Abstract:
This disclosure provides example methods, devices, and systems for an ultra-miniature, multi-hole flow angle probe. The construction, packaging of a multitude of absolute and or differential pressure transducers or sensors are invented for the purpose of providing highly accurate measurement of flow properties, flow angle in particular. The unique placement of sensors leads to further miniaturization relative to current state of the art. Further the use of closely coupled, differential transducer or transducers achieves higher accuracy measurement of small pressure variations coupled with large mean or average baseline pressures, as is demanded in modern aerodynamic or turbo-machinery devices. The use and installation of ultra-miniature sensors insider the device invented herein achieves higher frequency response than allowable via previous state of the part.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to multi-hole pressure probes and more particularly to ultra-miniature, multi-hole flow angle probes. 
       BACKGROUND 
       [0002]    The use of multi-hole pressure probes is a longstanding approach for measuring flow angles, stagnation and static pressures. Orthogonal flow angles as well as stagnation and static pressure may all be deduced from pressures measured at, for instance, several well chosen locations on the probe. Since the Mach number is a unique function of the ratio of stagnation to static pressure, the Mach number may also be derived from the pressures measured by a multi-hole pressure probe. A larger number of measurement locations on a multi-hole pressure probe may generally improve measurement accuracy but in exchange for an increased probe size. Probe size may be important for reducing disturbances in the flow field. However, a reduction in probe size typically leads to reducing the number of measurements, which may result in fewer flow variables. Furthermore, to enable fabrication of small probes, the static pressure ports on these steady state probes are usually connected to remote pressure transducers over long lengths of small diameter tubing, which may restrict their time response to several seconds or longer. The need to obtain higher frequency measurements leads to the development of high frequency probes. The high frequency response of these probes may be set by three factors: a frequency response of the transducer, which is generally higher than other factors and may not be limiting; a resonant frequency of any cavity between the surface of the probe and a diaphragm of a transducer; and a vortex shedding frequency of the body of the probe, which may scale with the size of the probe and fluid velocity. The latter two factors may scale with the size of the probe, resulting in smaller probes yielding a higher usable frequency response. Using silicon-on-insulator (SOI) sensor fabrication techniques as described in U.S. Pat. No. 5,286,671, “FUSION BONDING TECHNIQUE FOR USE IN FABRICATING SEMICONDUCTOR DEVICES,” provides small multi-hole probes with improved high frequency operation, as described in U.S. Pat. No. 8,069,732, entitled “ULTRA-MINIATURE MULTI-HOLE PROBES HAVING HIGH FREQUENCY, HIGH TEMPERATURE RESPONSES,” and U.S. Pat. No. 7,484,418, entitled “ULTRA MINIATURE MULTI-HOLE PROBES HAVING HIGH FREQUENCY RESPONSE,” all of which are assigned to Kulite Semiconductor Products, Inc. These tubular probes have a front probe surface that includes four or five apertures, wherein each aperture is associated with a separate high frequency transducer exposed to the pressure media. However, the use of absolute transducers in the probes to perform measurements of very small changes in pressure may introduce errors. Such errors may be associated with the use of separate high pressure absolute transducers for measuring very small changes in pressure riding on top of the stagnation pressure, which is a typical occurrence with low speed turbo-machinery. Accordingly, there is a need for improved techniques for ultra-miniature multi-hole flow angle probes. In addition, other desirable features and characteristics of the present disclosure will become apparent from the subsequent detailed description and claims, taken in conjunction with the accompanying figures and the foregoing technical field and background. 
       SUMMARY OF THE DISCLOSURE 
       [0003]    Briefly described, embodiments of the present invention relate to ultra-miniature, multi-hole flow angle probes. According to one aspect, a probe may comprise a housing, a first aperture, a second aperture, a first transducer and a second transducer. The housing may be configured to have a front portion with a first oblique side and a second oblique side. The first aperture may be disposed on the first oblique side of the front portion of the housing. Further, the second aperture may be disposed on the second oblique side of the front portion of the housing. The first transducer may be disposed in the housing. Further, the first transducer may be proximate the first aperture. The first transducer may be configured to measure a first environmental condition received at the first aperture. Similarly, the second transducer may be disposed in the housing. Further, the second transducer may be proximate the second aperture. The second transducer may be configured to measure a second environmental condition received at the second aperture. In addition, at least one of the first transducer and the second transducer may be configured as a differential transducer and a width of the housing may be less than five-tenths of an inch. 
         [0004]    According to another aspect, a probe by a process may include providing a housing having a front portion with a first oblique side and a second oblique side. Further, the housing may be configured to include a first aperture disposed on the first oblique side and a second aperture disposed on the second oblique side. The probe by the process may include inserting a first transducer into the housing proximate the first aperture. The first transducer may be configured for measuring a first environmental condition received at the first aperture. The probe by the process may include inserting a second transducer into the housing proximate the second aperture. The second transducer may be configured for measuring a second environmental condition received at the second aperture. The probe by the process may include coupling the first transducer to the first aperture. Similarly, the probe by the process may include coupling the second transducer to the second aperture. In addition, at least one of the first transducer and the second transducer may be configured as a differential transducer and a width of the housing may be less than five-tenths of an inch. 
         [0005]    According to another aspect, a method may include receiving, from a first aperture disposed on a first oblique side of a front portion of a housing, by a first transducer disposed in the housing proximate the first aperture, a first environmental condition. The method may include measuring, by the first transducer, the first environmental condition to generate a first environmental condition signal. Also, the method may include outputting, by the first transducer, the first environmental condition signal. The method may include receiving, from a second aperture disposed on the second oblique side of the front portion of the housing, by a second transducer disposed in the housing proximate the second aperture, a second environmental condition. The method may include measuring, by the second transducer, the second environmental condition to generate a second environmental condition signal. The method may include outputting, by the second transducer, the second environmental condition signal. In addition, at least one of the first transducer and the second transducer may be configured as a differential transducer and a width of the housing may be less than five-tenths of an inch. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0006]    The present disclosure is illustrated by way of examples, embodiments and the like and is not limited by the accompanying figures, in which like reference numbers indicate similar elements. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. The figures along with the detailed description are incorporated and form part of the specification and serve to further illustrate examples, embodiments and the like, and explain various principles and advantages, in accordance with the present disclosure, where: 
           [0007]      FIG. 1  illustrates a cross-sectional view of one embodiment of a probe in accordance with various aspects as described herein. 
           [0008]      FIG. 2  illustrates a perspective view of one embodiment of a probe in accordance with various aspects described herein. 
           [0009]      FIG. 3  illustrates a cross-sectional view of another embodiment of a probe in accordance with various aspects as described herein. 
           [0010]      FIG. 4  illustrates a perspective view of another embodiment of a probe in accordance with various aspects described herein. 
           [0011]      FIG. 5  illustrates a perspective view of another embodiment of a probe in accordance with various aspects described herein. 
           [0012]      FIG. 6  illustrates a perspective view of another embodiment of a probe in accordance with various aspects described herein. 
           [0013]      FIG. 7  illustrates a cross-sectional view of another embodiment of a probe in accordance with various aspects described herein. 
           [0014]      FIG. 8  illustrates a cross-sectional view of another embodiment of a probe in accordance with various aspects described herein. 
           [0015]      FIG. 9  is a flowchart of one embodiment of a probe by a process in accordance with various aspects set forth herein. 
           [0016]      FIG. 10  is a flowchart of one embodiment of a method of performing a measurement of an environmental condition in accordance with various aspects set forth herein. 
           [0017]      FIG. 11  illustrates a cross-sectional view of another embodiment of a probe in accordance with various aspects described herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The following detailed description is merely illustrative in nature and is not intended to limit the present disclosure, or the application and uses of the present disclosure. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding field of use, background, or summary of the disclosure or the following detailed description. The present disclosure provides various examples, embodiments and the like, which may be described herein in terms of functional or logical block elements. Various techniques described herein may be used for ultra-miniature, multi-hole flow angle probes. The various aspects described herein are presented as methods, devices (or apparatus), and systems that may include a number of components, elements, members, modules, nodes, peripherals, or the like. Further, these methods, devices, and systems may include or not include additional components, elements, members, modules, nodes, peripherals, or the like. 
         [0019]    Throughout the specification and the claims, the following terms take at least the meanings explicitly associated herein, unless the context clearly dictates otherwise. The terms “connect,” “connecting,” and “connected” mean that one function, feature, structure, or characteristic is directly joined to or in communication with another function, feature, structure, or characteristic. The terms “couple,” “coupling,” and “coupled” mean that one function, feature, structure, or characteristic is directly or indirectly joined to or in communication with another function, feature, structure, or characteristic. Relational terms such as “first” and “second,” and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The term “or” is intended to mean an inclusive or. Further, the terms “a,” “an,” and “the” are intended to mean one or more unless specified otherwise or clear from the context to be directed to a singular form. The term “include” and its various forms are intended to mean including but not limited to. The terms “substantially,” “essentially,” “approximately,” “about” or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within 1% and in another embodiment within 0.5%. 
         [0020]    In the following description, numerous specific details are set forth. However, it is to be understood that embodiments of the disclosed technology may be practiced without these specific details. References to “one embodiment,” “an embodiment,” “example embodiment,” “various embodiments,” and other like terms indicate that the embodiments of the disclosed technology so described may include a particular function, feature, structure, or characteristic, but not every embodiment necessarily includes the particular function, feature, structure, or characteristic. Further, repeated use of the phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may. 
         [0021]    This disclosure presents an ultra-miniature, multi-hole flow angle probe. For instance, by configuring a probe in accordance with various aspects described herein, an improved pressure measurement capability of a probe is provided. For example,  FIG. 1  illustrates a cross-sectional view of one embodiment of a probe  100  in accordance with various aspects as described herein. In  FIG. 1 , the probe  100  may be configured to include a first transducer  101 , a second transducer  103 , a first tube  105 , a second tube  107 , a third tube  109 , a housing  111 , a first aperture  113  in the housing  111 , a second aperture  115  in the housing  111 , a first set of connectors  117 , a second set of connectors  119 , and a cavity  125 . Dimensions of the probe  100  may include a height  131  and a width  133 . The probe  100  may be configured to utilize one or more absolute transducers, one or more differential transducers or any combination thereof, which may be strategically disposed in the housing  111  such as near environmental conditions received at the first aperture  113  and the second aperture  115 . The first transducer structure  101  may be configured to include a first transducer and a first header. The first transducer may be an absolute transducer or a differential transducer. In one example, the first transducer is an absolute transducer, which may be fabricated to include an internal reference environmental condition such as an internal hermetically-sealed vacuum reference pressure. The second transducer structure  103  may be configured to include a second transducer. The second transducer may be an absolute transducer or a differential transducer. In one example, the second transducer may be a differential transducer, which may be fabricated to include a reference tube or reference aperture. An integrated packaging of the first transducer structure  101  and the second transducer structure  103  in the housing  111  may provide a location of the first transducer and the second transducer proximate to the environmental conditions to be measured. 
         [0022]    Furthermore, each of the first transducer and the second transducer may include SOI piezoresistive elements. In one example, each of the first transducer and the second transducer may be fabricated in accordance with techniques such as described by U.S. Pat. No. 5,286,671, entitled “FUSION BONDING TECHNIQUE FOR USE IN FABRICATING SEMICONDUCTOR DEVICES,” U.S. Pat. No. 7,439,159, entitled “FUSION BONDING PROCESS AND STRUCTURE FOR FABRICATING SILICON-ON-INSULATOR (SOI) SEMICONDUCTOR DEVICES,” U.S. Pat. No. 7,709,897, entitled “FUSION BONDING PROCESS AND STRUCTURE FOR FABRICATING SILICON-ON-INSULATOR (SOI) SEMICONDUCTOR DEVICES,” U.S. Pat. No. 7,989,894, entitled “FUSION BONDING PROCESS AND STRUCTURE FOR FABRICATING SILICON-ON-INSULATION (SOI) SEMICONDUCTOR DEVICES,” U.S. Pat. No. 5,955,771, entitled “SENSORS FOR USE IN HIGH VIBRATIONAL APPLICATIONS AND METHODS FOR FABRICATING SAME,” and U.S. Pat. No. 5,973,590, entitled “ULTRA THIN SURFACE MOUNT WAFER SENSOR STRUCTURES AND METHODS FOR FABRICATING SAME,” all of which are assigned to Kulite Semiconductor Products, Inc. A shape of a front portion of the probe  100  may be angled, conical, wedge-shaped, pointed, pyramidal, spherical, tapered or the like. Further, the shape of the front portion of the probe  100  may not impact dimensions of the probe  100 . Depending on, for instance, a desired frequency response, a minimal probe size and shape may be obtained using the configuration of the probe  100 . A person of ordinary skill in the art will recognize the utility of various shapes of the front portion of a probe for specific applications. 
         [0023]    In  FIG. 1 , a first end of the first tube  105  may be coupled to the first aperture  113  of the housing  111 , which may be used to receive a first environmental condition such as pressure. Further, the first transducer  101  may be coupled to a second end of the first tube  105 . The housing  111  may be disposed around and define the first tube  105  and the first aperture  113 . Furthermore, the second transducer  103  may be coupled to the second tube  107  and the third tube  109 . A first end of the second tube  107  may be coupled to the second aperture  115 . A first end of the third tube  109  may be coupled to the first aperture  111  or to another aperture in the housing  111 . A second end of the second tube  107  may be coupled to a first side of the second transducer  103 . A second end of the third tube  109 , which may also be referred to as a reference tube, may be coupled to a reference side of the second transducer. The housing  111  may be disposed around and define the second tube  107 , the third tube  109  or the second aperture  113 . A length, a shape or the like of a tube may be selected to provide filtering of a fluid flow. 
         [0024]    In  FIG. 1 , the first or main side of the second transducer  103  such as a differential pressure transducer may be positioned near the second aperture  115  of the housing  111 . The second side of the second transducer  103 , which may also be referred to as the reference side of the second transducer  103 , may be coupled to the first aperture  113  using the third tube  109 . The first tube  105  and the third tube  109  may share the first aperture  113  of the housing  111 , which may allow for contemporaneous measurements of an environmental condition received at the first aperture  113  of the housing  111  by the first transducer  101  and the second  103 . The first set of connectors  117  may be configured to couple the first transducer  101  to a first electronic circuit. Further, the first set of connectors  117  may allow the first transducer  101  to communicate with the first electronic circuit. In one example, the first transducer of  101  may provide a first environmental condition signal associated with a measured first environmental condition to the first electronic circuit using the first set of connectors  117 . In another example, the first electronic circuit may configure the first transducer  101  using the first set of connectors  117 . Also, the first electronic circuit may provide power to the first transducer  101  using the first set of connectors  117 . The first set of connectors  117  may be disposed in the cavity  125  defined by the housing  111 . 
         [0025]    Similarly, the second set of connectors  119  may be configured to couple the second transducer  103  to a second electronic circuit. Further, the second set of connectors  119  may allow the second transducer  103  to communicate with the second electronic circuit. In one example, the second transducer  103  may provide a second environmental condition signal associated with a measured second environmental condition to the second electronic circuit using the second set of connectors  119 . In another example, the second electronic circuit may configure the second transducer  101  using the second set of connectors  119 . Also, the second electronic circuit may provide power to the second transducer  103  using the second set of connectors  119 . Also, the second set of connectors  119  may provide power to the second transducer  103 . The second set of connectors  119  may be disposed in the cavity  125  defined by the housing  111 . Each of the first electronic circuit and the second electronic circuit may be placed in the housing  111  or may be located outside the housing  111 . Further, the first electronic circuit and the second electronic circuit may be the same electronic circuit. A person of ordinary skill in the art will recognize various techniques for designing circuits to interface with a transducer. 
         [0026]    The configuration of the probe  100  may allow for the height  131  or the width  133  of the housing  111  to be miniaturized. For example, the height  131  of the housing  111  may be about five-tenths of an inch (0.5 inches) nominally and can carry from 0.2 inches to 1 inch depending on the installation. In another example, the width  133  of the housing  111  may be about two-tenths of an inch (0.2 inches) and vary larger or smaller depending on the installation. 
         [0027]    Furthermore, the housing  111  may also be used to attach or secure the probe  100  to another structure, protect all or a portion of the probe  100 , provide a means to handle or place the probe  100  or the like. In one example, the housing  111  may be used to form an O-ring seal, may be threaded, may include a series of O-rings or bolts, or the like so that the probe  100  may be attached to another structure. The housing  111  may be composed of a thermally isolative or conductive material such as a ceramic material, metal or the like. 
         [0028]    In this embodiment, in operation, the first transducer of the first transducer structure  101 , which may be an absolute transducer, may receive, at the first transducer, from the first aperture  113  using the first tube  105 , the first environmental condition. The first transducer  101  may measure the first environmental condition to generate a first environmental condition signal. The first transducer  101  may output the environmental condition signal using the first set of connectors  117 . The second transducer  103 , which may be a differential transducer, may receive from the second aperture  115  using the second tube  107 , the second environmental condition. In one example, the first environmental condition may be equivalent to the second environmental condition. In another example, the first environmental condition may be different from the second environmental condition. Further, the second transducer  103  may receive from the first aperture  113  using the third tube  109 , the first environmental condition. The second transducer  103  may determine a difference between the first environmental condition and the second environmental condition. Further, the second transducer  103  may measure the difference between the first environmental condition and the second environmental condition to generate a difference signal. The second transducer  103  may output the difference signal using the second set of connectors  119 . 
         [0029]      FIG. 2  illustrates a longitudinal perspective view of one embodiment of a probe  200  in accordance with various aspects described herein. In  FIG. 2 , the probe  200  may be configured to include a housing  211 , a first aperture  213 , a second aperture (not shown), a first oblique face  225  and a second oblique face (not shown). The housing  211  may be disposed around and may define the first aperture  213 . The first aperture  213  may be disposed on a first oblique face  225  of a front portion of the housing  211 . Similarly, the second aperture may be positioned on a second oblique face of the front portion of the housing  211 . Each of the first aperture  213  and the second aperture may be positioned on opposite sides of the first oblique face  225  and the second oblique face of the front portion of the housing  211 , respectively. In one example, each of the first aperture  213  and the second aperture may be symmetrically positioned on opposite sides of the first oblique face  225  and the second oblique face of the front portion of the housing  211 , respectively. Furthermore, the front portion of the housing  211  may have a shape of a wedge defined by the first oblique face  225  and the second oblique face. The probe  200  may allow for measurements of two angles defined by the first oblique face and the second oblique face  225  of the front portion of the housing  211 . Further, these measurements may include stagnation pressure, static pressure, Mach number, and the like. In one example, the probe  200  may allow for high accuracy, high frequency measurements of two orthogonal angles associated with the first oblique face  225  and the second oblique face. 
         [0030]    In another embodiment, a first aperture may be positioned on a first oblique face of a front portion of a housing so that a first flow associated with a first environmental condition may be received at the first aperture. Further, a second aperture may be positioned on a second oblique face of the front portion of the housing so that a second flow associated with a second environmental condition may be received at the second aperture. 
         [0031]    In another embodiment, a first flow of a first environmental condition at a first oblique face of a front portion of a housing may be about equivalent to a second flow of a second environmental condition at a second oblique face of the front portion of the housing. 
         [0032]    In another embodiment, a first flow of a first environmental condition at a first oblique face may be different from a second flow of a second environmental condition at a second oblique face. 
         [0033]    In another embodiment, each of a first aperture and a second aperture may be positioned about equidistant from a front end of a housing on a first oblique face and a second oblique face of a front portion of the housing, respectively. 
         [0034]    In another embodiment, each of a first aperture and a second aperture may be positioned about equidistant along a longitudinal axis of a probe. 
         [0035]    In another embodiment, a differential sensor may determine a difference between an environmental condition having a static component and a dynamic component and a filtered environmental condition having the static component to obtain a difference signal. Further, an absolute sensor may measure the environmental condition to obtain an absolute signal. A third tube may be used to filter the environmental condition to obtain the filtered environmental condition having the static component. 
         [0036]    In another embodiment, a first transducer and a second transducer may be positioned about equidistance along a longitudinal axis of a probe. By doing so may result in the first transducer structure and the second transducer structure operating in about equivalent conditions such as pressure. 
         [0037]      FIG. 3  illustrates a cross-sectional view of another embodiment of a probe  300  in accordance with various aspects as described herein. In  FIG. 3 , the probe  300  may be configured to include a first transducer  301 , a second transducer  303 , a first tube  305 , a second tube  307 , a third tube  309 , a housing  311 , a first aperture  313  in the housing  311 , a second aperture  315  in the housing  311 , a first set of connectors  317 , a second set of connectors  319 , and a cavity  325 . Dimensions of the probe  300  may include a height  331  and a width  333 . The probe  300  may be configured to utilize one or more absolute transducers, one or more differential transducers or any combination thereof, which may be strategically disposed in the housing  311  such as near an environmental condition such as a pressure media received at the first aperture  313  and the second aperture  315 . The first transducer may be an absolute transducer or a differential transducer. In one example, the first transducer is an absolute transducer, which may be fabricated to include an internal environmental condition reference such as an internal hermetically-sealed vacuum reference pressure. The second transducer may be an absolute transducer or a differential transducer. In one example, the second transducer may be a differential transducer, which may be fabricated to include a reference tube or reference aperture. An integrated packaging of the first transducer  301  and the second transducer  303  in the housing  311  may provide a location proximate to the environmental conditions to be measured. Furthermore, each of the first transducer and the second transducer may include SOI piezoresistive elements. A shape of a front portion of the probe  300  may be angled, conical, wedge-shaped, pointed, pyramidal, spherical, tapered or the like. 
         [0038]    In  FIG. 3 , a first end of the first tube  305  may be coupled to the first aperture  313  of the housing  311 , which may be used to receive a first condition such as pressure. Further, the first transducer structure  301  may be coupled to a second end of the first tube  305 . The housing  311  may be disposed around and define the first tube  305  and the first aperture  311 . The second transducer  303  may be coupled to the second tube  307  and the third tube  309 . A first end of the second tube  307  may be coupled to the second aperture  315 . A first end of the third tube  309  may be coupled to the first aperture  311  or to another aperture in the housing  311 . A second end of the second tube  307  may be coupled to a first or main side of the second transducer  303 . A second end of the third tube  309 , which may also be referred to as a reference tube, may be coupled to a second or reference side of the second transducer  303 . The housing  311  may be disposed around and define the second tube  307 , the third tube  309  or the second aperture  313 . 
         [0039]    In this embodiment, the first tube  305  and the third tube  309  may share the first aperture  313  of the housing  311 , which may allow for contemporaneous measurements of the first environmental condition received at the first aperture  313  of the housing  311  by the first transducer  301  and the second transducer  303 . The first set of connectors  317  may be configured to couple the first transducer  301  to a first electronic circuit. Further, the first set of connectors  317  may allow the first transducer  301  to communicate with the first electronic circuit. In one example, the first transducer  301  may provide a first environmental condition signal associated with a measured first environmental condition to the first electronic circuit using the first set of connectors  317 . In another example, the first electronic circuit may configure the first transducer  301  using the first set of connectors  317 . Also, the first electronic circuit may provide power to the first transducer  301  using the first set of connectors  317 . The first set of connectors  317  may be disposed in the cavity  325  defined by the housing  311 . 
         [0040]    Similarly, the second set of connectors  319  may be configured to couple the second transducer  303  to a second electronic circuit. Further, the second set of connectors  319  may allow the second transducer  303  to communicate with the second electronic circuit. In one example, the second transducer  303  may provide a second environmental condition signal associated with a measured second environmental condition to the second electronic circuit using the second set of connectors  319 . In another example, the second electronic circuit may configure the second transducer  303  using the second set of connectors  319 . Also, the second electronic circuit may provide power to the second transducer  303  using the second set of connectors  319 . Also, the second set of connectors  319  may provide power to the second transducer  303 . The second set of connectors  319  may be disposed in the cavity  325  defined by the housing  311 . Each of the first electronic circuit and the second electronic circuit may be placed in the housing  311  or may be located outside the housing  311 . Further, the first electronic circuit and the second electronic circuit may be the same electronic circuit. A person of ordinary skill in the art will recognize various techniques for designing circuits to interface with a transducer. 
         [0041]    In  FIG. 3 , the width  333  of the probe  300  may also be reduced by extending the length of the front portion of the housing  311 , which may increase a length of each of the first tube  305 , the second tube  307  or the third tube  309 . Further, a width of the front portion of the housing  311  may be associated with a width of each of the first tube  305 , the second tube  307  and the third tube  309 . In one example, the width  333  of the housing  311  may be about thirteen-hundredths of an inch (0.13 inches). In another example, the width  333  of the housing  311  may be less than about two-tenths of an inch (0.2 inches). In another example, the width  333  of the housing  311  may be in a range from about two-hundredths of an inch (0.02 inches) which may vary more or less depending on field installation. In another example, the width  333  of the housing  311  may be associated with a width of each of the first tube  305 , the second tube  307  and the third tube  309 . In addition, the height  331  of the housing  311  may be adjusted to conform to the width  333  of the housing  311  or various widths of the front portion of the housing  311 . A trade-off may occur between the size of the probe  300  and the desired measurement frequency content. 
         [0042]    In the current embodiment, the housing  311  may also be used to attach or secure the probe  300  to another structure, protect all or a portion of the probe  300 , provide a means to handle or place the probe  300  or the like. In one example, the housing  311  may be used to form an O-ring seal, may be threaded, may include a series of O-rings or bolts, or the like so that the probe  300  may be attached to another structure. The housing  311  may be composed of a thermally conductive material such as a ceramic material, metal or the like. 
         [0043]    In  FIG. 3 , in operation, the first transducer  301 , which may be an absolute transducer, may receive, at the first transducer, from the first aperture  313  using the first tube  305 , the first environmental condition. The first transducer  301  may measure the first environmental condition to generate a first environmental condition signal. The first transducer  301  may output the first environmental condition signal using the first set of connectors  317 . The second transducer  303 , which may be a differential transducer, may receive, at the first or main side of the second transducer, from the second aperture  315  using the second tube  307 , the second environmental condition. Further, the second transducer  303  may receive, at the second or reference side of the second transducer, from the first aperture  313  using the third tube  309 , the first environmental condition. The second transducer  303  may determine a difference between the first environmental condition and the second environmental condition. Further, the second transducer  303  may measure the difference between the first environmental condition and the second environmental condition to generate a difference signal. The second transducer  303  may output the difference signal using the second set of connectors  319 . 
         [0044]      FIG. 4  illustrates a perspective view of another embodiment of a probe  400  in accordance with various aspects described herein. In  FIG. 4 , the probe  400  may be configured to include a housing  411 , a first aperture  413 , a second aperture (not shown), a first oblique face  425  and a second oblique face (not shown). The housing  411  may be disposed around and may define the first aperture  413 . The first aperture  413  may be disposed on a first oblique face  425  of a front portion of the housing  411 . Similarly, the second aperture may be positioned on a second oblique face of the front portion of the housing  411 . Each of the first aperture  413  and the second aperture may be positioned on opposite sides of the first oblique face  425  and the second oblique face of the front portion of the housing  411 , respectively. In one example, each of the first aperture  413  and the second aperture may be symmetrically positioned on opposite sides of the first oblique face  425  and the second oblique face of the front portion of the housing  411 , respectively. Furthermore, the front portion of the housing  411  may have a shape of a wedge defined by the first oblique face  425  and the second oblique face. The probe  400  may allow for measurements of two angles defined by the first oblique face and the second oblique face of the front portion of the housing. Further, these measurements may include stagnation pressure, static pressure, Mach number, and the like. In addition, a height of the front portion of the housing  411  may be increased to allow for a width of at least a portion of the front portion of the housing  411  to be decreased. 
         [0045]      FIG. 5  illustrates a perspective view of another embodiment of a probe  500  in accordance with various aspects described herein. In  FIG. 5 , the probe  500  may be configured to include a housing  511 , a first aperture  513 , a second aperture (not shown), a first oblique face  525 , a second oblique face  526 , a third oblique face (not shown)  527  and a fourth oblique face (not shown)  528 . A front portion of the housing  511  may be a shape of a pyramid with the first oblique face  525 , the second oblique face  526 , the third oblique face  527  and the fourth oblique face  528  forming the sides of the pyramid. The first oblique face  525  may be opposite to the third oblique face  527 . Also, the second oblique face  526  may be opposite to the fourth oblique face  528 . The first aperture  513  may be disposed on the first oblique face  525  of the front portion of the housing  511 . The housing  511  may be disposed around and may define the first aperture  513 . Similarly, the second aperture may be positioned on the third oblique face  527  of the front portion of the housing  511 . The housing  511  may be disposed around and may define the second aperture. The first aperture  513  and the second aperture may be positioned on opposite sides of the front portion of the housing  511  on the first oblique face  525  and the third oblique face  527 , respectively. In one example, each of the first aperture  513  and the second aperture may be symmetrically positioned on opposite sides of the front portion of the housing  511  on the first oblique face  525  and the third oblique face  527 , respectively. The probe  500  may allow for measurements of two angles defined by the first oblique face  525  and the third oblique face  527  of the front portion of the housing, and by adding additional apertures on oblique faces  526  and  528 . Further, the probe  500  may be positioned at different angles relative to a fluid flow, resulting in changing the fluid flow across each of the first oblique face  525  and the third oblique face  527 . These measurements may include stagnation pressure, static pressure, Mach number, or the like. In one example, the probe  500  may allow for high accuracy, high frequency measurements of two orthogonal angles defined by the first oblique face  525  and the third oblique face  527  of the front portion of the housing. A shape of the front portion of the housing  511  may not impact a height or width of the front portion of the housing  511 . However, the shape of the front portion of the housing  511  may impact measurement performance of the probe  500  such as for a particular flow, speed or the like. Thus, the shape of the front portion of the housing  511  may be selected to increase measurement performance of the probe  500 . 
         [0046]      FIG. 6  illustrates a longitudinal perspective view of another embodiment of a probe  600  in accordance with various aspects described herein. In  FIG. 6 , the probe  600  may be configured to include a housing  611 , a first aperture  613 , a second aperture  615 , and a plurality of front oblique sides. A front portion of the housing  611  may be a shape of a sphere with the plurality of front oblique sides combining to form the sphere. The first aperture  613  may be disposed on a first front oblique side of the plurality of front oblique sides. The housing  611  may be disposed around and may define the first aperture  613 . Similarly, the second aperture  615  may be positioned on a second front oblique side of the plurality of front oblique sides. The housing  611  may be disposed around and may define the second aperture. The first aperture  613  and the second aperture  615  may be positioned on opposite sides of the front portion of the housing  611 . In one example, the first aperture  613  and the second aperture may be symmetrically positioned on opposite sides of the front portion of the housing  611 . The probe  600  may allow for measurements of two angles defined by the first front oblique side and the second front oblique side of the plurality of front oblique sides and by apertures in addition to  613  and  615 . Further, these measurements may include stagnation pressure, static pressure, Mach number, or the like. In one example, the probe  600  may allow for high accuracy, high frequency measurements of two orthogonal angles defined by the first front oblique side and the second front oblique side of the plurality of front oblique sides. A shape of the front portion of the housing  611  may not impact a height or width of the front portion of the housing  611 . However, the shape of the front portion of the housing  611  may impact measurement performance of the probe  600  such as for a particular flow, speed or the like. Thus, the shape of the front portion of the housing  611  may be selected to increase measurement performance of the probe  600 . 
         [0047]      FIG. 7  illustrates a cross-sectional view of another embodiment of a probe  700  in accordance with various aspects described herein. In  FIG. 7 , the probe  700  may be configured to include a first transducer  701 , a second transducer  703 , a third transducer  704 , a first tube  705 , a second tube  707 , a housing  711 , a first aperture  713  in the housing  711 , a second aperture  715  in the housing  711 , a first set of connectors  717 , a second set of connectors  719 , a third set of connectors  721 , a cavity  725 , a third tube  727  and a fourth tube  729 . Dimensions of the probe  700  may include a height  731  and a width  733 . The probe  700  may be configured to utilize one or more absolute transducers, one or more differential transducers or any combination thereof, which may be strategically disposed in the housing  711  near environmental conditions received at the first aperture  713  or the second aperture  715 . The first transducer structure  701  may be configured to include a first transducer and a first header. The first transducer may be an absolute transducer or a differential transducer. In one example, the first transducer is a differential transducer. The second transducer may be an absolute transducer or a differential transducer. In one example, the second transducer may be a differential transducer, which may be fabricated to include a reference tube or reference aperture. The third transducer may be an absolute transducer or a differential transducer. In one example, the third transducer is an absolute transducer, which may be fabricated to include an internal reference environmental condition such as an internal hermetically-sealed vacuum pressure. 
         [0048]    In  FIG. 7 , an integrated packaging of the first transducer  701  and the second transducer  703  in the housing  711  may provide a location of the first transducer and the second transducer proximate to the environmental conditions to be measured. Further, the third transducer  704  may be disposed in the cavity  725  of the housing  711 . In addition, each of the first transducer, the second transducer and the third transducer may include SOI piezoresistive elements. A shape of a front portion of the probe  700  may be angled, conical, wedge-shaped, pointed, pyramidal, spherical, tapered or the like. The shape of the front portion of the probe  700  may not impact the dimensions of the probe  700 , including the height  731  and the width  733  of the probe  700 . Further, the shape of the probe  700  may be selected for a certain flow or speed application. 
         [0049]    In this embodiment, a first end of the first tube  705  may be coupled to the first aperture  713  of the housing  711 , which may be used to receive a first environmental condition such as pressure. Further, the first transducer  701  may be coupled to a second end of the first tube  705 . In addition, a first end of the third tube  727 , which may also be referred to as a reference tube, may be coupled to a second or reference side of the first transducer. A second end of the third tube  727  may be disposed in the cavity  725  of the housing  711  or may be coupled to another tube or another aperture in the housing  711 . The housing  711  may be disposed around and may define the first tube  705 , the first aperture  713  or the third tube  727 . 
         [0050]    Furthermore, the first set of connectors  717  may be configured to couple the first transducer  701  to a first electronic circuit. The first set of connectors  717  may allow the first transducer  701  to communicate with the first electronic circuit. In one example, the first transducer  701  may provide a first environmental condition signal associated with a measured first environmental condition to the first electronic circuit using the first set of connectors  717 . In another example, the first electronic circuit may configure the first transducer  701  using the first set of connectors  717 . Also, the first electronic circuit may provide power to the first transducer  701  using the first set of connectors  717 . The first set of connectors  717  may be disposed in the cavity  725  defined by the housing  711 . 
         [0051]    In  FIG. 7 , the second transducer  703  may be coupled to the second tube  707  and the fourth tube  729 . A first or main side of the second transducer  703  such as a differential pressure transducer may be positioned near the second aperture  715  of the housing  711 . A second side of the second transducer  703 , which may also be referred to as the reference side, may be exposed to the cavity  725  of the housing  711  using the fourth tube  729 . A first end of the second tube  707  may be coupled to the second aperture  715 . A second end of the second tube  707  may be coupled to a first side of the second transducer  703 . A first end of the fourth tube  729 , which may also be referred to as a reference tube, may be coupled to a second or reference side of the second transducer. A second end of the fourth tube  729  may be disposed in the cavity  725  of the housing  711  or may be coupled to another tube or another aperture in the housing  711 . The housing  711  may be disposed around and may define the second tube  707 , the second aperture  715  or the fourth tube  729 . 
         [0052]    Furthermore, the second set of connectors  719  may be configured to couple the second transducer  703  to a second electronic circuit. Further, the second set of connectors  719  may allow the second transducer  703  to communicate with the second electronic circuit. In one example, the second transducer  703  may provide a second environmental condition signal associated with a measured second environmental condition to the second electronic circuit using the second set of connectors  719 . In another example, the second electronic circuit may configure the second transducer  703  using the second set of connectors  719 . Also, the second electronic circuit may provide power to the second transducer  703  using the second set of connectors  719 . The second set of connectors  719  may be disposed in the cavity  725  defined by the housing  711 . 
         [0053]    In this embodiment, the third transducer structure  704  may be disposed in the cavity  725  of the housing  711 . Further, the third transducer, which may be an absolute pressure transducer, of the third transducer  704  may be exposed to the cavity  725  of the housing  711  using, for instance, a reference tube. The third set of connectors  721  may be configured to couple the third transducer  704  to a third electronic circuit. Further, the third set of connectors  721  may allow the third transducer  704  to communicate with the third electronic circuit. In one example, the third transducer  704  may provide a third environmental condition signal associated with a measured third environmental condition to the third electronic circuit using the third set of connectors  721 . In another example, the third electronic circuit may configure the third transducer  704  using the third set of connectors  721 . Also, the third electronic circuit may provide power to the third transducer  704  using the third set of connectors  721 . The third set of connectors  721  may be disposed in the cavity  725  defined by the housing  711 . Each of the first electronic circuit, the second electronic circuit or the third electronic circuit may be placed in the housing  711  or may be located outside the housing  711 . Further, the first electronic circuit, the second electronic circuit or the third electronic circuit may be part of the same electronic circuit. 
         [0054]    In this embodiment, there may also be a filter structure  726  such as described in U.S. patent application Ser. No. 13/28,037 between the outside of the probe and the internal cavity  725 . This filter structure  726  may act to limit the frequency response of the internal cavity to give a true static reference pressure regardless of the dynamic pressure outside of the probe and regardless of the angle of attack of the probe. In a typical probe, the static pressure must be run through a long tube or be on an external stable structure. 
         [0055]    In  FIG. 7 , the probe  700  may allow for the height  731  or the width  733  of the housing  711  to be miniaturized, since each of the first transducer and the second transducer may be a differential transducer. In one example the width  733  can be approximately  0 . 2 , more or less depending on the application installation. Since a reference tube such as the third tube  109  of probe  100  in  FIG. 1  is not used by the probe  700 , a gap between the first transducer structure  701  and the second transducer structure  703  of the probe  700  may be less than a gap between the first transducer  101  and the second transducer  103  of the probe  100 . Thus, the configuration of the probe  700  may allow for more miniaturization than the configuration of the probe  100 , resulting in the width  733  of the probe  700  being less than the width  133  of the probe  100 . Further, a differential transducer may have higher sensitivity or accuracy or may operate at higher frequencies than an absolute transducer. Thus, the probe  700  having two differential transducers may have higher sensitivity or accuracy or may operate at higher frequencies than the probe  100  having one differential transducer and one absolute transducer. 
         [0056]    In operation, for the probe  700  having the two differential transducers, the first or main side of the first transducer  701  may receive the first environmental condition from the first aperture  713  while the second or reference side of the first transducer may receive a reference environmental condition such as from the cavity  725  of the housing  711 . The first transducer may determine a first difference between the first environmental condition and the reference environmental condition to generate a first difference signal. Similarly, the first or main side of the second transducer  703  may receive the second environmental condition from the second aperture  715  while the second or reference side of the second transducer may receive the reference environmental condition such as from the cavity  725  of the housing  711 . The second transducer may determine a second difference between the second environmental condition and the reference environmental condition to generate a second difference signal. The third transducer  704 , which may be an absolute transducer, may receive the reference environmental condition such as from the cavity  725  of the housing  711  to generate a reference signal. The reference signal may be used in conjunction with the first difference signal and the second difference signal to determine a first absolute environmental condition at the first aperture  713  and a second absolute environmental condition at the second aperture  715 , respectively, which may be used to determine a flow angle. 
         [0057]    In another embodiment, a first transducer, a second transducer or the third transducer may be the same. 
         [0058]    In another embodiment, a first transducer, a second transducer and a third transducer may share the same semiconductor substrate or packaging. 
         [0059]      FIG. 8  illustrates a cross-sectional view of another embodiment of a probe  800  in accordance with various aspects described herein. In  FIG. 8 , the probe  800  may be configured to include a first transducer  801 , a second transducer  803 , a third transducer  804 , a first tube  805 , a second tube  807 , a housing  811 , a first aperture  813  in the housing  811 , a second aperture  815  in the housing  811 , a first set of connectors  817 , a second set of connectors  819 , a third set of connectors  821 , a cavity  825 , a third tube  827  and a fourth tube  829 . Dimensions of the probe  800  may include a height  831  and a width  833 . The probe  800  may be configured to utilize one or more absolute transducers, one or more differential transducers or any combination thereof, which may be strategically disposed in the housing  811  near environmental conditions at the first aperture  813  or the second aperture  815 . 
         [0060]    In  FIG. 8 , the first transducer  801  may be configured to be an absolute transducer or a differential transducer. In one example, the first transducer is a differential transducer, which may be fabricated to include a reference tube or a reference aperture. The second transducer  803  may be configured to be an absolute transducer or a differential transducer. In one example, the second transducer may be a differential transducer, which may be fabricated to include the fourth tube  807  or a reference aperture. The third transducer structure  804  may be configured to be an absolute transducer or a differential transducer. In one example, the third transducer is an absolute transducer, which may be fabricated to include an internal reference environmental condition such as an internal hermetically-sealed vacuum reference pressure. 
         [0061]    In this embodiment, an integrated packaging of the first transducer  801  and the second transducer  803  in the housing  811  may provide a location of the first transducer and the second transducer proximate to the environmental conditions to be measured. Further, the third transducer  804  may be disposed in the cavity  825  of the housing  811 . In addition, each of the first transducer, the second transducer and the third transducer may include SOI piezoresistive elements. A shape of a front portion of the probe  800  may be angled, conical, wedge-shaped, pointed, pyramidal, spherical, tapered or the like. The shape of the front portion of the probe  800  may not impact the dimensions of the probe  800 , including the height  831  and the width  833  of the probe  800 . Further, the shape of the probe  800  may be selected to meet criteria for a certain flow or speed application. 
         [0062]    In  FIG. 8 , the first transducer  801  may be coupled to the first tube  805  and the third tube  827 . The first side of the first transducer  801  such as a differential pressure transducer may be positioned near the first aperture  813  of the housing  811 . The second side of the first transducer  801 , which may also be referred to as the reference side, may be coupled to the cavity  825  of the housing  811  using the third tube  827 . A first end of the first tube  805  may be coupled to the first aperture  813  of the housing  811 , which may be used to receive a first environmental condition such as pressure. Further, the first transducer  801  may be coupled to a second end of the first tube  805 . In addition, a first end of the third tube  827 , which may also be referred to as a reference tube, may be coupled to a second side of the first transducer  801 . A second end of the third tube  827  may be disposed in the cavity  825  of the housing  811  or may be coupled to another tube or another aperture in the housing  811 . The housing  811  may be disposed around and may define the first tube  805 , the first aperture  813  or the third tube  827 . The first transducer  801  may be used to couple the housing  811 . In one example, the first transducer may be used to attach, secure, bond or the like to the housing  811 . 
         [0063]    Furthermore, the first set of connectors  817  may be configured to couple the first transducer  801  to a first electronic circuit. The first set of connectors  817  may allow the first transducer  801  to communicate with the first electronic circuit. In one example, the first transducer  801  may provide a first environmental condition signal associated with a measured first environmental condition to the first electronic circuit using the first set of connectors  817 . In another example, the first electronic circuit may configure the first transducer  801  using the first set of connectors  817 . Also, the first electronic circuit may provide power to the first transducer  801  using the first set of connectors  817 . The first set of connectors  817  may be disposed in the cavity  825  defined by the housing  811 . 
         [0064]    In  FIG. 8 , the second transducer  803  may be coupled to the second tube  807  and the fourth tube  829 . The first or main side of the second transducer  803  such as a differential pressure transducer may be positioned near the second aperture  815  of the housing  811 . The second side of the second transducer  803 , which may also be referred to as the reference side, may be exposed to the cavity  825  of the housing  811  using the fourth tube  829 . A first end of the second tube  807  may be coupled to the second aperture  815 . A second end of the second tube  807  may be coupled to a first side of the second transducer. A first end of the fourth tube  829 , which may also be referred to as a reference tube, may be coupled to a second side  803 . A second end of the fourth tube  829  may be disposed in the cavity  825  of the housing  811  or coupled to another tube or another aperture in the housing  811 . The housing  811  may be disposed around and may define the second tube  807 , the second aperture  815  or the fourth tube  829 . The second transducer may determine a second difference between the second environmental condition and the reference environmental condition to generate a second difference signal. 
         [0065]    Furthermore, the second set of connectors  819  may be configured to couple the second transducer  803  to a second electronic circuit. Further, the second set of connectors  819  may allow the second transducer  803  to communicate with the second electronic circuit. In one example, the second transducer  803  may provide a second environmental condition signal associated with a measured second environmental condition to the second electronic circuit using the second set of connectors  819 . In another example, the second electronic circuit may configure the second transducer  803  using the second set of connectors  819 . Also, the second set of connectors  819  may provide power to the second transducer  803 . The second set of connectors  819  may be disposed in the cavity  825  defined by the housing  811 . 
         [0066]    In this embodiment, the third transducer  804  may be disposed in the cavity  825  of the housing  811 . The third transducer  804  may be exposed to the cavity  825  of the housing  811  using, for instance, a reference tube. The third transducer  804 , which may be an absolute transducer, may receive the reference environmental condition such as from the cavity  825  of the housing  811  to generate an absolute signal. The absolute signal may be used to determine absolute environmental conditions at the first aperture  813  and the second aperture  815 , which may be used, for instance, to determine a flow angle. 
         [0067]    Furthermore, the third set of connectors  821  may be configured to couple the third transducer  804  to a third electronic circuit. Further, the third set of connectors  821  may allow the third transducer  804  to communicate with the third electronic circuit. In one example, the third transducer  804  may provide a third environmental condition signal associated with a measured third environmental condition to the third electronic circuit using the third set of connectors  821 . In another example, the third electronic circuit may configure the third transducer  804  using the third set of connectors  821 . Also, the third electronic circuit may provide power to the third transducer  804  using the third set of connectors  821 . The third set of connectors  821  may be disposed in the cavity  825  defined by the housing  811 . Each of the first electronic circuit, the second electronic circuit or the third electronic circuit may be placed in the housing  811  or may be located outside the housing  811 . Further, the first electronic circuit, the second electronic circuit or the third electronic circuit may be part of the same electronic circuit. 
         [0068]    In this embodiment, a differential transducer may have higher sensitivity or accuracy or may operate at higher frequencies than an absolute transducer. Thus, the probe  800  having two differential transducers may have higher sensitivity or accuracy or may operate at higher frequencies than the probe  300  having one differential transducer and one absolute transducer. The width  833  of the probe  800  may be further reduced by extending the length of the front portion of the housing  811 , which may increase a length of each of the first tube  805 , the second tube  807  or the third tube  809 . Further, a width of the front portion of the housing  811  may be associated with a width of each of the first tube  805 , the second tube  807  and the third tube  809 . 
         [0069]      FIG. 9  is a flowchart of one embodiment of a probe by a process  900  in accordance with various aspects set forth herein. In  FIG. 9 , the probe by the process  900  may start, for instance, at  901 , where it may include providing a housing having a front portion with a first oblique side and a second oblique side. Further, the housing may be configured to include a first aperture disposed on the first oblique side and a second aperture disposed on the second oblique side. At block  903 , the probe by the process  900  may include inserting a first transducer into the housing proximate the first aperture. The first transducer may be configured to include a first transducer for measuring a first environmental condition received at the first aperture. At block  905 , the probe by the process  900  may include inserting a second transducer into the housing proximate the second aperture. The second transducer may be configured to include a second transducer for measuring a second environmental condition received at the second aperture. 
         [0070]    In  FIG. 9 , at block  907 , the probe by the process  900  may include coupling the first transducer to the first aperture. The first transducer may include a first header. The first header may be configured to couple the first transducer to the housing. In one example, the first header may be configured to attach, secure, bond or the like the first transducer to the housing. Similarly, at block  909 , the probe by the process  900  may include coupling the second transducer to the second aperture. The second transducer may include a second header. The second header may be configured to couple the second transducer to the housing. In one example, the second header may be configured to attach, secure, bond or the like the second transducer to the housing. In addition, at least one of the first transducer and the second transducer may be configured as a differential transducer. In one example, the first transducer may be an absolute transducer configured to measure the first environmental condition. Further, the second transducer may be a differential transducer configured to determine a difference between the first environmental condition and the second environmental condition. In another example, each of the first transducer and the second transducer may be a differential transducer. In addition, a width of the housing of the probe may be less than five-tenths of an inch (0.5 inches). 
         [0071]    In another embodiment, a probe by a process may include providing a first tube having a first end and a second end. Further, the first end of the first tube may be coupled to a first aperture and the second end of the first tube may be coupled to a first transducer. 
         [0072]    In another embodiment, a probe by a process may include providing a second tube having a first end and a second end. Further, the first end of the second tube may be coupled to a second aperture and the second end of the second tube may be coupled to a second transducer. 
         [0073]    In another embodiment, a probe by a process may include providing a housing that is disposed around and defines a first tube, a second tube or a third tube. 
         [0074]    In another embodiment, a probe by a process may include providing a third tube having a first end and a second end. Further, the probe by the process may include providing a second differential transducer having a first or main side and a second or reference side. The first side of the second transducer may be coupled to the second end of the second tube and the second side of the second transducer may be coupled to the second end of the third tube. 
         [0075]    In another embodiment, a probe by a process may include providing a second transducer configured to measure a difference between a second environmental condition and a first environmental condition. 
         [0076]    In another embodiment, a probe by a process may include providing each of a first transducer and a second transducer as a silicon-on-insulator (SOI) transducer. 
         [0077]    In another embodiment, a probe by a process may include providing each of a first transducer and a second transducer as a piezoresistive transducer. 
         [0078]    In another embodiment, a probe by a process may include providing a first transducer as an absolute transducer and a second transducer as a differential transducer. 
         [0079]    In another embodiment, a probe by a process may include providing each of a first transducer and a second transducer as a differential transducer. 
         [0080]    In another embodiment, a probe by a process may include providing a first oblique side of a front portion of a housing as about opposite to a second oblique side of a front portion of a housing. 
         [0081]    In another embodiment, a probe by a process may include providing a first aperture on a first oblique side of a front portion of a housing as symmetrically opposite to a second aperture on a second oblique side of the front portion of the housing. 
         [0082]    In another embodiment, a probe by a process may include providing a housing having a first aperture on a first oblique side of a front portion of a transducer and a second aperture on a second oblique side of the front portion of the transducer. Further, a first distance from a front end of the front portion of the housing to the first aperture is about equidistant to a second distance from the front end of the front portion of the housing to the second aperture. 
         [0083]    In another embodiment, a probe by a process may include providing a housing having a first oblique side and a second oblique side. Further, a first angle of the first oblique side of the front portion of the housing may be about orthogonal to a second angle of the second oblique side of the front portion of the housing. 
         [0084]    In another embodiment, a probe by a process may include providing a front portion of a housing having a shape of a sphere, a pyramid, a wedge, a cone or the like. 
         [0085]    In another embodiment, a probe by a process may include providing a housing having a width less than about two-tenths of an inch. 
         [0086]    In another embodiment, a probe by a process may include providing a front portion of a housing having a width less than about two-tenths of an inch. 
         [0087]    In another embodiment, a probe by a process may include providing a housing having a height of less than about five-tenths of an inch. 
         [0088]    In another embodiment, a probe by a process may include providing a front portion of a housing having a height of less than about five-tenths of an inch. 
         [0089]    In another embodiment, a probe by a process may include providing a cavity. The housing may be disposed around and may define the cavity. Further, the probe by the process may include providing a first transducer a first or main side and a second or reference side. The first side of the first transducer may be coupled to a second end of a first tube. Further, the second side the first transducer may be coupled to the cavity. In addition, the probe by the process may include providing a second transducer a first side and a second side. The first side of the second transducer may be coupled to the second end of the second tube. Also, the second side second transducer may be coupled to the cavity. Furthermore, the probe by the process may include providing a third transducer having a third transducer for measuring a third environmental condition in the cavity of the housing. The third transducer structure may be disposed in the cavity of the housing proximate the first transducer structure and the second transducer structure. 
         [0090]    In another embodiment, a probe by a process may include inserting a third transducer structure into a housing. The third transducer structure may be configured to include a third transducer for measuring a third environmental condition received from a cavity defined by the housing. The third transducer may be an absolute transducer. An absolute measurement of a third environmental condition by the third transducer may be used to determine an absolute measurement of a first environmental condition measured by a first transducer and an absolute measurement of a second environmental condition measured by a second transducer. 
         [0091]      FIG. 10  is a flowchart of one embodiment of a method  1000  of performing a measurement of an environmental condition in accordance with various aspects set forth herein. In  FIG. 10 , the method  1000  may start, for instance, at block  1001 , where it may include receiving, from a first aperture disposed on a first oblique side of a front portion of a housing, by a first transducer disposed in the housing proximate the first aperture, a first environmental condition. At block  1003 , the method  1000  may include measuring, by the first transducer, the first environmental condition to generate a first environmental condition signal. Also, at block  1005 , the method  1000  may include outputting, by the first transducer, the first environmental condition signal. 
         [0092]    In  FIG. 10 , at block  1007 , the method  1000  may include receiving, from a second aperture disposed on the second oblique side of the front portion of the housing, by a second transducer disposed in the housing proximate the second aperture, a second environmental condition. At block  1009 , the method  1000  may include measuring, by the second transducer, the second environmental condition to generate a second environmental condition signal. At block  1011 , the method  1000  may include outputting, by the second transducer, the second environmental condition signal. In addition, at least one of the first transducer and the second transducer may be configured as a differential transducer. In one example, the first transducer may be an absolute transducer configured to measure the first environmental condition. Further, the second transducer may be a differential transducer configured to determine a difference between the first environmental condition and the second environmental condition. In another example, each of the first transducer and the second transducer may be a differential transducer. In addition, a width of the housing of the probe may be less than five-tenths of an inch (0.5 inches). 
         [0093]    In another embodiment, a method may include receiving, at a first tube having a first end and a second end, from a first aperture, a first environmental condition. The first end of the first tube may be coupled to the first aperture. Also, the second end of the first tube may be coupled to a first transducer. 
         [0094]    In another embodiment, a method may include receiving, at a second tube having a first end and a second end, from a second aperture, a second environmental condition. The first end of the second tube may be coupled to the second aperture. Also, the second end of the second tube may be coupled to the second transducer. 
         [0095]    In another embodiment, a housing may be disposed around and may define a first tube. 
         [0096]    In another embodiment, a housing may be disposed around and may define a second tube. 
         [0097]    In another embodiment, a method may include receiving, at a third tube having a first end and a second end, from a first aperture, a third environmental condition. 
         [0098]    In another embodiment, a method may include receiving, at a first or main side a second transducer, from a second end of a second tube, a second environmental condition. The first side of the second transducer may be coupled to the second end of the second tube. Further, the method may include receiving, at a second or reference side of the second transducer, from a second end of a third tube, a third environmental condition. The second side the second transducer may be coupled to the second end of the third tube. 
         [0099]    In another embodiment, a method may include receiving, at a first or main side of a first transducer, from a first aperture of a housing, a first environmental condition. Further, the method may include receiving, at a second or reference side of the first transducer, from a cavity defined by the housing, a third environmental condition. The method may include measuring a first difference between the first environmental condition and the third environmental condition to generate a first difference signal. 
         [0100]    In another embodiment, a method may include receiving, at a first or main side of a second transducer, from a second aperture of a housing, a second environmental condition. Further, the method may include receiving, at a second or reference side of the second transducer, from a cavity defined by the housing, a third environmental condition. The method may include measuring a second difference between the second environmental condition and the third environmental condition to generate a second difference signal. 
         [0101]      FIG. 11  illustrates a cross-sectional view of another embodiment of a probe  1100  in accordance with various aspects described herein. In  FIG. 11 , the probe  1100  may be configured to include a first transducer  1101 , a second transducer  1103 , a third transducer  1104 , a first tube  1105 , a second tube  1107 , a housing  1111 , a first aperture  1113  in the housing  1111 , a second aperture  1115  in the housing  1111 , a first set of connectors  1117 , a second set of connectors  1119 , a third set of connectors  1121 , a cavity  1125 , a third tube  1127  and a fourth tube  1129 . Dimensions of the probe  1100  may include a height  1131  and a width  1133 . The probe  1100  is similar to the embodiment shown in  FIG. 7  except instead of the cavity  1125  being referenced to the outside static pressure through a side wall it is referenced to the stagnation pressure through a front tube  1126 . This front tube  1126  may also contain a micro-filter  1128  used to attenuate dynamic pressure signals present at the stagnation point. This embodiment has the advantage of allowing an absolute measurement of the stagnation pressure as well as referencing the two flow angle measurements to the stagnation pressure directly. 
         [0102]    In another embodiment, a method may include receiving, at a third transducer, from a cavity defined by a housing, a third environmental condition. 
         [0103]    In another embodiment, a third transducer structure may be configured to include a third transducer for measuring a third environmental condition in a cavity of a housing. The third transducer structure may be disposed in the housing. 
         [0104]    In another embodiment, a third environmental condition may be a reference environmental condition. 
         [0105]    It is important to recognize that it is impractical to describe every conceivable combination of components or methodologies for purposes of describing the claimed subject matter. However, a person having ordinary skill in the art will recognize that many further combinations and permutations of the subject technology are possible. Accordingly, the claimed subject matter is intended to cover all such alterations, modifications, and variations that are within the spirit and scope of the claimed subject matter. 
         [0106]    Although the present disclosure describes specific examples, embodiments, and the like, various modifications and changes may be made without departing from the scope of the present disclosure as set forth in the claims below. For example, although the example methods, devices and systems, described herein are in conjunction with a configuration for the aforementioned ultra-miniature, multi-hole flow angle probe, the skilled artisan will readily recognize that the example methods, devices or systems may be used in other methods, devices or systems and may be configured to correspond to such other example methods, devices or systems as needed. Further, while at least one example, embodiment, or the like has been presented in the foregoing detailed description, many variations exist. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure. Any benefits, advantages, or solutions to problems that are described herein with regard to specific embodiments are not intended to be construed as a critical, required, or essential feature or element of any or all of the claims. Any benefits, advantages, or solutions to problems that are described herein with regard to specific examples, embodiments, or the like are not intended to be construed as a critical, required, or essential feature or element of any or all of the claims.