DEVICE FOR MEASURING THE PERCEIVED TEMPERATURE

Abstract

Device (S) for measuring the perceived temperature of an environment comprising: at least one first sensitive element (1), exposed to the environment for which the perceived temperature is to be estimated, configured to be supplied with a variable power, so as to dissipate a thermal power equal to the power that would be dissipated by conduction, convection and radiation from the human skin exposed to the same environment; means for measuring the temperature of said first sensitive element (1); calculation and control means (8); electrical supply means controlled by said calculation means (8) and adapted to supply said sensitive element (1) with an electrical power determined by said calculation and control means (8).

Claims

1. A device (S) for measuring a perceived temperature of an environment comprising: at least one first sensitive element (1), exposed to an environment for which the perceived temperature is to be estimated, configured to be supplied with a variable power, so as to dissipate a thermal power equal to the power that would be dissipated by conduction, convection and radiation from the human skin exposed to the same environment means for measuring a temperature of said first sensitive element (1), calculation and control means (8), electrical supply means controlled by said calculation means (8) and adapted to supply said sensitive element (1) with an electrical power determined by said calculation and control means (8); at least one second sensitive element (3), configured to measure a temperature (T.sub.amb) and relative humidity (UR.sub.a) of the ambient air, said device (S) characterized in that: said sensitive element (1) consists of a thermo-resistance having a thin planar shape and configured to measure of its own temperature by means of its Temperature Coefficient of Resistance (TCR) and from the fact that: said thermo-resistance consists of a metal element having a sufficiently high TCR; said thermo-resistance has both sides directly facing the external environment.

2. The device (S) for measuring a perceived temperature of an environment according to claim 1, further comprising means (12) for selecting a value of metabolic activity (MET) for which to measure the perceived temperature and customization means of said value of the metabolic activity.

3. The device (S) for measuring a perceived temperature of an environment according to claim 1, wherein said sensitive element (1) has a surface/volume ratio in the range 10÷50 mm.sup.−1.

4. The device (S) for measuring a perceived temperature of an environment according to claim 1, wherein said sensitive element (1) has a resistance value in the range 1÷100 ohm.

5. The device (S) for measuring a perceived temperature of an environment according to claim 1, wherein said sensitive element (1) consists of a double polygonal spiral winding of a small section metal wire with a diameter between 0.10÷0.05 mm.

6. The device (S) for measuring a perceived temperature of an environment according to claim 1, wherein said sensitive element (1) is made from thin metal sheet with a thickness between 0.10÷0.05 mm laser cut or sheared according to interdigital geometries to obtain a track conformation developed according to a serpentine-shape inside an insulating frame.

7. The device (S) for measuring a perceived temperature of an environment according to claim 1, wherein said sensitive element (1) is integrated in a microelectronic system able to carry out all or part of the processing, by adoption of hybrid technologies that can provide for the making of the sensitive element (1) through “wire-bonding”.

8. The device (S) for measuring the perceived temperature of an environment according to claim 1, wherein said electrical supply means of the sensitive element (1) adopt PWM (Pulse Width Modulation) technique to provide the sensitive element (1) for a short period of time with a higher power than the required one, then repeating the operation after a period of time such that the mean power value is exactly the desired one.

9. The device (S) for measuring the perceived temperature of an environment according to claim 1, wherein said control means (8) carries out a closed-loop control based on the measurement of the temperature derivative of said sensitive element (1) in order to accelerate thermal regulation.

10. The device (S) for measuring the perceived temperature of an environment according to claim 1, wherein said sensitive element (1) is provided with a mechanical protection adapted to allow air to flow freely and not to significantly obstruct the solid angle subtended by the sensor and by the fact that an electrostatic potential is applied to said metal protection so that it also acts as an electrostatic protection system against dust.

11. The device (S) for measuring the perceived temperature of an environment according to claim 10, wherein said mechanical protection is configured to act as a casing for the entire device (S) so as to allow connection of the device to common power outlets or to common lamp holders, according to current standards.

12. The device (S) for measuring the perceived temperature of an environment according to claim 10, wherein said mechanical protection is also configured to make the device able to interact with equipment and machines for the thermoregulation of environments in an integrated mode or remotely by using a most recent transmission protocols, such as wireless, and bluetooth.

13. The device (S) for measuring the perceived temperature of an environment according to claim 1, further comprising a third sensitive element (2) placed inside a casing, configured so that said third sensitive element (2) is exposed to an environment having a temperature equal to that of the environment for which the perceived temperature is to be measured, walls isothermal with it and zero air velocity.

14. A method for measuring the perceived temperature in an ambient by means of a device according to claim 1, comprising the steps of: (10) Measuring the ambient air temperature (T.sub.amb) and the relative ambient humidity (UR.sub.a) by means of the said second sensitive element (3); (20) Estimating the total specific power (Q.sub.a) dissipated by the skin as a function of the metabolic activity and as a function of the value set by said personalization means (30) Estimate the specific power dissipated by the skin by evaporation/perspiration (Q.sub.trp) as a function of: the ambient temperature (T.sub.amb) measured at point (10), the relative ambient humidity (UR.sub.a) measured in point (10), the temperature (T.sub.s) of said first sensitive element (1); (40) Powering said first sensitive element (1) with a specific power equal to the difference between said specific powers (Q, Q.sub.trp) calculated at points (10) and (20); (50) Measuring the temperature (T.sub.s (i) of said sensitive element (1); (60) Updating the estimate of said specific power dissipated through the skin by evaporation/perspiration (Q.sub.trp) as a function of: the ambient temperature (T.sub.amb) measured at point (10), the relative ambient humidity (UR.sub.a) measured at point (10), the temperature (T.sub.s (i)) of said sensitive element (1) measured at point (50). (70) Repeating steps (40) to (60) until the convergence of the value of said temperature (T.sub.s (i)) of said first sensitive element (1), thus determining the temperature of the skin (T.sub.skin=T.sub.s(i)); (80) Estimating the specific power exchanged for evaporation/perspiration from the skin exposed to the reference environment (Q.sub.trp2) as a function of: the ambient temperature (T.sub.amb) measured at point (10), the relative humidity assumed equal to 50%; the skin temperature (T.sub.skin) determined at point (70), (90) Determining the specific power (P.sub.2) that would be dissipated in the reference environment by conduction, convection and irradiation as the difference between the specific powers (Q.sub.a, Q.sub.trp2) estimated at points (20) and (80), (100) Estimating the value of the perceived temperature (T.sub.p) as a function of the specific power (P.sub.2) calculated at point (90) and of said skin temperature (T.sub.skin) calculated at point (70).

15. The method according to claim 14 wherein said estimate of the value of the perceived temperature (T.sub.p) estimated at point (100) is calculated by obtaining the value of the perceived temperature (T.sub.p) by interpolation in a two-input data table, stored in said means of calculation (8), which contains the values of the perceived temperature (T.sub.p), corresponding to various values of the specific power (P.sub.2) that would be dissipated by conduction/convection/radiation in the reference environment, and of the temperature of the skin (T.sub.skin).

16. The method according to claim 15 wherein said device (S) further comprises a third sensitive element (2), constructed in the same manner as said first sensitive element (1) and located inside a casing configured to expose said third sensitive element (2) to an environment having a temperature equal to the room temperature, walls isothermal with it and zero air velocity in that said third sensitive element (2) is supplied with said specific power (P.sub.2) calculated at point (90) and from the fact that said perceived temperature (T.sub.p) is estimated through the relationship) $T_p=T_{s1}-\frac{P_1}{P_2}\left(T_{s2}-T_{\mathrm{air}}\right)$

17. A plurality of “slave” sensors (S.sub.s), each consisting of a simplification of the sensor S in which only the first sensitive element (1) is present but both the second sensitive element (3) and the third sensitive element (2) are missing, said slave sensors (S.sub.s) being designed to supply local temperatures by delegating the measurement of ambient temperature and humidity to a single “master” sensor S, the latter carries out an appropriate average of the perceived temperatures as estimated by the sensors (Ss) and provide the mediated value in output.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The invention will now be described with reference to the attached drawings, which illustrate some non-limiting examples of embodiments, wherein:

[0075] FIG. 1 shows the procedure adopted for estimating the perceived temperature and the relative means for regulating the parameters of the procedure itself,

[0076] FIG. 2-a is a 3-D view of the sensitive element in the form of planar spiral of the wire wound,

[0077] FIG. 2-b shows a second possible alternative realization of the shape of the sensitive element that is characterized by being made from thin metal sheet suitably laser cut or sheared according to interdigitated geometries,

[0078] FIG. 3 shows a heating transient, with the temperature trend over time, of the wire of which the sensitive element is composed,

[0079] FIG. 4 shows means of communication to the user of the value of the perceived temperature, the values of ambient temperature and humidity measured by the sensitive element, said means may comprise a display (FIG. 4-a) connected to the processing unit of the sensor or may include a wireless communication system, e.g. via wifi, bluetooth, zigbee, etc. (FIG. 4b), e.g. via wired serial network (FIG. 4c).

[0080] FIG. 5 shows an alternative embodiment of the device, in which the sensor object of the present invention can estimate the perceived temperature using a third sensitive element (2) which is completely identical to the sensitive element (1), in place of using the calculation and interpolation table,

[0081] FIG. 6 shows an embodiment of the device through which it is possible to monitor the convective and radiant components in several points of a given room (or in several premises). To this end, a plurality of “slave” sensors (Ss) can be combined with the device S already described, each consisting of a simplification of the sensor S in which only the first sensitive element (1) is present, but both the second sensitive element (3) and the third sensitive element (2) are missing. These slave sensors (Ss) are able to supply the local temperatures of the skin without repeating the measurement of ambient temperature and humidity, delegated to the sensor S.

[0082] FIG. 7 shows the flow chart of the measurement procedure,

[0083] FIG. 8 shows the flow chart of the procedure, for determining the temperature of the skin (Tskin=Ts (i)), once the thermal regulation is completed and the iterative calculation converges, said sensitive element (1) reaches a temperature completely equivalent to the temperature that would be assumed by bare skin exposed to the same environmental conditions,

[0084] FIG. 9 shows the flow chart of the second step of the procedure implemented by the sensor object of the present invention for the purpose of estimating the perceived temperature consists in estimating the temperature of that “reference environment” which would achieve an equal heat exchange with the human body. Since the temperature of the skin is known as measured by the sensitive element (1) (Tskin=Ts (i)), and all the characteristics of the reference environment are fixed, except for its temperature (zero air velocity, walls isothermal with air, humidity of 50%), the temperature of this environment, corresponding to the perceived temperature, can be determined with this second step of the procedure.

DETAILED DESCRIPTION OF THE DEVICE

[0085] According to a preferential embodiment of the present invention, the sensitive element (1) consists of a thermoresistance in the form of a metal conductor, or in another material suitable for the purpose, having known electrical and physical properties, through which it is passed a current capable of dissipating by Joule effect the electric power P.sub.1 calculated with the relationship 4. The same thermoresistance allows the measurement of its own temperature by means of its own TCR (Temperature Coefficient of Resistance).

[0086] In order to minimize the electrical consumption of the sensor, especially with a battery power supply, the sensitive element (1) must have a heat exchange surface with the environment as limited as possible, since the power P.sub.1 is directly proportional to this surface.

[0087] Said sensitive element (1), moreover, must be configured so as to exchange heat exclusively with the ambient air in order to avoid parasitic heat dissipation by conduction towards other bodies, thus affecting the measurement of the temperature of the skin. This requirement preferentially leads to excluding contact of the conductor with surfaces other than ambient air, such as supports or substrates. Finally, the thermal capacity of said sensitive element must be as small as possible for the same surface exposed to the environment, in order to ensure small time constants and therefore rapid thermal regulation.

[0088] To this end, the present invention provides for the realization of said sensitive element (1) either in the form of a metal wire, suitably shaped and supported, or in the form of a thin metal sheet. This metal element (wire or foil) can conveniently be made of platinum, but also nickel, copper, tungsten, molybdenum and other materials can be suitable. More specifically, said sensitive element is characterized by the fact of (i) being a thermoresistance consisting of a metal element having a sufficiently high TCR, (ii) having a thin planar shape, so as to avoid three-dimensional geometries which, enclosing volumes of air, would increase the thermal inertia of the sensor, (iii) be free of support elements (substrates on which the thin film or thick film resistance could be deposited, or spools on which the metal wire of the thermoresistance could be wound) which would increase the thermal capacity of the sensor, consequently increasing response times. In other words, the fact that the sensitive element is free of support elements is equivalent to saying that the thermoresistance has both sides directly facing the external environment. The typical values of the surface/volume ratio are positioned in the range 10÷50 mm.sup.−1. The resistance value must be suitable for the functions that the sensor must perform and therefore is positioned in the range 1÷100 ohm.

[0089] Conveniently, the temperature measurement of the sensitive element (1) can be carried out by measuring the electrical resistance of the wire or foil during the passage of the current that heats it up. The measurement of the resistance of said metal element which constitutes said sensitive element (1) is obtained by the jointly measurement of the voltage falling across its terminals and the current that runs through it. These quantities are also used by the calculation unit (8) to control the power supplied.

[0090] Diameter and length of the wire, or thickness, width and length of the foil, must be chosen in order to best meet the requirements set out above as well as in order to guarantee a sufficiently low measurement error of the absolute temperature of the sensitive element, for example lower or equal to 0.1° C., compatibly with the technological repeatability of realization of the sensitive element itself.

[0091] As an illustrative but not limiting example, in the case of platinum, whose temperature coefficient is equal to about 0.0039, the relative error ΔR/R of realization of the resistance of the sensitive element (1) must therefore be less than 0,00039 (3.9 parts per ten thousand).

[0092] Given the good repeatability of the composition of the platinum and therefore of its temperature coefficient, subject to specific regulations, the precision of realization of the resistance of said sensitive element, in the case of wire, essentially depends on the precision with which its length is made. For example, if the technological precision header of said wire terminals on the main conductors is of the order of tenths of a millimeter, the total length L of said wire, in the case of realization in platinum, must be such that ΔL/L <0,00039. Therefore if ΔL=0.1 mm we obtain L ≥256 mm.

[0093] As said, it is useful to try to minimize the time of thermal regulation and, therefore, the relationship between volume and surface. In the exemplary but non-limiting case of cylindrical section wire, the ratio between volume and surface of the wire is proportional to the diameter of the wire itself. It is therefore desirable to use the smallest diameter compatible with the technological limits relating to the realization and shape of the wire.

[0094] According to the present invention, the shape to be given to said wire provides the following guidelines in a non-limiting way.

[0095] First of all, it is observed that the useful surface of said sensitive element (1), i.e. the surface exposed to the environment, depends on how the wire is wound. It should be noted, in particular, that if the wire is wound according to some geometry, the overlapping of the turns must be avoided in order to maximize the dissipating surface for the same length.

[0096] Finally, in choosing the type of winding of said wire, it is necessary to avoid that there is material enclosed by the coils system, not only in the form of a support for the winding but also simply air, such as for example in the case of windings in cylindrical or spherical shape which contain a volume of air inside. This material enclosed within the windings (even if only air) contributes to the thermal capacity of said sensitive element (1) by slowing down its readiness.

[0097] Therefore, according to a preferential mode of realization, the sensitive element (1) is realized in the form of a planar winding, consisting for example of concentric coils. In particular, a preferential embodiment consists of a double polygonal spiral winding of a small section metal wire (with a value of the diameter typically in the range between 0.10÷0.05 mm), as shown e.g. in FIG. 2-a. This geometry allows to keep the angles that the metal wire assumes within low values, avoiding structural problems, ensures a good effective surface/total surface ratio and has minimal points of contact with the support structure, minimizing dissipation towards the latter. This support structure is realized by means of thin-rays but of adequate depth (as shown in FIG. 2-a) and provided with incisions in which it engages the wire in its winding coils. The realization of the winding can adequately be carried out using robotic arms typical of wire-bonding technology.

[0098] The use of parallel conductors crossed by current in the opposite direction has the advantage of making its ends available on the periphery of the winding and at the same time minimizing the inductance of the winding itself. The planar winding also has the advantage of being representative of an element of human skin, characterized by surfaces with low curvature.

[0099] In the case of a planar winding with adjacent turns, the effective surface for thermal exchange is reduced by a factor of 2/π in relation to the surface of the bare wire, where 2/π corresponds to the ratio of twice its longitudinal cross-section and the lateral surface of the bare wire, it being understood that both sides of this planar winding must be exposed to the environment.

[0100] A second possible alternative realization of the shape of the sensitive element is characterized by being made from thin metal sheet suitably laser cut or sheared according to interdigitated geometries, as shown in FIG. 2-b. The same sheet, after punching or laser cutting, it becomes a track with the shape of a serpentine. The low thickness of the sheet and the minimum track width give the element a resistance value in the specified range.

[0101] The sheet, cut as described above, is then locked in an insulating frame along the orthogonal sides to the development of the track, as shown in FIG. 2-b. The contact with the frame does not affect the heat exchange because the contact zone is not part of the track and therefore does not heat. The thickness of the metal sheet is typically between 0.10÷0.05 mm.

[0102] As an alternative to the adoption of planar windings or thin metal lamellas “stand-alone”, the sensitive element (1) can also be integrated into a microelectronic system capable of realizing all or part of the processing by adoption of hybrid technologies that can provide for the realization of the sensitive unit through “wire-bonding”

[0103] In the illustrative example of the platinum wire with a length equal to 256 mm, the diameter of said wire can conveniently, but not necessarily, be between 0.04 mm and 0.10 mm. With these diameters, time constants of 60 seconds are obtained.

[0104] Still with reference to illustrative, but not limiting, case of a platinum wire with a length of 256 mm and a diameter of 0.04 mm, the wire wound in the form of planar spiral, as shown in FIG. 2-a, has the following characteristics: electric resistance at room temperature 21.6 ohm; mass 6.9 mg; thermal capacity 0.90 mJ/K.

[0105] Still with reference to said example, assuming for the MET a value of 1, and also assuming that the power dissipated Q.sub.trp by evaporation/perspiration is equal to 1.125 mW/cm.sup.2, a power of 0.96 mW must be supplied to said sensitive element (1).

[0106] As already described, said sensitive element (1), crossed by the current capable of ensuring the delivery of this power, leads itself to an equilibrium temperature that corresponds to the temperature of the skin of a human being exposed to the same environmental conditions.

[0107] According to the present invention, the metallic element of which said sensitive element (1) is made must have a coating capable of giving it an average emissivity on the visible-infrared spectrum similar to that one typical of human skin (ε=0.94). This can be done by a suitable painting or by oxidation, passivation, anodizing, etc.

[0108] Said metallic element, if in the form of a wire, can also be equipped with the insulating coating used in the usual production processes of insulated electric wires, and the high emissivity coating can be added subsequently to said already shaped wire (spiral, raster, etc.) with the dual purpose of increasing its emissivity and consolidating its shape, acting as a glue.

[0109] This filler material, which will typically have a thickness of the order of one hundredth of a millimeter, gives rise to a thermal resistance towards the environment, which in the model of human skin consisting of said sensitive element (1) it plays the same role that clothing plays on man.

[0110] However, it has previously been shown that the principle of estimating the perceived temperature on which the present invention is based is not affected by clothing. Therefore, the mentioned coating does not affect the estimate of the perceived temperature.

[0111] However, the presence of a coating affects the time constant of the sensor. This effect can be compensated, as described below.

[0112] A preferential but non-limiting method is now described, with which the electrical power to be supplied to the sensitive element 1 can be supplied and controlled.

[0113] In general, the measurement of the electrical power supplied on an unknown resistive load requires the measurement of the current and voltage at its ends. For this purpose, a precision shunt resistance (5) characterized by a very low thermal coefficient is provided for measuring the current; the voltage drop is measured by means of a suitable detection system (6b), the output of which is converted into digital signal from an analog-digital converter (7) which supplies it to said calculation unit (8). The value of the shunt resistance is typically equal to a small fraction of the resistance of the wire from which the sensitive element is made (1), a fraction that can for example be between a fiftieth and a hundredth. Similar means (6-a) are provided for measuring the voltage across terminals of said sensitive element (1).

[0114] Based on the low values of the power to be supplied to said sensitive element (1), the preferential embodiment of the system for supplying the electric power to the sensitive element (1), according to the present invention, provides for the adoption of the PWM technique (Pulse Width Modulation).

[0115] According to this technique, the wire is supplied with a much higher power than the target one for a short period of time, and the operation is repeated after such an interval of time that the average value of the power is exactly as desired. FIG. 3 shows a heating transient of the wire of which said sensitive element (1) is composed according to the example previously illustrated. The advantage of the PWM technique consists in the possibility of delegating all the actuation precision of the power to be supply to said sensitive element (1) to the accuracy of the opening and closing times of the fast switch (4 a), consisting of a suitable device in its state solid (made with e.g. CMOS technology), characterized by low impedance in the “closed” condition and high impedance in the “open” condition. Furthermore, the supply voltage of said sensitive element (1) does not need to be adjusted according to the power to be supplied but can be stabilized at a predetermined value (e.g. 1.1 Volt in the example illustrated above).

[0116] For this purpose, FIG. 1 shows means (10) suitable for regulating the voltage of a battery (11) to the desired voltage value, and electrical storage means (9) suitable to guarantee constant voltage during the supply period of the power.

[0117] In another possible embodiment, the battery (11) can be replaced by a power supply system connected to the network suitable for generating the same voltage.

[0118] In order to further decrease the average power dissipated by the sensor (S) object of the present invention (and therefore increase the duration of the supply batteries), the measurement made with said sensitive element (1) can be carried out at predetermined time intervals, for example one or more minutes. If, for example, the measurement interval chosen is 10 minutes, taking into account that the regulation time of the sensitive element (1) is about 60 seconds, the average power is reduced by about one tenth.

[0119] In order to improve the rapidity of measurement of the sensor object of the present invention, for the benefit of applications where high readiness is required, such as for example applications in means of transport (e.g. thermal transient in a car having an initial temperature far from comfort conditions), said sensitive element (1) can conveniently use a “warm-up” strategy aimed at significantly accelerating the transient regulation. In a convenient embodiment, said calculation unit (8) with which the sensor (S) is provided can deliver the same amount of energy necessary for the thermal regulation of the sensitive element in a more limited time, by realizing a closed chain control based on the measurement of the temperature derivative of said sensitive element (1).

In detail, a possible embodiment of said control is based on the following steps: [0120] i) supply of the target power for two PWM cycles, e.g. actuation of two current pulses; [0121] ii) measurement of the difference in temperatures recorded at the beginning of the two current pulses; [0122] iii) determination of a temporary power increase to be implemented according to a PID (Proportional-Integrative-Derivative) algorithm with appropriately calibrated parameters; [0123] iv) implementation of increased power by lengthening the closing interval of the switch 4a for a single cycle; [0124] v) repetition of the process with new execution of two normal cycles of implementation.

[0125] Once the regulation has been made, the algorithm will find that it is no longer necessary to increase the power.

[0126] The second step of the procedure implemented by the sensor object of the present invention for the purpose of estimating the perceived temperature consists in estimating the temperature of that “reference environment” which would achieve an equal heat exchange with the human body. Since the temperature of the skin is known as measured by the sensitive element (1) (T.sub.skin=Ts (i)), and all the characteristics of the reference environment are fixed, except for its temperature (zero air velocity, walls isothermal with air, humidity of 50%), the temperature of this environment, corresponding to the perceived temperature, can be determined with the following procedure, described in the flow chart in FIG. 9.

[0127] In the first part of this second step of the procedure, the calculation unit (8) estimates the power per unit area that would compete with the evaporative/by perspiration exchanges for the skin exposed “to the reference environment” (Q.sub.trp2) using the formula 2, in which it is assumed: [0128] i) 50% relative humidity (U.sub.ra); [0129] ii) skin temperature (T.sub.skin) measured with said sensitive element (1) according to the previously illustrated procedure; [0130] iii) ambient temperature equal to estimate of the perceived temperature;

[0131] In the first iteration of the calculation, for which a perceived temperature value produced by the previous iteration is not yet available, the ambient temperature provided by the sensitive element (3) is taken as the initialization value.

[0132] The power that would be dissipated by conduction/convection/radiation in the “reference environment” shall be determined by means of the following relationship:

P.sub.2=A.Math.(Q.sub.a−Q.sub.trp2)  (Eq. 5)

[0133] Given the values of P.sub.2 and T.sub.skin, the calculation unit (8) derives the value of the perceived temperature (T.sub.p) by interpolating in a two-input data table, stored in the same unit (8), in which the values of T.sub.p are reported corresponding to various values of P.sub.2 and T.sub.skin.

The construction of this table requires prior execution of measures to be carried out, one-time, in a laboratory equipped with: [0134] i) a climatic cell designed to create isothermal “reference environments” characterized by different temperatures within a range suitable for covering all the conditions of use of the sensor; [0135] ii) a sensitive element completely identical to said sensitive element (1) to which average power values are provided in a range suitable to cover all possible conditions of use (MET and environmental).
The temperature value provided by the above interpolation calculation in the table corresponds to the perceived temperature value T.sub.p.

[0136] In order to communicate the value of T.sub.p, the device object of the present invention preferably comprises means of communication to the user of the value of the perceived temperature (T.sub.p) and, possibly, also of the values of ambient temperature and humidity measured by the sensitive element (3).

[0137] With reference to FIG. 4, said means may comprise a display (13) connected to the processing unit (8) of the sensor, or may include a wireless communication system, e.g. via wifi, bluetooth, zigbee, etc. (FIG. 4b), e.g. via wired serial network (FIG. 4c).

[0138] In an alternative embodiment shown in FIG. 5, the sensor object of the present invention can estimate the perceived temperature using a third sensitive element (2) which is completely identical to the sensitive element (1), in place of the calculation and interpolation in the table just described.

[0139] Said third sensitive element (2) is placed inside the sensor casing and therefore exposed to an environment having a temperature equal to that of the environment, isothermal walls with it and zero air velocity. The power value P.sub.2 provided by equation 5 is supplied to the sensitive element (2). Conveniently the sensitive element (2) can share the same shunt resistance (5) with the sensitive element (1) and be activated with the PWM technique described above when the sensitive element (1) is not active, according to an alternation which is repeated with a constant period. The duration of the activations of the sensitive elements (1) and (2) must allow their thermal regulation, possibly accelerated by means of the algorithm previously illustrated. The temperature reached by the sensitive element (2) is used by the calculation means (8) to estimate the perceived temperature (T.sub.p) through the following relations.

The heat exchange between the sensitive element (2) and the environment inside the sensor (isothermal environment at room temperature), can be described with a good approximation from the relationship:

P.sub.2=A.Math.h.Math.(T.sub.S2−T.sub.aria)  (Eq. 6)

where A is the heat exchange surface of said third sensitive element (2), identical to that of the first sensitive element (1), T.sub.S2 is the temperature reached by said third sensitive element (2), while the heat exchange coefficient h is function of T.sub.S2 and T.sub.air.

[0140] The heat exchange coefficient h accounts for the conductive/convective and radiative heat exchanges in calm air for the sensor geometry, with the approximation of a linearization of the radiative exchanges in the temperature range between T.sub.S2 and T.sub.air, which is generally contained within a tens Kelvin degrees. As part of the approximation adopted with the equation 6, we can assume that, for the reference environment which would ensure to the sensitive element (1) the same thermal exchange observed in the real environment, the following relationship applies:

P.sub.1=A.Math.h.Math.(T.sub.S−T.sub.percepita)  (Eq. 7)

wherein T.sub.s is the temperature of the first sensitive element (1) and the coefficient h is the same that appears in equation (6). The approximation of constancy of the heat exchange coefficient h is acceptable because in both environments the air is calm and the walls are isothermal with the air. The second order errors, attributable to the dependence of h on the temperature of the heat exchange surface, can be neglected since the values of the temperatures that appear in equations 6 and 7 are never excessively different (in the ordinary operating ranges of the sensor object of the present invention T.sub.s1 and T.sub.s2 differ at most by 10° C.; a similar maximum difference can be recorded between T.sub.air and T.sub.perceived).

[0141] By combining the relations 6 and 7, the following estimate is obtained for the perceived temperature:

[00001]$\begin{array}{cc}{T}_p=T_{s1}-\frac{P_1}{P_2}\left(T_{s2}-T_{\mathrm{aria}}\right)& \left(\mathrm{Eq}.8\right)\end{array}$

[0142] Conveniently with the device according to the present invention it is possible to monitor the convective and radiant components in several points of a given room (or in several premises). To this end, a plurality of “slave” sensors (Ss) can be combined with the device S already described, each consisting of a simplification of the sensor S in which only the first sensitive element (1) is present, but both the second sensitive element (3) and the third sensitive element (2) are missing, as indicated in FIG. 6.

[0143] These slave sensors (Ss) are able to supply the local temperatures of the skin without repeating the measurement of ambient temperature and humidity, delegated to the sensor S. The latter, in the case of several “slave” sensors, it provides for an appropriate average of the perceived temperatures as estimated by the sensors (Ss), using a weighing that can be possibly set by the user based on the relevance of the different environmental zones. Each sensor (Ss) must be equipped with a wireless communication unit suitable for transmitting the measurement data to the master sensor S.

[0144] In order to control the climate of multiple environments, it is expected to use a system of sensors, one of which is configured as a “master” (equipped with all the sensitive elements provided) and the other as “slave”; depending on the type of environments and the expected climatic conditions (for example in case of rooms with different enthalpy loads within the same building), the “slave” sensors can be equipped with all the sensitive elements (as in the case of the master) or only with necessary elements; depending on the type of system and associated actuators, the “slave” sensors can be used to control the local actuators (in wireless or wired mode), or send the measurement data to the “master sensor”.

[0145] Conveniently, the device can include the mechanical protection of the sensitive element by means of a suitable metal grid, designed to allow air to flow freely and not to significantly obstruct the solid angle subtended by the sensor. The same metal grid can be used to create an electrostatic protection system against dust, by applying an electrostatic potential in which the metal grid and the sensitive element are connected to the negative pole, while a suitable metal ring placed around the sensor is connected to the positive pole. In this way, after having polarized or acquired a negative charge, the dust particles will preferentially be attracted to the positively charged ring and rejected by the sensitive element. The geometry of said metal protection can act as a casing for the entire device (including the power supply and control electronics of the sensitive element) and be shaped in such a way in order to allow the device to be connected to common power outlets or to common lamp holders, according to current standards.

[0146] This casing would make the device able to interact with equipment and machines (for example, plant terminals such as convectors, radiators, etc.) for the thermoregulation of environments in an integrated mode (sensor installed on the terminal) or remotely by using the most recent data transmission protocols (wireless, bluetooth, etc.). The device would then be compatible with the latest Smart Buildings management and monitoring technologies, contributing to energy efficiency and sustainability of buildings (Green Building), as the IoT technology, Big Data, Cloud computing and Monitoring, etc.