IL155352A

IL155352A - Non-invasive electronic thermometer

Info

Publication number: IL155352A
Application number: IL155352A
Authority: IL
Original assignee: Seb Sa
Priority date: 2000-10-13
Filing date: 2003-04-10
Publication date: 2007-06-17
Also published as: IL155352A0; FR2815407B1; WO2002031457A1; FR2815407A1; AU2001295686A1; EP1325292A1

Description

NON-INVASIVE ELECTRONIC THERMOMETER A NON-INVASIVE ELECTRONIC THERMOMETER The present invention relates to an appliance for measuring body temperature, the appliance being of the non-invasive electronic thermometer type using a temperature sensor in direct contact with a zone of the human body whose temperature is to be determined. The invention also provides a method of measuring the internal temperature of the human body.

The devices most commonly used for measuring internal temperature are glass thermometers containing alcohol or mercury, which thermometers nevertheless present the drawback of requiring quite a long time for the measurement to stabilize and thus for it to be possible to read temperature.

Another category of thermometers are ear thermometers, in particular having an infrared sensor. Under such circumstances, measurement takes place more quickly than with analog thermometers based on mercury or alcohol, but the measured temperature value depends to a large extent on how the sensor is positioned facing the eardrum.

A thermometer of that type is described in document US 3 581 570. The thermometer comprises a sensor for remotely measuring infrared radiation, the sensor being placed at the center of a parabolic mirror and being mounted in a flexible support so as to adapt to being fixed in the auditory canal of the person whose temperature is to be measured. The sensor for remotely measuring the infrared radiation emitted by the eardrum and its flexible support provides better adaptation to the auditory canal. Nevertheless, remote measurement of temperature is often influenced not only by the positioning of the sensor relative to the eardrum, but also by the shape of the auditory canal, by the hairs therein, or by the presence of ear wax. In addition, measuring temperature in the auditory canal can be difficult with subjects who are sensitive, or with small children .

Another type of thermometer uses sensors comprising a resistive element that is put directly into contact with the skin. Such thermometers can be constituted by hypodermic needles or by probes for insertion into a cavity of the human body.

Thus, document US 4 487 208 describes an electronic thermometer having a rectal, mouth, or axillary probe, in the form of a tube having one end with electrical connections and means for fixing to a case, while its opposite end is terminated by a metal plate extending across the longitudinal axis of the probe and supporting the sensor. The sensor is a thermistor fixed inside the probe on the metal plate that is to come directly into contact with human body tissue. One of the main drawbacks of appliances of that type is that they are invasive instruments, that patients find difficult to accept, and they can lead to injury.

Document US 5 725 308 describes an electronic thermometer comprising a resistive element sensor for measuring the internal temperature of the human body based on measuring a surface temperature thereof. The sensor is mounted at the dome-shaped projecting end of the insulating support of the probe in such a manner that the sensor is the first part to come into contact with the surface of the human body when the probe is placed thereon. Temperature is determined quickly by an electronic circuit which detects the rate at which the resistance of the sensor varies, and on the basis of said rate it calculates the internal temperature of the human body. The drawback of that apparatus lies in that measurements performed at the surface of the skin can be falsified by variations in temperature on the surface of the human body. As a result, it is necessary to take several temperature measurements and to use a device for correcting the values as measured prior to displaying the real value. Such an appliance therefore turns out to be complex and expensive.

The surface temperature of the skin is very different from the temperature of the internal layers of the human body. The temperature at the periphery of the organism varies easily as a function of external temperature conditions, with the skin acting as an insulator between the internal layers of the organisms and the outside. This makes it possible to maintain an internal temperature or a central organ temperature at the level which is appropriate for each organism, in particular as a function of its state of health.

Thus, in order to determine the state of health of a person, it is necessary to measure the temperature of that person's internal organs. To perform such a measurement, it is necessary to eliminate the temperature gradient which exists between the internal layers and the outside medium. The solutions that have been proposed consist in particular in using sensors to estimate this gradient and then to heat the measurement zone locally so as to generate a flow of heat opposing that from the human body, thereby eliminating the temperature gradient which exists between the inner layers of the body and the outside. Such solutions are described in the publication entitled "Capteurs medicaux bioelectriques et thermiques de surface" [Bioelectrical and thermal medical surface sensors] by A. Dittmar and G. Delhomme, in the proceedings of the AUEF/COMETT-GBM Conference, Lyon, June 26-28, 1990, make use of appliances that are complex, difficult to use, and the time needed to make a measurement is very long.

The object of the present invention is to remedy the above-mentioned drawbacks by proposing a sensor for an electronic thermometer which is capable of measuring the central temperature or the temperature of the internal layers of the human body in a manner which is fast, simple, and accurate.

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

Another object of the invention is to provide an electronic thermometer which is easy, practical, inoffensive, and painless to use while remaining easy to manufacture in large numbers and at low cost.

These objects are achieved with a non-invasive electronic thermometer for measuring body temperature, the thermometer comprising a case having arranged at its end a temperature sensor mounted on a insulating support, the case containing electronic processing means communicating with said sensor to transform the signals received from the sensor into values for the temperature of the human body and for displaying them, because the support includes at least one cavity surrounding the sensor in leaktight manner when the sensor is brought into contact with the skin.

A non-invasive thermometer is for use by making contact with the skin of the human body. Unfortunately, it is known that the temperature at the periphery of the organism varies readily, e.g. over the range 20°C to 40°C for a subject in good health whose internal temperature remains around 37 °C. The temperature at the surface of the skin is practically the same as the temperature of the ambient medium. Nevertheless, by insulating a portion of said surface from said medium, it will reach the same temperature as the internal layers.

Consequently, by efficiently insulating the peripheral zone of the organism whose temperature is to be measured, it is possible to eliminate the temperature difference which exists between the inside and the outside of the organism.

In the invention, the sensor is placed at the center of a thermally insulating support, e.g. a support presenting a cavity that surrounds the sensor. The peripheral cavity may be of various shapes, for example it may be in the form of a bell, the sensor being placed on an insulating support in the form of a rod, a cylinder,, or a cone at the center of the bell, or equally it may be annular in shape, surrounding the sensor support. The peripheral cavity surrounds the sensor in leaktight manner at the moment the sensor is applied to the skin, thereby defining and separating the measurement zone from the outside medium. By "leaktight", it should be understood that the air is held captive and no longer flows, being confined around the sensor. In this respect, it can be accepted, for example, that the peripheral cavity has a small orifice allowing the air which was initially in the peripheral cavity to escape to the outside so as to enable the sensor to be placed in better contact with the skin. Consequently, the non-renewed air that is held captive between the skin and the cavity of the sensor support acts as a very good insulator for the measuring zone whose temperature becomes close to that of the internal layers of the organism.

Thereafter, by taking at least two measurements of the temperature of the sensor as heated by direct conduction while in contact with the skin, and at a determined time interval, it is possible to estimate the exact internal temperature of the body, given knowledge of the relationship whereby the temperature of the sensor varies and without it being necessary to wait for the temperature of the sensor to stabilize, thus making it possible to obtain a temperature measurement of a human body very quickly.

Advantageously, the cavity is surrounded by a flexible outer peripheral lip projecting relative to the sensor .

Thus, the flexible peripheral lip is the first part to press against the skin when a measurement is being taken, and by deforming it provides a close fit around the measurement point, while simultaneously enclosing a pocket of air acting as an insulator around the sensor. This lip can deform axially and/or radially, thus avoiding heat losses in those directions and making it possible for the sensor, which is advantageously situated in the center of the lip, to be well located in the plane of the skin and thus to make good contact with the skin over the entire area of the measuring zone.

Preferably, the walls of the peripheral cavity reflect electromagnetic radiation over at least a fraction of their area.

Thus, the infrared radiation coming from the skin is reflected by the walls of the peripheral cavity back towards the skin, thereby eliminating radiant heat losses to the support.

In another advantageous variant embodiment of the invention, the support includes a first lateral annular cavity.

Such a cavity restricts the lateral extent of the support by means of a peripheral cushion of air which makes it possible to have a strong solid support providing good retention of the sensor while also insulating it effectively from the outside medium. In addition, a configuration can be devised in which the inside surface of such a cavity has rounded edges so as to make it easier to clean after it has been used.

Advantageously, the support includes a second cavity situated behind the sensor relative to the skin.

The sensor should have very low thermal inertia and it should be insulated in order to avoid transmitting heat to its support, thus ensuring that it is heated more quickly by the body whose temperature is to be measured. The presence of a cavity behind the sensor makes it possible to avoid heat being lost by conduction, and thus to insulate the sensor from its support, particularly in the center of the sensor where measurement needs to be the most accurate. Said cavity may be evacuated or filled with an organic foam, e.g. a polyurethane foam.

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

The sensor may thus be held at its periphery, in particular by adhesive on the shoulder formed in the support. The central zone, which is the measuring zone, thus does not come into contact with the support and its thermal inertia is thus unaffected by that of the support .

Advantageously, the walls of the second cavity reflect electromagnetic radiation over at least a fraction of their area.

Thus, any heat radiation coming from the skin or from the sensor is reflected on the sensor, thus increasing measurement accuracy and the speed of response of the sensor.

Preferably, the sensor comprises a temperature pickup mounted on or facing the inside face of a base made of a material of predetermined thickness and thermal conductivity .

The sensor is thus mounted on or facing the inside face of said base, whereas the outside face of the base comes into contact against the zone of the human body where the measurement is made. Such a base is of predetermined thickness, as a function of the nature of the material from which it is made, so as to constitute a support that is sufficiently rigid for the sensor in contact with the skin.

To a first approximation, the material of said base is considered as being a material that is thermally transparent, such that in order to estimate the relationship whereby measured temperature varies, essentially only the relationship for conductivity of layers of the skin is taken into account.

For finer evaluation, said base is made of an electrically insulating material which transmits heat radiation through its thickness with a predetermined conductivity relationship. Thus, knowing the thickness of the base and the thermal conductivity coefficients of the material used, it is possible to determine the conductivity relationship between the outside face in contact with the skin and the insulated inside face against or facing which the pickup is applied. In this case, in order to estimate temperature variation of the sensor, account needs also to be taken of conductivity within the skin and within the plate holding the pickup coming into contact with the skin.

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

Advantageously, said space is constituted by a substantially plane plate or by a curved plate corresponding to the portion of the human body against which it is applied.

Thus, the entire area of the sensor is applied against the skin, thus making it possible to have better contact with the body whose temperature is to be measured, and thus enabling the accuracy of the measurement to be increased.

In a first embodiment of the invention, said temperature pickup is constituted by at least one resistive element mounted on a ceramic base.

A ceramic base provides good electrical insulation of the resistive element for a base having relatively small mass. Thus, such a base having a large exchange area and small mass guarantees that temperature rises quickly. A ceramic base can thus be dimensioned for small thicknesses and it then provides a good compromise between good electrical insulation and good heat transfer from the surface of the skin to the sensor. Measurement can be performed using a single resistive element whose relationship for variation in resistance with temperature is known, or with a plurality of resistive elements for performing measurements using a Wheatstone bridge.

In a preferred embodiment of the invention, the resistive element is a thermistor made using thick film technology or of technology comprising depositing metallization on an insulating base.

Such a thermistor made using thick film technology, in particular silkscreen printing, or using metal deposition, or by etching, presents good properties of responding to temperature variations and of reliability, while nevertheless being small in size.

In a second embodiment of the invention, said pickup is constituted by an infrared sensor facing towards the inside face of said plate.

Such a sensor is capable of remotely measuring the heat radiation emitted by the inside face of said base or plate and of determining body temperature by means of appropriate processing electronics. Other sensors responsive to the heat radiated by the human body such as a photodiode, a photomultiplier, etc. could also be used.

In a third embodiment of the invention, said pickup is constituted by an antenna forming part of a radiometer and fitted to one of the faces of said plate. Such an antenna is suitable for picking up electromagnetic waves in the 2 gigahertz (GHz) to 4 GHz frequency band, with the power picked up being directly proportional to the temperature of the outside face of the plate against which the antenna is applied.

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 provides a good connection between the sensor and the processing and display electronics, while also limiting heat losses via the connections, given that they are of small thickness.

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

The term "generating diameter" of the sensor is used to mean the diameter of the measuring head containing the sensor. Thus, it has been found that the depth at which internal temperature can be measured is directly proportional to the generating diameter of the sensor, since the greater said diameter, the better the thermal insulation, and thus the more deeply internal temperature can be seen. In the context of a sensor of the invention, the ratio of generating diameter of the sensor over measurement depth is about 2:1.

As shown by medical studies that have already been performed, the actual temperature of the human body which it is useful to know is the temperature of its internal organs, and in particular the temperature of the brain. More precisely, temperature is. regulated by the hypothalamus, a member which serves to maintain temperature equilibrium in the organism by causing peripheral blood vessels to dilate or to become constricted. It is thus important to follow the temperature variations of the brain directly in order to have exact information about the state of health of an organism. Thus, the ideal sensor should be placed on the skull, and likewise should be capable of reading the temperature of the brain.

The sensor of the invention can thus be suitable for measuring brain temperature, providing its generating diameter is greater than twice the thickness of the skull.

In an advantageous embodiment of the invention, the thermometer includes means for heating the sensor.

This makes it possible to preheat the sensor to a temperature that is close to and slightly less than the temperature of the human body so as to increase the response speed of the sensor.

The invention also provides a method of measuring temperature using a thermometer of the invention, which method consists in: - placing the support of the sensor with its peripheral lip in contact with the zone of the human body where temperature is to be measured; - pressing the support of the sensor against said zone until the sensor comes into intimate contact with the skin and the appliance detects and indicates this contact ; - taking a first temperature measurement; - taking at least one second temperature measurement after a predetermined time interval; and - determining the actual temperature of the human body by a digital method as a function of the previously-measured temperature values, and displaying the actual temperature .

The invention will be better understood on studying embodiments taken in non-limiting manner and shown in the accompanying figures, in which: - Figure 1 is a side view of an electronic thermometer including a sensor of the invention; - Figure 2 is a diagrammatic view of a sensor constituting a first embodiment of the invention; - Figure 3 is an axial section view of the portion of the appliance supporting the sensor of 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 are axial views of the portion of the appliance supporting the sensor while it is being used; - Figures 6 and 7 show variant embodiments of the support for the sensor of the invention; and - Figure 8 shows the operating principle of a sensor in a third embodiment of the invention.

Figure 1 shows an electronic thermometer 1 using a sensor 10 of the invention, the thermometer comprising a case 2 for holding in the hand and having one end including a measuring head 3 for application to a zone of the skin in order to measure its temperature. The case 2 contains: a processing electronics card 5, a display device 8, and power supply batteries 7.

The measuring head 3, as shown in particular in Figure 3, comprises a tubular support 30 -or holding body for the sensor 10, which support is surrounded by a peripheral lip 32.

The sensor 10 is fixed to the support 30 in a shoulder 27 formed in the projecting central portion 29 thereof. A central cavity 36 with rounded edges is formed behind the sensor 10 facing the skin. The central portion 29 of the support 30 co-operates with the peripheral portion 31 of the support to define an annular cavity 34 with rounded edges extending along the sensor 10. The depth of this annular cavity 34 must be sufficient to ensure that air is present inside the measuring head 3, without the cavity being closed off by the skin of the patient.

The support 30 is rigid to provide good retention of the sensor 10 and good positioning thereof in contact with the skin. The central portion 29 projects relative to the peripheral portion 31 so that the portion supporting the sensor 10 is the first portion to come into contact with the skin when measuring temperature.

The support 30 or holding body for the sensor 10 is made of a rigid material that is thermally and electrically insulating, for example a plastic material of the ABS type, by a plastic injection molding technique. The bottom portion of the support 30 facing the skin mainly comprising the central and annular cavities 36 and 34 is metal-plated, in particular with gold, silver, aluminum, nickel, or any other reflecting metal, so as to obtain a very precise finish of the mirror polish type. Thus, any infrared radiation coming G38563 from the skin is returned by the inside surfaces of the cavities towards the sensor 10 and towards the skin.

Advantageously, the cavities 34 and 36 present rounded shapes, possibly parabolic shapes, and they are of dimensions that are determined so that the infrared radiation is reflected once only before returning to the skin. In its top portion remote from its portion in contact with the skin, the support 30 has a lid 33 which is covered on the inside in a coating that reflects infrared radiation.

The central cavity 36 serves mainly to insulate the sensor 10. Its dimensions are determined in such a manner as to define a closed space in which the transmission of heat through the sensor 10 both by conduction and by convection is minimized. Thus, the depth of the cavity 36 should lie in the range 0.5 millimeters (mm) to 8 mm, and preferably in the range 1 mm to 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 projects relative to the central portion 29 of the support 30. Thus, when the measuring head 3 is applied to the skin, the flexible lip 32 is the first portion to bear against the skin, thereby ensuring that the head is properly fitted around the measurement point and enclosing an internal pocket of air which insulates the measuring zone and the sensor 10 from the outside medium. The flexible lip or collar 32 is inserted by being deformed around the support 30, and it is easily changed, in particular for reasons of hygiene.

In the variant embodiments of the invention shown in Figures 6 and 7, the insulating support 30 may be hemispherical or bell-shaped, having a respective central portion 29' or 29" supporting the sensor 10. The central portion 29' of the insulating support 30 shown in Figure 6 is in the form of a hollow rod having a bottom portion supporting the resistive element 10. Figure 7 G38567 shows another variant in which the central portion 29" of the support 30 is made in the form of a cylindrical, conical, frustoconical , or equivalent block capable of being contained inside the cavity 34 and made of an insulating material based on a ceramic lattice. Such a structure provides good mechanical strength and excellent thermal insulating properties for the sensor support 29".

In a first embodiment of the invention, the temperature sensor 10 is constituted by one or more thermal resistors such as thermistors 22 silkscreened-printed on the inside face 23 of an insulating plate or base 24. In order to detect temperature variation it is possible, for example, to use a bridge circuit for the thermistors 22. The- sensor 10 bears against the support 30 and has connections 26 passing through the support 30 connecting it to the power supply batteries 7, to the processing electronics card 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 has tracks of small thickness and serves to limit heat losses via the connections.

An example of such a sensor 10 is shown in Figure 2 where there can be seen the silkscreened track 22 ' deposited on the inside face 23 of a plane ceramic insulating base 24 of thickness lying in the range 150 micrometers ( m) to 250 μπι, by way of example. The connections of the thermistor 22 are provided by a circuit carrying conductor tracks 16 and 18. By way of example, these tracks 16 and 18 may be made of copper or of nickel gold alloy of small thickness, in particular being about 10 μιτι thick, and they are deposited on a flexible insulating support 12. Such an insulating support may advantageously be made of a polyimide of the Kapton® type which provides good electrical insulation for very small thickness. An insulating layer 14 protects the tracks except in those locations that are to be make connections.

G38547 The sensor 10 is fixed in the shoulder 27 of the support 30, e.g. by adhesive, a layer of adhesive 28 being applied between the peripheral surface of the sensor 10 and the front surface of the shoulder 27.

With the flexible collar 32 removed, the bottom portion of the measuring head 3 is easily cleaned, in particular by being washed, for reasons of hygiene when the same appliance is used for taking temperature measurements on another person.

The dimensions of the measuring head 3 determine the performance of the appliance. Thus, in various experiments, it has been established that the diameter of the measuring head 3, or for measuring heads of non-circular shape the diameter of the circle circumscribing the peripheral lip of the measuring head, is directly proportional to the depth at which internal temperature is measured. Thus, a measuring head 3 having a diameter 0 greater than 30 mm is capable of reading the temperature of the brain merely by measuring on the forehead, i.e. through the entire thickness of the skull.

The appliance is thus suitable for displaying an exact measurement of the internal temperature of the human body merely by taking measurements at the skin surface. These measurements may be taken on the forehead, on the temple, on the limbs, or on any other part of the human body by using a measuring head of appropriate diameter.

In operation, the measuring head 3 is directed towards the skin of the person whose temperature is to be measured by moving in the direction of the arrow shown in Figure 5a and pressing against the zone of the skin until the sensor 10, and in particular the outside face 25 of the plate 24, comes into contact with the skin. As shown in Figure 5b, the flexible lip 32 deforms outwards in the direction represented by the arrows, thus enabling the entire area of the sensor to come into contact with the skin. The appliance can advantageously be provided with a G38547 contact detector which indicates when the measuring head 3 is properly in place against the skin.

When contact with the skin is detected, or after a few seconds depending on the thickness of the ceramic base 24 of the thermistor 22, the appliance is ready to perform a first temperature measurement, the zone of the skin being insulated from the outside medium by the flexible lip 32. The user may be warned by an audible or visible signal emitted by the appliance.

The air held captive inside the measuring head 3, and in particular around the sensor 10, greatly restricts heat exchange with the outside. Thermal radiation is reflected back towards the skin by the annular cavity 34 and towards the sensor by the central cavity 36. This is shown in Figure 4 where the arrows I show the direction in which radiation is emitted by the skin P, and arrows II show the direction of the radiation as reflected by the cavities 34 and 36. Consequently, the temperature gradient that exists between the inside of the organism and the ambient medium decreases quickly and the sensor in direct contact with the skin can promptly read the in-depth temperature.

At this moment, the sensor 10 can measure a first temperature value which is transmitted to the processing electronics card 5. A second measurement is performed after a predetermined length of time has elapsed and it too is sent to the processing electronics card 5 which calculates the final temperature of the organism. Given knowledge of the relationship whereby temperature in the sensor 10 varies when the sensor is put into contact with the body whose temperature is to be measured, the exact temperature of the body can be estimated by a method of digitally analyzing the heating curve of the sensor, without it being necessary to wait for its temperature to stabilize .

Thus, the exact temperature of the human body can be estimated quickly, on the basis of at least two temperature values and one time interval. Preferably, G38547 three or even about ten temperature readings are taken in order to increase the accuracy of the measurement.

Nevertheless, it is still also possible to take a plurality of measurements in order to determine final temperature with greater accuracy.

Numerous variant embodiments of the sensor of the invention can be devised without going beyond the ambit of the claims.

Thus, instead of using positive temperature coefficient (PTC) or negative temperature coefficient (NTC) thermistors 22, it is possible to use one or more thermistors obtained by depositing metal or by etching or any other type of sensor for which the relationship of temperature variation as a function of time is known. The shapes, sizes, and materials of the support 30, of the sensor 10, and of the measuring head 3 may be varied in order to adapt them to the specific features of the morphology of the zone of the human body where measurement is to be performed, or as a function of the sensitivities of the person using it, etc.

In another embodiment of the invention, the sensor 10 may include a heating circuit made, for example, in the form of a silkscreened electrical circuit deposited on the same ceramic base 24 as the resistive element e.g. thermistor 22. Such a low power heating element serves to preheat the measuring zone to a temperature close to that of the human body, for example a temperature in the range 32°C to 35°C. Thus, the outside face 25 of the ceramic base 24 of the thermistor 22, when placed in contact with the skin, reaches the intended temperature more quickly, thus enabling the sensor 10 to measure temperature faster.

In a second embodiment of the invention, the sensor 10 may comprise a ceramic plate or base that is preferably covered in a layer of copper on its inside face, and, disposed at a distance from said plate, an infrared G38547 sensor which reads the radiation emitted by the inside face of the plate, its outside face being in contact with the zone of the body whose temperature is being measured. In a third embodiment, the sensor is constituted by an electrically insulating plate having a plane antenna of a radiometer applied thereto. Such a radiometer may, for example, be as described in document FR 2 673 470. Figure 8 shows the operating principle of such a radiometer in which the radiation III emitted by the skin is picked up by an antenna 38 applied to one of the faces of the plate 24. The antenna 38 directs the signals it receives to connections IV and thus to signal processor means which enable the internal temperature of the zone of the human body under consideration to be determined.

Claims

155352/2 ometer for measuring body temperature, the thermometer comprising a case having arranged at its end a temperature sensor mounted on a insulating support, the case containing electronic processing means communicating with said sensor to transform the signals received from the sensor into values for the temperature of the human body and for displaying them, the thermometer being characterized in that the support includes at least one cavity surrounding the sensor in leaktight manner when the sensor is brought into contact with the skin.

2. A thermometer according to claim 1, characterized in that the cavity is surrounded by a flexible outer peripheral lip projecting relative to the sensor.

3. A thermometer according to claim 1 or claim 2, characterized in that the walls of the peripheral cavity reflect electromagnetic radiation over at least a fraction of their area.

4. A thermometer according to claim 1 , characterized in that the support includes a first lateral annular cavity.

5. A thermometer according to claim 4, characterized in that the support includes a second cavity situated behind the sensor relative to the skin.

6. A thermometer according to claim 4 or claim 5, characterized in that the sensor is fixed via its periphery on a shoulder formed in said support.

7. A thermometer according to claim 5, characterized in that the walls of the second cavity reflect electromagnetic radiation over at least a fraction of their area. G32313 155352/2 20

8. A thermometer according to claim 1 , characterized in that the sensor comprises a temperature pickup mounted on or facing the inside face of a base made of a material of predetermined thickness and thermal conductivity. 1

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

10. A thermometer according to claim 8 or claim 9, characterized in that said base is constituted by a substantially plane plate or by a curved plate corresponding to the portion of the human body against which it is applied.

1 1. A thermometer according to any one of claims 8 to 10, characterized in that said temperature pickup is constituted by at least one resistive element mounted on a ceramic base.

12. A thermometer according to claim 11, characterized in that the resistive element is a thermistor made using thick film technology or of technology comprising depositing metallization on an insulating base.

13. A thermometer according to claim 9 or claim 10, characterized in that said pickup is constituted by an infrared sensor facing towards the inside face of said plate.

14. A thermometer according to claim 9 or claim 10, characterized in that said pickup is constituted by an antenna forming part of a radiometer and fitted to one of the faces of said plate.

15. A thermometer according to any one of claims 1 1, 13, or 14, characterized in that the electrical connections of the resistive element, of the G32313 155352/2 21 infrared sensor, or of the radiometer are provided by a flexible circuit on an insulating support.

16. A 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 generating diameter of the sensor.

17. A thermometer according to any preceding claim, characterized in that it includes means for heating the sensor.

18. A method of measuring temperature with a thermometer according to any preceding claim, the method being characterized in that it consists in: - placing the support of the sensor with its peripheral lip in contact with the zone of the human body where temperature is to be measured; - pressing the support of the sensor against said zone until the sensor comes into intimate contact with the skin and the appliance detects and indicates this contact; - taking a first temperature measurement; - taking at least one second temperature measurement after a predetermined time interval; and - determining the actual temperature of the human body by a digital method as a function of the previously-measured temperature values, and displaying the actual temperature. For the Applicnt: Seligsohn Gabrieli Levit