 the linear drift rate shown in the example, the example measurement circuitry 238 can calculate other drift curves, such as polynomial drift curves. The drift curve can be based on fitting a predetermined drift curve trend to the observed temperature-compensated output and time stamps. For example, the measurement circuitry 238 can perform regression analysis and / or any other type of analysis to determine the drift curve.

[0081] Additionally or alternatively, the measurement circuitry 238 may store all calibration data (e.g., timestamps, output signals, measured temperature, etc.) in a storage device for subsequent retrieval. For example, the calibration data may be stored permanently, or at least stored for a predetermined or configurable time, and / or at most stored up to the memory limit of the measurement circuitry 238. The stored calibration data may be output to a maintenance system (e.g., via the communication circuitry 240). The maintenance system may analyze the calibration data of the pressure sensor 200 in order to update, for example, the approximation curve coefficients (e.g., for performing curve fitting) based on the observed data and / or for a specific application or use of the pressure sensor 200. The maintenance system then loads the updated coefficients back into the measurement circuitry 238 for storage and updated drift compensation determination. The coefficients determined based on the first pressure sensor 200 may be further loaded into a replacement pressure sensor 200, such that the new pressure sensor 200 may have more accurate curve fitting coefficients for the same or similar applications.

[0082] Figure 4 is a flowchart representative of example machine-readable instructions 400 that may be executed by Figure 2 the pressure sensor 200 to compensate pressure measurement results for sensor drift. Example instructions 400 are described below with reference to the measurement circuitry 238. In the following instructions 400, baseline measurement results of pressure V1, time t1, and temperature T1 may be captured in advance when the pressure sensor 200 is started or initialized.

[0083] At block 402, the measurement circuitry 238 determines whether to calibrate the pressure sensor 200. For example, the measurement circuitry 238 may receive an input signal from a control device (e.g., via the communication circuitry 240) or via a user input device (e.g., a calibration button). If calibration is to be performed (block 402), the measurement circuitry 238 inputs a predetermined pressure into the fluid input line 208. For example, a source of known input pressure may be connected to the input line 208, or the connected system may be configured to input a predetermined input pressure.

[0084] At block 406, the measurement circuitry 238 captures a pressure measurement result, a timestamp, and a temperature measurement result. For example, the measurement circuitry 238 may receive a signal from the electrodes 212, a timestamp from a timer or clock, and a temperature measurement result of the ambient temperature or surrounding temperature from the temperature sensor 244 to represent Figure 3 one of the calibration measurement results 302, 304, 306. At block 408, the measurement circuitry 238 determines a temperature-compensated current pressure measurement result. For example, the measurement circuitry 238 may determine the temperature-compensated current pressure measurement V2' based on the thermal shift calculated using Equation 1 above.

[0085] At block 410, the measurement circuitry 238 determines the current sensor drift rate (e.g., S12, S23, etc.) as a curve based on the previously measured pressure (e.g., baseline or temperature compensated pressure) and the temperature compensated current pressure measurement. For example, the measurement circuitry 238 may determine a linear drift rate using Equation 2 or Equation 6 or may determine a polynomial drift curve or other nonlinear drift curve.

[0086] After determining the sensor drift rate (block 410), or if the pressure sensor is not calibrated (block 402), at block 412, the measurement circuit system 238 determines whether a pressure measurement has been captured. For example, the measurement circuit system 238 may determine the pressure measurement signal V from the electrode 212 at regular or irregular time intervals and / or in response to a trigger or event. If a pressure measurement has not been captured (block 412), control returns to block 412.

[0087] When pressure measurements are not captured (block 412 ), at block 414 measurement circuitry 238 captures temperature measurements via temperature sensor 244 .

[0088] At block 416 , measurement circuitry 238 uses the current sensor drift rate, the timestamp of the pressure measurement, and the temperature measurement to compensate the pressure measurement signal V. For example, measurement circuitry 238 may determine the corrected pressure output using Equation 3. Control then returns to block 402 .

[0089] Figure 7 is a schematic diagram of another example pressure sensor 700 that can be used to implement Figure 1A and / or Figure 1B pressure sensor. Figure 8A and Figure 8B It is connected to the pressure sensor 700 Figure 7 1. Other views of an example contaminant shield 730. The example pressure sensor 700 includes a pressure measurement assembly 202, an inner housing 204, an outer housing 206, a fluid input line 208, a diaphragm 210, an electrode 212, a gap 214, a first body 216, a reference pressure chamber 218, a second body 220, a test pressure chamber 222, a reference electrode 226, a signal port 228, a measurement circuit system 238, a communication circuit system 240, a vent port 242, and a temperature sensor 244, as described above with reference to FIG. Figure 2 described.

[0090] Figure 7Example pressure sensor 700 further includes a contaminant shield 730 positioned between the fluid input line 208 and the diaphragm 210 to block contaminants, thereby reducing the accumulation of contaminants on the diaphragm 210. Example contaminant shield 730 improves the response time by reducing the free volume between the fluid input line 208 and the diaphragm 210 in a manner similar to the Figure 2 contaminant shield. Compared to the Figure 2 contaminant shield 230, contaminant shield 730 can provide improved conductivity, thereby further improving the response time compared to contaminant shield 230.

[0091] Example contaminant shield 730 is positioned within the second body 220 and includes a shield body 732. The shield body 732 includes a first portion 732a that obstructs the direct path between the fluid input line 208 and the diaphragm 210, and a second portion 732b that occupies the volume between the fluid input line 208 and the diaphragm 210.

[0092] The shield body 732 includes circumferentially arranged passages 734 and a central passage 736 that allow fluid to pass between the fluid input line 208 and the diaphragm 210. The circumferentially arranged passages 734 provide a higher flow rate through the longer flow path between the fluid input line 208 and the diaphragm 210, which helps deposit any particulate contaminants onto the body 732 (e.g., onto the fins 738 and / or onto the inner and / or outer surfaces of the body 732). The circumferentially arranged passages 734 can be configured to provide a more controlled flow, thereby causing gas flow along the desired flow path and / or causing contact with the surfaces of the body 732 and / or the fins 738.

[0093] The central passage 736 provides a smaller, more direct flow path between the fluid input line 208 and the diaphragm 210, which improves conductivity and response time. Example central passage 736 can also drive turbulence around the shield body 732 during a pressure change to better capture contaminant particles onto the shield body 732.

[0094] Although example shield body 732 includes three example circumferentially arranged passages 734, in other examples, shield body 732 can include one, two, four, or more circumferentially arranged passages 734. Additionally or alternatively, the circumferentially arranged passages 734 can be evenly or unevenly spaced around the circumference of the body 732.

[0095] Although the exemplary occlusion member body 732 includes a single central passage 736, in other examples, the occlusion member body 732 may include a plurality of central passages 736 disposed on a surface of the occlusion member body 732 (e.g., facing the fluid input line 208 and the diaphragm 210). In other examples, the occlusion member body 732 does not have a central passage 736, and the circumferentially disposed passages 734 are the only passages fluidly connected to the fluid input line 208 and the diaphragm 210.

[0096] Although the examples disclosed above are described with reference to CDG sensors, the disclosed example systems and methods are applicable to other types of pressure sensors affected by drift, such as piezoresistive pressure sensors, magnetic pressure sensors, resonant frequency pressure sensors, optical pressure sensors, piezoelectric pressure sensors, and / or any other type of pressure sensor.

[0097] In some examples, the pressure sensor 200 does not have a temperature sensor 244 and does not compensate for temperature changes in the pressure measurements (e.g., pressure measurements 302, 304, 306). Instead, the measurement circuitry 238 may capture calibration measurements at substantially consistent pressures and substantially consistent temperatures (e.g., within a predetermined pressure range of a target calibration pressure, within a predetermined temperature range of a target calibration temperature). In such examples, the measurement circuitry 238 may record a first pressure measured via the electrodes and record a first timestamp in response to a first calibration trigger, record a second pressure measured via the electrodes and record a second timestamp in response to a second calibration trigger. The measurement circuitry 238 then calculates a first sensor drift rate as a first curve between the first measured pressure and the temperature-compensated second measured pressure, and may then compensate the pressure measurements after the second timestamp based on the calculated first sensor drift rate. The measurement circuitry 238 may perform additional calibrations and subsequent corrections in a similar manner.

[0098] As used herein, "and / or" refers to any one or more of the items in a list joined by "and / or". As an example, "x and / or y" refers to any element in the three-element set {(x), (y), (x, y)}. In other words, "x and / or y" means "one or both of x and y". As another example, "x, y, and / or z" refers to any element in the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, "x, y, and / or z" means "one or more of x, y, and z". As used herein, the term "exemplary" is used to mean a non-limiting example, instance, or illustration. As used herein, the terms "e.g.," and "for example" introduce a list of one or more non-limiting examples, instances, or illustrations.

[0099] Although the method and / or system have been described with reference to certain embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted without departing from the scope of the method and / or system. For example, the blocks and / or components of the disclosed examples can be combined, divided, rearranged, and / or otherwise modified. Additionally, many modifications can be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the scope of the present disclosure. Accordingly, the method and / or system are not limited to the particular embodiments disclosed. Instead, the method and / or system will include all embodiments that fall within the scope of the appended claims, either literally or under the doctrine of equivalents.

Claims

1. A pressure sensor, comprising: A first body that defines a reference pressure chamber; A second body that defines a test pressure chamber and has an inlet configured to receive a fluid; A diaphragm that is disposed between the reference pressure chamber and the test pressure chamber; An electrode that is separated from the diaphragm by a gap to form a capacitance between the electrode and the diaphragm; A measurement circuit system configured to determine the pressure in the test pressure chamber based on the capacitance; And A contaminant shield configured to reduce contaminants on a first surface of the diaphragm, the contaminant shield comprising: A first portion configured to block a direct path between the inlet and the diaphragm; And A second portion configured to occupy a volume within the test pressure chamber.

2. The pressure sensor according to claim 1, wherein, The first portion includes a first surface facing the inlet, the first surface being configured to provide a tortuous path for the fluid between the inlet and the diaphragm.

3. The pressure sensor according to claim 2, further comprising a housing external to the first body and the second body, the first portion being configured to cooperate with the housing to provide the tortuous path.

4. The pressure sensor according to claim 1, wherein, The size of the second portion of the contaminant shield is determined to provide a gap between the second portion of the contaminant shield and the second body to allow the fluid to flow.

5. The pressure sensor according to claim 4, wherein Around the circumference of the second portion of the contaminant shield, the gap is less than 0.05 inches.

6. The pressure sensor according to claim 1, further comprising a housing, the housing being external to the housing configured to provide a tortuous path for the fluid between the inlet and the diaphragm.

7. The pressure sensor according to claim 1, wherein, The second body provides a tortuous path for the fluid between the inlet and the diaphragm.

8. The pressure sensor according to claim 1, further comprising a temperature sensor and a measurement circuit system, the measurement circuit system being configured to: In response to a first calibration trigger, record a first pressure measured via the electrode, a first timestamp, and a first temperature measurement result measured via the temperature sensor; In response to a second calibration trigger, record a second pressure measured via the electrode, a second timestamp, and a second temperature measurement result measured via the temperature sensor; Calculate a first sensor drift rate by: Determining a temperature-compensated second measured pressure by removing a first thermal shift from the second pressure; And Determining the first sensor drift rate as a first curve between the first measured pressure and the temperature-compensated second measured pressure; And Compensating pressure measurement results after the second timestamp based on the calculated first sensor drift rate.

9. The pressure sensor according to claim 8, wherein, The temperature sensor is configured to measure the ambient temperature.

10. The pressure sensor according to claim 8, wherein, The measurement circuit system is configured to compensate pressure measurement results after the second timestamp based on the calculated first sensor drift rate.

11. The pressure sensor according to claim 8, wherein, The measurement circuit system is further configured to: In response to a third calibration trigger, record a third pressure measured via the electrode, a third timestamp, and a third temperature measurement result measured via the temperature sensor; and Calculate a second sensor drift rate by: Determine a temperature-compensated third measured pressure by removing a second thermal shift from the third pressure; And Determine the second sensor drift rate as a second curve between the temperature-compensated third measured pressure and at least one pressure prior to the third timestamp.

12. The pressure sensor according to claim 11, wherein, The measurement circuit system is configured to compensate pressure measurement results after the third timestamp based on the calculated second sensor drift rate.

13. The pressure sensor according to claim 12, wherein, The measurement circuit system is configured to determine the curve as a linear slope from the temperature-compensated second measured pressure and the temperature-compensated third measured pressure, and is configured to compensate the pressure measurement results after the third timestamp based on the slope.

14. The pressure sensor according to claim 11, wherein, The measurement circuit system is further configured to calculate an additional sensor drift rate based on a corresponding calibration trigger, and to compensate subsequent pressure measurement results based on the most recent sensor drift rate.

15. The pressure sensor according to claim 8, wherein, The first calibration trigger signal and the second calibration trigger signal are received via an operator input device, or are generated by an external controller based on an external measurement sensor determining that an input pressure is a predetermined reference pressure.

16. The pressure sensor according to claim 8, wherein The first thermal shift is based on the difference between the first temperature measurement result and the second temperature measurement result.

17. The pressure sensor according to claim 16, wherein, The measurement circuit system is configured to determine the temperature-compensated second measured pressure based on a stored thermal model of the pressure sensor.

18. The pressure sensor according to claim 8, wherein, The measurement circuit system is configured to determine the drift rate as a linear slope.

19. The pressure sensor according to claim 8, wherein, The measurement circuit system is configured to determine the drift rate as a polynomial curve.

20. The pressure sensor according to claim 1, wherein, The pressure measurement assembly includes at least one of a capacitance diaphragm gauge, a piezoresistive pressure sensor (CDG), a magnetic pressure sensor, a resonant frequency pressure sensor, an optical pressure sensor, or a piezoelectric pressure sensor.

21. The pressure sensor according to claim 1, further comprising a measurement circuit system configured to: In response to a first calibration trigger, record a first pressure measured via the electrode and a first timestamp; In response to a second calibration trigger, record a second pressure measured via the electrode and a second timestamp; Calculate a first sensor drift rate as a first curve between the first measured pressure and the temperature-compensated second measured pressure; And Compensate pressure measurement results after the second timestamp based on the calculated first sensor drift rate.

22. The pressure sensor according to claim 1, wherein, The contaminant shield includes one or more circumferentially arranged passages and one or more direct passages.

23. The pressure sensor according to claim 22, wherein, Each of the one or more circumferentially arranged passages provides a longer flow path and a larger flow area than the direct passage.

24. The pressure sensor according to claim 1, wherein, The contaminant shield includes a body and a plurality of fins extending from the body to capture contaminants.

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