Abstract:
The present application discloses instruments, systems, and methods for measuring temperature. In one example, an instrument or heat sensor probe includes a housing that defines a chamber, which is configured for a fluid to circulate therein, and a body of material disposed over the housing. The body has a first side proximal to the housing and a second side distal from the housing. The probe further includes a heat sensor configured for sensing heat at a position spaced inwardly from the second side of the body.

Description:
BACKGROUND 
     Temperature or heat sensors are available for measuring temperature in a variety of circumstances. In one example, a heat sensor can be used to measure the effect that a heat source has when brought into proximity with human skin. Illustratively, the heat source can be an electronic device operating under conditions of normal operation, misuse, or abuse. In this example, heat sensors can be used to analyze the potential burn hazard that the heat source may present to a person. 
     One instrument for analyzing potential burn hazard includes a probe with an embedded heat sensor and a temperature regulator. Generally, in use, the temperature regulator is controlled to heat the probe to around the average temperature of human skin, a heat source is brought into proximity or contact with the probe, and the embedded heat sensor is used to measure a temperature increase caused by the heat source. This instrument, which is sometimes referred to as a thermesthesiometer, is used to analyze the potential burn hazard that a heat source may present when brought into proximity with human skin for relatively short exposure times, such as up to about eight seconds. 
     It is desired to improve upon prior art arrangements or at least provide one or more useful alternatives. 
     SUMMARY 
     The present disclosure improves on existing heat sensing instruments or at least provides a useful alternative by accounting for the role of blood circulation in dissipating heat and regulating temperature in the human body. One example heat sensing instrument of the present disclosure includes a heat sensing probe that is configured to circulate fluid within a body of the probe and near a heat sensing face of the probe to model the flow of blood in the human body. 
     Generally, in one example of this heat sensing instrument in use, fluid is circulated through the probe at a temperature and flow-rate close to that of human blood in the body. This fluid flow acts to dissipate excess build-up of heat from the probe face in order to provide an accurate representation of the temperature that a human would experience when a heat source is brought into proximity with the skin. 
     These and other aspects of the present disclosure provide a heat sensing instrument that more accurately represents the expected tissue temperatures that human skin is expected to experience when brought into proximity with heat sources for longer exposure times, such as minutes or even hours. Consequently, the heat or temperature sensing instruments disclosed herein can be used to analyze potential burn hazards for longer exposure times. Such a heat sensing instrument can be used to test electronic devices, such as medical prostheses, that are configured to be in contact with human skin for long exposure times in order to establish compliance with safety standards, for example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a heat sensor system according to an embodiment. 
         FIG. 2  is an isometric view of a heat sensor probe according to an embodiment. 
         FIG. 3  is an isometric view of a heat sensor probe according to an embodiment, with portions removed for clarity and including a body of material at a heat sensing face of the probe. 
         FIG. 4  is an exploded isometric view of a heat sensor probe according to an embodiment. 
         FIG. 5  is a cross-sectional view of a heat sensor probe taken generally along lines  5 - 5  of  FIG. 2  and including a probe face. 
         FIG. 6  is an isometric view of a fluid circulation conduit for use with a heat sensor probe in accordance with an embodiment. 
         FIG. 7  is a cross-sectional view of a heat sensor probe that is similar to  FIG. 5 , but with portions removed for clarity, and including the fluid circulation conduit of  FIG. 6 . 
         FIGS. 8-10  are isometric views of a heat sensor probe coupled to a support jig in accordance with embodiments. 
         FIG. 11  is a cross-sectional view of a heat sensor probe and support jig taken generally along lines  11 - 11  of  FIG. 10 . 
         FIG. 12  is a flowchart showing a method for measuring temperature. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description describes various features, functions, and attributes with reference to the accompanying figures. In the figures, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described herein are not meant to be limiting. Certain features, functions, and attributes disclosed herein can be arranged and combined in a variety of different configurations, all of which are contemplated in the present disclosure. 
     Referring now to  FIG. 1 , an example heat sensor system  20  includes a probe  22 , a pump  24 , and a fluid reservoir  26 . The probe  22 , pump  24 , and fluid reservoir  26  are fluidly coupled together by any suitable connections  28 , such as conduits, tubes, piping, valves, joints, flow regulators, and the like. In this non-limiting example, the arrows indicate a direction of fluid flow or circulation from the fluid reservoir  26 , through the pump  24  and the probe  22 , and back to the fluid reservoir. Generally, the pump  24  is the component that controls the fluid flow through the probe  22 . Illustratively, the pump  24  can be a peristaltic pump or an in-line submersible pump with adjustable flow rates. In  FIG. 1 , the probe  22 , pump  24 , and fluid reservoir  26  are illustrated as separate blocks, although, in other examples these components can be configured as a single unit or multiple operational units. 
     The heat sensor system  20  of  FIG. 1  also includes a temperature controller  30  that is illustrated as being coupled to the fluid reservoir  26  and the probe  22 . In this example, the temperature controller  30  is configured to regulate the temperature of one or more of the probe  22  itself or of a fluid that is circulated through the probe. In  FIG. 1 , the temperature controller  30  includes or is otherwise coupled to a temperature sensor  32  and a temperature regulator  34 . Generally, the temperature controller  30  compares an input temperature from the temperature sensor  32  to a set temperature point and responsively controls the temperature regulator  34  (e.g., a heating element) to heat the probe  22  and/or the fluid, as needed. In one example, the temperature controller  30  is a proportional-integral-derivative (PID) feedback temperature controller that is configured to maintain the set temperature point with minimal overshoot by turning the temperature regulator  34  on/off a number of times before the input temperature reaches the set point. An example of a suitable PID controller is from OMRON Corporation of Kyoto, Japan, and is identified as model number E5CN-Q2ML-500 AC/DC 24. 
     In one non-limiting example, the temperature controller  30  and the fluid reservoir  26  are configured as a temperature controlled water bath, which includes the temperature sensor  32  and the temperature regulator  34 . In another non-limiting example, the temperature controller  30  and the probe  22  are configured with the probe including the temperature sensor  32  (such as a PT-100 temperature sensor or some other resistance thermometer) embedded in the probe and the temperature regulator  34  (e.g., a heating element such as nichrome wire) coupled to the probe. Other configurations are also possible with the temperature controller  30  (and components thereof), being integrated with or separate from the fluid reservoir  26  and/or the probe  22 . 
     Further, the heat sensor system  20  of  FIG. 1  includes a temperature monitor  36  that is illustrated as being coupled to the probe  22  and the temperature controller  30 . Other configurations are also possible. Generally, the temperature monitor  36  is configured to display a temperature measured by a heat sensor coupled to the probe  22 , as will be described in greater detail hereinafter. The temperature monitor  36  can also record and log real-time data from the probe heat sensor and provide the temperature data through a graphical interface. An example of a suitable temperature monitor is from Omega Engineering, Inc. in Stamford, Conn., and is identified as model number HH147U. 
     Generally, in use, the pump  24  is controlled to circulate a heated fluid through the probe  22 . This fluid circulation is used to model the role of blood circulation in regulating temperature in the human body. The temperature controller  30  is configured to maintain the temperature of the fluid, e.g., water, to around the average temperature of human blood, which is about 36.6° C. Further, the pump  24  is configured to adjust a flow rate of the fluid through the probe  22  to provide a generally non-directional, low-velocity perfusion of the fluid through the probe. These adjustable flow rates will vary depending on fluid flow characteristics of the fluid reservoir  26 , the pump  24 , the probe  22 , and the connections  28  therebetween. 
     The temperature controller  30  can also be configured to at least initially maintain the temperature of the probe  22  to about the average surface temperature of human skin. This average surface temperature correlates to maintaining the temperature of the probe to about 33° C. With this example arrangement, the probe  22  provides a model of human skin such that a heat source that is brought into proximity with the probe can be analyzed for potential burn hazards for short (a few seconds) or long (minutes or hours) exposure times. 
     Referring now to  FIGS. 2-4 , example embodiments of the probe  22  are illustrated. More particularly, in  FIGS. 2-4 , the probe  22  includes a handle portion  40 , an inner core or housing  42 , and an outer core or housing  44 . In these examples, the inner core  42  is disposed generally in the outer core  44  and the handle  40  is coupled to an end of the inner and outer cores to provide a structure for holding and manipulating the probe  20 . Further, portions of the inner core  42  and the outer core  44  make up a heat sensing face  46  of the probe. Referring to  FIG. 3 , the heat sensing face  46  includes a body of material  48  that simulates human skin. 
     In the present examples, the heat sensing face  46  of the probe  22  includes the body of material  48 , which has a thermal characteristic similar to average human skin. This thermal characteristic can be defined by the thermal inertia of the material  48 , which can be selected to be around the average thermal inertia of human skin, e.g., around 1.5*10 3  J m −2  K −1  s −1/2 . In one non-limiting example, the body of material  48  can be formed from silicone, such as silicone EPM1-2493 from NuSil Technology of Carpinteria, Calif. This example body of material has a thermal inertia of about 1.52*10 3  J m −2  K −1  s −1/2 . Although, in other examples, the body of material can be made from other types of silicone or other materials that have thermal inertias that approximate human skin. 
     Further, in one example, the heat sensing face  46  and the body of material  48  have a circular surface with a diameter between about 40-80 mm. In other examples, the shape and size of the heat sensing face  46  and the body of material  48  can be modified. In any event, the present example provides a large enough surface area to analyze the potential burn hazard of a wide variety of heat sources that are brought into proximity with the probe  20 . In one particular example, the heat source can be a battery-powered medical device that is in contact with human skin for long periods of time when in use. One such medical device is a hearing prosthesis, which can include a behind-the-ear component that rests against the skull behind a recipient&#39;s ear. 
     In one example, the handle  40  and the outer core  44  are formed from a material with relatively low thermal conductivity. Example materials include moldable or machined polymers, such as polyoxymethylene or polytetrafluoroethylene. These types of materials help to insulate the inner core  42  and the body of material  48 . Further, in one example, the inner core  42  (or portions thereof) is made from a thermally conductive material, such as copper, such that the flow of fluid therethrough can more effectively dissipate heat from the body of material  48 , similarly to the role of blood under the skin. Generally, in this example, any thermally conductive material with a thermal conductivity above about 100 Wm −1 K −1  can be used to form portions of the inner core  42 . 
     Referring now to  FIG. 5 , an example probe  22  is similar to the probes of  FIGS. 2-4  and includes a handle portion  40 , an inner core  42 , an outer core  44 , a heat sensing face  46 , and a body of material  48  that models human skin. In this example, the body of material  48  is shown as encapsulating a majority of the inner core  42 . 
     The probe of  FIG. 5  also includes a heat sensor  50  configured to sense heat at a position spaced inwardly from the heat sensing face  46  of the body of material  48 . Any suitable heat sensor  50  can be used in the probe  22 , such as a T-type thermocouple. In  FIG. 5 , the heat sensor  50  is illustrated as being coupled to a bridge  52  portion of the inner core  42  (also illustrated generally in  FIG. 2 ). 
     The positioning of the heat sensor  50  with respect to the body of material  48  is modeled after the depth of heat sensing nerves underneath human skin. This depth varies depending on the portion of the human body that is to be modeled but is generally between about 70-150 um. In one example, the heat sensor  50  is positioned to measure temperature at a position about 70-80 um inwardly from the heat sensing face  46 . This depth approximately models the depth of heat sensing nerves around the human skull. In another example, the heat sensor  50  is positioned to measure temperature at a position about 95-105 um inwardly from the heat sensing face  46 . This depth approximately models the depth of heat sensing nerves at the fingertips. 
     The probe of  FIG. 5  also includes a cavity  54 , which in this example is defined generally by portions of the inner core  42 . The cavity  54  also includes an inlet  56  and an outlet  58  that are configured so that a fluid flows into the cavity through the inlet, circulates within the cavity, and flows out of the cavity through the outlet. In one example, the inlet  56  and outlet  58  are positioned to promote a non-directional flow of liquid, similar to blood perfusion in human tissue. This non-directional flow of liquid can be accomplished by spacing the axes of the inlet and the outlet from one another, as illustrated generally in  FIG. 5 . Other arrangements of the inlet  56  and the outlet  58  are also contemplated, such as angling the inlet and the outlet with respect to one another. 
     Further, the inlet  56  can be generally axially aligned with the position at which the heat sensor  50  is configured to measure temperature. This arrangement of the inlet  56  over the heat sensor  50  increases the effect that the heated fluid has in dissipating heat. 
     As was discussed generally hereinabove, the fluid flow can be controlled by a pump that is further coupled to a fluid reservoir, such as a temperature controlled fluid reservoir. This fluid flow is used to model the role of human blood in regulating temperature in the human body. In one example, the cavity  54  includes a porous material  60  to aid in the random perfusion of fluid throughout the cavity, similar to blood perfusion in human tissue. Illustratively, the porous material  60  can be a heat-conductive material, such as steel wool, or can be some other type of a non-heat-conductive sponge-like material. 
     The example probe  22  illustrated in  FIG. 5  also includes a second temperature sensor  62  (e.g., a resistance thermometer) for measuring a temperature of the body of material  48  and a temperature regulator  64  (e.g., a nichrome wire) used to heat the body of material to about the average temperature of human skin (e.g., about 33° C.). In this example, the second temperature sensor  62  is embedded relatively deeply within the body of material  48 . For example, the second temperature sensor can be embedded about 25 mm from the heat sensing face  46 . Further, in the present example, the temperature regulator is a nichrome wire wound around the inner core  42  and is controlled (for example, by the temperature controller  30  of  FIG. 1 ) to heat the body of material, as needed. In another embodiment, the temperature regulator  64  can be omitted and the heated fluid circulating through the probe  22  can be used to heat the body of material to about the average temperature of human skin. 
     Referring now to  FIGS. 6 and 7 , an example probe  22  is illustrated with a cavity  54  for fluid circulation similar to the example of  FIG. 5 . In this example, the cavity  54  includes fluid conduit  70  with an inlet  72 , an outlet  74 , and a flat coil structure  76 , which is disposed generally against the heat sensing face  46 . In this example, the fluid conduit  70  is formed from a heat-conductive material, such as copper or any other material with a thermal conductivity above about 100 Wm −1 K −1 . In use, as described hereinabove, a heated fluid is circulated through the fluid conduit  70  to model the role of human blood through the human body. 
       FIGS. 8-11  illustrate a probe  22  coupled to support jigs  80 . Generally, the support jigs  80  are used to hold the probe in a stationary vertical or horizontal (or potentially an angled) position so that a user need not manually hold the probe against a heat source for short or long exposure times. Generally, the support jigs  80  include a base  82  and an opening  84 , in which the probe  22  can be disposed. 
     Referring now to  FIG. 12 , an example method  100  is illustrated, which can be implemented by the systems and devices described hereinabove. Generally, the method  100  may include one or more operations, functions, or actions as illustrated by one or more of blocks  102 - 110 . Although the blocks  102 - 110  are illustrated in sequential order, these blocks may also be performed concurrently and/or in a different order than illustrated. The method  100  may also include additional or fewer blocks, as needed or desired. For example, the various blocks  102 - 110  can be combined into fewer blocks, divided into additional blocks, and/or removed based upon a desired implementation. 
     In  FIG. 12 , at block  102 , a heat sensor system, such as the system described above, regulates a fluid temperature. For example, a temperature controlled water bath can maintain the water temperature to around the average temperature of human blood (about 36.6° C.). At block  104 , a pump can be used to circulate fluid through a heat sensor probe. As described above, the heat sensor probe generally includes a cavity that is adjacent a heat sensing face of the probe. At block  104 , the heated fluid is circulated adjacent the heat sensing face of the probe to model blood circulation in the human body. 
     At block  106 , a temperature controller can be used to regulate the heat sensor probe temperature to around the average surface temperature of human skin (about 33° C.). This temperature regulation can be accomplished by circulating the heated fluid through the probe. In another example, the temperature regulation is aided by using a separate heating element (e.g., nichrome wire wound around the probe) to heat the probe. 
     At block  108 , a heat source is brought into proximity with the probe and, at block  110 , the probe temperature is measured. More particularly, the probe can be exposed to the heat source of any desired length of time and the probe temperature is measured generally at a position spaced inwardly from a heat sensing face of the probe. As discussed above, this process of measuring temperature can be used to model a human temperature response when skin is exposed to a heat source. 
     While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims.