BACKGROUND ART Body sensors are known in which a sensitive portion of the sensor is pressed lightly onto a surface portion of a body portion, in particular onto the skin, to determine chemical-physical characteristics of the body portion, e. g. the pH value of the skin.

The chemical-physical characteristic measurements depend on a number of parameters (e. g. the moisture of the body portion), which in turn depend largely on the surface temperature of the body portion.

Moreover, the surface temperature of the body portion is largely affected by the temperature of the external environment in which the measurement is made, and by the temperature of the subject.

Consequently, measurements made in environments at different temperatures and/or on the same subject in different physical conditions (e. g. in normal health and when feverish) result in different readings, on account of the variation in temperature caused by extraneous factors (ambient temperature and temperature of the subject) altering the measuring parameters.

DISCLOSURE OF INVENTION It is an object of the present invention to provide a sensor of the above type, wherein the measurement is unaffected by variations in extraneous factors (ambient and subject temperatures).

According to the present invention, there is provided a body sensor, characterized by comprising: detecting means having at least one sensitive portion which is placed in contact with a body portion, in particular a skin portion, to determine chemical- physical characteristics of the body portion; and conditioning means cooperating with said detecting means to maintain said body portion at a predetermined temperature.

The temperature of the body portion is thus made independent of ambient temperature and/or the temperature of the subject, the measuring results are no longer affected by extraneous factors, and the measurement is made repeatable by different measurements being made on body portions at the same temperature.

BRIEF DESCRIPTION OF DRAWINGS A non-limiting embodiment of the invention will be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows, schematically, a body sensor in accordance with the teachings of the present invention and operating in conjunction with a detecting device for detecting chemical-physical characteristics of a body portion; Figure 2 shows a logic operating diagram of the Figure 1 device.

BEST MODE FOR CARRYING OUT THE INVENTION Number 1 in Figure 1 indicates as a whole a body sensor wherein an insulating casing 3 (e. g. made of plastic material) supports a sensing device 5 (known) for determining chemical-physical characteristics of a body portion 7, and a conditioning device 10 which, in use, maintains body portion 7 at a substantially constant predetermined temperature.

Insulating casing 3 comprises a cylindrical tubular wall 3a coaxial with an axis 12 and closed, at a first end, by a flat end wall 3b perpendicular to axis 12. At , a second end, cylindrical tubular wall 3a has a circular opening 15.

Wall 3a has a through hole 16 coaxial with axis 12 and engaged by sensing device 5, which is cylindrical on the outside and comprises an end 5a fitted with a flat

sensitive portion 18 which is suitable to be placed on the outer surface 7a of body portion 7 to determine at least one chemical-physical characteristic (e. g. the pH value) of portion 7. More specifically, sensitive portion 18 is positioned substantially coplanar with a plane P perpendicular to axis 12 and through the free peripheral edges of wall 3a.

The conditioning device comprises a first flat annular disk 21 internally defining a circular opening 22; and a second annular disk 23 over, coaxial with, and spaced with respect to first disk 21. A number of Peltier-effect heating-cooling devices 25 connected by electric supply cables 27 are interposed between first and second disks 21 and 23, and comprise two dissimilar conductors (not shown), e. g. antimony and bismuth, arranged contacting each other. As is known, when such conductors are supplied with a current of intensity i, heat is evolved or absorbed, depending on the direction of the current (Peltier effect).

Disks 21 and 23 are made of good heat-conducting material, and are housed inside tubular wall 3a, coaxially with axis 12, with first disk 21 substantially coplanar with plane P.

A temperature sensor 29 is interposed between disks 21 and 23, and is connected by an electric cable 30 to a measuring device 34 controlling, among other things, devices 25. Device 34 is also connected by a cable 37 to

sensing device 5, and comprises display devices 40 for displaying the measurement (e. g. the pH value) of the chemical-physical quantity measured by sensing device 5.

1 In actual use, the tubular casing 3 is placed on a body portion 7, e. g. the back of a hand, with first annular disk 21 contacting the outer surface 7a of body portion 7; and sensing device 5 is moved along axis 12 so that sensitive portion 18 is pressed lightly onto surface (skin) 7a to enable the measurement to be made.

In the above position, sensitive portion 18 is located inside opening 22 and substantially coplanar with plane P.

Device 34 is then activated.

The operations performed by device 34 are shown by way of example in Figure 2.

To begin with, a block 100 determines a reference temperature To set and entered into device 34 beforehand as a reference data item, e. g. To = 32°C.

Block 100 is followed by a block 110 which, by means of sensor 29, determines a measured temperature Tmis representing the temperature of body portion 7 beneath, and within the perimeter of, disk 21.

Block 110 is followed by a block 120 which compares measured temperature Tmis with reference temperature To and is followed by : a block 130 if measured temperature Tmis is higher than the reference temperature-Tmis > To;

a block 140 if measured temperature Tmis is lower than the reference temperature-Tmis < To; and a block 150 if measured temperature Tmis is substantially equal to the reference temperature- Tmis-To.

Block 130 supplies devices 25 with a current i in a first direction to withdraw heat inside devices 25 and cool disk 21 connected thermally to devices 25, thus cooling body portion 7. Block 130 then goes back to block 120.

Block 140 supplies devices 25 with a current-i in a second direction to generate heat inside devices 25 and heat disk 21 connected thermally to devices 25, thus heating body portion 7. Block 140 then goes back to block 120.

A two-way heat flow may therefore be generated from device 10 to portion 7 (heat-block 140) and from body portion 7 to device 10 (cool-block 130) until a <BR> <BR> <BR> <BR> <BR> temperature close to reference temperature To (Tmis _ To) is reached and block 150 is selected.

Block 150 supplies devices 25 with a hold current to maintain body portion 7 beneath and within the perimeter of disk 21 at the attained predetermined temperature To.

The measurement is then made (block 160 downstream from block 150) and the result displayed (block 170 downstream from block 160) on a display device 40.

The body sensor and the detecting device for detecting chemical-physical characteristics of a body portion therefore clearly provide for eliminating the drawbacks of known devices, by the temperature of the body portion within the perimeter of disk 21 being set to temperature To prior to each measurement. Sensitive portion 18 is positioned contacting the outer surface 7a of body portion 7 set to a constant temperature To.

The measurement is thus made independent of ambient temperature and/or the temperature of the subject, so that the results of the measurement are unaffected by extraneous factors.

Clearly, changes may be made to the body sensor and to the detecting device for detecting chemical-physical characteristics of a body portion as described herein without, however, departing from the scope of the present invention.