Patent Publication Number: US-9846083-B2

Title: Ambient temperature measurement sensor

Description:
BACKGROUND 
     Thermopile sensors convert thermal energy into electrical energy. These sensors may utilize several thermocouples to generate an output voltage proportional to a local temperature difference (e.g., a temperature gradient). These thermopile sensors may be utilized in the medical industry to measure body temperature, in heat flux sensors, and/or gas burner safety controls. 
     SUMMARY 
     The present disclosure is directed to a sensor package having a thermopile sensor, a reference thermopile sensor, and a reference temperature sensor disposed therein to determine an ambient temperature. In one or more implementations, the sensor package includes a substrate having a substrate surface, a thermopile sensor disposed over the substrate surface, a reference thermopile sensor disposed over the substrate surface, a reference temperature sensor disposed over the substrate surface, and a lid assembly disposed over the thermopile sensor and the reference thermopile sensor. The lid assembly includes a structure having a transparent portion that passes electromagnetic radiation occurring in a limited spectrum of wavelengths (e.g., infrared radiation [IR]). The reference thermopile sensor generates a reference thermopile sensor signal representing a temperature difference between a temperature associated with the substrate surface and a temperature associated with a lid assembly surface. An external ambient temperature can be determined based upon the reference thermopile sensor signal. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description is described with reference to the accompanying figures. The use of the same reference numbers in different instances in the description and the figures may indicate similar or identical items. 
         FIG. 1  is a partial cross-sectional side view illustrating a sensor package including a thermopile sensor, a reference thermopile sensor, and a reference temperature sensor disposed therein. 
         FIG. 2  is a partial cross-sectional side view illustrating another implementation of a sensor package including a sensor package including a thermopile sensor, a reference thermopile sensor, a reference temperature sensor, and a heating element. 
         FIG. 3  is a partial cross-sectional side view illustrating the sensor package shown in  FIG. 1 , where the thermopile sensor, the reference thermopile sensor, and the reference temperature sensor are communicatively connected to a temperature sensor. 
         FIG. 4  illustrates a thermal equivalent model of the sensor package shown in  FIG. 1 . 
         FIG. 5  is a partial cross-sectional side view illustrating the sensor package shown in  FIG. 1 , where the thermopile sensor, the reference thermopile sensor, two heating elements, and the reference temperature sensor are communicatively connected to a temperature sensor. 
         FIG. 6  is a flow diagram illustrating an example method for determining a temperature of an ambient environment proximate to the a sensor package. 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     Thermopile sensors are utilized in a variety of applications. For example, a thermopile is an infrared radiation (IR) detector (e.g., electromagnetic radiation) that can be used for making non-contact temperature measurements. A thermopile can include several thermocouples coupled together. Thermopiles are used to provide an output in response to temperature as part of a temperature measuring device, such as the infrared thermometers, used to measure body temperature. In some applications, an ambient temperature, such as an external ambient temperature, can be utilized for calibration purposes. 
     Therefore, the present disclosure is directed to a sensor package having a thermopile sensor, a reference thermopile sensor, and a reference temperature sensor disposed therein to determine an ambient temperature. For example, the ambient temperature may be defined as the temperature of the air external to the sensor package  100  (e.g., the environment surrounding the sensor package  100 ). In one or more implementations, the sensor package includes a substrate having a substrate surface, a thermopile sensor disposed over the substrate surface, a reference thermopile sensor disposed over the substrate surface, a reference temperature sensor disposed over the substrate surface, and a lid assembly disposed over the thermopile sensor and the reference thermopile sensor. The lid assembly includes a transparent structure that passes electromagnetic radiation occurring in a limited spectrum of wavelengths (e.g., infrared radiation [IR]) and an infrared radiation blocker disposed over the lid assembly. The electromagnetic blocker defines an aperture over the thermopile sensor such that at least a portion of the electromagnetic blocker is positioned over the reference thermopile sensor. The reference thermopile sensor generates a reference thermopile sensor signal representing a temperature difference between a temperature associated with the substrate surface and a temperature associated with a lid assembly surface. An external ambient temperature can be determined based upon the reference thermopile sensor signal. 
     Example Implementations 
       FIG. 1  illustrates an example sensor package  100  in accordance with an example implementation of the present disclosure. As shown, the sensor package  100  includes a thermopile sensor  102  that senses electromagnetic radiation transfer between the thermopile sensor  102  and an object. The thermopile sensor  102  senses changes in electromagnetic radiation transfer and translates the electromagnetic radiation change into a corresponding electrical signal (e.g., converts thermal energy into corresponding electrical energy). For instance, the thermopile sensor  102  translates the electromagnetic radiation change into a corresponding voltage signal. In implementations, the thermopile sensor  102  detects electromagnetic radiation having a first limited spectrum of wavelengths (e.g., wavelengths between a first wavelength and a second wavelength). For example, the thermopile sensor  102  is configured to detect electromagnetic radiation occurring within the infrared spectrum. In some implementations, the thermopile sensor  102  includes an absorber to improve the efficiency of the electromagnetic radiation absorption. For example, the radiation has a wavelength range and an integrated intensity that depends on the temperature of the object. 
     As shown, the thermopile sensor  102  is positioned over a substrate  106 . A first wall structure  108  and a second wall structure  110  are employed adjacent to the substrate  106  to at least partially enclose the thermopile sensor  102 . The substrate  106  and the wall structures  108 ,  110  comprise material that at least substantially prevents the transmission of radiation. For example, the substrate  106  and the wall structures  108 ,  110  may comprise metal materials, metallic alloys, and ceramic materials, such as glass, SiO 2 , AlN, and/or Al 2 O 3 . 
     As shown in  FIG. 1 , the sensor package  100  includes a reference temperature sensor  112  and a reference thermopile sensor  113 . The reference temperature sensor  112  may be positioned over the substrate  106  and adjacent to the thermopile sensor  102  and the reference thermopile sensor  113 . As shown, the example sensor package  100  also includes a reference thermopile sensor  113 . As discussed herein, the thermopile sensor  102  detects electromagnetic (e.g., infrared) radiation exchange associated the components within the sensor package  100  and an object of interest. The reference thermopile sensor  113  is configured to detect the electromagnetic (e.g., infrared) radiation associated with the components within the sensor package  100 . In implementations, as discussed herein, a signal representing the signal from the thermopile sensor  102  is subtracted from the signal from the reference thermopile sensor  113 . The subtraction may occur within the digital domain or the analog domain. 
     In an implementation, the reference temperature sensor  112  detects signals that relate to the temperature reference for the thermopile sensor  102  and the reference thermopile sensor  113 . As shown in  FIG. 1 , the sensor package  100  includes a structure  114  positioned over the thermopile sensor  102  and the object. In implementations, a portion of the structure  114  is transparent to electromagnetic radiation of interest and the other portions of the structure  114  may serve as an electromagnetic blocker. In some instances, the thermopile sensor  102  and the reference thermopile sensor  113  may be integrated together on the same integrated circuit die. In another instance, the thermopile sensor  102  and the reference thermopile sensor  113  may be separate sensors (e.g., fabricated as standalone die). Additionally, in some implementations, the reference temperature sensor  112  may also be incorporated on or integrated with the standalone die having the thermopile sensor  102  and the reference thermopile sensor  113 . The reference temperature sensor  112  may comprise a resistive temperature detector (RTD), a complementary metal-oxide semiconductor based temperature sensor, a thermistor, or the like. 
     Together, the substrate  106 , the wall structures  108 ,  110 , and the structure  114  at least partially comprises a package that encloses the thermopile sensor  102  and the reference temperature sensor  112 . In implementations, the structure  114  is configured to pass radiation occurring within the limited spectrum of wavelengths (e.g., infrared radiation) and to filter light occurring having a wavelength not within the limited spectrum of wavelengths. In some embodiments, the structure  114  comprises silicon, germanium, other metal alloys, an infrared-transparent polymer, combinations thereof, or the like. As shown, the sensor package  100  includes an electromagnetic blocker  116  positioned at least partially over the structure  114 . The electromagnetic blocker  116  is configured to at least substantially prevent transmission of the electromagnetic radiation occurring within the limited spectrum of wavelengths (as well as other stray electromagnetic radiation). The electromagnetic blocker  116  may comprise a metal or any other material that does not transmit the IR wavelengths of interest. Together, the structure  114  and the electromagnetic blocker  116  may form a lid assembly  117 . In other implementations, the structure  114  forms the lid assembly  117 . In some implementations, the lid assembly  117  comprises two separate (e.g., distinct) structures. For example, a first structure comprises a metal and/or metallic alloys that block (e.g., prevent transmission) electromagnetic radiation occurring within the limited spectrum of wavelengths. The second structure may comprise an infrared transparent material that allows passage (e.g., transmission) of electromagnetic radiation. In some instances, as described below, the second structure may define an aperture  118 . 
     As shown, the lid assembly  117  defines an aperture  118  over the thermopile sensor  102  such that electromagnetic radiation may be transmitted from the object  104  to the thermopile sensor  102  and prevents the transmission of the electromagnetic radiation from the object to the reference thermopile sensor  113 . As shown, the aperture  118  can be defined on the interior surface of the package cavity. However, the aperture  118  can be defined on the exterior surface of the package structure  114  (e.g., side opposite the interior surface). Thus, the thermopile sensor  102  and the reference thermopile sensor  113  are configured to detect temperature variations/gradients within the sensor package  100  (e.g., detect electromagnetic radiation occurring with the limited spectrum of wavelengths emitted from the substrate  106 , the wall structures  108 ,  110 , and the structure  114 ). The thermopile sensor  102  also detects electromagnetic radiation occurring with the limited spectrum of wavelengths emitted from the object. In other words, the thermopile sensor  102  generates an electrical signal that corresponds to the electromagnetic radiation emitted from the object  104  (as well as within the package) and the reference thermopile sensor  113  generates an electrical signal that corresponds to electromagnetic radiation emitted within the sensor package  100 . 
     In some implementations, the sensor package  100  includes a berm (e.g., barrier) structure  120  that would be configured to mitigate electromagnetic radiation that entered through the aperture  118  to reach the reference thermopile sensor  113 . The berm structure  120  may comprise any suitable material that prevents transmission of electromagnetic radiation within the limited spectrum of wavelengths. 
     The reference thermopile sensor  113  is configured to measure the temperature of ambient air. For example, the reference thermopile sensor  113  outputs an electrical signal that is a function of a temperature associated with the lid assembly  117  and a temperature associated with a first (e.g., bottom) surface  122  of the sensor package  100 . For example, the output of the reference thermopile sensor  113  can be modeled by: 
     
       
         
           
             
               
                 
                   
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       FIG. 2  illustrates a sensor package  100  in accordance with another example implementation of the present disclosure. In this implementation, the sensor package  100  includes a reference temperature sensor  124  disposed over a second (e.g., top) surface  125  that is opposite the first surface  122 . For example, the reference temperature sensor  124  is positioned over the lid assembly  117 . In an implementation, the reference temperature sensor  124  comprises a thermistor disposed over the lid assembly  117 . The reference temperature sensor  124  is configured to detect signals that relate to the temperature reference for the thermopile sensor  102  and the reference thermopile sensor  113 . For example, these signals may be utilized to provide additional temperature references for corrective measures, or the like. In some implementations, the reference thermopile sensor  113  may not be employed when the sensor package  100  employs the reference temperature sensor  124 . 
     Referring to  FIG. 3 , a temperature sensor  200  may be employed to generate a signal representing the ambient air temperature. In implementations, the temperature sensor  200  may comprise application-specific integrated circuitry configured to receive signals generated by the thermopile sensor  102 , the reference temperature sensor  112 , the reference thermopile sensor  113 , and/or the reference temperature sensor  124  and generate a signal representing the ambient temperature about the sensor package  100 . For example, the temperature sensor  200  generates a signal representing the ambient temperature outside of the sensor package  100 . In some implementations, the temperature sensor  200  may employ an orientation detection sensor  202  that is configured to provide a signal representing an orientation of the sensor package  100 . In an implementation, the orientation detection sensor  202  comprises a gyroscope. 
       FIG. 4  illustrates a thermal equivalent model of the sensor package  100 , and the ambient temperature can be modeled by (where G represents thermal conductance):
 
 G air( T ambient− T package top )= G package( T package top   −T package bottom )  EQN. 2
 
     EQN. 2 can be rewritten to: 
     
       
         
           
             
               
                 
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     EQN. 3 can be rewritten to: 
                   Tambient   =         (     1   +     Gpackage   Gair       )     ⁢     (       Tpackage   top     -     Tpackage   bottom       )       +     Tpackage   bottom               EQN   .           ⁢   4               
which can be written to:
 
 T ambient= T package bottom +γ( T package top   −T package bottom )  EQN. 5
 
     The term γ is a package characteristic which depends on package thermal resistance. In another form, the ambient temperature can be modeled by:
 
 T ambient= T package bottom +γ(φ, T )( T package top   −T package bottom )  EQN. 6
 
     The term γ(φ,T) is experimentally and/or analytically characterized for different values of ambient temperatures, ambient humidity, and/or pressure (where φ represents sensor orientation detected by the orientation detection sensor  202  and T represents ambient temperature). There may be additional correction terms (factors) that depends on factors such as but not limited to sensor orientation (s) and air flow (v). As described above, the orientation detection sensor  202  is configured to determine an orientation of the orientation detection sensor  202 , which provides a signal representing an orientation of the sensor package  100 . 
     Thus, measurement of ambient temperature depends on measuring of the temperature associated with the first surface  122  (e.g., Tpackage bottom ) and determining (Tpackage top −Tpackage bottom ). The temperature associated with the first surface  122  is measured by reference temperature sensor  112  positioned over the first surface  122  (e.g., the reference temperature sensor  112  measures the temperature associated with the bottom of the sensor package  100 ) and generates a signal representing the temperature associated with the first surface  122 . The reference thermopile sensor  113  measures the temperature difference associated with the second surface  125  (e.g., reference thermopile sensor  113  measures a temperature associated with the lid assembly  117  [i.e., the top of the sensor package  100 ]) and the temperature associated with the first surface  122 . For example, the reference thermopile sensor  113  generates a signal that represents the temperature difference between the top of the sensor package  100  and the bottom of the sensor package  100  (e.g., (Tpackage top −Tpackage bottom )). 
     Relating the term (Tpackage top −Tpackage bottom ) with EQN. 1, the ambient temperature can be modeled by
 
 T   ambient   =T   package     bottom     +μ·V   TP-dark   EQN. 7
 
     The term T package     bottom    models the temperature associated with the first surface  122 , which is measured by the reference temperature sensor  112  (or other temperature sensors), u is a variable of sensor package  100  temperature, ambient humidity, pressure, and/or the orientation of the sensor. The term V TP-dark  represents the output signal generated by the reference thermopile sensor  113 . The term μ may be derived from experimental and/or analytical calculation. For example, the temperature sensor  200  may employ a lookup table  204  such that a low-power processor can avoid calculating complex fitting equation. 
     As shown in  FIG. 5 , the sensor package  100  may employ a heating element  300  that generates a known amount of electromagnetic radiation (e.g., generates a known amount of heat). The heating element  300  can be positioned proximate to the first surface  122  to change the temperature of the first surface  122  relative to the other components that comprise the sensor package  100 . The sensor package  100  may also employ a second heating element  302  that is positioned over the second surface  125  to change the temperature of the second surface  125  relative to the other components that comprise the sensor package  100 . It is contemplated that the heating elements  300 ,  302  may be employed within the lid assembly  117 . For example, the heating elements  300 ,  302  may be embodied as metallization layers that provide current through the layer to heat the sensor package  100 . 
     Assuming that μ is an unknown parameter, the temperature associated with the first surface  122  (e.g., T package     bottom   ) and/or the temperature associated with the second surface  125  (e.g., T package     top   ) can be modified by utilizing the respective heating element  300 ,  302  that results in two different measurements. Also, assuming γ and T ambient  will not change, both μ and T ambient  can be determined utilizing the aforementioned equations. 
     As shown in  FIG. 5 , the temperature sensor  200  is operatively connected to the heating elements  300 ,  302  and is configured to cause the heating elements  300 ,  302  to cause the respective surfaces  122 ,  125  to change temperature. The temperature sensor  200  is also configured to receive the signals from the thermopile sensor  102 , the reference temperature sensor  112 , and the reference thermopile sensor  113 . The temperature sensor  200  provides functionality to determine ambient temperature external to the sensor package  100 . In one or more implementations, the temperature sensor  200  may be implemented utilizing hardware (e.g., fixed logic circuitry such as integrated circuits), software, firmware, or a combination thereof. 
     In an implementation, a first measurement is obtained. For example, the heating element  302  (and/or heating element  300 ) is caused to operate in a first operational state. For instance, the heating element  302  (and/or heating element  300 ) may be emitting radiation in a first operational state (or not operational) to cause the first surface  122  and the second surface  125  to have a first known temperature. The first measurement may be modeled by:
 
 T   ambient   =T   package     bottom1     +μ·V   TP-dark1   EQN. 8
 
     The temperature sensor  200  receives the signals generated by the thermopile sensor  102 , the reference temperature sensor  112 , and/or the reference thermopile sensor  113 . A second measurement may then be obtained, and the second measurement may be modeled by:
 
 T   ambient   =T   package     bottom2     +μ·V   TP-dark2   EQN. 9
 
     For example, the heating element  302  (and/or heating element  300 ) is caused to operate in a second operational state. For instance, the heating element  302  (and/or heating element  300 ) may be emitting radiation to cause the first surface  122  and the second surface  125  to have a second known temperature. 
     Having the two measurements, T ambient  and μ can be determined by the temperature sensor  200  utilizing the first measurements and the second measurements obtained from the reference temperature sensor  112  and the reference thermopile sensor  113 . For example, the ambient temperature can be modeled by:
 
 T   ambient   =T   package   _   bottom1 +( T   package     bottom2     −T   package     bottom1   )/( V   TP-dark1   −V   TP-dark2 )× V   TP-dark1   EQN. 10
 
     Thus, the temperature sensor  200  utilizes EQN. 10 to determine the ambient temperature external to the sensor package  100 . In an implementation, the sensor package  100  has the capability to do self-calibration during the measurement and/or when in use. In another implementation, this calibration is done during automatic testing and an initial value for μ is stored in the temperature sensor  200  (or other type of memory associated with the sensor package  100 ). The dependency of this initial value with temperature, humidity, pressure and orientation is determined further experimentally or analytically and stored in a memory device (e.g., stored in the look-up table  204 ). 
     In other implementations, a temperature associated with a surface adjacent to the sensor package  100  may be taken into account. For example, this surface may be a surface associated with a cover of a device employing the sensor package  100  (e.g., a smart phone, a tablet, etc.). In yet another implementation, an alternating current signal may be applied to the heating element  300  and/or the heating element  302 . In this implementation, the reference thermopile sensor  113  is configured to detect the change in the emitted radiation based upon the changing alternating current signal. The temperature sensor  200  can utilize the alternating current signal to calculate the ambient temperature. For example, the temperature of the lid assembly  117  and the temperature associated with the surface  122  corresponds (e.g., is related to) the respective heating elements  300 ,  302 . Thus, (T package   _   bottom −T package   _   top ) and/or V TP-Dark  is a function of (I bottom −I top ), and the alternating current difference can be utilized to determine T ambient  and/or μ utilizing the above-referenced equations. In other words, a change in the alternating currents through the respective heating elements  300 ,  302  (top and bottom heating elements) can be used to determine the ambient temperature. 
     Example Method 
       FIG. 6  illustrates an example method  600  for determining (e.g., calculating) the temperature of the ambient environment proximate to a sensor package  100 . As shown in  FIG. 6 , measurement data pertaining to a sensor package is received (Block  602 ). For instance, as described above, the heating element  302  (and/or heating element  300 ) is caused to operate in a first operational state. For instance, the heating element  302  (and/or heating element  300 ) may be emitting radiation in a first operational state (or not operational) to cause the first surface  122  and the second surface  125  to have a first known temperature. Additionally, the temperature sensor  200  receives the signals generated by the thermopile sensor  102 , the reference temperature sensor  112 , and/or the reference thermopile sensor  113 . For example, the heating element  302  (and/or heating element  300 ) is caused to operate in a second operational state. For instance, the heating element  302  (and/or heating element  300 ) may be emitting radiation to cause the first surface  122  and the second surface  125  to have a second known temperature. 
     Referring to  FIG. 6 , an ambient temperature external to the sensor package is determined based upon the measurement data (Block  602 ). For instance, T ambient  and μ can be determined by the temperature sensor  200  utilizing the first measurements and the second measurements obtained from the reference temperature sensor  112  and the reference thermopile sensor  113  (see EQN. 10). Thus, the temperature sensor  200  can determine the ambient temperature external to the sensor package  100 . 
     In some implementations, the sensor package  100  can measure an ambient temperature of an indoor environment. For instance, the object  104  may comprise a wall, ceiling, window, or floor of an indoor (e.g., interior) environment. The sensor package  100  may be positioned such that the aperture  118  is oriented (e.g., aligned) to the object  104  such that electromagnetic radiation from the object  104  passes through the aperture  118  and is received at the thermopile sensor  102 . Thus, the sensor package  100  and/or the temperature sensor  200  can determine an ambient temperature of the indoor environment utilizing the signals generated by the thermopile sensor  102 , the reference temperature sensor  112 , and/or the reference thermopile sensor  113  as discussed above. For instance, a user may can orient (e.g., point, align) the sensor package  100  to an interior surface of an enclosed room to measure the ambient temperature of the enclosed room. 
     CONCLUSION 
     Generally, any of the functions described herein can be implemented using hardware (e.g., fixed logic circuitry such as integrated circuits), software, firmware, or a combination thereof. Thus, the blocks discussed in the above disclosure generally represent hardware (e.g., fixed logic circuitry such as integrated circuits), software, firmware, or a combination thereof. In the instance of a hardware configuration, the various blocks discussed in the above disclosure may be implemented as integrated circuits along with other functionality. Such integrated circuits may include all of the functions of a given block, system, or circuit, or a portion of the functions of the block, system, or circuit. Further, elements of the blocks, systems, or circuits may be implemented across multiple integrated circuits. Such integrated circuits may comprise various integrated circuits, including, but not necessarily limited to: a monolithic integrated circuit, a flip chip integrated circuit, a multichip module integrated circuit, and/or a mixed signal integrated circuit. In the instance of a software implementation, the various blocks discussed in the above disclosure represent executable instructions (e.g., program code) that perform specified tasks when executed on a processor. These executable instructions can be stored in one or more tangible computer readable media. In some such instances, the entire system, block, or circuit may be implemented using its software or firmware equivalent. In other instances, one part of a given system, block, or circuit may be implemented in software or firmware, while other parts are implemented in hardware. 
     Although the subject matter has been described in language specific to structural features and/or process operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.