Patent Publication Number: US-2015059483-A1

Title: Sensors for measuring at least one of pressure and temperature, and related assemblies and methods

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/873,149, filed Sep. 3, 2013 entitled “SENSORS FOR MEASURING AT LEAST ONE OF PRESSURE AND TEMPERATURE, AND RELATED ASSEMBLIES AND METHODS,” the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     Embodiments of the present disclosure relate to sensors for measurement of at least one of a pressure and temperature and, more particularly, to quartz resonator sensors for measurement of at least one of a pressure and temperature and related assemblies and associated methods. 
     BACKGROUND 
     Thickness shear mode quartz resonator sensors have been used successfully in the downhole environment of oil and gas wells for several decades and are an accurate means of determining downhole pressures in widespread use in hydrocarbon (e.g., oil and gas) exploration and production, as well as in other downhole applications. Quartz resonator pressure sensors typically have a crystal resonator located inside a housing exposed to ambient bottom-hole fluid pressure and temperature. Electrodes on the resonator element coupled to a high frequency power source drive the resonator and result in shear deformation of the crystal resonator. The electrodes also detect the resonator response to pressure and temperature and are electrically coupled to conductors extending to associated power and processing electronics isolated from the ambient environment. Ambient pressure and temperature are transmitted to the resonator, via a substantially incompressible fluid within the housing, and changes in the resonator frequency response are sensed and used to determine the pressure and/or temperature and interpret changes in same. For example, a quartz resonator sensor, as disclosed in U.S. Pat. Nos. 3,561,832 and 3,617,780, includes a cylindrical design with the resonator formed in a unitary fashion in a single piece of quartz. End caps of quartz are attached to close the structure. 
     Generally, a pressure transducer comprising a thickness shear mode quartz resonator sensor assembly may include a first sensor in the form of a primarily pressure sensitive thickness shear mode quartz crystal resonator exposed to ambient pressure and temperature, a second sensor in the form of a temperature sensitive quartz crystal resonator exposed only to ambient temperature, a third reference crystal in the form of quartz crystal resonator exposed only to ambient temperature, and supporting electronics. The first sensor changes frequency in response to changes in applied external pressure and temperature with a major response component being related to pressure changes, while the output frequency of the second sensor is used to temperature compensate temperature-induced frequency excursions in the first sensor. The reference crystal, if used, generates a reference signal, which is only slightly temperature-dependent, against or relative to which the pressure- and temperature-induced frequency changes in the first sensor and the temperature-induced frequency changes in the second sensor can be compared. Such comparison may be achieved by, for example, frequency mixing frequency signals and using the reference frequency to count the signals from the first and second sensors for frequency measurement. 
     Prior art devices of the type referenced above including one or more thickness shear mode quartz resonator sensors exhibit a high degree of accuracy even when implemented in an environment such as a downhole environment exhibiting high pressures and temperatures. However, each of the quartz resonator sensors that are included in a pressure transducer may be relatively expensive to fabricate, as each quartz resonator sensor must be individually manufactured. Further, the size of the housing required to carry the sensor assembly may be dictated by the desired frequency output of the resonator of each quartz resonator sensor of the assembly. The overall size and positioning requirements of each of such quartz resonator sensor in a pressure transducer may limit the size, shape, and configuration of the assembly, which is usually of significant concern given size constraints imposed by inner diameters of drill string and production string tubular components in which the sensor assembly may be disposed. Furthermore, the size of each of such quartz resonator sensors and the resonating portion thereof will affect the speed and accuracy with which the sensor adjusts to changes in pressure and/or temperature and how quickly the sensor can reach thermal equilibrium. 
     BRIEF SUMMARY 
     In some embodiments, the present disclosure includes a thickness shear mode resonator pressure sensor. The thickness shear mode resonator pressure sensor includes a housing having a longitudinal axis. The housing includes a resonator having a resonating portion, a first end cap forming first recess between a first side of the resonating portion of the resonator and the first end cap, and a second end cap forming second recess between a second side of the resonating portion of the resonator and the first end cap. An outer dimension of the housing taken in direction transverse the longitudinal axis of the housing may be less than 0.575 inch (14.605 millimeters). 
     In additional embodiments, the present disclosure includes a quartz resonator pressure transducer assembly. The quartz resonator pressure transducer assembly includes a pressure housing comprising at least one chamber, an electronics housing comprising an electronics assembly, and a quartz pressure sensor in communication with the at least one chamber and for measuring pressure of a fluid disposed within the at least one chamber. The electronics assembly is configured to drive the quartz pressure sensor at a selected frequency and to sense a pressure-related frequency response from the quartz pressure sensor. The quartz resonator pressure transducer assembly further includes a quartz reference sensor where the electronics assembly is configured to drive the quartz reference sensor at a selected frequency and to sense a reference frequency response from the quartz reference sensor. The electronics assembly may be configured to drive at least one of the quartz pressure sensor and the quartz reference sensor at a frequency greater than 10 MHz. 
     In additional embodiments, the present disclosure includes a quartz resonator pressure transducer assembly. The quartz resonator pressure transducer assembly includes a pressure housing comprising at least one chamber, an electronics housing comprising an electronics assembly, and a quartz pressure sensor in communication with the at least one chamber and for measuring pressure of a fluid disposed within the at least one chamber. The electronics assembly is configured to drive the quartz pressure sensor at a selected frequency and to sense a pressure-related frequency response from the quartz pressure sensor. An outer dimension of the pressure transducer assembly is less than 0.75 inch (19.05 millimeters). 
     In yet additional embodiments, the present disclosure includes a transducer assembly including an electronics assembly configured to drive at least one quartz sensor of the transducer assembly at a frequency greater than 10 MHz. 
     In yet additional embodiments, the present disclosure includes sensors and related assemblies and methods of forming and operating sensors and related assemblies as described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       While the specification concludes with claims particularly pointing out and distinctly claiming what are regarded as embodiments of the present disclosure, various features and advantages of embodiments of the disclosure may be more readily ascertained from the following description of example embodiments of the disclosure provided with reference to the accompanying drawings, in which: 
         FIG. 1  is a partial cross-sectional view of a transducer in accordance with an embodiment of the present disclosure; 
         FIG. 2  is a perspective view of sensor in accordance with an embodiment of the present disclosure; 
         FIG. 3  is a cross-sectional side view of the resonator sensor shown in  FIG. 1 ; 
         FIG. 4  is a simplified schematic block diagram of a circuit suitable for use with sensors and transducer assemblies according to an embodiment of the present disclosure. 
         FIG. 5  is a simplified schematic block diagram of another circuit suitable for use with sensors and transducer assemblies according to an embodiment of the present disclosure. 
         FIG. 6  is a simplified schematic block diagram of yet another circuit suitable for use with sensors and transducer assemblies according to an embodiment of the present disclosure. 
         FIG. 7  is a simplified schematic block diagram of yet another circuit suitable for use with sensors and transducer assemblies according to an embodiment of the present disclosure. 
         FIG. 8  is a simplified schematic block diagram of yet another circuit suitable for use with sensors and transducer assemblies according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings that depict, by way of illustration, specific embodiments in which the disclosure may be practiced. However, other embodiments may be utilized, and structural, logical, and configurational changes may be made without departing from the scope of the disclosure. The illustrations presented herein are not meant to be actual views of any particular sensor, transducer, or component thereof, but are merely idealized representations that are employed to describe embodiments of the present disclosure. The drawings presented herein are not necessarily drawn to scale. Additionally, elements common between drawings may retain the same numerical designation. 
     Although some embodiments of sensors of the present disclosure are depicted as being used and employed in pressure transducer assemblies, persons of ordinary skill in the art will understand that the embodiments of the present disclosure may be employed in any assembly or system for measurement of at least one of pressure and temperature with a quartz resonator sensor. 
       FIG. 1  is a perspective view of a pressure transducer  100  including one or more sensors. As shown in  FIG. 1 , the pressure transducer  100  may include a pressure housing  102  having a pressure sensor  104  disposed in a chamber  106  in the pressure housing  102 . The chamber  106  in the pressure housing  102  may be in communication with an environment exterior to the pressure transducer  100  in order to determine one or more environmental conditions in the exterior environments (e.g., a pressure and/or temperature of the exterior environment). For example, the chamber  106  may be in fluid communication with an isolation element  108  (e.g., a diaphragm assembly, a bladder assembly, a bellows assembly, as well as combinations of the foregoing). The isolation element  108  may act to transmit pressure and/or temperature exterior to the pressure transducer  100  to sensors within the pressure transducer  100  (e.g., via a fluid within the pressure transducer). The chamber  106  in the pressure housing  102  may be in fluid communication with isolation element  108  (e.g., via channel  110 ). Fluid may be disposed in the chamber  106  around the pressure sensor  104 , in the channel  110 , and in the isolation element  108  to transmit the pressure and/or temperature from the exterior of the pressure transducer  100 . In some embodiments, the fluid within pressure transducer  100  may comprise a highly incompressible, low thermal expansion fluid such as, for example, oil (e.g., a Paratherm or sebacate oil). The pressure and thermal expansion of the fluid may be sensed by the pressure sensor  104  (e.g., a quartz crystal sensing element). 
     As further depicted in  FIG. 1 , the pressure transducer  100  may include one or more additional sensors that are utilized along with the pressure sensor  104  to determine and compensate for environmental conditions affecting output of the pressure sensor  104 , as well as providing a reference signal. The pressure transducer  100  may include a temperature sensor  112  that is at least partially isolated from (e.g., by a pressure feedthrough portion  114  that includes bulkhead  115 ) from the fluid within the pressure housing  102  that is in communication with the exterior environment. The temperature sensor  112  is utilized to sense the temperature of the exterior environment (e.g., as is it transmitted to temperature sensor  112  through the housing of the pressure transducer  100 ) to enable compensation for temperature-induced inaccuracies in the output of pressure sensor  104 . 
     In some embodiments, the pressure transducer  100  may include a reference sensor  116  that is isolated from (e.g., by the pressure bulkhead  115 ) from the fluid within the pressure housing  102  that is in communication with the exterior environment. As known in the art, an output of such a references sensor  116  may be utilized for comparison with other sensors (e.g., the pressure sensor  104 , the temperature sensor  112 , or combinations thereof). It is noted that while the embodiment of  FIG. 1  illustrates the temperature sensor  112  being positioned relatively closer to the pressure sensor  104  than the reference sensor  118 , in other embodiments, the reference sensor  118  may be positioned relatively closer to the pressure sensor  104  than temperature sensor  112 . 
     As depicted in the  FIG. 1 , each of the sensors  104 ,  112 ,  118  may be positioned along a longitudinal axis L 100  of the pressure transducer  100 . For example, the sensors  104 ,  112 ,  118  may be positioned in-line along the longitudinal axis L 100  of the pressure transducer  100 . 
     As discussed below in further detail, the pressure sensor  104  may have an outer dimension (e.g., diameter) that is less than conventional pressure sensors (e.g., conventional quartz pressure resonator sensors). For example, some conventional pressure sensors have an outer dimension of about 0.575 inch (14.605 millimeters). The pressure sensor  104  may have an outer dimension less than 0.575 inch (14.605 millimeters) (e.g., about 0.375 inch (9.525 millimeters)). Such a pressure sensor  104  may enable the size of the pressure transducer  100  to be reduced. For example, the pressure transducer  100  may have an outer dimension D 100  (e.g., a maximum outer dimension such as an outer diameter) taken in a direction transverse to the longitudinal axis L 100  of the pressure transducer  100  that is less than conventional pressure transducer (e.g., conventional pressure transducer utilizing quartz resonator sensors). For example, some conventional pressure transducers have an outer dimension of about 0.75 inch (19.05 millimeters). The pressure sensor  104  may have an outer dimension less than 0.75 inch (19.05 millimeters). For example, the outer dimension D 100  of the pressure transducer  100  may be less than 0.70 inch (17.78 millimeters), less than 0.60 inch (15.24 millimeters), less than 0.50 inch (12.7 millimeters), or lower. By way of further example, the outer dimension D 100  of the pressure transducer  100  may be between about 0.40 inch (10.16 millimeters) and 0.60 inch (15.24 millimeters) (e.g., about 0.50 inch (12.7 millimeters)). 
     An electronics housing  118  is coupled to the pressure housing  102 . As depicted, the electronics housing  118  include an electronics assembly  120  that is at least partially isolated from the fluid within the pressure housing  102  that is in communication with the exterior environment. The electronics assembly  120  may be electrically coupled to each of the sensors  104 ,  112 ,  116  in the pressure transducer  100  (e.g., via electrical feedthrough pins (not shown)) and may be utilized to operate (e.g., drive) one or more of the sensors  104 ,  112 ,  116  and to receive the output of the sensors  104 ,  112 ,  116 . 
     In some embodiments, pressure transducers in accordance with the instant disclosure may include methods of fabrication, orientations, quartz structures, electronics, assemblies, housings, reference sensors, and components similar to the sensors and transducers disclosed in, for example, U.S. Pat. No. 6,131,462 to EerNisse et al., U.S. Pat. No. 5,471,882 to Wiggins, U.S. Pat. No. 5,231,880 to Ward et al., U.S. Pat. No. 4,550,610 to EerNisse et al., and U.S. Pat. No. 3,561,832 to Karrer et al., the disclosure of each of which patents is hereby incorporated herein in its entirety by this reference. 
     As mentioned above, pressure sensor  104  may comprise a quartz crystal sensing element. In some embodiments, a pressure transducer having a quartz crystal pressure sensor (e.g., such as that described in U.S. Pat. No. 6,131,462 to EerNisse et al.) will also include a quartz crystal reference sensor  116  and a quartz crystal temperature sensor  112  that are utilized in comparing the outputs of the crystal sensors (e.g., via frequency mixing and/or using the reference frequency to count the signals from the other two crystals) for temperature compensation and to prevent drift and other pressure signal output anomalies. In other embodiments, one or more of the sensors (e.g., the temperature sensor  112 ) may comprise an electronic sensor (e.g., a silicon temperature sensor using, for example, integrated electronic circuits to monitor temperature rather than a sensor exhibiting temperature-dependent variable mechanical characteristics (e.g., frequency changes of a resonator element) such as a quartz crystal resonator). For example, the sensor configurations may be similar to those described in U.S. patent application Ser. No. 13/934,058, filed Jul. 2, 2013, the disclosure of which is hereby incorporated herein in its entirety by this reference, which application describes the use of an electronic temperature sensor in a pressure transducer. 
     In yet additional embodiments, the pressure sensor  104  may comprise a dual-mode sensor configured to sense both pressure and temperature, for example, such as those described in U.S. patent application Ser. No. 13/839,238, filed Mar. 15, 2013, the disclosure of which is hereby incorporated herein in its entirety by this reference. 
       FIG. 2  is a perspective view of a resonator sensor  200  (e.g., a quartz resonator sensor) that may be utilized in a transducer assembly (e.g., pressure transducer  100 ) to sense one of pressure and temperature. For example, one or more of the sensors  104 ,  112 ,  116  discussed above with reference to  FIG. 1 , may be formed as sensor  200 . 
     As shown in  FIG. 2 , the quartz resonator sensor  200  includes a resonator element  202  at least partially disposed in a housing  201 . A portion of the resonator element  202  may be bounded on sides thereof. For example, the housing  201  may include two end caps (e.g., a first end cap  204  end and a second end cap  206 ) and the resonator element  202  may disposed between the end caps  204 ,  206  to form the housing  201 . In some embodiments, each of the end caps  204 ,  206  includes a flat  208  to facilitate alignment (e.g., alignment of the orientation of the quartz crystal) of the end caps  204 ,  206  during assembly of the resonator sensor  200 . 
     In some embodiments, one or more components of resonator sensor  200  may be fabricated from single crystal quartz, for example, from quartz plates cut to exhibit an AT-cut, BT-cut, or other suitable orientation. For example, the resonator sensor  200  may be formed as a thickness-shear-mode quartz resonator element  202  with two quartz end caps  204 ,  206 , each component being formed from quartz plates (e.g., AT-cut quartz plates). 
       FIG. 3  is a cross-sectional side view of the resonator sensor  200 . As shown in  FIG. 3 , the end caps  204 ,  206  may be coupled to the resonator element  202  at joints  212 ,  214  (e.g., butt joints) by, for example, an adhesive or bonding process (e.g., a fused glass frit). Each of the end caps  204 ,  206  may include one or more chamfers (e.g., an inner diameter chamfer  216  and an out diameter chamfer  218  proximate (e.g., at) the joints  212 ,  214  between the end caps  204 ,  206  and the resonator element  202 . 
     The resonator element  202  may include a resonating portion  210  that is enabled to resonate freely (e.g., displace, vibrate, etc.) when driven or forced (e.g., driven by electrodes (not shown) formed on the resonator element  202 ) at one or more selected frequencies by driving electronics (e.g., driving electronics of the electronics assembly  120  ( FIG. 1 )). For example, a recessed portion  220  in the end cap  204  and another recessed portion  222  in the end cap  206  may enable the resonating portion  210  of the resonator element  202  to resonate within the housing  201  of the resonator sensor  200 . In some embodiments, one or more recessed portions may be formed as part of the resonator element  202  (e.g., in addition to or in place of the recessed portions  220 ,  222  in the end caps  204 ,  206 ) to enable the resonating portion  210  of the resonator element  202  to resonate within the housing  201  of the resonator sensor  200 . 
     In some embodiments, the recessed portion  220  of the end cap  204  may be substantially aligned with the recessed portion  222  of the end cap  206  such that each point on the outer boundary of the recessed portion  220  is substantially collinear to a similar point of the recessed portion  222 . 
     The housing  201  of the resonator sensor  200  has a longitudinal axis L 201  extending through both the end caps  204 ,  206  and the resonating portion  210  along the length of the resonator sensor  200 . 
     Referring still to  FIG. 3 , the resonating portion  210  may have a rounded shape (e.g., a bi-convex resonator). In other embodiments, a resonating portion  210  or a portion thereof may comprise other shapes such as, for example, piano-piano, plano-convex, etc. In some embodiments, the outer portion of the resonator element  202  surrounding the resonating portion  210  may be substantially flat to enable coupling to the end caps  204 ,  206 . 
     As depicted, the resonator sensor  200  (e.g., the housing  201 ) has an outer dimension D 201  (e.g., a maximum outer dimension such as an outer diameter) taken in a direction transverse (e.g., perpendicular) to the longitudinal axis L 201  of the housing  201  that may be less than the outer dimension of conventional resonator sensors. For example, some conventional resonator sensors have an outer dimension of about 0.575 inch (14.605 millimeters). Resonator sensor  200  has outer dimension D 201  less than about 0.575 inch (14.605 millimeters). For example, outer dimension D 201  of the resonator sensor  200  may be about 0.50 inch (12.7 millimeters), 0.40 inch (10.16 millimeters), or lower, such as, for example, about 65% of the size of a conventional resonator sensor (e.g., 0.375 inch (9.525 millimeters)). By way of further example, the outer dimension D 201  of the resonator sensor  200  may be between about 0.30 inch (7.62 millimeters) and about 0.50 inch (12.7 millimeters) or between about 0.30 inch (7.62 millimeters) and about 0.40 inch (10.16 millimeters). 
     In some embodiments, the resonator sensor  200  (e.g., a pressure resonator sensor) may have a similar size to another sensor in a transducer (e.g., one or more of the temperature sensor  112  and the reference sensor  116  of pressure transducer  100  discussed above with reference to  FIG. 1 ). For example, the outer dimension D 201  of the resonator sensor  200  may be within plus or minus twenty-five percent (±25%), plus or minus ten percent (±10%), plus or minus five percent (±5%), or lower (e.g., substantially equal) of a maximum outer dimension of another sensor in the same transducer. 
     In some embodiments, the relatively smaller resonator element  202  of the resonator sensor  200  may resonate at a frequency about one and half times (1.5×), two times (2×), three times (3×), or greater than conventional sensors. For example, the relatively smaller resonator element  202  of the resonator sensor  200  may resonate at over 10 MHz, over 14 MHz (e.g., 14.4 MHz), or over 21 MHz (e.g., 21.6 MHz), which is about one and half times, two, or three times the frequency of about 7.2 MHz of a conventional sensor. 
       FIG. 4  is a schematic block diagram of a circuit  300  suitable for use with transducers (e.g., the electronics assembly  120  of the pressure transducer  100  ( FIG. 1 )) and sensors (e.g., pressure and/or temperature sensor  200  ( FIGS. 2 and 3 )). In particular, circuit  300  may be particularly suited for use with the resonator sensor  200  having a relatively smaller outer diameter than similar conventional sensors and transducers including such sensors  200 . The relatively smaller outer dimension D 201  of resonator sensor  200  may dictate the overall size of the resonator element  202  and resonating portion  210  of the resonator element  202 . In other words, the relatively smaller outer dimension D 201  of resonator sensor  200  may require the resonator element  202  and resonating portion  210  of the resonator element  202  to be reduced. 
     In some embodiments, such a relatively smaller resonator element  202  and resonating portion  210  thereof will require an electronics assembly (e.g., electronics assembly  120 ) having circuitry capable of providing the relatively higher frequencies output by the resonator element  202 . For example, a transducer (e.g., the pressure transducer  100 ) including one or more resonator sensors  200  and, optionally, one or more other conventional resonator sensors includes an electronics assembly (e.g., electronics assembly  120 ) having one or more of the circuits discussed below to enable the electronics assembly of the transducer to operate the various resonator sensors of the transducer (e.g., to drive the sensor via an amplifier and receive a frequency response therefrom). 
     As shown in  FIG. 4 , the circuit  300  includes a first oscillator having a first resonator  302  (e.g., a crystal resonator) driven by a first amplifier  304 . The first amplifier  304  drives the first resonator  302  (e.g., at relatively higher frequency) to provide a sensor for measuring a pressure and/or temperature (e.g., resonator sensor  200  ( FIGS. 2 and 3 ) for measuring pressure). The first amplifier  304  may drive the first resonator  302  at a relatively higher frequency such as, for example, over 14 MHz (e.g., about 14.45 MHz). 
     The circuit  300  includes a second oscillator having a second resonator  306  (e.g., a crystal resonator) driven by a second amplifier  308 . The second amplifier  308  drives the second resonator  306  (e.g., at a frequency lower than the first resonator  302  and the first amplifier  304 ) to provide a reference sensor (e.g., reference sensor  116  ( FIG. 1 )). The second amplifier  308  may drive the second resonator  306  at a relatively lower frequency such as, for example, about 7 MHz (e.g., about 7.2 MHz). 
     In some embodiments, the circuit  300  includes a third oscillator having a third resonator  310  (e.g., a crystal resonator) driven by a third amplifier  312 . The third amplifier  312  drives the third resonator  310  (e.g., at a frequency lower than the first resonator  302  and the first amplifier  304 ) to provide a temperature sensor (e.g., temperature sensor  112  ( FIG. 1 )). As discussed above, in some embodiments, one resonator sensor may be configured as a dual-mode resonator sensor for acting as both the pressure sensor and the temperature sensor. The third amplifier  312  may drive the third resonator  310  at a relatively lower frequency such as, for example, about 7 MHz (e.g., about 7.15 MHz). 
     The relatively higher frequency signal produced by the first resonator  302  may be sent to a frequency divider  314  (e.g., a pressure-related frequency response) where the relatively higher frequency signal may be altered to be closer in value to the relatively lower frequency signals produced by one or more of the second resonator  306  (e.g., a reference frequency response) and the third resonator  310  (e.g., a temperature-related frequency response). For example, the relatively higher frequency signal produced by the first resonator  302  may be reduced (e.g., by half, by a third, etc.) by the frequency divider  314  and sent to mixer  316  to be combined with the signal of the reference sensor generated by the second resonator  306 . 
     The two, now relatively lower frequency signals from the first resonator  302  and the second resonator  306  (e.g., two frequency signals created by driving the pressure sensor and reference sensor) may be mixed by mixer  316 , which creates a sum of the signals and a difference of the signals, and the resultant signal is sent to output  318  (e.g., pressure output) via a filter  320  (e.g., a low-pass filter) and amplifier  322 . For example, the sum of the two frequency signals may be filtered by the low-pass filter  320  and the difference of the two frequency signals (e.g., a signal having in a value in the kilohertz range (i.e., below 1 MHz))) may be utilized to calculate the pressure at the output  318 . 
     The frequency signal produced by the second resonator  306  (e.g., the frequency signal created by driving the reference sensor) may also be sent to output  324  (e.g., reference output) via amplifier  326 . 
     The frequency signals produced by the second resonator  306  and the third resonator  310  (e.g., two frequency signals created by driving the reference sensor and temperature sensor) may be mixed by mixer  328 , which creates a sum of the signals and a difference of the signals, and the resultant signal is sent to output  330  (e.g., temperature output) via a filter  332  (e.g., a low-pass filter) and amplifier  334 . For example, the sum of the two frequency signals may be filtered by the low-pass filter  332  and the difference of the two frequency signals (e.g., a signal having in a value in the kilohertz range (i.e., below 1 MHz))) may be utilized to calculate the temperature at the output  330 . 
       FIG. 5  is a schematic block diagram of a circuit  400  suitable for use with transducers (e.g., the electronics assembly  120  of the pressure transducer  100 ) and sensors (e.g., pressure and/or temperature sensor  200 ). In some embodiments, circuit  400  may be somewhat similar to circuit  300  described above with reference to  FIG. 4  and may be particularly suited for use with resonator sensor  200  having a relatively smaller outer diameter than similar conventional sensors and transducers including such sensors  200 . However, as shown in  FIG. 5  and discussed below, both the first resonator  302  and a second resonator  406  (e.g., a crystal resonator) may be selected to produce a relatively higher frequency signal and a frequency divider  414  may be positioned such that the relatively higher signal from the second resonator  406  is divided before being mixed with the signal from the third resonator  310 . 
     As shown in  FIG. 5 , the circuit  400  includes the first resonator  302  driven by the first amplifier  304  at a relatively higher frequency such as, for example, over 14 MHz (e.g., about 14.45 MHz) to provide the pressure sensor. 
     The circuit  400  includes the second resonator  406  driven by a second amplifier  408  (e.g., at a relatively higher frequency similar to the first resonator  302  and the first amplifier  304 ) to provide a reference sensor (e.g., reference sensor  116  ( FIG. 1 )). The second amplifier  408  may drive the second resonator at a relatively higher frequency such as, for example, over 14 MHz (e.g., about 14.4 MHz). 
     In some embodiments, the circuit  400  includes the third resonator  310  driven by the third amplifier  312  at a relatively lower frequency such as, for example, about 7 MHz (e.g., about 7.15 MHz) to provide the temperature sensor. 
     The two, now relatively higher frequency signals from the first resonator  302  and the second resonator  406  (e.g., two frequency signals created by driving the pressure sensor and reference sensor) may be mixed by mixer  316 , which creates a sum of the signals and a difference of the signals, and the resultant signal is sent to output  318  (e.g., pressure output) via a filter  320  (e.g., a low-pass filter) and amplifier  322 . For example, the sum of the two frequency signals may be filtered by the low-pass filter  320  and the difference of the two frequency signals (e.g., a signal having in a value in the kilohertz range (i.e., below 1 MHz))) may be utilized to calculate the pressure at the output  318 . 
     The relatively higher frequency signal produced by the second resonator  406  (e.g., the frequency signal created by driving the reference sensor) may also be sent to output  324  (e.g., reference output) via amplifier  326 . 
     The relatively higher frequency signal produced by the second resonator  406  may be sent to a frequency divider  414  where the relatively higher frequency signal may be altered to be closer in value to the relatively lower frequency signals produced by the third resonator  310 . For example, the relatively higher frequency signal produced by the second resonator  406  may be reduced (e.g., by half, by a third, etc.) by the frequency divider  414  and sent to mixer  328  to be combined with the signal of the temperature sensor generated by the third resonator  310 . 
     The frequency signals produced by the second resonator  406  and the third resonator  310  (e.g., two frequency signals created by driving the reference sensor and temperature sensor) may be mixed by mixer  328 , which creates a sum of the signals and a difference of the signals, and the resultant signal is sent to output  330  (e.g., temperature output) via a filter  332  (e.g., a low-pass filter) and amplifier  334 . For example, the sum of the two frequency signals may be filtered by the low-pass filter  332  and the difference of the two frequency signals (e.g., a signal having in a value in the kilohertz range (i.e., below 1 MHz))) may be utilized to calculate the temperature at the output  330 . 
       FIG. 6  is a schematic block diagram of a circuit  500  suitable for use with transducers (e.g., the electronics assembly  120  of the pressure transducer  100 ) and sensors (e.g., pressure and/or temperature sensor  200 . In some embodiments, circuit  500  may be somewhat similar to circuit  300  described above with reference to  FIG. 4  and may be particularly suited for use with resonator sensor  200  having a relatively smaller outer diameter than similar conventional sensors and transducers including such sensors  200 . However, as shown in  FIG. 6  and discussed below, a first resonator  502 , a second resonator  506 , and a third resonator  510  may each be selected to produce a relatively higher frequency signal (e.g., over 14 MHz). 
     As shown in  FIG. 6 , the circuit  500  includes the first resonator  502  driven by a first amplifier  504  for driving at a relatively higher frequency such as, for example, over 14 MHz (e.g., about 14.45 MHz) to provide the pressure sensor. 
     The circuit  500  includes the second resonator  506  driven by a second amplifier  508  (e.g., at a relatively higher frequency similar to the first resonator  502 ) to provide the reference sensor. The second amplifier  508  may drive the second resonator  506  at a relatively higher frequency such as, for example, over 14 MHz (e.g., about 14.4 MHz). 
     In some embodiments, the circuit  500  includes the third resonator  510  driven by a third amplifier  512  (e.g., at a relatively higher frequency similar to the first resonator  502  and the second resonator  506 ) to provide the temperature sensor. The third amplifier  512  may drive the third resonator  510  at a relatively higher frequency such as, for example, over 14 MHz (e.g., about 14.35 MHz). 
     The two, relatively higher frequency signals produced by the first resonator  502  and the second resonator  506  (e.g., two frequency signals created by driving the pressure sensor and reference sensor) may be mixed by mixer  316 , which creates a sum of the signals and a difference of the signals, and the resultant signal is sent to output  318  (e.g., pressure output) via a filter  320  (e.g., a low-pass filter) and amplifier  322 . For example, the sum of the two frequency signals may be filtered by the low-pass filter  320  and the difference of the two frequency signals (e.g., a signal having in a value in the kilohertz range (i.e., below 1 MHz))) may be utilized to calculate the pressure at the output  318 . 
     The relatively higher frequency signal produced by the second resonator  506  (e.g., the frequency signal created by driving the reference sensor) may also be sent to output  324  (e.g., reference output) via amplifier  326 . 
     The two, relatively higher frequency signals produced by the second resonator  506  and the third resonator  510  (e.g., two frequency signals created by driving the reference sensor and temperature sensor) may be mixed by mixer  328 , which creates a sum of the signals and a difference of the signals, and the resultant signal is sent to output  330  (e.g., temperature output) via a filter  332  (e.g., a low-pass filter) and amplifier  334 . For example, the sum of the two frequency signals may be filtered by the low-pass filter  332  and the difference of the two frequency signals (e.g., a signal having in a value in the kilohertz range (i.e., below 1 MHz))) may be utilized to calculate the temperature at the output  330 . 
       FIG. 7  is a schematic block diagram of a circuit  600  suitable for use with transducers (e.g., the electronics assembly  120  of the pressure transducer  100 ) and sensors (e.g., pressure and/or temperature sensor  200 . In some embodiments, circuit  600  may be somewhat similar to circuit  300  described above with reference to  FIG. 4  and may be particularly suited for use with resonator sensor  200  having a relatively smaller outer diameter than similar conventional sensors and transducers including such sensors  200 . However, as shown in  FIG. 7  and discussed below, a frequency doubler  614  may be positioned such that the relatively lower frequency signal from the second resonator  306  is multiplied before being mixed with the relatively higher signal from the first resonator  302 . 
     As shown in  FIG. 7 , the circuit  600  includes the first resonator  302  driven by the first amplifier  304  at a relatively higher frequency such as, for example, over 14 MHz (e.g., about 14.45 MHz) to provide the pressure sensor. 
     The circuit  600  includes the second resonator  306  driven by the second amplifier  308  at a relatively lower frequency such as, for example, about 7 MHz (e.g., about 7.2 MHz) to provide the temperature sensor. 
     In some embodiments, the circuit  600  includes the third resonator  310  driven by the third amplifier  312  at a relatively lower frequency such as, for example, about 7 MHz (e.g., about 7.15 MHz) to provide the temperature sensor. 
     The relatively lower frequency signal produced by the second resonator  306  may be sent to a frequency doubler  614  where the relatively lower frequency signal may be altered to be closer in value to the relatively higher frequency signal produced by the first resonator  302 . For example, the relatively lower frequency signal produced by the second resonator  306  may be multiplied (e.g., by two times, by three times, etc.) by the frequency doubler  614  and sent to mixer  316  to be combined with the signal of the pressure sensor generated by the second resonator  302 . 
     The two, now relatively higher frequency signals from the first resonator  302  and the second resonator  306  (e.g., two frequency signals created by driving the pressure sensor and reference sensor) may be mixed by mixer  316 , which creates a sum of the signals and a difference of the signals, and the resultant signal is sent to output  318  (e.g., pressure output) via a filter  320  (e.g., a low-pass filter) and amplifier  322 . For example, the sum of the two frequency signals may be filtered by the low-pass filter  320  and the difference of the two frequency signals (e.g., a signal having in a value in the kilohertz range (i.e., below 1 MHz))) may be utilized to calculate the pressure at the output  318 . 
     The frequency signal produced by the second resonator  306  (e.g., the frequency signal created by driving the reference sensor) may also be sent to output  324  (e.g., reference output) via amplifier  326 . 
     The frequency signals produced by the second resonator  306  and the third resonator  310  (e.g., two frequency signals created by driving the reference sensor and temperature sensor) may be mixed by mixer  328 , which creates a sum of the signals and a difference of the signals, and the resultant signal is sent to output  330  (e.g., temperature output) via a filter  332  (e.g., a low-pass filter) and amplifier  334 . For example, the sum of the two frequency signals may be filtered by the low-pass filter  332  and the difference of the two frequency signals (e.g., a signal having in a value in the kilohertz range (i.e., below 1 MHz))) may be utilized to calculate the temperature at the output  330 . 
       FIG. 8  is a schematic block diagram of a circuit  600  suitable for use with transducers (e.g., the electronics assembly  120  of the pressure transducer  100 ) and sensors (e.g., pressure and/or temperature sensor  200 . In some embodiments, circuit  600  may be somewhat similar to circuits  300 ,  500 ,  600  described above with reference to  FIGS. 4 ,  6 , and  7  and may be particularly suited for use with resonator sensor  200  having a relatively smaller outer diameter than similar conventional sensors and transducers including such sensors  200 . However, as shown in  FIG. 8  and discussed below, the circuit  700  may include an electronic temperature sensor  710  (e.g., a silicon temperature sensor as disclosed in the above-incorporated U.S. patent application Ser. No. 13/934,058) rather than a resonator sensor. 
     As shown in  FIG. 8 , the circuit  700  includes the first resonator  302  driven by the first amplifier  304  at a relatively higher frequency such as, for example, over 14 MHz (e.g., about 14.45 MHz) to provide the pressure sensor. 
     The circuit  700  includes the second resonator  306  driven by the second amplifier  308  at a relatively lower frequency such as, for example, about 7 MHz (e.g., about 7.2 MHz) to provide the reference sensor. In other embodiments, the second resonator (e.g., second resonator  406 ) may drive the reference sensor at a relatively higher frequency such as, for example, over 14 MHz (e.g., about 14.4 MHz). 
     The circuit  700  includes an electronic temperature sensor  710  for electronic measurement of temperature (e.g., a sensor utilizing integrated electronic circuits to monitor temperature rather than a sensor exhibiting temperature-dependent variable mechanical characteristics such as a quartz crystal resonator). 
     The relatively lower frequency signal produced by the second resonator  306  may be sent to a frequency doubler  614  where the relatively lower frequency signal may be altered to be closer in value to the relatively higher frequency signal produced by the first resonator  302 . For example, the relatively lower frequency signal produced by the second resonator  306  may be multiplied (e.g., by two times, by three times, etc.) by the frequency doubler  614  and sent to mixer  316  to be combined with the signal of the pressure sensor generated by the second resonator  302 . In other embodiments, a frequency divider may be utilized on the relatively higher frequency signal produced by the first resonator  302 . 
     The two, now relatively higher frequency signals from the first resonator  302  and the second resonator  306  (e.g., two frequency signals created by driving the pressure sensor and reference sensor) may be mixed by mixer  316 , which creates a sum of the signals and a difference of the signals, and the resultant signal is sent to output  318  (e.g., pressure output) via a filter  320  (e.g., a low-pass filter) and amplifier  322 . For example, the sum of the two frequency signals may be filtered by the low-pass filter  320  and the difference of the two frequency signals (e.g., a signal having in a value in the kilohertz range (i.e., below 1 MHz))) may be utilized to calculate the pressure at the output  318 . 
     The frequency signal produced by the second resonator  306  (e.g., the frequency signal created by driving the reference sensor) may also be sent to output  324  (e.g., reference output) via amplifier  326 . 
     The temperature signal produced by the electronic temperature sensor  710  is sent to output  330  (e.g., temperature output). 
     Embodiments of the present disclosure may be particularly useful in providing relatively smaller sensors having a robust applicability in many different applications. In downhole applications, relatively smaller sensors enable the overall size of a transducer assembly to be reduced, enabling more efficient production of current, smaller wellbore diameter wells as well as exploration of new, more challenging formations using so-called “slimhole” drilling techniques with small diameter drilling strings and bottomhole components. For example, relatively smaller transducers also enable the ability to pass wires past the transducer between components above and below such transducers when disposed in a drill sting in ways that were not possible before with conventional sized transducers. Furthermore, smaller sensors are also believed to reach thermal equilibrium faster, resulting in less pressure measurement error while temperature is variable or during a transient temperature event. When implemented as a pressure sensor in a pressure transducer, the relatively smaller pressure sensor is closer in size to the temperature crystal, resulting in more similar responses to temperature change. Additionally, temperature gradients within the pressure sensor which may cause stress within the sensor that changes the natural frequencies of the pressure sensor and leads to pressure measurement error may be reduced. 
     While the disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the disclosure is not intended to be limited to the particular foams disclosed. Rather, the disclosure encompasses all modifications, variations, combinations, and alternatives falling within the scope of the disclosure as defined by the following appended claims and their legal equivalents.