HK1042550B - Infrared thermometer with heatable probe head and a combination of a protective cover and a probe head - Google Patents

Description

Infrared thermometer with heatable probe and combination of protective cover and probe

Technical Field

The invention relates to an infrared thermometer with a heatable probe, in particular to a clinical thermometer for measuring the temperature in the ear of a patient, and to a heatable protective cover.

Background

A thermometer with A heatable probe is known from US-A-3,491,569. The probe has a cavity at its front end in which a heating element is installed, and an field effect transistor functions as a heat sensing device. The walls of the cavity are made of a material that is a good conductor of heat, such as copper. The field effect transistor is thermally coupled to the wall of the cavity. The radiant heat energy radiated from the outside to the probe is transferred to the field effect transistor and responded by emitting a corresponding temperature measurement signal. The field effect transistor is preheated by the heating element to a temperature close to the temperature corresponding to the human body temperature. This is to reduce the response time compared to a sensing device that is not heated.

From US-4,602,642 an ear thermometer is known, the probe of which comprises a waveguide which extends from the front end of the probe into the interior of the probe. At its rear end the waveguide is fixed to a metal housing in which a thermocouple infrared detector is arranged. The metal shell and the infrared detector connected thereto in good heat-conducting relation can be heated by the heated transistor and a control device to a temperature corresponding to approximately the temperature of the human body. However, in order to heat such a large part of the thermometer, a relatively long heating time and a correspondingly large amount of energy are required.

By heating the probe that is insertable into the ear canal, heat flow between the probe and the ear canal is largely avoided, in other words, the probe and the ear canal are in thermal equilibrium at the time of temperature measurement. In this way, erroneous readings can be avoided, which would otherwise be caused by the cooling effect of the ear canal, since the probe inserted into the ear canal is at a temperature below the temperature of the ear canal, with the result that the temperature of the reading is too low. Such measurement errors depend not only on the initial temperature difference between the probe and the ear canal and the cooling time or delay in the measurement process, but also on the respective positioning, or alignment of the probe within the ear canal.

When the probe is directed directly against the wall of the ear canal, the infrared radiation emitted by the cold probe is reflected by the wall portion (reflection factor about 3 to 5%) and detected by the probe, as a result of which not only the infrared radiation emitted by the cooled ear canal wall but also the reflected infrared radiation emitted by the probe itself is measured, resulting in a correspondingly too low temperature reading. However, in contrast, when the probe is correctly directed at the tympanic membrane, the radiation emitted by the cold probe is first reflected a number of times in the ear canal with corresponding losses before it is coupled into the probe again, so that the measurement results are correspondingly reduced.

Another disadvantage of infrared thermometers with unheated probes is that the temperature of the protective cover mounted on the probe is subject to relatively severe variations depending on the difference between the ambient temperature and the temperature of the ear canal when the probe is introduced into the ear canal. This also causes variations in the radiation energy emitted by the shield, introducing corresponding measurement errors. However, if the shield is heated, the temperature of the shield varies little during the entire measurement operation, since this temperature is determined by the temperature of the probe.

Disclosure of Invention

It is an object of the present invention to provide an infrared thermometer with a heatable probe in which so little thermal energy is required that it can be obtained from a battery in the thermometer.

According to the invention, this object is achieved in that: the probe and/or a shield adapted to fit over the probe in a manner well known in the art are configured in such a way that: only the front area of the probe and/or shield may be heated to a temperature close to that consistent with typical ear canal temperatures.

The structure of the infrared thermometer probe disclosed by the invention utilizes the fact that the infrared sensor mounted in the probe has only a limited field of view. It is sufficient that the part of the probe that is in thermal interaction with the part of the ear canal that is in the field of view of the infrared sensor exhibits the same temperature as the ear canal. In a probe constructed according to the invention, therefore, only the forward end of the probe, in particular its front face, is designed to be heatable. This relatively small area lends itself to heating in a highly energy efficient manner and is preferably thermally insulated from the unheated portion of the probe.

The infrared thermometer of the invention has a radiation inlet area at the front end of its probe and a heating element, which is preferably electrically heatable. Either the heating element is built into the probe or a protective cover adapted to be fitted to the probe is provided with a heating element. It is also possible to provide two heating elements, one of which is mounted in the probe and the other of which is connected to a protective shield adapted to fit over the probe.

The heating element comprises, for example, at least one NTC or PCT resistor or transistor mounted at the front end of the probe. However, it is also possible that the heating element is, for example, a metal coating in the form of a conductive path or a coating made of electrically conductive plastic applied to a radiation entrance window arranged at the front end of the probe, the protective cover or the probe itself preferably surrounding the radiation entrance area in an annular manner.

In a preferred embodiment of the infrared thermometer according to the invention, the radiation entrance area is delimited by an infrared-transparent window, which can be heated by means of a heating element. This is particularly simple to produce by means of heating wires, for example made of constantan, which are laid around the window and are connected thereto in good heat-conducting relationship. The window may be made of, for example, chalcogenide glass, which transmits infrared radiation and is easily shaped. In a particularly elaborate implementation, the window is made of a semiconductor, in particular silicon, wherein the electrically conductive path can function as a resistively heating conductor formed by doping. An advantage of these implementations with a heatable window is that the heating element enables the entire front end of the probe, in other words the entire front surface of the probe including the radiation inlet zone, to be heated to a desired temperature, so that the thermal equilibrium in the ear canal is practically undisturbed by the probe, whereby the resulting erroneous readings are minimized.

The infrared thermometer of the present invention also includes a heating element control device that is connected to the heating element and to a source of energy, such as a battery. The control device serves to determine and/or regulate the temperature of the probe. For this purpose it is connected to a heat flux sensor for detecting heat flow between the probe and the ear canal of the user and/or to a temperature sensor which is preferably arranged at the front end of the probe. However, in a preferred embodiment of an infrared thermometer of the present invention, the heating element itself serves as the sensor without an additional sensor. Such a control determines the temperature of the heating element, and thus of the front end of the probe, from a measurable characteristic quantity of the heating element, for example the resistance, the threshold voltage value or the forward voltage.

In an infrared thermometer according to the invention, which provides particular convenience, the control means also controls the activation and deactivation of the heating element before and after the temperature measurement, respectively. The heating process is automatically initiated no later than when the probe is introduced into the ear canal of the user. The insertion and withdrawal operations are likewise automatically terminated when the temperature is measured, for example by detecting a change in the radiation temperature measured by a radiation temperature sensor connected to the control device, or by detecting a change in the temperature of the probe measured by a temperature sensor, or by detecting a corresponding signal from a thermal flow sensor. In this way, error factors are eliminated and a sufficiently high measurement accuracy is ensured at all times.

Preferably, for an idealised measurement accuracy, the measurement of the heat flow between the probe and the ear canal of the user is determined by means of a heat flow sensor, and the heating output is controlled such that this heat flow is minimised. In order to keep the heat flux to a minimum from the beginning, the probe is preferably constructed such that the thermal capacity and the thermal conductivity of the probe in the region of contact with the auditory canal are as low as possible. The surfaces of these areas are therefore preferably made of plastic.

In the protective hood according to the invention, the electrical heating element can be used for heating over the entire front area of the protective hood. The hood is conically shaped in a manner well known in the art and has an entrance region at its forward end through which infrared radiation passes. The heating element is preferably formed by a layer of electrically conductive wire in the form of a cladding of metal or electrically conductive plastics material annularly surrounding the radiation inlet region. The energy supply to the heating element is by means of an electrical or electromagnetic connection, preferably a battery using an infrared thermometer. The thermometer has, for example, suitably arranged contacts which, when mounted, form an electrical connection with the coating in the form of the conductive track of the protective cover. Alternatively, a device configured as a short-circuit coil may be provided for inductively transmitting energy to the heating element.

Drawings

Other features and advantages of the invention will be apparent from the appended claims, as well as from the following description of a preferred embodiment of the infrared thermometer probe of the invention shown in the accompanying drawings. Like parts are designated by like reference numerals in the accompanying drawings and the drawings are diagrammatic representations.

FIG. 1 is a first embodiment of the probe of the present invention, mounted with an annular heating element and shield;

FIG. 2 is a second embodiment of the probe of the present invention, mounted with a ring-shaped heating element and shield;

FIG. 3 is a third embodiment of the probe of the present invention, mounted with a heatable infrared transparent window and shield;

FIG. 4 is a fourth embodiment of the probe of the present invention having a heatable infrared transparent window;

figure 5 shows a detail of the probe shown only schematically in figure 3; while

Fig. 6 is a cross-sectional and top view of a shield with a heating element.

Detailed Description

Fig. 1 shows that the probe 10 according to the invention has a probe housing 14 which tapers conically in the direction of the radiation inlet 12 and has a ring-shaped heating element 16 at its front end, which surrounds the radiation inlet 12. The heating element 16 is preferably electrically heatable. An infrared waveguide 18 extends longitudinally from the radiation inlet 12 through the probe housing 14 to an infrared sensor, not shown in the drawing, which serves to convert the detected infrared radiation into an electrical output signal, which is analyzed by means of an electronic measuring device, also not shown, and then displayed by an associated indicating device. The front end of the infrared waveguide 18 is provided with an infrared-transparent window 20, and a space 22 is maintained between the infrared waveguide 18 and the probe housing 14 for thermal insulation. To protect the window from contamination or damage, the opposite probe forward end is slightly recessed. Fitted to the probe 10 in a known manner is a replaceable shield conforming to the shape of the probe housing.

The probe 10 of the invention shown in fig. 2 differs from the embodiment shown in fig. 1 only in that the width of the electrically heatable annular heating element 16 is enlarged so as to completely cover the space 22 between the probe housing 14 and the infrared waveguide 18. The inner diameter of the ring 16 corresponds approximately to the inner diameter of the infrared waveguide 18. In this way the heating element covers the front end of the probe except for the radiation inlet 12.

The probe 10 of the invention shown in fig. 3 differs from that shown in fig. 1 in that the front end of the infrared waveguide 18 is not closed through the infrared window 20, but the radiation entrance 12 is closed. The heating element 16 is connected to the window 20 so as to establish a good heat transfer relationship therewith. The window is preferably made of a suitable thermally conductive material, such as silicon.

Fig. 5 shows a detail of the heating element 16 shown only schematically in fig. 3. It comprises a frame 26 which can be heated by the heating wire 16' and which surrounds the window 20, the temperature of which can be measured by a temperature sensor 28. This frame provides a particularly uniform heating of the window 20 in addition to protecting the window 20 from damage. The frame is made of, for example, aluminum, or a material having relatively good thermal conductivity characteristics, and is thermally insulated from the probe housing 14.

The probe shown in fig. 4 differs from the embodiment shown in fig. 1 in that the front end of the probe terminates in an arched, infrared-transparent window 20 which can be heated directly by a heating element, not shown. The window 20 also contains a temperature sensor, also not shown in the figure, for determining the window temperature. The heating element is, for example, an electrically conductive track made of metal or electrically conductive plastic applied on the window. Preferably, however, the window is made of silicon, so that the heating element 1 can be incorporated directly into the window by doping at the respective section of the window. The temperature of the window can be determined by the resistance of the doped section so that a separate temperature sensor can be dispensed with. Furthermore, it is of course possible to provide a temperature sensor which is preferably configured in the same way as the heating element.

The window has a preferably conically extending side wall 20a and a front surface 20b that is arched in the forward direction for easy insertion into the ear canal. With this heatable window, neither the contact of the auditory canal with the side wall 20a nor the corresponding contact with the front surface 20b produces a perceptible heat exchange between the window 20 and the auditory canal, with correspondingly lower measurement configuration errors as a result. It is also possible to do without a shield to take measurements, taking into account that in practice the entire front area of the probe 10 is tightly enclosed by the window 20.

In all embodiments the heating element is connected to a control device, not shown in the figures, to which in addition a temperature sensor and/or a heat flow sensor may be connected to detect the heat flow between the front part of the probe and the ear canal of the user. The control means acts to initiate the heating process when the probe is inserted into the ear canal, preferably automatically to maintain the temperature of the probe at a constant level or to adjust it to minimize the heat flux at which radiation temperature measurements are taken, and to terminate the heating process, preferably automatically, when the probe is withdrawn from the ear canal.

The heatable hood shown in fig. 6 comprises a conically shaped plastic body 30 and a radiation inlet area 32 at its front end in a manner known in the art. A heating element in the form of an electrically conductive track 34, which is applied by vapor deposition to the interior of the plastic body 30 by means of a metal coating, annularly surrounds the radiation inlet 32. The ends of the conductive lines are widened to form contacts. It should be understood, however, that a conventional non-heatable protective cover could equally be used instead of a heatable protective cover, provided that the probe itself is equipped with a heating element.

Claims (15)

1. An infrared thermometer for taking the temperature of a patient's ear has a probe which can be heated by a heating element and has a radiation inlet at its forward end,

characterized in that the heating element (16) is placed at the front end of the probe (10).

2. An infrared thermometer according to claim 1 characterised in that the heating element is connected to a protective cover (24) adapted to fit over the probe.

3. An infrared thermometer according to claim 1, characterised in that the heating element (16) is fixed to the forward end of the probe (10).

4. An infrared thermometer according to claim 1 or 3, characterised in that it comprises a transparent infrared window (20) at the forward end of the probe (10), which window can be heated by the heating element (16).

5. An infrared thermometer according to claim 4, characterised in that the window (20) is made of semiconductor and that conductive tracks capable of functioning as resistive heating conductors are formed on the window by doping.

6. An infrared thermometer according to claim 1, 2 or 3 wherein said infrared thermometer includes means for controlling the heat output of said heating element.

7. An infrared thermometer according to claim 6, characterised in that it comprises a temperature sensor (28) and/or a heat flow sensor connected to the control device.

8. An infrared thermometer as claimed in claim 6, characterised in that the control means are capable of measuring the temperature of the probe by measuring a determined characteristic quantity of the heating element (16).

9. An infrared thermometer according to claim 6 wherein said control means is operable to adjust said heating element to a constant temperature and/or to activate and deactivate it in the presence of a change in temperature of said probe.

10. An infrared thermometer according to one of the claims 1 to 3, characterised in that the heating element is constructed as an electrically conductive track-shaped coating (34) of metal or electrically conductive plastic material.

11. An infrared thermometer according to claim 2 wherein said means for energizing said heating element is connected to said protective cover.

12. An infrared thermometer according to claim 11 wherein the energy supply means comprises an electrical connection means or an electromagnetic transmission means.

13. In combination with a probe head, a protective cover adapted to be fitted to the probe head and usable with an infrared thermometer, the protective cover having a radiation entry region at a forward end thereof, the protective cover comprising a heating element which is disposed at the forward end of the probe head when the protective cover is fitted to the probe head.

14. The shield of claim 13 wherein the heating element comprises a metal coating and/or a plastic coating made of an electrically conductive plastic material.

15. The shield of claim 13 or 14 wherein the heating element is configured in the shape of an electrically conductive track and annularly surrounds the radiation inlet region.