WO2002031457A1

WO2002031457A1 - Non-invasive electronic thermometer

Info

Publication number: WO2002031457A1
Application number: PCT/FR2001/003149
Authority: WO
Inventors: André Dittmar; Gérald SERRES-VIVES; Georges Delhomme; Benoit Linglin; Bénédicte SIMOND; Laure Schwenzfeier
Original assignee: Seb S.A.
Priority date: 2000-10-13
Filing date: 2001-10-11
Publication date: 2002-04-18
Also published as: FR2815407B1; FR2815407A1; IL155352A0; IL155352A; AU2001295686A1; EP1325292A1

Abstract

The invention concerns a non-invasive electronic thermometer for measuring body temperature comprising a housing at the end of which is arranged a temperature sensor (10) mounted on an insulating support (30), the housing containing electronic processing means communicating with said sensor to transform the signals received from the sensor into human body temperature values and display them. More particularly, the invention is characterised in that the support (30) comprises at least a peripheral cavity (34) which sealingly encloses the sensor (10) when the latter is brought in contact with the skin.

Description

NON-INVASIVE ELECTRONIC THERMOMETER

The present invention relates to a body temperature measurement device of the non-invasive electronic thermometer type using a temperature sensor in direct contact with an area of the human body whose temperature is to be known. The invention also relates to a method for measuring the internal temperature of the human body.

The devices most often used to measure the internal temperature are alcohol or mercury glass thermometers, thermometers which however have the disadvantage of requiring a fairly long time for stabilization of the measurement and therefore for reading the temperature.

Another category of thermometers are ear thermometers, in particular with infrared sensor. In this case, the measurement is faster than with analog mercury or alcohol thermometers, but the value of the temperature measured largely depends on how the sensor is positioned opposite the eardrum.

A thermometer of this type is described in document US Pat. No. 3,581,570. The thermometer comprises a sensor for measuring infrared radiation at a distance, the sensor being placed in the center of a parabolic mirror and mounted in a flexible support to adapt to the fixation in the ear canal of the person whose temperature is to be measured. The sensor remotely measures the infrared radiation emitted by the eardrum and its flexible support allows better adaptation to the ear canal. However, the remote temperature measurement is often influenced not only by the positioning of the sensor relative to the eardrum, but also by the shape of the ear canal, by the hair system of the latter or by the presence of earwax. Furthermore, the measurement of the temperature in the ear canal can be troublesome for sensitive subjects or for small children. Another type of thermometer uses sensors comprising a resistive element brought directly into contact with the skin. Such thermometers can be formed by hypodermic needles or by probes intended to be inserted into a cavity of the human body.

Thus, document US Pat. No. 4,487,208 describes an electronic thermometer comprising a rectal, buccal or axillary probe, a tubular probe of which one end comprises the electrical connections and means for fixing to the housing, while the opposite end ends in a metal plate arranged transversely to the longitudinal axis of the probe and supporting the sensor. The sensor is a thermistor fixed inside the probe on the metal plate intended to come into direct contact with the tissues of the human body. One of the main drawbacks of devices of this type is that they are invasive instruments, difficult for patients to bear and capable of causing injury.

Document US Pat. No. 5,725,308 describes an electronic thermometer comprising a sensor with a resistive element intended to measure the internal temperature of the human body based on a measurement of the surface temperature of the latter. The sensor is mounted at the protruding dome end of the insulating support of the probe, so that the sensor is the first to come into contact with the surface of the human body when the probe is placed on the latter. . The temperature is quickly determined by an electronic circuit which detects the rate of change of the resistance of the sensor and calculates, on this basis, the internal temperature of the human body. The disadvantage of this device is that the measurements made on the surface of the skin can be distorted by surface variations in the temperature of the human body. Therefore, it is necessary to carry out several temperature measurements and to use a device for correcting the measured values before displaying the actual value. Such a device therefore proves to be complex and expensive.

Indeed, the surface temperature of the skin is very different from that of the inner layers of the human body. The temperature of the periphery of the organism easily varies according to the external temperature conditions, the skin acting as an insulator between the internal layers of the organism and the exterior. This makes it possible to keep an internal temperature, or temperature of the central organs, at the level which is suitable for each organism, depending in particular on its state of health.

Thus, to determine the state of health of a person, it is necessary to measure the temperature of its internal organs. To carry out such a measurement, it is necessary to cancel the temperature gradient which exists between the internal layers and the external medium. The solutions proposed consist in particular in using sensors to estimate this gradient and then in locally heating the area to be measured so as to generate a heat flow opposite to that of the human body and thus cancel the temperature gradient existing between the internal layers of the latter. and the outside. Such solutions, described in the publication "Bioelectric and surface thermal medical sensors" by A. Dittmar, G. Delhomme, proceedings of the AUEF / COMETT-GBM Seminar, Lyon June 26-28, 1990, use complex, difficult devices to be implemented, the time required to carry out a measurement being very long.

The object of the present invention is to remedy the aforementioned drawbacks by proposing a sensor for an electronic thermometer which is capable of quickly, simply and precisely measuring the central temperature or the internal layers of the human body.

Another object of the invention is an electronic thermometer which is reliable in operation, without being influenced by variations in the outside temperature or by the peripheral blood circulation of the area whose temperature is to be measured.

Another object of the invention is an electronic thermometer which is easy to use, practical, harmless, painless, while remaining easy to manufacture, in large numbers and at reduced cost. These goals are achieved with a non-invasive electronic thermometer for measuring body temperature comprising a housing at the end of which is arranged a temperature sensor mounted on an insulating support, housing containing electronic processing means communicating with said sensor to transform the signals. received from the sensor into values of the temperature of the human body and display them, because the support comprises at least one peripheral cavity which sealingly surrounds the sensor when the latter is brought into contact with the skin.

A non-invasive thermometer is intended for use by contact with the skin of the human body. However, it is known that the temperature of the periphery of the organism varies easily, for example between 20 and 40 ° C, for a healthy subject, whose internal temperature remains around 37 ° C. The temperature of the skin's surface is practically that of the surrounding environment. However, by isolating part of this surface from this medium, it will reach the temperature of the internal layers. Therefore, by effectively isolating the peripheral area of the body where we want to perform the measurement, we manage to cancel the temperature difference between the inside and the outside of the latter.

According to the invention, the sensor is placed in the center of a thermally insulating support, for example a support having a cavity surrounding the sensor. The peripheral cavity can have various shapes, it can be, for example, in the form of a bell, the sensor being placed on an insulating support in the form of rod, cylinder or cone in the center of the latter, or it can also have an annular shape, surrounding the support of the sensor. The peripheral cavity sealingly surrounds the sensor when the latter is applied to the skin, delimiting and separating the measurement zone from the external medium. By waterproof, it is understood above all that the trapped air no longer circulates, that it is confined around the sensor. As such, one could imagine, for example, that the peripheral cavity includes a small orifice allowing the air initially escaping in the peripheral cavity to escape, in order to allow the sensor to be better placed in contact with the skin. Through Consequently, the non-renewed air trapped between the skin and the cavity of the sensor support acts as a very good insulator of the measurement area, the temperature of which is now close to that of the internal layers of the organism.

Then, by carrying out at least two measurements of the temperature of the sensor, heated by direct conduction while being in contact with the skin, in a determined time interval, one can estimate the exact internal temperature of the body by knowing the law of evolution of the temperature of the sensor without waiting for a stabilization of the temperature of the sensor, which makes it possible to obtain a very rapid measurement of the temperature of a human body.

Advantageously, said annular cavity is bordered by a flexible external peripheral lip projecting relative to the sensor.

Thus, the flexible peripheral lip is the first to bear on the skin when the measurement is taken, thus ensuring, by its deformation, a good adaptation around the measurement point, while enclosing inside, around the sensor, an air pocket acting as insulation. This lip can deform axially and / or radially, which avoids thermal leakage in these directions and allows the sensor, advantageously located in the center of the lip, to be well arranged in the plane of the skin and therefore to have a good contact, over its entire surface, with the measurement area.

Preferably, the walls of said peripheral cavity reflect electromagnetic radiation on at least part of their surface.

Thus, the infrared radiation coming from the skin will be returned by the walls of the peripheral cavity towards the skin, which cancels the radiative heat losses towards the support.

In an advantageous variant embodiment of the invention, the support comprises a first lateral annular cavity. Such a cavity limits the lateral extent of the support by a peripheral air cushion which makes it possible to have a consistent, solid support, ensuring good retention of the sensor, while effectively isolating it from the outside environment. In addition, one can imagine a configuration with rounded edges of the internal surface of such a cavity to facilitate cleaning after use.

Advantageously, the support comprises a second cavity located behind the sensor relative to the skin.

The sensor must be of very low thermal inertia and it must be insulated in order to avoid the transmission of heat to its support and, therefore, so that it is heated more quickly by the body whose temperature is measured. The presence of a cavity behind the sensor makes it possible to avoid heat losses by conduction and therefore to isolate the sensor from its support, in particular at the center of the sensor where the measurement must be rigorous. Said cavity can be empty or filled with an organic foam, for example polyurethane foam.

Preferably, the sensor is fixed by its periphery in a shoulder formed in said support.

Thus, the sensor can be held at its periphery, in particular by gluing in the shoulder made in the support. The central zone which is therefore the measurement zone does not come into contact with the support and its thermal mass is therefore not affected by that of the support.

Advantageously, the walls of the second cavity reflect the electromagnetic radiation on at least part of their surface.

Thus, any thermal radiation from the skin or the sensor is returned to the latter, which increases the measurement accuracy and the response speed of the sensor.

Preferably, the sensor for a thermometer according to the invention comprises a thermal sensor mounted on or facing the internal face of a base made of a material of predetermined thickness and thermal conductivity.

The sensor is therefore mounted on or facing the internal face of said base, while the external face of the base makes contact with the area of the human body where the measurement is made. Such a base has a predetermined thickness, depending on the nature of its material, so as to constitute a sufficiently rigid support for the sensor in contact with the skin.

According to a first approximation, the material of said base is considered to be a thermally transparent material, so that for the estimation of the law of evolution of the measured temperature, essentially the law of conductivity of the epidermal layers is taken into account. .

According to a more detailed evaluation, said base is made of an electrical insulating material which transmits thermal radiation through its thickness according to a predetermined conductivity law. Thus, by knowing the thickness of the base and the coefficients of thermal conductivity of the material used, one can determine the law of conductivity between the external face of contact with the skin and the internal insulated face against or opposite which is applied the sensor. In this case, to estimate the evolution of the temperature of the sensor, it is also necessary to take into account the conductivity within the skin and within the sensor holding plate coming into contact with the skin.

Preferably, said base is a plate made of a ceramic material, a polyimide or an epoxy resin. Such a material provides good electrical insulation for a small thickness of the wafer.

Advantageously, said base is constituted by a substantially flat plate or by a left plate corresponding to the human part to which it is applied.

Thus, the entire surface of the sensor is applied to the skin, which makes it possible to have better contact with the body whose temperature is to be measured and therefore to increase the accuracy of the measurement.

In a first embodiment of the invention, said thermal sensor consists of at least one resistive element mounted on a ceramic base.

A ceramic base provides good electrical insulation of the resistive element for a relatively low mass of said base. Thus, such a base having a large exchange surface and a low mass guarantees a rapid rise in temperature. A ceramic base can therefore be dimensioned for small thicknesses and it therefore provides a good compromise between good electrical insulation and good thermal transfer from the skin surface to the sensor. The measurement can be made with a single resistive element for which the law of variation of its resistance with temperature is known or with several resistive elements in a Wheatstone bridge measurement.

In a preferred embodiment of the invention, the resistive element is a thermistor in thick film technology or in metallization technology deposited on an insulating base.

Such a thermistor, produced in thick film technology in particular by screen printing, or by metallic deposition or by etching, has good properties of response to variations in temperature and reliability, while being of small dimensions.

In a second embodiment of the invention, said sensor is constituted by an infrared sensor oriented towards the internal face of said wafer.

Such a sensor is capable of remotely measuring the thermal radiation emitted by the internal face of said base or plate and determining, by suitable processing electronics, the body temperature. We could certainly consider the use of other sensors sensitive to thermal radiation emitted by the human body, such as a photodiode, a photomultiplier, etc. In a third embodiment of the invention, said sensor consists of an antenna belonging to a radiometer, antenna attached to one of the faces of said wafer. Such an antenna is capable of reading electromagnetic waves in the frequency band 2 - 4 GHz, the power received being directly proportional to the temperature of the external face of the wafer against which the antenna is attached.

Advantageously, the electrical connections of the resistive element, of the infrared sensor or of the radiometer are provided by a flexible circuit on an insulating support.

Such a flexible circuit ensures good connection of the sensor to the processing and display electronics, while limiting thermal losses via the connectors, the latter having a small thickness.

Usefully, a thermometer according to the invention is designed to measure the internal temperature of the human body at a depth equal to about half the generator diameter of the sensor.

By generator diameter of the sensor is understood the diameter of the measuring head containing the sensor. Thus, it has been established that the value of the depth where one can measure the internal temperature is directly proportional to the generator diameter of the sensor, because the larger this diameter, the better the thermal insulation and this allows to see more deeply internal temperature. In the context of a sensor according to the invention, the ratio between the generator diameter of the sensor and the measurement depth is approximately 2: 1.

As demonstrated by previous medical studies, the effective and useful temperature of the human body is that of its internal organs, in particular that of the brain. More precisely, the temperature is regulated by the hypothalamus, an organ which ensures the maintenance of thermal balance in the body by ordering the dilation or constriction of the peripheral vessels. It is therefore important to directly follow the changes in brain temperature to get accurate information about an organism's health. Thus, the ideal sensor should be placed on the skull and also, it should be able to read the temperature of the brain.

The sensor according to the invention would therefore be able to measure the temperature of the brain, provided that its generator diameter is greater than twice the thickness of the skull.

According to an advantageous embodiment of the invention, the thermometer comprises means for heating the sensor.

This allows the sensor to preheat to a temperature close to, slightly lower than that of the human body in order to improve the response speed of the sensor.

The invention also relates to a method of measuring the temperature with a thermometer according to the invention, which method consists in:

- place the sensor support with the peripheral lip in contact with the area of the human body where the temperature is to be measured;

- press the sensor support on said area until the sensor comes into intimate contact with the skin and the device detects and signals this contact;

- make a first temperature measurement; - perform at least a second measurement at a predetermined time interval;

- determine by a numerical method, according to previously measured values, the effective temperature of the human body and display it.

The invention will be better understood from the study of the embodiments taken without any limitation being implied and illustrated in the appended figures in which:

- Figure 1 is a side view of an electronic thermometer comprising a sensor according to the invention; - Figure 2 is a schematic view of a sensor according to a first embodiment of the invention;

- Figure 3 shows in axial section the part of the device supporting the sensor according to the invention; - Figure 4 is a view similar to that of Figure 3 showing the sensor in contact with the skin;

- Figures 5a and 5b illustrate axial views of the part of the device supporting the sensor during its use.

- Figures 6 and 7 illustrate alternative embodiments of the sensor support of the invention;

- Figure 8 illustrates the operating principle of the sensor according to a third embodiment of the invention.

FIG. 1 illustrates an electronic thermometer 1 using a sensor according to the invention, a thermometer comprising a housing 2 intended to be held in the hand and one of the ends of which comprises a measuring head 3 which is applied to an area of skin so take a temperature measurement. The box 2 contains: an electronic processing card 5, a display device 8, as well as supply batteries 7.

The measuring head 3 shown in particular in FIG. 3 comprises a tubular support 30 or sensor holding body 10, support encircled by a peripheral lip 32.

The sensor 10 is fixed to the support 30 in a shoulder 27 formed in the protruding central part 29 of the latter. A central cavity 36 with rounded edges is formed behind the sensor 10 facing the skin. The central part 29 of the support 30 defines with its peripheral part 31 an annular cavity 34 with rounded edges extending around the sensor. The depth of this cavity must be sufficient to ensure the presence of air inside the head 3, without it being blocked by the patient's skin.

The support 30 is rigid in order to allow good retention of the sensor as well as a good positioning of the latter in contact with the skin. The central part 29 is prominent relative to the peripheral part 31 so that the part supporting the sensor is the first to come into contact with the skin during the temperature measurement.

The support 30 or retaining body of the sensor 10 is made of a rigid, thermally and electrically insulating material, for example a plastic material of the ABS type, by a plastic injection technique. The lower part of the support 30 facing the skin, mainly comprising the central 36 and annular 34 cavities, is metallized in particular with gold, silver, aluminum, nickel or any other reflecting metal, for a very precise finish, of the polishing type. mirror. Thus, any infrared radiation coming from the skin will be returned by the internal surface of the cavities towards the sensor and towards the skin. Advantageously, the cavities 34, 36 have rounded, even parabolic, shapes and dimensions calculated so that the infrared radiation is reflected only once before being returned to the skin. The support 30 comprises in its upper part, opposite that in contact with the skin, a cover 33 covered inside a coating reflecting infrared radiation.

The central cavity 36 mainly insulates the sensor 10. Its dimensions are calculated so as to define an enclosed space where the transmission of heat through the sensor both by conduction and by convection is minimized. Thus, the depth of the cavity 36 should be between 0.5 and 8 mm and, preferably, between 1 and 4 mm.

The peripheral lip 32 surrounding the rigid support 30 is made of a flexible and insulating material of the rubber or silicone type and it is prominent relative to the central part 29 of the support 30. Thus, at the time of application of the measuring head 3 on the skin, the flexible lip 32 is the first to bear against the skin, ensuring good adaptation of the head around the measurement point and enclosing an air pocket inside which isolates the measurement area and the external environment sensor. The flexible lip or flange 32 is inserted by deformation around the support 30 and it can be easily changed, in particular for hygienic reasons.

In the variant embodiments of the invention shown in FIGS. 6 and 7, the insulating support 30 can have a hemispherical or bell-shaped shape, comprising a central part 29 ′, respectively 29 ″ for supporting the sensor. The central part 29 ′ of the insulating support 30 of FIG. 6 has the shape of a hollow rod comprising a lower part supporting the resistive element 10. FIG. 7 illustrates another variant in which the central part 29 "of the support 30 is produced in the form of a block of cylindrical, conical, frustoconical, or equivalent shape which can be inscribed inside the cavity 34, in an insulating material produced on the basis of a ceramic mesh. Such a structure provides good mechanical resistance and excellent thermal insulation properties to the 29 "sensor support.

In a first embodiment of the invention, the temperature sensor 10 consists of one or more screen-printed thermistors 22 on the internal face 23 of an insulating base or plate 24. To detect the variation in temperature, it is possible to use, for example, a bridge installation of thermistors. The sensor is supported on the support 30 and it is connected, by the connections 26 passing through the support 30, to the power supply 7, to a processing electronics 5, and to the display device 8. The connections of the thermistor (s) 22 are provided by a flexible printed circuit on an insulating support. Such a circuit comprises tracks of small thickness and it makes it possible to limit the heat losses via the connections.

An example of such a sensor 10 is presented in FIG. 2 where the screen-printed track 22 is deposited on the internal face 23 of a flat ceramic insulating base 24 with a thickness comprised, for example, between 150 to 250 μm. The thermistor connections are ensured by a circuit comprising conductive tracks 16,18. These tracks 16, 18 may for example be made of copper or a thin nickel-gold alloy, in particular of the order of ten μm, deposited on a flexible insulating support 12. Such an insulating support may advantageously be a polyimide Kapton ^® type which ensures a good electrical insulation for a very small thickness. An insulating layer 14 protects the tracks except the places intended to be connected.

The sensor 10 is fixed in the shoulder 27 of the support 30, for example by gluing, by applying a layer of adhesive 28 between the peripheral surface of the sensor 10 and the front surface of the support 27.

The flexible collar 32 being removed, the lower part of the head 3 can be easily cleaned, in particular by washing, for hygienic reasons in the case of the use of the same device for carrying out a temperature measurement on another person.

The dimensions of the measuring head 3 determine the performance of the device. Thus, it has been established during the various experiments, that the diameter of the measuring head 3, or for non-circular shapes of the measuring head, the diameter of the circle circumscribed at the peripheral lip of the latter, is directly proportional to the depth of measurement of the internal temperature. Thus, a measuring head 3 having a diameter Φ greater than 30 mm is capable of reading the cerebral temperature by a simple frontal measurement, therefore through the entire thickness of the cranial box.

The device is therefore able to display the exact measurement of the internal temperature of the human body by simple measurements made on the surface of the skin. These measurements can be taken on the forehead, temple, limbs or any other part of the human body using an adequate diameter of the measuring head.

In operation, the measuring head 3 is directed towards the skin of the person whose temperature is to be measured in the direction of the arrow shown in FIG. 5a, by pressing it on the skin area until the sensor 10, in particular the external face 25 of the wafer 24, makes contact with the latter. As visible in FIG. 5b, the flexible lip 32 deforms towards outside, in the direction shown by the arrows, which allows the sensor 10 to come into contact with the skin over its entire surface. The device can advantageously be provided with a contact detector which signals the correct positioning of the head 3 on the skin.

When contact with the skin is detected, or after a few seconds depending on the value of the thickness of the ceramic base 24 of the thermistor, the device is ready to carry out a first measurement of the temperature, the area of skin being isolated from the external environment by the flexible lip 32. The user can be warned by an audible or light signal emitted by the device.

The air trapped inside the head 3, in particular around the sensor 10, greatly restricts the heat exchange with the outside. As for the thermal radiation, it is returned to the skin by the annular cavity 34 and to the sensor by the central cavity 36. This is represented in FIG. 4 where the arrows I indicate the direction of the radiation emitted by the skin P and the arrows They indicate the radiation returned by the cavities 34,36. Consequently, the temperature gradient between the interior of the organism and the surrounding environment decreases rapidly and the sensor in direct contact with the skin can quickly read the temperature in depth.

At this time, the sensor 10 can measure a first value of the temperature which is transmitted to the processing electronics 5. A second measurement is carried out after a predetermined period of time and it is also sent to the processing electronics which calculates , the final temperature of the organism. By knowing the law of variation of the temperature in the sensor 10 when the latter is brought into contact with the body whose temperature is to be measured, the exact temperature of the latter can be estimated by a numerical method of analysis of the curve d heating of the sensor, without waiting for the temperature to stabilize.

Thus, the exact temperature of the human body can be estimated quickly, by knowing at least two temperature values and a time interval. Preferably, three or even ten temperature measurements are made in order to increase the accuracy of the measurement. Several measurements can, however, be carried out to more precisely determine the final temperature.

Many alternative embodiments of the sensor according to the invention can be imagined without departing from the scope of its claims.

Thus, in place of the thermistor or thermistors 22, CTP or CTN, it is possible to use one or more thermistors obtained by metal deposition or etching or any other type of sensor for which the law of variation of the temperature over time is known. The shapes, dimensions and materials of the support 30 of the sensor 10 and of the measuring head 3 can vary in order to adapt them to the specifics of the morphology of the area of the human body where the measurement is carried out, or according to the sensitivity of the person using it, etc.

According to another embodiment of the invention, the sensor may include a heating circuit produced, for example, in the form of a screen-printed electrical circuit deposited on the same ceramic base 24 of the resistive element 22, behind the latter. Such a low-power heating element makes it possible to preheat the measurement zone to a temperature close to that of the human body, for example from 32 to 35 ° C. Thus, the external face 25 of the ceramic base 24 of the resistive element 22, placed in contact with the skin, reaches the target temperature more quickly, which ensures an improved reading speed of the sensor.

According to a second embodiment of the invention, the sensor may comprise a base or ceramic plate preferably covered with a layer of copper on its internal face, and, arranged at a distance from this plate, an infrared sensor which reads the radiation emitted by the internal face of the wafer, its external face being in contact with the area of the body whose temperature is measured. According to a third embodiment, the sensor consists of an electrically insulating plate on which is attached a planar antenna of a radiometer. Such a radiometer can be, for example, that described in the document FR 2 673 470. FIG. 8 illustrates the operating principle of such a radiometer where the radiation III emitted by the skin is picked up by an antenna 38 attached to the one of the faces of the plate 24. The antenna 38 directs the signals received to the connections IV and from here to signal processing means which make it possible to determine the internal temperature of the area of the human body considered.

Claims

1. Non-invasive electronic thermometer (1) for measuring body temperature comprising a housing at the end of which is arranged a temperature sensor (10) mounted on an insulating support (30), housing containing electronic processing means communicating with said sensor for transforming the signals received from the sensor into values of the temperature of the human body and displaying them, characterized in that the support (30) comprises at least one peripheral cavity (34) which sealingly surrounds the sensor (10) when the latter is brought into contact with the skin.

2. Thermometer according to claim 1, characterized in that the cavity (34) is bordered by a flexible external peripheral lip (32) projecting relative to the sensor (10).

3. Thermometer according to one of claims 1 or 2, characterized in that the walls of the peripheral cavity (34) reflect the electromagnetic radiation on at least part of their surface.

4. Thermometer according to claim 1, characterized in that the support (30) comprises a first lateral annular cavity (34).

5. Thermometer according to claim 4, characterized in that the support (30) comprises a second cavity (36) located behind the sensor (10) relative to the skin.

6. Sensor (10) according to one of claims 4 or 5, characterized in that it is fixed by its periphery in a shoulder (27) formed in said support (30).

7. Thermometer according to claim 5, characterized in that the walls of the second cavity (36) reflect the electromagnetic radiation on at minus part of their surface.

8. Sensor (10) for a thermometer according to claim 1, characterized in that it comprises a thermal sensor mounted on or facing the internal face of a base made of a material of predetermined thickness and thermal conductivity.

9. Sensor according to claim 8, characterized in that said base is a plate made of a ceramic material, a polyimide or an epoxy resin.

10. Sensor (10) according to one of claims 8 or 9, characterized in that said base is constituted by a substantially flat plate or by a left plate corresponding to the human part on which it is applied.

11. Sensor (10) for a thermometer according to one of claims 8 to 10, characterized in that said thermal sensor consists of at least one resistive element (22) mounted on a ceramic base (24).

12. Sensor (10) according to claim 11, characterized in that the resistive element (22) is a thermistor in thick film technology or in metallization technology deposited on an insulating base (24).

13. Sensor (10) according to one of claims 9 to 10, characterized in that said sensor is constituted by an infrared sensor oriented towards the internal face of said wafer.

14. Sensor (10) according to one of claims 9 to 10, characterized in that said sensor is constituted by an antenna belonging to a radiometer and attached to one of the faces of said wafer.

15. Sensor according to one of claims 11, 13 or 14, characterized in that the electrical connections of the resistive element (22), of the infrared sensor or radiometer are provided by a flexible circuit (14,16,18) on an insulating support (12).

16. Thermometer according to claim 1, characterized in that it is designed to measure the internal temperature of the human body at a depth equal to about half the generator diameter of the sensor.

17. Thermometer according to one of the preceding claims, characterized in that it comprises means for heating the sensor (10).

18. Method for measuring the temperature with a thermometer according to one of the preceding claims, characterized in that it consists in:

- Place the support (30) of the sensor (10) with the peripheral lip (32) in contact with the area of the human body where one wants to measure the temperature; - press the support (30) of the sensor (10) on said area until the sensor (10) comes into intimate contact with the skin (P) and the device detects and signals this contact;

- make a first temperature measurement;

- perform at least a second measurement at a predetermined time interval;