Thermowells with pressure sensing capability

Abstract

A process fluid multivariable measurement system is provided. The multivariable measurement system includes a thermowell configured to be coupled to a process fluid pipeline and extend through a wall of the process fluid pipeline. The system also includes a temperature sensor assembly disposed within the thermowell, the temperature sensor assembly having at least one temperature sensitive element disposed therein. The system also includes a pressure sensor assembly coupled to the thermowell, the pressure sensor assembly having at least one pressure sensitive element disposed therein. The system also includes transmitter circuitry communicatively coupled to the temperature sensor assembly and the pressure sensor assembly, the transmitter circuitry configured to receive a temperature sensor signal from the at least one temperature sensitive element and responsively generate a temperature measurement output based on the temperature sensor signal. The transmitter circuitry is further configured to receive a pressure sensor signal from the at least one pressure sensitive element and responsively generate a pressure measurement output based on the pressure sensor signal.

Description

Technical Field

[0001] The present invention relates to a process fluid multivariable measurement system and a multivariable thermowell. Background Art

[0002] Many industrial processes convey process fluids through pipes or other conduits. Such process fluids may include liquids, gases, and sometimes entrained solids. These process fluids may be found in any of a variety of industries, including but not limited to sanitary food and beverage production, water treatment, high-purity pharmaceutical manufacturing, chemical processing, the hydrocarbon fuel industry, including industries such as hydrocarbon extraction and processing and hydraulic fracturing using abrasive and corrosive slurries.

[0003] Industrial process transmitters and sensor assemblies are used to sense the properties of process fluids flowing through pipelines or contained within vessels and to communicate information related to these process properties to control, monitoring, and / or safety systems located remotely from the process measurement location. Process transmitters are typically electrically connected to the sensor assembly via sensor wires, which transmit analog current- or voltage-based sensor output signals reflecting the process parameter. Each transmitter reads these sensor output signals and converts them into measurements of the process parameter. Ultimately, the transmitter transmits this information to the control system.

[0004] It is common to place a temperature sensor within a thermowell, which is then inserted into the process fluid stream through an orifice located in the pipe. In typical industrial process environments, adding additional measurement points to obtain measurements of different process characteristics can be difficult due to the complex nature of the process environment. For example, measuring different process characteristics in a typical industrial process environment typically requires extensive changes to the process environment infrastructure, along with the associated significant financial costs of such changes. Therefore, the use of thermowells in industrial process environments, while beneficial for providing accurate process fluid temperatures, is subject to numerous limitations. Summary of the Invention

[0005] A multivariable measurement system for a process fluid is provided. The multivariable measurement system includes a thermowell configured to be coupled to a process fluid pipeline and extend through a wall of the process fluid pipeline. The multivariable measurement system also includes a temperature sensor assembly disposed within the thermowell, the temperature sensor assembly having at least one temperature sensitive element disposed therein. The multivariable measurement system also includes a pressure sensor assembly coupled to the thermowell, the pressure sensor assembly having at least one pressure sensitive element disposed therein. The multivariable measurement system further includes transmitter circuitry communicatively coupled to the temperature sensor assembly and the pressure sensor assembly, configured to receive a temperature sensor signal from the at least one temperature sensitive element and responsively generate a temperature measurement output based on the temperature sensor signal. The transmitter circuitry is further configured to receive a pressure sensor signal from the at least one pressure sensitive element and responsively generate a pressure measurement output based on the pressure sensor signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a schematic diagram of a multivariable thermowell for use in a multivariable measurement system for a process fluid in which embodiments of the present invention are particularly useful.

[0007] Figure 2 is a schematic diagram of a multivariable thermowell for implementing a multivariable measurement system for a process fluid according to another embodiment of the present invention.

[0008] Figure 3 is a schematic diagram of a multivariable thermowell for implementing a multivariable measurement system for a process fluid according to an embodiment of the present invention.

[0009] Figure 4 is a block diagram of the circuitry of a process fluid multivariable measurement system to which embodiments of the present invention are particularly applicable.

[0010] Figures 5A to 5B is a schematic diagram of a process fluid multivariable measurement system to which embodiments of the present invention are particularly applicable.

[0011] Figure 6 is a schematic diagram of a multivariable thermowell with a strain gauge pressure sensor according to an embodiment of the present invention.

[0012] Figure 7 is a schematic diagram of a multivariable thermowell with a capacitive pressure sensor according to an embodiment of the present invention.

[0013] Figure 8is a schematic diagram of a multivariable sensor for implementing a multivariable measurement system for a process fluid according to an embodiment of the present invention.

[0014] Figure 9 is a schematic diagram of a multivariable thermowell for implementing a multivariable measurement system for a process fluid according to another embodiment of the present invention. DETAILED DESCRIPTION

[0015] As explained above, due to the complex nature of industrial process environments, adding additional measurement points for obtaining measurements of different process characteristics is difficult. For example, to add a system capable of detecting pressure within an industrial process environment, significant intrusion and modification of the process environment infrastructure would typically be necessary, such as creating new access points within the infrastructure for measuring the new process characteristic. Furthermore, such modifications are difficult due to the high temperatures present within the piping of an industrial process environment.

[0016] Figure 1 FIG. 1 is a schematic diagram of a multivariable thermowell for a process fluid multivariable measurement system in which embodiments of the present invention are particularly suitable. As shown, the thermowell 100 is configured to be coupled to a process fluid conduit (such as a Figures 5A to 5B ) and extends through the wall of the process fluid pipeline. The thermowell 100 is further configured to generally contact the process fluid within the process fluid pipeline to obtain a measurement of the process fluid, such as temperature and / or pressure. In one embodiment, the thermowell 100 is a threaded thermowell. However, in other embodiments, the thermowell 100 can be a flanged thermowell or other thermowell design capable of being coupled to the process fluid pipeline. The thermowell 100 further includes a temperature sensor assembly 110 and a sensor enclosure 112, which is generally disposed within the thermowell 100. The term "enclosure" is not intended to imply any particular structure or shape and, therefore, can be formed in a variety of different shapes, sizes, and configurations. The temperature sensor assembly 110 generally includes one or more temperature sensitive elements 114, such as a resistance temperature device (RTD). The temperature sensitive element 114 is electrically connected to a transmitter circuit (not shown) via an access hole 116 and is configured to obtain one or more temperature measurements. The access hole 116 is generally configured to allow a coupling 140 of the temperature sensor assembly to pass through the access hole 116. The sensor enclosure 112 can be electrically connected to the transmitter circuit via a transmission loop, a fiber optic cable, a wireless link, or some other connection.

[0017] The thermowell 100 also includes a pressure sensor assembly 118 that is generally disposed within the thermowell 100 and includes one or more pressure sensitive elements 120 disposed within the pressure sensor assembly 118 and configured to obtain one or more pressure measurements. In one embodiment, the pressure sensor assembly 118 includes a strain gauge sensor. In another embodiment, the pressure sensor assembly 118 may include a capacitive pressure sensor. Of course, in other embodiments, the pressure sensor assembly 118 may include different types of pressure sensors, such as potentiometer sensors, resonant line sensors, or other pressure sensors capable of obtaining pressure measurements. Additionally, in one embodiment, the pressure sensor assembly 118 may include a multivariable sensor, such as described below in Figure 8 As described in

[15] , the multivariable sensor is configured to simultaneously obtain both pressure and temperature measurements in the process fluid multivariable measurement system and responsively generate a temperature sensor signal and a pressure sensor signal. By incorporating the multivariable sensor into the pressure sensor assembly 118, additional temperature measurements can be obtained. The additional temperature measurements obtained by the multivariable sensor provide an alternative mode of measuring temperature in the event of any instrument error. For example, the redundant temperature measurements obtained by both the multivariable sensor and the temperature sensor assembly 110 can provide a backup temperature measurement if the other temperature measurements fail.

[0018] In one embodiment, the pressure sensitive element 120 can be disposed within the sensor enclosure 112. However, in alternative embodiments, the pressure sensitive element 120 can be disposed external to the sensor enclosure 112. The pressure sensitive element 120 is electrically connected to a transmitter circuit (not shown) via an access hole 122, which is configured to allow a connector (not shown) of the pressure sensor assembly 118 to pass through the access hole. As shown, the access hole 122 is disposed adjacent to the temperature sensor assembly 110 and is generally disposed within the wall of the thermowell 100. In particular, the access hole 122 is disposed separate from and adjacent to the access hole 116. As further illustrated, the access hole 122 is parallel to the temperature sensor assembly 110. However, in alternative embodiments, the access hole 122 can be disposed proximate to the temperature sensor assembly 110 in other manners that allow the pressure sensitive element 120 to be coupled to the transmitter circuit.

[0019] The access hole 122 can be incorporated into the wall of the thermowell 100 in a variety of ways. For example, the access hole 122 can be incorporated by utilizing EDM machining or gun drilling techniques. Incorporating the access hole 122 into the thermowell 100 allows the pressure sensor assembly 118 to be added without extensive changes to the process environment infrastructure.

[0020] Figure 2 is a schematic diagram of a multivariable thermowell for implementing a multivariable measurement system for a process fluid according to another embodiment of the present invention. Figure 2 The system shown in the figure is Figure 1 There are some similarities, and similar components are numbered similarly. As shown, the thermowell 200 is configured to be coupled to a process fluid conduit (such as in Figures 5A to 5B ) and extends through a wall of the process fluid pipeline. Thermowell 200 is further configured to generally contact a process fluid within the process fluid pipeline to obtain a measurement of the process fluid, such as temperature and / or pressure. In one embodiment, thermowell 200 is a threaded thermowell. However, in other embodiments, thermowell 200 may be a flanged thermowell or other thermowell design capable of coupling to the process fluid pipeline.

[0021] Thermowell 200 further includes a temperature sensor assembly 210 and a pressure sensor assembly 218, which are typically disposed within the thermowell 200, and a sensor enclosure 212. Sensor enclosure 212 typically contains one or more temperature sensitive elements 214 and / or one or more pressure sensitive elements 220. In one embodiment, temperature sensor assembly 210 and / or pressure sensor assembly 218 may include strain gauge sensors. However, in other embodiments, different types of pressure sensors (e.g., capacitive pressure sensors) may be utilized. Additionally, in one embodiment, pressure sensor assembly 218 may include a multivariable sensor, such as described below. Figure 8 As described in , the multivariable sensor is configured to simultaneously obtain both pressure and temperature measurements in the process fluid multivariable measurement system. By incorporating a multivariable sensor into the pressure sensor assembly 218, additional temperature measurements can be obtained.

[0022] The temperature sensor 214 and the pressure sensor 220 are electrically connected to a transmitter circuit (not shown) via an access hole 216 and are configured to obtain one or more temperature measurements and / or one or more pressure measurements. The access hole 216 is generally configured to allow the connector 240 of the temperature sensor assembly 210 and the pressure sensor assembly 218 to pass through the access hole 216. The temperature sensor 214 and the pressure sensor 220 can be electrically connected to the transmitter circuit via a transmission loop, a fiber optic cable, a wireless link, or some other connection. Figure 2As shown in FIG, in one embodiment, pressure sensor assembly 218 shares the same access hole 216 as temperature sensor assembly 210. By incorporating pressure sensor assembly 218 into the same access hole 216 as temperature sensor assembly 210, no additional modifications to thermowell 200, such as the addition of additional access holes, are required. For example, in thermowell embodiments where the wall thickness of the thermowell is limited, using the same access hole for pressure sensor assembly 218 as for temperature sensor assembly 210 allows for multivariable sensing of process fluid properties. In one embodiment, pressure sensor 220 is incorporated into the end of sensor enclosure 212 by drilling a hole through the end of thermowell 200 to allow for coupling of the pressure sensor to sensor enclosure 212, such as by welding.

[0023] Figure 3 is a schematic diagram of a multivariable thermowell for implementing a multivariable measurement system for a process fluid according to an embodiment of the present invention. Figure 3 The system shown in the figure is Figure 1 and Figure 2 There are some similarities, and similar components are numbered similarly. As shown, the thermowell 300 is configured to be coupled to a process fluid conduit (such as in Figures 5A to 5B ) and extends through the wall of the process fluid pipeline. The thermowell 300 is further configured to generally contact the process fluid within the process fluid pipeline to obtain measurements of the process fluid, such as temperature and / or pressure. In one embodiment, the thermowell 300 is a threaded thermowell. However, in other embodiments, the thermowell 300 may be a flanged thermowell or other thermowell design capable of being coupled to the process fluid pipeline. The thermowell 300 further includes a temperature sensor assembly 310, which is generally disposed within the thermowell 300. The temperature sensor assembly 310 generally includes one or more temperature sensitive elements 314, such as resistance temperature devices (RTDs). The temperature sensitive elements 314 are electrically connected to transmitter circuitry (not shown) via an access port 316 and are configured to obtain one or more temperature measurements. The access port 316 is generally configured to allow a connector 340 of the temperature sensor assembly to pass through the access port 316. Temperature sensor assembly 310 may be electrically connected to transmitter circuitry via a transmission loop, a fiber optic cable, a wireless link, or some other connection.

[0024] Thermowell 300 also includes a pressure sensor assembly 318, which is generally disposed within the thermowell 300 and includes one or more pressure sensitive elements 320 disposed within the pressure sensor assembly 318. As shown, the pressure sensor assembly 318 further includes an access port 322. In one embodiment, the access port 322 is filled with a pressure-transmitting substance 324, and the pressure sensitive element 320 includes a membrane 326 that fluidically couples the process fluid within the process fluid conduit to the pressure-transmitting substance 324. The pressure-transmitting substance 324 may be, for example, oil. However, in other embodiments, the pressure-transmitting substance 324 may be another fluid capable of transmitting an indication of pressure. The access port 322 further includes a conduit 328 that allows the pressure-transmitting substance 324 to couple to the pressure sensor 330 via a pressure-deflecting diaphragm (generally indicated as 332). The pressure-deflecting diaphragm can be, for example, a thin-film diaphragm, a bellows diaphragm, or other diaphragm capable of coupling the pressure sensor 330 to the pressure-transmitting substance 324. Thus, as illustrated, the pressure sensor 330 can be remotely located relative to the thermowell and can generate a pressure sensor signal, which is subsequently received by transmitter circuitry (not shown), via an indication of the pressure transmitted through the pressure-transmitting substance 324 in the access hole 322. This prevents harsh process conditions (such as higher temperature processes) from interfering with the pressure sensing capabilities of the multivariable thermowell 300.

[0025] Figure 4 is a block diagram of a circuit for a process fluid multivariable measurement system to which embodiments of the present invention are particularly applicable. Figures 1 to 3 There are some similarities between the elements of the multivariable thermowell described in

[0045] and similar components are numbered similarly. System 400 may also include other items, as indicated by block 436. System 400 includes communication circuitry 422 coupled to controller 424. Communication circuitry 422 may be a circuit capable of transmitting information to and from the multivariable thermowell, such as in

[0046] Figures 1 to 3 and Figure 9 The communication circuit 422 allows the multivariable thermowell provided in the process fluid multivariable measurement system to communicate the process fluid temperature and / or pressure output over a process communication loop or segment (such as a transmission loop). Examples of suitable process communication loop protocols include 4-20 mA protocol, Highway Addressable Remote Transducer (HART), and the like. ) agreement, FOUNDATION TMFieldbus protocol, and WirelessHART protocol (IEC 62591).

[0026] The system 400 also includes a power supply module 426 that provides power to all components of the system 400, as indicated by arrow 428. Loop or FOUNDATION TM In embodiments where a process communication loop is used (e.g., a fieldbus segment), the power supply module 426 may include appropriate circuitry to condition the power received from the loop or segment to operate the various components of the system 400. Thus, in such embodiments where a wired process communication loop is used, the power supply module 426 may provide appropriate power conditioning to allow the entire device to be powered by the loop to which the device is connected. In other embodiments, where wireless process communication is used, the power supply module 426 may include a power source such as a battery or appropriate conditioning circuitry.

[0027] Controller 424 can be communicatively coupled to communication circuitry 422 and include any suitable arrangement to generate a process fluid temperature output and a process fluid pressure output based on heat flow using measurements from temperature sensor assembly 410 and pressure sensor assembly 418. For example, controller 424 can receive a temperature sensor signal from temperature sensitive element 414 within temperature sensor assembly 410 and responsively generate a temperature measurement output based on the temperature sensor signal. Alternatively or additionally, controller 424 can receive a pressure sensor signal from pressure sensitive element 420 within pressure sensor assembly 418 and responsively generate a pressure measurement output based on the pressure sensor signal. The output can be provided to an operator, machine, or other device. Additionally, the output can be a visual output, an audible output, or other output capable of indicating temperature and / or pressure measurements within the process fluid multivariable measurement system. In one example, controller 424 is a microprocessor.

[0028] Measurement circuitry 430 is coupled to controller 424 and provides digital indications of measurements obtained from temperature sensor assembly 410 and pressure sensor assembly 418. Measurement circuitry 430 may include one or more analog-to-digital converters and / or suitable multiplexing circuitry for interfacing the one or more analog-to-digital converters with temperature sensor assembly 410 and pressure sensor assembly 418. Additionally, measurement circuitry 430 may include suitable amplification and / or linearization circuitry that may be appropriate for the various different types of sensors employed.

[0029] Temperature sensor assembly 410 illustratively includes a temperature sensitive element 414 and may also include other items, as indicated by block 432. One example of such an additional item is a vibration sensor. Temperature sensitive element 414 is coupled to the electronic circuitry of system 400 via an access port (not shown) and is used to generate a temperature sensor signal indicative of the temperature of the process fluid within the process fluid multivariable measurement system. Pressure sensor assembly 418 illustratively includes a pressure sensitive element 420 and may also include other items, as indicated by block 434. An example of such an additional item is a vibration sensor. Pressure sensitive element 420 is coupled to the electronic circuitry of system 400 via an access port (not shown) and is used to generate a pressure sensor signal indicative of the pressure of the process fluid multivariable measurement system. In one embodiment, pressure sensitive element 420 is coupled to the electronic circuitry of system 400 via the same access port as the temperature sensitive element. However, in other embodiments, the pressure sensitive element utilizes an additional access port separate from the access port used in temperature sensor assembly 410. For example, the access hole may be positioned adjacent to the temperature sensor assembly, positioned parallel to the temperature sensor assembly, or positioned in another manner within the wall of the thermowell.

[0030] Figures 5A to 5B is a schematic diagram of a process fluid multivariable measurement system to which embodiments of the present invention are particularly applicable. Figure 5A The system shown in the figure is Figure 5B There are some similarities, and similar components are numbered similarly. As shown, the system 500 generally includes a thermowell 502 that is configured to be coupled to a process fluid conduit 504 and extend through a wall 506 of the process fluid conduit. The thermowell 502 is further configured to generally contact a process fluid 508 within the process fluid conduit 504 to obtain measurements of the process fluid, such as temperature and / or pressure. The thermowell 502 further includes a temperature sensor assembly 510 that is generally disposed within the thermowell 502 and includes a sensor enclosure, which is further Figures 1 to 3 The system 500 generally includes one or more temperature sensitive elements (not shown) disposed within a thermowell 502, such as those described above with respect to Figure 1 The temperature sensitive element 114 is electrically connected to the transmitter circuit. Figure 4 As shown in FIG, the variable temperature sensitive element is configured to obtain one or more temperature measurements.

[0031] The process fluid multivariable measurement system 500 also includes a pressure sensor assembly 518 coupled to the thermowell 502. The pressure sensor assembly 518 typically has one or more pressure sensitive elements (not shown) disposed therein, such as those described above with respect to the pressure sensor assembly 518. Figure 1 When in contact with process fluid 508 in process fluid conduit 504, the temperature sensor assembly and the pressure sensor assembly are configured to use the temperature sensor and the pressure sensor disposed within thermowell 502, respectively, to generate a temperature sensor signal and / or a pressure sensor signal for transmission to a transmitter circuit. The transmitter circuit (such as the one described above with respect to Figure 4 504) receives the temperature sensor signal and / or the pressure sensor signal and responsively generates a temperature measurement output and / or a pressure measurement output based on the received signal. The output generally indicates the temperature and / or pressure of the process fluid 508 within the process fluid conduit 504. Alternatively or additionally, the output may indicate the temperature and / or pressure of the environment within the process fluid conduit 504.

[0032] like Figure 5A As shown in FIG, the thermowell 502 includes a flange fitting. However, in Figure 5B In FIG. 5 , the thermowell 502 includes threaded fittings. Figure 5A , flange fitting 524 generally includes bolts 526 configured to couple thermowell 502 to nozzle 530 of process fluid conduit 504. Flange fitting 524 also includes a sealing ring 528 configured to prevent process fluid from flowing therethrough. Sealing ring 528 can be an O-ring seal or any other seal capable of sealing process fluid 508 to process fluid conduit 504.

[0033] like Figure 5B , thermowell 502 may alternatively include a threaded fitting 532 configured to couple to threads (not shown) on thermowell 502 to join thermowell 502 to process fluid piping 504. Threaded fitting 532 includes a weld 534 configured to couple threaded fitting 532 to wall 506 of process fluid piping 504. By utilizing a multivariable thermowell in either a threaded or flanged embodiment, this allows for a variety of different thermowell installations in a process fluid environment to achieve temperature and / or pressure sensing capabilities.

[0034] Figure 6is a schematic diagram of a multivariable thermowell with a strain gauge pressure sensor according to an embodiment of the present invention. Thermowell body 600 generally includes an access hole 602 disposed therein and configured to allow a coupling of the pressure sensor assembly to pass therethrough. Thermowell body 600 further includes a strain gauge sensor 604 configured to generate a pressure sensor signal in response to a sensed pressure within the process fluid conduit. The strain gauge sensor includes an adapter collar 606 configured to couple strain gauge sensor 604 to thermowell body 600. Strain gauge sensor 604 is coupled to adapter collar 606 at a coupling mechanism 608. Coupling mechanism 608 may be, for example, a weld that joins adapter collar 606 to strain gauge sensor 604.

[0035] Strain gauge sensor 604 further includes a pressure sensor element 610 configured to detect pressure in the process fluid conduit and generate a pressure signal indicative of the detected pressure. In one embodiment, strain gauge sensor 604 further includes a pressure-transmitting substance generally disposed in channel 614. The pressure-transmitting substance is fluidically isolated from the process fluid by an isolation diaphragm 620 and transmits a pressure indication to pressure sensor element 610. In this manner, a pressure indication can be transmitted from the process fluid through the pressure-transmitting substance and transmitted to pressure sensor element 610, responsively generating a pressure sensor signal. The pressure-transmitting substance may be, for example, oil. However, in other embodiments, the pressure-transmitting substance may be another fluid capable of transmitting a pressure indication.

[0036] Isolation diaphragm 620 is coupled to pressure sensor 604 via latching point 616 and is configured to isolate the process fluid from the pressure-transmitting substance and pressure sensor element 610. In one embodiment, latching point 616 is a weld. Strain gauge sensor 604 further includes screen 612. By incorporating screen 612 at the end of strain gauge sensor 604, the strain gauge sensor can be encapsulated and protected from debris while also preventing wake frequency limitation. In other words, flow characteristics are optimized, which in turn can improve pressure and / or temperature measurements.

[0037] Figure 7FIG2 is a schematic diagram of a sensor enclosure for a multivariable thermowell with a capacitive pressure sensor according to an embodiment of the present invention. Thermowell body 700 generally includes an access hole 702 configured to allow a connector 704 of the pressure sensor assembly to pass therethrough. As shown, connector 704 comprises a cable. However, in other embodiments, connector 704 may be a pressure transmitting material, two or more cables, or a wireless link. Thermowell body 700 also includes a capacitive pressure sensor 714 configured to generate a pressure sensor signal in response to a detected pressure within the process fluid conduit. By utilizing a capacitive pressure sensor assembly, the connector of the pressure sensor assembly can be positioned in a variety of different locations within thermowell body 700, such as within access hole 702.

[0038] Capacitive pressure sensor 714 also includes a capacitor plate 708 disposed near the end of the thermowell configured to couple to a process fluid within a process fluid conduit. In one embodiment, capacitor plate 708 includes a pressure-deflecting diaphragm 712 and an electrode 710 configured to generate and transmit an indication of pressure within the process fluid conduit. In one embodiment, capacitor plate 708 is formed from a glass material. In this manner, a vacuum can be formed in the chamber between pressure-deflecting diaphragm 712 and electrode 710 to allow for the generation and transmission of a pressure indication. In one embodiment, pressure-deflecting diaphragm 712 is a corrugated diaphragm. However, in other embodiments, pressure-deflecting diaphragm 712 can be a thin-film diaphragm.

[0039] Figure 8 is a schematic diagram of a multivariable sensor for implementing a process fluid multivariable measurement system according to an embodiment of the present invention. Sensor 800 is generally configured to obtain one or more temperature measurements and / or one or more pressure measurements. In particular, sensor 800 can be configured to simultaneously obtain both pressure measurements and temperature measurements in a process fluid multivariable measurement system. In one embodiment, sensor 800 is a strain gauge sensor. As shown, sensor 800 includes resistors 802-808, the resistance of which depends on both strain and temperature. When the temperature (V ref When the pressure (related to V out As the pressure (correlation) increases, the resistance of resistors 802 and 806 increases by similar values, while the resistance of resistors 804 and 808 decreases by similar values. In this manner, sensor 800 can simultaneously obtain pressure and temperature measurements within a process fluid measurement system.

[0040] Figure 9 is a schematic diagram of a multivariable thermowell for implementing a multivariable measurement system for a process fluid according to another embodiment of the present invention. Figure 9 The system shown in the figure is Figure 1 There are some similarities, and similar components are numbered similarly. As shown, the thermowell 900 is configured to be coupled to a process fluid conduit (such as in Figures 5A to 5B ) and extends through a wall of the process fluid pipeline. Thermowell 900 is further configured to generally contact a process fluid within the process fluid pipeline to obtain a measurement of the process fluid, such as temperature and / or pressure. In one embodiment, thermowell 900 is a threaded thermowell. However, in other embodiments, thermowell 900 may be a flanged thermowell or other thermowell design capable of coupling to the process fluid pipeline.

[0041] Thermowell 900 further includes a multivariable sensor 920, which is generally disposed within a sensor enclosure 912 of the thermowell 900. The sensor enclosure 912 may include, for example, a multivariable sensor 920 similar to that described above with respect to Figure 8 916. In one embodiment, the multivariable sensor 920 is a strain gauge sensor. However, in other embodiments, different types of multivariable sensors may be utilized. The multivariable sensor 920 is electrically connected to a transmitter circuit (not shown) via an access port 916 and is configured to obtain one or more temperature measurements and / or one or more pressure measurements. In particular, the multivariable sensor 920 may be configured to simultaneously obtain both pressure measurements and temperature measurements in a process fluid multivariable measurement system and responsively generate a temperature sensor signal and a pressure sensor signal. The multivariable sensor 920 illustratively includes one or more multivariable sensitive elements, which are typically disposed within the multivariable sensor 920 and are configured to obtain one or more temperature measurements and pressure measurements. The access port 916 is typically configured to allow a connector 940 of the multivariable sensor 920 to pass through the access port 916. The multivariable sensor 920 may be electrically connected to the transmitter circuit via a transmission loop, a fiber optic cable, a wireless link, or some other connection, such as described above with respect to Figure 4 In operation, the transmitter circuit may receive the temperature and pressure sensor signals from the at least one multivariable sensitive element and responsively generate temperature and pressure measurement outputs based on the received sensor signals. Figure 8Similar to the multivariable sensor described, both the temperature and pressure of the process environment can be determined without the need for separate sensor components.

[0042] Although the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, although embodiments of the present invention have been described with respect to a thermowell having pressure sensing capabilities, other process variable sensors may be implemented in the thermowell, including but not limited to flow, level, pH, vibration, and corrosion.

Claims

1. A process fluid multivariable measurement system comprising: a thermowell configured to be coupled to a process fluid conduit and to extend through a wall of the process fluid conduit; a temperature sensor assembly disposed within the thermowell, the temperature sensor assembly having at least one temperature sensitive element disposed therein; a pressure sensor assembly coupled to the thermowell, the pressure sensor assembly having at least one pressure sensitive element disposed therein and fluidly isolated from the process fluid conduit; a transmitter circuit communicatively coupled to the temperature sensor assembly and the pressure sensor assembly, the transmitter circuit being configured to: receiving a temperature sensor signal from the at least one temperature sensitive element and responsively generating a temperature measurement output based on the temperature sensor signal; and receiving a pressure sensor signal from the at least one pressure sensitive element and responsively generating a pressure measurement output based on the pressure sensor signal, Wherein the pressure sensor assembly includes a multivariable sensor configured to simultaneously obtain both pressure and temperature measurements in the process fluid multivariable measurement system and responsively generate additional temperature measurements and pressure sensor signals.

2. The process fluid multivariable measurement system of claim 1, wherein: The transmitter circuit is configured to couple to the pressure sensor assembly through the access hole of the thermowell.

3. The process fluid multivariable measurement system of claim 2, wherein: The access hole is disposed adjacent to the temperature sensor assembly.

4. The process fluid multivariable measurement system of claim 3, wherein: The access hole is arranged parallel to the temperature sensor assembly.

5. The process fluid multivariable measurement system of claim 3, wherein: The access hole is provided in a wall of the thermowell.

6. The process fluid multivariable measurement system of claim 1, wherein: The pressure sensitive element includes a strain gauge pressure sensor configured to generate the pressure sensor signal in response to a pressure detected within the process fluid conduit.

7. The process fluid multivariable measurement system of claim 1, wherein: The pressure sensitive element includes a capacitive pressure sensor configured to generate the pressure sensor signal in response to a pressure detected within the process fluid conduit.

8. The process fluid multivariable measurement system of claim 2, wherein: The pressure sensitive element includes a pressure-deflecting diaphragm communicatively coupled to a pressure sensor disposed remotely from the thermowell.

9. The process fluid multivariable measurement system of claim 8, wherein: The pressure-deflecting diaphragm is communicatively coupled to the pressure sensor via a pressure transmitting substance disposed within the access aperture.

10. The process fluid multivariable measurement system of claim 9, wherein: The pressure transmitting substance is oil.

11. A method of obtaining measurement results of a process fluid in a pipeline by using the process fluid multivariable measurement system according to any one of claims 1 to 10, the measurement results indicating pressure and temperature of the process fluid, the method comprising: coupling a thermowell to a process fluid conduit, the thermowell including a pressure sensitive element fluidly isolated from the process fluid conduit; detecting a process fluid variable indicative of a pressure of a process fluid within the process fluid conduit; generating a pressure signal in response to the sensed process fluid variable; obtaining the pressure signal from the pressure sensitive element and measuring the pressure of the process fluid in the process fluid pipeline based on the obtained pressure signal; generating an output indicative of the pressure of the process fluid within the process fluid conduit, and Both pressure and temperature measurements are simultaneously obtained by a multivariable sensor disposed in a pressure sensor assembly of the process fluid multivariable measurement system, and an additional temperature measurement and a pressure sensor signal are responsively generated.

12. The method according to claim 11, wherein The thermowell includes an access hole.

13. The method according to claim 11, wherein Generating a pressure signal includes generating a pressure signal using a strain gauge pressure sensor in response to the sensed process fluid variable.

14. The method according to claim 11, wherein Generating a pressure signal includes generating a pressure signal using a capacitive pressure sensor in response to the sensed process fluid variable.

15. The method according to claim 11, wherein Sensing the process fluid variable includes sensing a pressure of the process fluid with a pressure-deflecting diaphragm communicatively coupled to a pressure sensor disposed remotely from the thermowell.

16. A multivariable thermocouple well comprising: a temperature sensor assembly having at least one temperature sensitive element disposed therein; a pressure sensor assembly having at least one pressure sensitive element disposed therein and fluidly isolated from a process fluid conduit; and an access hole disposed within the thermowell, the access hole being configured to allow a coupling of the pressure sensor assembly to pass through the access hole, Wherein the pressure sensor assembly includes a multivariable sensor configured to simultaneously obtain both pressure and temperature measurements and responsively generate additional temperature measurements and pressure sensor signals.

17. The multivariable thermowell of claim 16, wherein: The access hole is disposed adjacent to the temperature sensor assembly.

18. The multivariable thermowell of claim 16, wherein: The pressure sensor assembly is configured to be coupled to transmitter circuitry through the access hole of the thermowell.

19. The multivariable thermowell of claim 16, wherein: The pressure sensitive element includes a pressure-deflecting diaphragm communicatively coupled to a pressure sensor disposed remotely from the multivariable thermowell.

20. The multivariable thermowell of claim 19, wherein: The pressure-deflecting diaphragm is communicatively coupled to the pressure sensor via a pressure transmitting substance disposed within the access aperture.

21. A process fluid multivariable measurement system comprising: a thermowell configured to be coupled to a process fluid conduit and to extend through a wall of the process fluid conduit; a multivariable sensor disposed in the pressure sensor assembly within the thermowell, the multivariable sensor having at least one multivariable sensitive element disposed therein and fluidly isolated from the process fluid conduit; transmitter circuitry communicatively coupled to the multivariable sensor, the transmitter circuitry configured to: receiving a temperature sensor signal from the at least one multivariable sensitive element and responsively generating a temperature measurement output based on the temperature sensor signal; and receiving a pressure sensor signal from the at least one multivariable sensitive element and responsively generating a pressure measurement output based on the pressure sensor signal, Wherein the multivariable sensor is configured to simultaneously obtain both pressure and temperature measurements in the process fluid multivariable measurement system and responsively generate additional temperature measurements and pressure sensor signals.

22. A process fluid multivariable measurement system comprising: a thermowell configured to be coupled to a process fluid conduit and to extend through a wall of the process fluid conduit; a temperature sensor assembly disposed within the thermowell, the temperature sensor assembly having at least one temperature sensitive element disposed therein; a multivariable sensor disposed in the pressure sensor assembly within the thermowell, the multivariable sensor configured to simultaneously obtain both pressure and temperature measurements in the process fluid multivariable measurement system, the multivariable sensor having at least one multivariable sensitive element disposed therein and fluidly isolated from the process fluid conduit; a transmitter circuit communicatively coupled to the temperature sensor assembly and the multivariable sensor, the transmitter circuit being configured to: receiving a temperature sensor signal from the at least one temperature sensitive element and responsively generating a temperature measurement output based on the temperature sensor signal; receiving a pressure sensor signal from the at least one multivariable sensitive element and responsively generating a pressure measurement output based on the pressure sensor signal; as well as Additional temperature sensor signals are received from the at least one multivariable sensitive element, and additional temperature measurement outputs are responsively generated based on the additional temperature sensor signals.

23. The process fluid multivariable measurement system of claim 22, wherein: The additional temperature sensor signal is configured to provide a backup temperature measurement.

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