Patent Publication Number: US-2007100253-A1

Title: Electronic thermometer with sensor location

Description:
BACKGROUND OF THE INVENTION  
      The invention pertains to the field of electronic thermometers and more particularly the field of fast response electronic thermometers employing a sensor probe.  
      Electronic thermometers are widely used in the healthcare field for measuring a patient&#39;s body temperature. Typical electronic thermometers have the form of a probe with an elongated shaft. Electronic temperature sensors such as thermistors or other temperature sensitive elements are contained within the shaft portion. In one version, the probe includes a cup-shaped aluminum tip at its free end. A thermistor is placed in thermal contact with the aluminum tip inside the probe. When a free end portion is placed, for example, in a patient&#39;s mouth, the tip is heated up by the patient&#39;s body and the thermistor measures the temperature of the tip. Additional electronics connected to the electronic sensor components may be contained within a base unit connected by wire to the shaft portion or may be contained within a handle of the shaft portion, for example. Electronic components receive input from the sensor components to compute the patient&#39;s temperature. The temperature is then typically displayed on a visual output device such as a seven segment numerical display device. Additional features of known electronic thermometers include audible temperature level notification such as a beep or tone alert signal. A disposable cover or sheath is typically fitted over the shaft portion and disposed after each use of the thermometer for sanitary reasons.  
      Electronic thermometers have many advantages over conventional thermometers and have essentially replaced the use of conventional glass thermometers in the healthcare field. One advantage of electronic thermometers over their conventional glass counterparts is the speed at which a temperature reading can be taken. Several procedures are used to promote a rapid measurement of the subject&#39;s temperature. One technique employed is to use predictive algorithms as part of thermometer logic to extrapolate the temperature measurements from the thermistor in contact with the tip to arrive at a temperature reading in advance of the tip reaching equilibrium with the body temperature. Another technique that can be employed simultaneously with a predictive algorithm is to heat the probe to near the body temperature so that part of the probe away from the tip does not act as a heat sink, allowing the tip to reach a temperature close to the body temperature more rapidly. Heating can be accomplished by a resistor placed in contact with the probe. Another thermistor may be placed in contact with the probe to measure the amount the resistor is heating the probe, which is used to control the heating. It is also known to use an isolator to reduce heat loss from the tip to other parts of the probe. Co-assigned U.S. Pat. No. 6,839,651 discloses the use of such an isolator and is incorporated herein by reference.  
      To assemble the probe the circuitry (e.g., the thermistors and resistor) is mounted on a flexible substrate that supports and provides electrical connection for the components. The combination of the components and the flexible substrate is commonly called a “flex circuit”. The substrate may be initially flat to facilitate ease of mounting the components, but can be bent into position upon assembly into the probe. More specifically, the flexible substrate is bent to place one thermistor in position for contacting the probe tip, and to place the resistor and other thermistor in contact with a separator adjacent to the probe tip. These components can be glued in place with a thermally conductive adhesive in the final assembly. However, before the adhesive is brought into contact with the components and/or before the adhesive sets, the components may undesirably move. The result of motion can be insufficient contact of the components with the tip and/or separator to heat or sense temperature in the final assembly. Preferably, such assembly failures should be minimized or avoided.  
     SUMMARY OF THE INVENTION  
      In one aspect of the present invention, an electronic thermometer generally comprises a probe tip adapted to be heated to the temperature by a subject for use in measuring the temperature of the subject. A deformable circuit element includes a deformable electrical conductor and at least one temperature sensor connected to the deformable electrical conductor for detecting the temperature of the probe tip. A probe shaft includes an end portion that is shaped to receive the deformable circuit element in a deformed position and to align the deformable circuit element in a predetermined position.  
      In another aspect of the present invention, a probe having the construction set forth in the preceding paragraph.  
      In yet another aspect of the present invention, a method of making a probe for an electronic thermometer generally comprises bringing together a probe shaft and a deformable circuit element into a selected position relative to one another. The deformable circuit element is bent to bring portions of the deformable circuit element into engagement with locating structure formed in the probe shaft. Motion of the bent deformable circuit element is restrained with the locating structure to retain a selected relative position of the deformable circuit element and probe shaft.  
      In still another aspect of the present invention, an electronic thermometer generally comprises a probe tip adapted to be heated to a temperature by a subject for use in measuring the temperature of the subject, and a deformable circuit element including a deformable electrical conductor. At least one temperature sensor connected to the deformable electrical conductor detects the temperature of the probe tip, and there is at least one other electrical device on the substrate. A probe shaft supports the probe tip and deformable circuit element. A tubular separator received on an end of the probe shaft has a receiving surface lying generally in a plane and engaging said other electrical device when the separator is received on the end of the probe shaft.  
      In a further aspect of the present invention, a probe for an electronic thermometer having the construction set forth in the preceding paragraph.  
      In yet a further aspect of the present invention, a method of making a probe for an electronic thermometer generally comprises positioning an electrical device generally at a flat surface formed in an end of the probe shaft. An adhesive is applied to the electrical device. A separator is moved onto the end of the probe shaft so that a generally flat surface on the separator engages the adhesive applied to the electrical device. The electrical device is positioned between the generally flat surfaces of the probe shaft and the separator.  
      In a still further aspect of the present invention, an electronic thermometer generally comprises a probe shaft, and a probe tip supported by the probe shaft and adapted to be heated to a temperature by a subject for use in measuring the temperature of the subject. A deformable circuit element supported by the probe shaft includes a deformable electrical conductor and at least one electrical device. A generally tubular separator on the probe shaft has first and second opposite ends. The probe shaft is formed with a shoulder generally at a distal end of the probe shaft, and the first end of the separator engages the shoulder and thereby is located relative to the probe shaft and probe tip.  
      In another aspect of the present invention, an electronic thermometer generally comprises a probe tip adapted to be heated to the temperature by a subject for use in measuring the temperature of the subject. A deformable circuit element includes a deformable electrical conductor, at least one temperature sensor connected to the deformable electrical conductor for detecting the temperature of the probe tip and at least one other electrical device. A probe shaft has a longitudinal axis and supports the probe tip and deformable circuit element. The probe shaft has a receiving surface engaging said other electrical device. A tubular separator received on an end of the probe shaft has a receiving surface and engages said other electrical device when the separator is received on the end of the probe shaft. The receiving surfaces of the probe shaft and tubular separator define acute angles relative to the longitudinal axis greater than about  5  degrees.  
      In yet another aspect of the present invention, an electronic thermometer generally comprises a probe tip adapted to be heated to a temperature by a subject for use in measuring the temperature of the subject. A deformable circuit element includes a deformable electrical conductor, at least one temperature sensor on the deformable electrical conductor for detecting the temperature of the probe tip and at least one other electrical device. A probe shaft having a longitudinal axis and supporting the probe tip and deformable circuit element has a receiving surface engaging said other electrical device. A tubular separator received on an end of the probe shaft has a receiving surface and engages said other electrical device when the separator is received on the end of the probe shaft. The tubular separator and probe shaft are constructed for snap on connection.  
      In still another aspect of the present invention, an electronic thermometer generally comprises a probe shaft and an electronic temperature sensor supported by the shaft. A probe tip supported by the shaft at a distal end thereof includes a receiving surface in thermal contact with the sensor and is adapted to be heated by a subject for detection by the sensor to measure the temperature of the subject. The probe tip receiving surface is shaped to indicate the position of the temperature sensor relative to the tip.  
      In one other aspect of the present invention, an electronic thermometer generally comprises a probe tip adapted to be heated to the temperature by a subject for use in measuring the temperature of the subject. A circuit element supported by the probe shaft includes an electrical conductor and at least one electrical temperature sensor in thermal contact with the probe tip. A probe shaft supporting the probe tip and circuit element is constructed for biasing the temperature sensor in a direction toward the probe tip.  
      Other features of the present invention will be in part apparent and in part pointed out hereinafter.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective of an electronic thermometer;  
       FIG. 2  is a perspective of a probe of the electronic thermometer;  
       FIG. 3  is a partially exploded perspective of a probe shaft of the probe with parts broken away to show internal construction;  
       FIG. 4  is an exploded perspective of a probe shaft element of the probe shaft, flex circuit, separator and probe tip;  
       FIG. 5  is a perspective of the probe shaft element receiving the flex circuit prior to deformation of the flex circuit;  
       FIG. 6  is a perspective similar to  FIG. 5 , but inverted to show connection of the flex circuit to the probe shaft element;  
       FIG. 7  is an enlarged, fragmentary elevation of a distal end of the probe with parts broken away to show internal construction;  
       FIG. 8  is an elevation similar to  FIG. 7  but showing the distal end of the probe from an opposite side;  
       FIG. 9  is a perspective of a probe shaft element of a probe shaft, flex circuit, separator and probe tip of a probe of a second embodiment with parts broken away to show internal construction;  
       FIG. 10  is a perspective of the probe shaft element of  FIG. 9 ;  
       FIG. 11  is an enlarged, fragmentary section of the distal end of the probe of  FIG. 9 ;  
       FIG. 12  is an enlarged, fragmentary section of the probe shaft element of  FIG. 9 ;  
       FIG. 13  is a further enlarged, fragmentary section similar to  FIG. 12  but showing positioning of a sensor between the separator and probe shaft element;  
       FIG. 14  is an enlarged, fragmentary section of a probe of a third embodiment;  
       FIG. 15  is a section like  FIG. 14  but with a tip removed and a separator partially pushed down on a probe shaft element;  
       FIG. 16  is a section similar to  FIG. 14 , but showing another version of the probe;  
       FIG. 17  is a section similar to  FIG. 14 , but showing yet another version of the probe;  
       FIG. 18  is a section similar to  FIG. 14 , but showing still another version of the probe;  
       FIG. 19  is a perspective of a separator;  
       FIG. 20  is a section similar to  FIG. 14 , but showing still yet another version of the probe;  
       FIG. 20A  is a perspective of a separator of the probe of  FIG. 20 ;  
       FIG. 21  is an enlarged, fragmentary perspective of a distal end of a probe of a fourth embodiment;  
       FIG. 22  is a perspective of the tip of the fourth embodiment;  
       FIG. 23  is a back side elevation of the tip with a sensor shown in phantom;  
       FIG. 24  is a fragmentary section of a probe of a fifth embodiment;  
       FIG. 25  is a perspective of a separator of the fifth embodiment; and  
       FIG. 26  is a top end view of the separator and illustrating locations of sensors. 
    
    
      Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.  
     DETAILED DESCRIPTION  
      Referring now to the drawings and in particular to  FIGS. 1 and 2 , an electronic thermometer constructed according to the principles of the present invention is indicated generally at  1 . The electronic thermometer comprises a temperature calculating unit, indicated generally at  3 , that is sized and shaped to be held comfortably in the hand H. The calculating unit  3  (broadly, “a base unit”) is connected by a helical cord  5  to a probe  7  (the reference numerals indicating their subjects generally). The probe  7  is constructed for contacting the subject (e.g., a patient, not shown) and sending signals to the calculating unit  3  representative of the temperature. The calculating unit  3  receives the signals from the probe  7  and uses them to calculate the temperature. Suitable circuitry for performing these calculations is contained within a housing  9  of the calculating unit  3 . The logic in the circuitry may include a predictive algorithm for rapidly ascertaining the final temperature of the patient. The circuitry makes the calculated temperature appear on a LCD display  11  on the front of the housing  9 . Other information desirably can appear on the display  11 , as will be appreciated by those of ordinary skill in the art. A panel  11 A of buttons for operating the thermometer  1  is located just above the display  11 .  
      The housing  9  includes a compartment (not shown) generally at the rear of the housing that can receive a distal portion of the probe  7  into the housing for holding the probe and isolating the distal portion from the environment when not in use.  FIG. 1  illustrates the probe  7  being pulled by the other hand H 1  from the compartment in preparation for use. The housing  9  also has a receptacle  13  that receives a suitable container such as a carton C of probe covers (not shown). In use, the top of the carton C is removed, exposing open ends of the probe covers. The distal portion of the probe  7  can be inserted into the open end of the carton C and one of the probe covers can be captured (e.g., snapped into) an annular recess  14 . Pushers  15  are located at the junction of a handle  17  of the probe  7  with a probe shaft  19 . The probe shaft is protected from contamination by the cover when the distal portion of the probe shaft  19  is inserted, for example, into a patient&#39;s mouth. A button  21  on the probe handle  17  can be depressed to cause the pushers  15  to move for releasing the probe cover from the probe shaft  19 . Subsequent to use, the probe cover can be discarded. Other ways of capturing and releasing probe covers may be used without departing from the scope of the present invention.  
      An aluminum tip  25  at the distal end of the probe shaft  19  is heated up by the patient and the temperature of the tip is detected, as will be described more fully hereinafter. The probe cover is preferably made of highly thermally conductive material, at least at its portion covering the tip  25 , so that the tip can be rapidly heated by the patient. Referring now to  FIGS. 3 and 4 , the tip  25  and distal end of the probe shaft  19  are partially broken away (or exploded) to reveal components used to measure the temperature of the tip. The probe shaft  19  includes a tube that  26  and a distal probe shaft element indicated generally at  27  that plugs into the distal end of the tube ( FIG. 3 ). The tube  26  has a central passage  26 ′ that receives a split lower cylindrical portion  27 ′ of the probe shaft element  27 . The cylindrical portion  27 ′ has an O-ring like protuberance  27 ″ near its bottom end that is snapped into an annular recess  26 ″ in the tube  26  upon assembly to connect the probe shaft element  27  to the tube (see,  FIG. 7 ). It will be appreciated that the protuberance  27 ″, like the lower cylindrical portion  27 ′ is split in two. A larger diameter, cylindrical portion  27 ′″ of the probe shaft element  27  engages the end of the tube  26  when the probe shaft element is assembled with the tube.  
      A generally tubular separator, generally indicated at  29 , is mounted on the distal end of the probe shaft element  27  and extends generally into the open bottom of the tip  25 . The probe shaft  19 , tip  25  and separator  29  may be operatively connected together in a suitable fashion such as by adhering with an epoxy (not shown). A flex circuit, generally indicated at  31 , includes a deformable substrate  33  (broadly, “an electrical conductor”) mounting a tip thermistor  35 , a separator thermistor  37  and a heating resistor  39  (see  FIG. 4 ). The tip thermistor  35  is in thermal contact with the tip  25 , and the separator thermistor  37  and heating resistor  39  are in thermal contact with the separator  29 . It will be appreciated that other electrical components and other arrangements and numbers of components (not shown) may be used without departing from the scope of the present invention.  
      The tip thermistor  35 , separator thermistor  37  and resistor  39  are powered by batteries (not shown) located in the housing  9  of the thermometer  1 . It will be understood that other suitable power sources could be employed. The power source need not be located in the calculating unit housing  9  and it is envisioned that the calculating unit  3  could be omitted within the scope of the present invention. The tip thermistor  35  generates a signal that is representative of the temperature of the tip  25 . The signal is transmitted by a conductor in the flex circuit substrate  33  to the circuitry in the housing  9  via the cord  5 . One way of constructing such a substrate  33  is to have copper that is covered by an electrically insulating, but deformable material. Electrical contact is made where needed by penetrating the insulating cover to access the copper. It will be understood that other kinds of electrical conductors, such as wire, may be used without departing from the scope of the present invention. The separator thermistor  37  generates a signal that is representative of the temperature of the separator  29 . The resistor  39  is powered by the batteries and heats the separator  29  so that the aluminum tip  25  can reach the temperature of the patient more rapidly. Monitoring the temperature of the separator  29  with the separator thermistor  37  allows the heating of the resistor  39  to be controlled to best effect. For instance, the separator  29  can be initially rapidly heated, but then heated intermittently as the separator nears or reaches a pre-selected temperature. The function and operation of these components are known to those of ordinary skill in the art.  
      Referring now to  FIG. 4 , the flex circuit  31  (broadly, “a deformable circuit element”) and separator  29  are schematically illustrated prior to assembly. The flex circuit substrate  33  has a flat, cruciform shape. An elongate base portion  41  of the substrate  33  can be inserted into an opening  42  near the top of the cylindrical portion  27 ′″ of the probe shaft element  27  and through the probe shaft element to the position shown in  FIG. 5 . Arms  43  of the flex circuit  31  are bent in the direction indicated by arrows A 1  in  FIG. 5  to wrap around the sides of a forming section (indicated generally at  45 ) of the probe shaft element  27 . The forming section  45  includes cylindrical surfaces and recesses  47  on opposite sides of the forming section. As bent around the forming section  45 , portions of the arms  43  mounting the separator thermistor  37  and resistor  39  generally overlie respective ones of the recesses. Locating tabs  49  on the bottom edges of the arms  43  can be received in respective slots  51  formed in holding members  53  of the probe shaft element  27  to capture the arms and hold them in their deformed configuration around the forming section  45 .  
      An elongate head  57  of the flex circuit substrate  33  is bent from the position shown in  FIG. 5  generally across the top of the forming section  45  between adjacent pairs of posts  59   a ,  59   b ,  59   c ,  59   d  projecting axially outwardly from the forming section  45  (see,  FIG. 6 ). The head  57  of the flex circuit  31  is formed with a pair of ears  61  defined in part by cutouts  63 . The tip thermistor  35  lies between the ears  61 . When the head  57  is bent across the top of the forming section  45 , the cutouts  63  receive respective ones of the posts  59   a - 59   d . The ears  61  project between respective adjacent pairs of posts  59   a ,  59   b  and  59   c ,  59   d . The head  57  extends across the top of the forming section  45  between pairs of posts  59   a ,  59   d  and  59   b ,  59   c . The distal end portion of the head  57  extends out from the posts  59   a - 59   d  and is bent over on the opposite side of the forming section  45 . An aperture  65  in the distal end portion of the head  57  is pushed onto a projection  67  formed as part of the forming section  45  of the probe shaft element  27 . A friction fit between the flex circuit substrate  33  at the edge of the aperture  65  and the projection  67  holds the distal end portion of the head  57  in the bent position shown in  FIG. 6 . It will be appreciated that the various formations on the probe shaft element  27  operate to temporarily hold the flex circuit  31  in position, with the tip thermistor  35 , separator thermistor  37  and resistor  39  located substantially in their final positions before any final fixation of these components. Moreover, these formations may operate to finally position the tip thermistor  35 , separator thermistor  37  and resistor  39  (i.e., without application of epoxy) within the scope of the present invention.  
      A suitable adhesive such as an epoxy (not shown) is applied to a portion of the substrate  33  opposite the separator thermistor  37  and to a portion of the substrate opposite the resistor  39 . The separator  29  is pushed down onto the probe shaft element  27  and flex circuit  31 . The natural resilience of the flex circuit substrate  33  causes the arms  43  of the flex circuit  31  to bow out at the sides so that the separator thermistor  37  and resistor  39  are biased radially outwardly. A neck  34  of the separator  29  engages respective portions of the arms  43  of the substrate  33  opposite the separator thermistor  37  and resistor  39  and pushes them inwardly. The recesses  47  in the forming section  45  allow the flex circuit substrate  33  to deform slightly into the recesses. The spring action of the flex circuit substrate  33  resists this deformation, which results in the substrate portions opposite the separator thermistor  37  and resistor  39  (respectively) being biased against an inner wall  71  of the separator  29 . This is desirable because it holds the portions of the arms  43  of the substrate  33  opposite the separator thermistor  37  and resistor  39  against the separator  29  until the epoxy can set, which may not occur until the epoxy is heated in an oven (not shown)after complete assembly of the probe  7 . An epoxy may also be used to secure the separator  29  to the probe shaft element  27 . Other ways of securing the separator  29  to the probe shaft  19  do not depart from the scope of the present invention.  
      The subassembly of the flex circuit  31 , probe shaft element  27  and separator  29  can be assembled with the tube  26  of the probe shaft  19 . The probe tip  25  can then be pushed down onto the separator  29  and flex circuit  31 . A central region  79  of the probe tip  25  engages the portion of the head  57  opposite the tip thermistor  35 . Attaching the distal end portion of the flex circuit head  57  to the probe shaft element  27  at the projection  67  causes the resilient flex circuit substrate  33  to act as a spring biasing the portion of the head  57  opposite the tip thermistor  35  against the probe tip  25 . This allows the tip thermistor  35  to have good contact with the tip  25  (through the substrate  33 ). The probe  7  can be placed in an oven to cure the epoxy and finally fix the separator thermistor  37  and the resistor  39  in place.  
      Referring now to  FIGS. 9-13 , a probe tip  125 , probe shaft element  127 , separator  129 , and flex circuit  131  a probe of a second embodiment are shown. Parts of the probe of the second embodiment corresponding to the probe  7  of the first embodiment are given the same reference numeral, plus “100”. The components of the probe not illustrated in the drawings can be substantially the same as those parts of the probe  7  of the first embodiment. The probe shaft element  127  includes a cylindrical portion  127 ′″ that engages a tube  126  of the probe shaft  119 . A base portion  141  of the flex circuit  131  can be threaded through an opening  142  at the bottom of a forming section  145  of the probe shaft element  127  into a central passage of the probe shaft element. The forming section  145  is generally conical in shape (or more specifically, the frustum of a cone), but is cut on opposite axial planes providing access to the opening  142 . The interior of the forming section  145  has a cavity  146  ( FIG. 12 ). One of two flat surfaces  148  of the cone can engage a flex circuit substrate  133  extending out of the central passage of the probe shaft element  127 . Arms  143  of the flex circuit  131  can be bent around curved surfaces  150  of the forming section  145  and secured in slots  151  formed in holding members  153  of the probe shaft element  127 , substantially in the same way as for the flex circuit  31  of the first embodiment.  
      The parts of the arms  143  mounting a separator thermistor  137  and a resistor  139  overlie the curved surfaces  150  of the forming section  145  and generally conform to the (conical) shape of these surfaces ( FIG. 11 ). As a result, the arms  143  and the separator thermistor  137  and resistor  139  on the arms lie at an angle θ to the axis of the probe shaft element  127 . In one embodiment, the angle θ that the curved surfaces  150  make with the axis is greater than about 5 degrees. In another embodiment, the angle θ that the curved surfaces  150  make with the axis is less than about 20 degrees and greater than about 5 degrees. The angle θ at which the separator thermistor  137  and resistor  139  are positioned by the curved surfaces  150  of the forming section  145  facilitates assembly with the separator  129 .  
      Epoxy or other suitable adhesive (not shown) may be applied to the portion of the arm  143  opposite the separator thermistor  137  and to the portion of the arm  143  opposite the resistor  139  prior to assembly with the separator  129 . Referring to  FIG. 11 , when the separator  129  is pushed onto the end of the probe shaft element  127  and flex circuit  131 , a larger diameter portion  132  of the separator passes the forming section  145  generally without engaging the flex circuit  131 . A neck  134  of the separator  129  having a smaller diameter than the larger diameter portion  132  moves onto the forming section  145 . An inner wall  171  of the neck  134  is angled so that it is substantially parallel to the angle of the curved surfaces  150  of the forming section  145 . The angle θ of the curved surfaces  150  and the inner wall  171  reduces the incidence of the separator  129  shearing off the epoxy previously applied to the portions of the arms  143  opposite the separator thermistor  137  and resistor  139  as the separator moves onto the flex circuit  131  and forming section  145 . Thus, the epoxy substantially remains on the portions of the arms  143  opposite the separator thermistor  137  and the resistor  139  so that these electrical components can be securely attached to the separator  129  in good thermal contact therewith.  
      As with the probe shaft  19  of the first embodiment, the probe shaft element  127  received in the distal end of the tube  126  is assembled with the separator  129  and flex circuit  131 . The tip  125  is pushed onto a subassembly of the probe shaft element  127 , tube  126 , separator  129  and flex circuit  131 .  
      The cavity  146  on the interior of the forming section  145  strategically weakens an end surface  152  of the forming section. The tip  125  is sized and shaped so that it pushes the head  157  and the tip thermistor  135  downward, deforming the end surface  152  of the forming section  145  ( FIG. 12 ). The material of the probe shaft element  127  is selected so that this deformation is resiliently resisted. Thus, the end surface  152  acts as a spring for forcing the portion of the head  157  opposite the tip thermistor  135  against a central region  179  of the tip  125 , providing good thermal contact. Similarly, the cavity  146  weakens the curved surfaces  150  of the forming section  145 . Thus when the separator  129  is applied to the probe shaft element  127  and flex circuit  131 , the engagement of the interior wall  171  of the separator in the neck  134  with the portions of the arms  143  opposite the separator thermistor  137  and resistor  139  deforms the curved surfaces  150  radially inward. The deformed curved surfaces  150  act as springs biasing the portions of the arms  143  opposite the separator thermistor  137  and resistor  139  against the interior wall  171  of the neck  134  to further facilitate good contact.  
       FIGS. 14 and 15  illustrate a fragmentary portion of a probe  207  of a third embodiment having a probe shaft element  227  formed for secure attachment of a separator  229  to the probe shaft element  227 . Parts of the third embodiment of the probe corresponding to those of the second embodiment will be given the same reference numerals as the second embodiment, plus “100”. The probe shaft element  227  may be formed as by molding from a resilient material either separately from the remainder of the probe shaft or as one piece with the probe shaft. The probe shaft element  227  is particularly formed to initially secure the separator  229  to the probe shaft without an adhesive.  
      A distal end portion of a forming section  245  of the probe shaft element has a radially projecting annular flange  254 . The flange includes a beveled surface  256  on its axially outward side and a retaining surface  258  on the opposite side extending generally orthogonally to the axis of the probe shaft  219 . The forming section  245  has a recess  260  between the retaining surface  258  of the flange  254  and a shoulder  262  formed on the probe shaft element  227 . A neck  234  of the separator  229  is retained in the recess  260  between the flange  254  and the shoulder  262  in the assembled probe.  
      The probe having the modified probe shaft  219  can be assembled in ways that are substantially similar to those previously described herein. A flex circuit  231  can be inserted into the probe shaft  219  through an opening (not shown) in the probe shaft element  227  so that arms  243  of the flex circuit are aligned generally with the recess  260  of the forming section  245 . The arms  243  can be bent around the forming section  245 . The probe shaft element  227  may include structure for retaining the arms (e.g., like holding members  53 ,  153  of the first and second embodiments), but such structure is not present in the illustrated embodiment of the probe shaft element. A head  257  of the flex circuit  231  can be bent over the distal end of the forming section  245  to position a tip thermistor  235  substantially as previously described. The forming section  245  includes a support column  264  underlying the location where the tip thermistor  235  is positioned for use in holding the tip thermistor against a tip  225  of the probe. Epoxy can be applied to portions of the arms  243  of the substrate  233  opposite a separator thermistor  237  and resistor  239  (respectively) as described before.  
      Movement of the separator  229  onto the probe shaft element  227  and flex circuit  231  subassembly begins with a larger diameter portion  232  of the separator  229  receiving the forming section  245  of the probe shaft element. The diameter of the larger diameter portion  232  is such that it does not have significant contact with the forming section  245  or the flex circuit  231  as it passes over the forming section. As illustrated in  FIG. 15 , when the smaller diameter neck  234  of the separator  229  reaches the flange  254 , it engages the beveled surface  256  of the flange. The beveled surface  256  acts as a wedge to facilitate deflection of the flange  254  radially inwardly as the separator  229  continues to be moved axially inwardly relative to the probe shaft element  227 . An annular gap  266  between the support column  264  and the outer wall of the forming section facilitates the deflection. This deflection allows the neck  234  to move over and pass the flange  254 . When the separator neck  234  reaches the position shown in  FIG. 14 , the beveled surface  258  of the flange  254  is cleared and the resilience of the probe shaft element material causes the forming section  245  and flange  254  to spring back substantially to their original configurations. The resilience of the flange  254  and forming section  245  places the retaining surface  258  of the flange in axially opposed relation with the distal end of the separator  229 . Thus, it will be seen that the neck  234  is captured in the recess  260  between the retaining surface  258  of the flange  254  and the shoulder  262  of the probe shaft element  227  thereby holding the separator  229  in an axial position relative to the probe shaft  219 . It will be understood that epoxy (not shown) may be used to affix the separator  229  to the probe shaft element  227  in addition to the mechanical fixation achieved by the flange  254  and shoulder  262 . However, the snap connection achieved by the flange  254  and shoulder  262  holds the separator  229  in place prior to the final fixation achieved when the epoxy is cured.  
      The tip  225  can be placed on the subassembly of the probe shaft element  227 , separator  229  and flex circuit  231  substantially as described previously herein. The support column  264  acts as a reaction surface to force the portion of the head  257  opposite the tip thermistor  235  against a central region  279  of the tip  225 .  
       FIG. 16  illustrates a probe  207 A having a modified probe shaft  219 A, which like the probe shaft  219  shown in  FIGS. 14 and 15  is constructed for snap connection of a separator to the probe shaft. Parts of the modified version of the probe shaft shown in  FIG. 16  have the same reference numerals as for the third embodiment shown in  FIGS. 14 and 15 , but with the suffix “A”. The probe shaft  219 A of  FIG. 16  has substantially the same construction as the probe shaft  219  of  FIGS. 14 and 15 . A flange  254 A and shoulder  262 A formed in a forming section  245 A of a probe shaft element  227 A mechanically capture and retain a neck  234 A of a separator  229 A.  
      An outer wall  270 A of the probe shaft element  227 A angles inwardly from the shoulder  262 A to the flange  254 A. The angulation of the outer wall  270 A has the same advantage as previously described for the curved surfaces  150  of the forming section  145  of the second embodiment shown in  FIGS. 9-13 . This construction helps to avoid having the separator  229 A wipe off the epoxy from portions of the arms  243 A opposite a separator thermistor  237 A and resistor  239 A when the separator is placed on a subassembly of the probe shaft element  227 A and flex circuit  231 A.  
      The modified version of  FIG. 16  also differs from the embodiment of  FIGS. 14 and 15  in that a support column  264 A is constructed to provide a spring bias to the head  257 A of the flex circuit  231 A and tip thermistor  235 A to press a portion of the head  257 A of the substrate  233 A opposite the tip thermistor against a central region  279 A of a tip  225 A of the probe. In that regard, the column  264 A has an internal cavity  246 A extending up to a support surface  272 A of the column. This cavity  246 A strategically weakens the support column  264 A so that the support surface  272 A can be slightly deflected when the tip  225 A is applied to the probe shaft element  227 A. The deflection is resiliently resisted by the material of the support column  264 A, causing it to act as a spring biasing the flex circuit head  257 A and tip thermistor  235 A mounted thereon upward against the central region  279 A of the tip  225 A.  
       FIG. 17  illustrates another modified version of the probe shaft  219 B of a probe  207 B. Parts of the modified version of the probe of  FIG. 17  will be given the same reference numerals as the corresponding parts of the probe illustrated in  FIGS. 14 and 15 , with the addition of the suffix “B”. Like the probe shaft element illustrated in  FIGS. 9-13 , a probe shaft element  227 B of  FIG. 17  includes a generally conically shaped forming section  245 B. The angles that the curved surfaces  250 B of the forming section  245 B and an inner wall  271 B of the separator neck  234 B have to the axis of the probe shaft  219 B provide the same advantage as described above.  
      The interior of the forming section  245 B includes a cavity  246 B. An end surface  272 B of the forming section  245 B is cupped. The end surface  272 B underlies a head  257 B of the flex circuit  231 B and a tip thermistor  235 B on the head. The end surface  272 B is capable of flexing downward when a tip  225 B is applied to the probe shaft element  227 B. The deflection causes the forming section  245 B to resiliently bias the flex circuit head  257 B and the tip thermistor  235 B against a central region  279 B of the tip  225 B.  
      A still further modified version of a probe shaft  219 C is shown in  FIGS. 18 and 19 . Parts of the modified version of the probe of  FIGS. 18 and 19  will be given the same reference numerals as the corresponding parts of the probe illustrated in  FIGS. 14 and 15 , with the addition of the suffix “C”. A forming section  245 C of a probe shaft element  227 C is somewhat similar to the probe shaft element  227 B of  FIG. 17  except that the side surfaces  250 C of the forming section are flat rather than curved. It is at these flat side surfaces  250 C that a separator thermistor and resistor are positioned. A separator  229 C is formed so that mating flat inner wall segments  276 C are present in a neck  234 C of the separator. Thus, when the separator  229 C is placed on the probe shaft element  227 C, the flat side surfaces  250 C of the forming section  245 C and the flat inner wall segments  276 C of the separator neck  234 C are in opposed relation. The flat side surfaces  250 C and flat inner wall segments  276 C sandwich the parts of the flex circuit arms mounting the separator thermistor and resistor (not shown) between them.  
      Yet another modified version of the probe shaft  219 D is illustrated in  FIGS. 20 and 20 A. Parts of the modified version of the probe of  FIGS. 20 and 20 A will be given the same reference numerals as the corresponding parts of the probe illustrated in  FIGS. 14 and 15 , with the addition of the suffix “D”. The probe shaft element  219 D of  FIG. 20  is similar to the probe shaft element  219 C of  FIGS. 18 and 19  in that a forming section  245 D of the probe shaft includes flat side surfaces  250 D. A separator  229 D has corresponding flat inner wall segments  276 D that lie in face to face opposition with the flat side surfaces. A separator thermistor  237 D (not shown) and resistor  239 D (only a portion of the resistor  239 D is illustrated) are sandwiched between respective flat side surfaces  250 D and flat inner wall segments  276 D, as in the version shown in  FIGS. 18 and 19 . A neck  234 D of the separator  229 D has a pair of holes  280 D on each side generally between the flat inner wall segments.  
      The probe shaft element  227 D is formed with aligning members  284 D to engage an inner wall  271 D of a larger diameter portion  232 D of the separator  229 D. These alignment members  284 D act to center the separator  229 D on the axis of the probe shaft  219 D. This provides for a more even and gentle application of force to the portions of the arms  243 D opposite the separator thermistor  237 D and resistor  239 D when they are engaged by the inner wall segments  276 D of the neck  234 D. The probe shaft element  227 D is formed with a shoulder  262 D that is positioned for engaging the end of the larger diameter portion  232 D of the separator  229 D. The shoulder  262 D allows the separator  229 D to be pushed down onto the probe shaft element  227 D so that the angled inner wall segments  276 D of the neck  234 D engage the portions of the arms  243 D opposite the separator thermistor  237 D and resistor  239 D (respectively) for achieving good thermal contact with the separator. The shoulder  262 D also prevents the separator  229 D from being pushed too hard against the portions of the arms  243 D opposite the separator thermistor  237 D and resistor  239 D.  
      The probe shaft element  227 D shown in  FIG. 20  is also formed for snap-on connection of the separator  229 D with the probe shaft element  227 D. To that end, the aligning members  284 D (only two are shown) are formed with radially outwardly projecting formations  286 D. When the separator  229 D is pushed axially onto the probe shaft element  227 D (as assembled with a flex circuit  231 D), the inner wall  271 D of the neck  234 D engages the projecting formations  286 D of the aligning members  284 D and deforms them. When the holes  280 D on the separator  229 D become aligned with respective ones of the projecting formations  286 D on the aligning members  284 D they snap back to their undeformed configurations. As undeformed, the projecting formations extend through the holes  280 D, attaching the separator  229 D to the probe shaft element  227 D and positioning the separator relative to the probe shaft element. In this way, the forming section  245 D captures the separator  229 D prior to any fixation with adhesive.  
      Referring now to  FIGS. 21-23 , a probe  307  of a fourth embodiment is shown to comprise a probe shaft  319  and a separator  329  mounted on the probe shaft. Parts of the probe  307  corresponding to those of the probe  7  of the first embodiment will be given the same reference numerals, plus “300”. An annular isolator  302  of a thermally insulating material is mounted on a neck  334  of the separator  329  and is interposed between the separator and a probe tip  325  of the probe  307 . The isolator  302  inhibits thermal communication between the separator  329  and the tip  325 . It is to be understood that the isolator  302  may not be thermally insulating, and may be broadly considered a “locating member” within the scope of the present invention. The probe shaft  319  does not include a forming section (e.g.,  45 ,  145 ,  245 ) as in the prior embodiments, but such structure could be present within the scope of the invention. A flex circuit  331  is deformed so that arms  343  (only one of which is shown) lie against opposite segments of an inner wall  371  of the separator  329 . A head  357  of the flex circuit  331  is bent over to position a portion of the head opposite a tip thermistor  335  against a central region  379  of the tip  325 . An aperture  365  near the distal end of the head  357  receives a projection  304  formed on the isolator  302  to hold the head in its bent over position. The flex circuit  331  acts as a spring to bias the portion of the head  357  opposite the tip thermistor  335  against the tip  325 .  
      The central region  379  of the tip  325  is shaped to indicate where to position the tip thermistor  335  relative to the tip. More specifically, the central region  379  is formed to lie in a plane that is generally perpendicular to the axis of the probe shaft  319  (see also  FIGS. 22 and 23 ). However, a region anywhere on a tip can be shaped in any manner which distinguishes the region from its surrounding to show proper location of an electrical component relative to the tip. The central region  379  thus provides a flat surface (broadly, “a receiving surface”) against which the portion of the head  357  opposite the tip thermistor  335  bears. Conventional rounded tips provide for only point contact between the portion of the head of the substrate that is opposite tip thermistor and the tip. Heat transfer occurs more quickly if a greater area of the portion of the head  357  opposite the tip thermistor  335  is engaging the tip  325 . It will be understood that a tip (not shown) may have other flat surfaces for receiving additional electrical components within the scope of the present invention.  
      A probe  407  of a fifth embodiment is shown in  FIGS. 24-26  to comprise a probe shaft  419  and a separator  429  mounted on a distal end of the probe shaft. Parts of the probe  407  corresponding to those of the probe  7  of the first embodiment will be given the same reference numerals, plus “300”. An isolator  402  mounted on the distal end of a neck  434  of the separator  429  is interposed between the separator and a probe tip  425  to substantially thermally isolate these two components. As with the probe  307  of the fourth embodiment, the probe shaft  419  of the fifth embodiment does not include a forming section (e.g.,  45 ,  145 ,  245 ), although such a structure could be used without departing from the scope of the present invention. The isolator  402  engages a bent over head  457  of a flex circuit  431 , but does not positively connect the flex circuit to the isolator. Frictional interaction keeps the head  457  in its bent configuration. However, a projection (e.g., like projection  304  of the fourth embodiment) or other structure could be used to more positively locate the head  457 .  
      As shown in  FIGS. 25 and 26 , the separator neck  434  tapers toward its distal end (opposite a larger diameter portion  432  of the separator). The neck  434  includes opposed curved side surfaces  406  and opposed flat side surfaces  408 . The flat side surfaces  408  are arranged so that when flex circuit arms  443  are bent, portions of the arms opposite a separator thermistor  437  and resistor  439  are adjacent to respective ones of the flat side surfaces  408 . The flex circuit arms  443 , separator thermistor  437  and resistor  439  are illustrated in phantom in  FIG. 26 . The flat side surfaces  408  allow for some variance in position of the separator thermistor  437  and/or resistor  439  while still achieving good contact with these components for the best heat transfer between the separator  429  and the components. Moreover, the separator thermistor  437  and resistor  439  are generally mounted on the flex circuit substrate  433  using flat solder pads (not shown, but represented schematically along with the separator thermistor and heating resistor). In the assembled probe  407 , the flexible resilience of the flex circuit substrate  433  causes the deformed arms  443  to bear radially outward against the inner wall  471  of the separator  429 . Moreover, the arms  443  try to conform to the shape of the inner wall  471 . However, because of the flat solder pads, there would tend to be gaps between the portions of the arm opposite the separator thermistor and resistor and circular inner walls of conventional cylindrical separators. The epoxy can fill this gap, but the distance increases the time for heat to transfer through the substrate  433  between the separator thermistor or resistor and the separator. The flat inner wall segments  408  of the separator  429  of  FIGS. 24-26  allow the portions of the arms  443  of the substrate  433  opposite the solder pad and the separator thermistor  437  or resistor  439  mounted to the solder pad to engage the separator without a substantial gap. Thus, the time for heat to transfer to the thermistor  437  from the separator  429  or from the resistor  439  to the separator is kept to a minimum.  
      When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of “up”, “down”, “top” and “bottom” and variations of these terms is made for convenience, but does not require any particular orientation of the components.  
      As various changes could be made in the above without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.