Magnetic element temperature sensors

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DESCRIPTION

Magnetic element temperature sensors.

Background of the invention

Field of the invention

The present invention relates in broad terms to magnetic element temperature sensors, to detectors for use with such sensors, to closed loop heating systems that make use of the sensors and detectors to wirelessly determine the temperature of an object and to control the temperature of the same, and to corresponding methods. More particularly, the invention relates to temperature sensors constituted by at least one magnetically susceptible sensor element, preferably formed with amorphous or nanocrystalline metal, and which has a re-magnetization response under the influence of an applied alternating magnetic field that is different by below and above at least one setpoint temperature, such as the Curie temperature of the sensing element. These temperature sensors can be used with correlated detectors, for temperature sensing, and as part of closed loop heating systems.

Description of the prior art

In the market, there are a variety of applications for temperature sensors that can be read wirelessly. These applications range from internal livestock temperature sensing and reporting to being part of a closed loop temperature feedback system that enables a magnetic induction heater to precisely control the temperature of insulated feed dispenser boxes. Many of these applications are disclosed in US Patent Nos. 5,954,984, 6,232,585, 6,320,169, and 6,953,919.

Many of those applications currently use the services of Radio Frequency Identification (RFID) temperature sensing systems. These RFID temperature sensing systems include an RFID reader and its associated RFID "tag", whereby the tag has some type of temperature sensor that is part of its circuitry.

These early RFID systems tend to be relatively expensive due to the cost of the tags, and cannot operate continuously above 125 ° C. Furthermore, they lack the ability to transmit information in close proximity to metal or other materials. conductive, particularly when the RFID tag is embedded within the conductive material.

Magnetic item markers (or "tags") are commonly used as part of electronic article protection (EAS) systems or other authentication systems. These markers or tags are passive, typically small in size, less economically expensive than RFID tags, can operate at high temperatures, and in some formats, can transmit their information wirelessly to a detector even when embedded within a conductor.

For example, US Patent No. 4,484,184 discloses EAS markers or labels made of soft magnetic amorphous alloy ribbons. These tapes have a composition consisting essentially of the formula M_to Nb Oc Xd Ye Zf, where M is at least one of iron and cobalt, N is nickel, O is at least one of chromium and molybdenum, X is at least one of boron and phosphorus, Y is silicon, Z is carbon, "a" to "f" are expressed in atomic percentage, a is between approximately 35 and 85, b is between approximately 0 and 45, c is between approximately 0 and 7, d is between between about 5 and 22, e is between about 0 and 15 and f is between about 0 and 2, and the sum of d + e + f is between about 15 and 25. Marker tapes are capable of producing field disturbances at frequencies that are harmonics of the frequency of an incident alternating magnetic field produced by a field transmitter. Detection means are arranged to detect disturbances of the magnetic field in selected tones of the harmonics produced in the vicinity of the interrogation zone, by the presence of the marker in it. The generation of harmonics by the marker is caused by a non-linear magnetization response of the marker to an incident magnetic field.

Document US 6 208 253 B1 discloses a sensor module for wirelessly monitoring temperature. The sensor module comprises a combination of a signal element with a bias element and / or a modulation element. The signal element can be stimulated by means of an alternating magnetic field that can be detected by a receiving antenna. To add a temperature dependence to the response generated by the signal element, the bias element and / or the modulation element must be provided.

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US 6 776 523 B2 describes a method of generating a temperature measurement for a batch or continuous flow of material, in which a particle that provides a signal that changes at a predetermined temperature is introduced into the batch or continuous flow.

Document US 6 270 591 B2 discloses metallic wires covered with amorphous and nanocrystalline glass, which have magnetic properties for different categories of application.

R. Varga et al. in Phys. Rev. Letters 94, 017201 (2005), describe mechanisms of propagation and damping of single domain walls during the magnetic switching of bistable amorphous microwires.

Document US 5 538 803 A discloses an identification tag that includes a plurality of magnetic elements, which can be interrogated and can be read remotely.

In the art, there is a need to provide wireless temperature sensing systems that use temperature sensing elements that are less economically expensive, and of reduced size, and that can operate continuously at temperatures above 125 ° C, and that have the ability to transmit information even in close proximity to metal or other conductive materials. Furthermore, it would be advantageous if said improved temperature sensor elements could carry predetermined data concerning the sensor itself or the object of which the temperature is to be detected, for example, the identity of the object, characteristics of the object, or heating instructions. Finally, it would be advantageous if the sensor elements could be used as part of a closed loop feedback heating system capable of controlling the output of a heating device and thus controlling the temperature of an object.

Summary of the invention

The present invention relates to a system for heating an object as defined in claim 1. Advantageous versions of the invention follow from the dependent claims.

The present invention provides an entirely new class of temperature sensors, temperature sensing methods, and closed loop heating systems. The invention is disclosed following the discovery that reliable temperature detection can be achieved through the use of temperature sensing magnetic elements, each having a characteristic re-magnetization response under the influence of an applied alternating magnetic field, where responses are temperature sensitive and can be easily monitored.

In more detail, a preferred temperature sensor is configured to be placed in thermal contact with an object in order to detect the temperature thereof, and comprises at least one magnetically susceptible sensing element that has a re-magnetization response under the influence of an applied alternating magnetic field, the re-magnetization response being defined by at least one short, detectable magnetic field disturbance pulse, of short defined duration, and which is different below and above at least one setpoint temperature. Preferably, the setpoint temperature is the Curie temperature of the sensing element, or a temperature close to (usually less than about 25 ° C) this Curie temperature. In most applications, the setpoint temperature is below approximately 400 ° C.

When a temperature sensing element of the aforementioned type is arranged in thermal contact with an object whose temperature is to be detected, and an alternating magnetic field is applied to the sensing element, of sufficient magnitude to achieve the desired re-magnetization response, the sensing element functions as a “temperature switch”. That is, when the object is below the setpoint temperature of the sensor element, a re-magnetization response of the sensor element is observed; when the object temperature reaches or exceeds the setpoint temperature, either no re-magnetization response is observed, or the response is altered.

Typically, the temperature sensors according to the invention make use of a plurality of sensor elements each having a different setpoint temperature than the other sensor elements. Preferably, these various sensor elements are designed to have different successive setpoint temperatures varying from lowest to highest and in at least somewhat uniform manner, so that the temperature of the object can be monitored over a range of temperatures. which corresponds to the design of the temperature sensors. In such a situation, the magnitude of the differences between adjacent setpoints defines the resolution of the temperature sensor.

In order to use the temperature sensor of the invention in the most efficient way possible, use is made of a detector correlated with the sensor elements. In general, a detector of the aforementioned type has a device for generating an alternating magnetic field of sufficient magnitude in order to interrogate the sensor elements (that is, to achieve re-magnetization responses of the sensor elements on the

ES 2 672 995 T3 base of the temperature of the object), and a device to detect said responses. In practice, the detector has a magnetic field generating coil and a field receiving coil, both coupled to a signal processing unit. In practice, the detector generates the required alternating magnetic field, and the receiving field coil detects the re-magnetization responses of the sensing elements, emitting output signals to the signal processing unit. The signal processing unit, preferably in the form of a digital microprocessor, uses a decoding algorithm that allows the temperature of the object to be determined. In preferred forms, the decoding algorithm comprises one or more look-up tables that correlate the re-magnetization responses of the sensor elements to the temperature of the object.

Advantageously, the magnetically susceptible sensor elements are formed as metallic bodies in an amorphous or nanocrystalline state. Preferably, said metal bodies are preferably in the form of very thin, elongated metal strips or wires, having a maximum cross-sectional dimension (eg diameter) of up to about 100 nm, and can be produced in a variety of ways. A particularly suitable form of metallic bodies is the microwire form, comprising an inner metallic core and an optional outer glass coating. Such microwires can be produced by the widely known Taylor method or in the form of water-molded amorphous bodies. However, in the context of the invention it is not necessary to make use of microwires, as long as the sensors include the required magnetically susceptible sensor elements.

In another aspect of the invention, novel microwire-based composite or combined microwires are envisioned. In constructions of this type, an inner microwire made up of an elongated metal body is shielded by means of an adjacent ferromagnetic jacket of known Curie temperature, which avoids or at least alters the re-magnetization response of the metal body of the microwire associated with temperatures. below the Curie temperature of the jacket (or to a known temperature close to the Curie temperature of the jacket). The jacket may be located in surrounding relationship with respect to the inner microwire, or disposed at least partially around the inner microwire in spacing relationship therewith. A particularly preferred composite microwire includes an internal, magnetically susceptible microwire body with a surrounding glass cover. The jacket is tubular and surrounds the glass cover, and has an external glass cover around the jacket. Such a composite design can easily be produced using a modified Taylor method. Specifically, a pair of inner and outer glass tubes are telescopically assembled together with the magnetically susceptible metal within the inner tube and the ferromagnetic jacket material between the inner and outer tubes. These components are fused and quickly pulled to create the desired composite structure.

In another aspect of the invention, a method of detecting the temperature of an object is provided. This method broadly comprises the steps of bringing a temperature sensor into thermal contact with said object, the sensor comprising at least one magnetically susceptible sensing element that has a re-magnetization response under the influence of an applied alternating magnetic field, and wherein the re-magnetization response is different below and above at least one setpoint temperature. Next, an alternating magnetic field is generated in the region of the sensor, and of sufficient magnitude to elicit the re-magnetization response of the sensor element. After that, the re-magnetization response of the sensing element is detected and used to determine at least in part whether the temperature of the body (and therefore the object) is above or below the setpoint temperature. (For example, other information may be used in conjunction with the detected re-magnetization response in temperature determination).

As previously indicated, the sensor normally has a plurality of magnetically susceptible sensor elements, each exhibiting a different re-magnetization response under the influence of an applied alternating magnetic field, and each re-magnetization response being different by below and above a setpoint temperature, and where the setpoint temperatures of the sensor elements are different from each other. In such a case, the re-magnetization responses of at least some of the various sensor elements are detected and used to measure the temperature of the sensor elements and the object.

When using a jacketed composite or combination microwire sensing element, the associated ferromagnetic jacket prevents the remagnetization responses of the associated microwire body by magnetically polarizing or saturating the body until the sensing elements and the object reach a temperature above the temperature of Curie, or at a certain fixed temperature near the Curie temperature, of the ferromagnetic jacket. The extent of magnetic polarization or saturation of the sensor element by the jacket can be designed to produce a series of different or altered re-magnetization responses over a range of temperatures in proximity to the Curie temperature of the jacket. Assuming that the correlated detector has sufficient resolution and discrimination, these different or altered responses can be detected and used for temperature detection. Thus, in such a case, a single microwire sensor element may have a plurality of different setpoint temperatures.

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The invention also provides a unique structure and method for selectively measuring the temperature of an object made up of at least one pair of components designed to be placed in close proximity to each other, at least one of the components being heatable. For example, in accordance with the invention the temperature of a heater and a correlated, heatable consumable item (eg, an induction heater and a container filled with heatable shaving cream) may be monitored and controlled. In such a design, an induction heatable nozzle, designed to connect to the container and to heat the fluid coming out of the latter, would be equipped with a temperature sensor according to the invention, while the container would be equipped with a magnetic field sensitive data item (eg a conventional microwire) correlated with the temperature sensor applied to the nozzle. The temperature sensor and the data element are correlated in such a way that the remagnetization response of the temperature sensor can only be decoded if both the temperature sensor and the data element are simultaneously subjected to an interrogating alternating magnetic field. This is usually accomplished by altering the decoding algorithm of the sensing device so that it does not detect or report object temperatures unless both the temperature sensor and the data element are present. When the container is placed in the induction heater in order to be heated, the temperature sensor and the data element are close to each other, and the sensor's re-magnetization responses can be detected and used for temperature detection.

This aspect of the invention is particularly advantageous since the manufacturer of the heater can make sure that only consumable items which he also manufactures can be used with the heater; that is, if the other manufacturer's consumable item is used with the heater, no temperature monitoring can occur because the other manufacturer's consumable item does not include the required magnetic field sensitive correlated data item. Also, the heater can be designed so that it will not function at all unless the proper consumable item is used.

The invention also provides systems for heating objects making use of a temperature sensor according to the invention. Such systems further include apparatus for heating the object, such as an induction or other heating unit, together with a re-magnetization response detector of the type described. A controller is also provided coupled to the detector and the heating apparatus, in order to receive output signals from the detector and to control the operation of the heating apparatus in response to said output signals. In these types of systems, the temperature of the object is monitored successively or continuously, and the controller varies the operation of the heating apparatus to heat the object or maintain it in a desired temperature range.

Brief description of the drawings

Figure 1 is a fragmentary, partial sectional view illustrating a prior art magnetic microwire element suitable for use in the present invention;

Fig. 2 is a graphical illustration of the magnetic characteristics of a microwire suitable for use in the present invention, at temperatures below the Curie temperature of the microwire alloy;

Fig. 3A is a graph of time versus re-magnetization of an amorphous strip typically used in conventional anti-theft EAS markers or labels;

Fig. 3B is a graph of time versus remagnetization of an amorphous microwire exhibiting a large Barkhausen discontinuity, used in markers or labels commercially available from Sensormatic Co .;

Fig. 3C is a graph of time versus re-magnetization of a glass-coated amorphous magnetic microwire produced with the Taylor method;

Fig. 4 is an essentially schematic cross-sectional view of a magnetic temperature sensor attached to an object of which detections are to be made and in accordance with a first embodiment of the invention;

FIG. 4A is an essentially schematic cross-sectional view similar to that of FIG. 4, but illustrating the components of a magnetic microwire temperature sensor divided between two objects designed to be placed in mutual proximity;

Fig. 5 is a schematic cross-sectional view of a temperature sensing element according to a second embodiment of the invention, representing a glass-coated amorphous microwire magnetic element, surrounded by a cylindrical jacket of a material of ferromagnetic metal or ferrite and having a desired Curie temperature;

ES 2 672 995 T3 Fig. 6 is an essentially schematic cross-sectional view of a magnetic temperature sensor according to the invention, which makes use of micro-wire data elements of the type illustrated in Fig. 1, and of temperature sensor elements according to illustrated in Fig. 5;

Fig. 7 is a schematic cross-sectional view of another temperature sensing element according to a third embodiment of the invention, showing glass-coated microwire magnetic elements as illustrated in Fig. 1 and located adjacent to a ferromagnetic metal material shield or ferrite having a desired Curie temperature;

Fig. 8 is an essentially schematic cross-sectional view of a magnetic element temperature sensor in accordance with the third embodiment of the invention, including data elements as illustrated in Fig. 1 and temperature sensing elements as illustrated in Fig. 7;

Fig. 9 is a graph illustrating the Curie temperature versus the percentage of copper for nickel-copper alloys suitable for use as jackets for the temperature sensing elements of the second embodiment of the invention, or as shields for the temperature sensing elements of the third embodiment of the invention;

Fig. 10 is a schematic block diagram of a temperature reader in accordance with the invention, which can function to interact with the magnetic element temperature sensors herein; and Fig. 11 is a schematic diagram illustrating a closed feedback temperature control induction heating unit based on magnetic element sensors in accordance with the invention.

Detailed description of the preferred embodiments

Prior Art Magnetic Elements and Sensing Systems

In order to better understand the present invention, it is useful to understand the nature and operation of current EAS and authentication systems that utilize magnetic elements (commonly referred to as "magnetic markers") and their corresponding detection systems. .

One of the frequently used types of magnetic element is a glass-coated amorphous microwire. These microwires, their production, their magnetic properties and their behavior below their Curie temperatures, have been disclosed in the technical and patent literature. See, for example, US Patent Nos. 6,441,737 and 6,747,559; Preparation and Characterization of Glass Covered Magnetic Wires, by Horia Chirac, Materials Science and Engineering A304-306, 166-71 (2001); The Preparation, Properties and Applications of Some Glass Coated Metal Filaments Prepared by the Taylor-Wire Process, from Donald et al., Journal of Materials Science, 31, 1139-48 (1996); Magnetic Properties of Amorphous Fe — P Alloys Containing Ga, Ge, and As, from Wiesner and Schneider, Phys. Stat. Sol. (A) 26, 71 (1974); and High Frequency Properties of Glass-Coated Microwires, by Antonenko et al., Journal of Applied Physics, vol. 83, 6587-89. Continuous lengths of microwires have been inexpensively produced by what is generally referred to in the art as the Taylor process, whereby either a pre-alloyed ingot or the required elemental components are fused in a disposed glass tube generally vertically and sealed at the bottom. Once the alloy has been converted to a molten state, using, for example, radio frequency ("rf") heating, the softened bottom of the glass tube is grasped and pulled into a continuous microwire. The rapid reduction in cross section of the alloy, coupled with the use of secondary cooling means, causes the alloy to become amorphous or nanocrystalline during drawing.

In Fig. 1, a typical microwire 20 is depicted, with an overall diameter that can range anywhere from ten or less microns to tens of microns. Wire 20 has an alloyed core 22, and a glass cladding 24, wherein the alloyed core 22 and the glass cladding 24 may be physically coupled to each other continuously or only at various spatially spaced points. The glass-to-metal ratio, although variable, can be tightly controlled. For example, the typical thickness of the glass coating 24 may be between approximately 1 and 5 microns for a microwire with a core diameter of between 45 and 60 microns, and typically between 1 and 3 microns for a microwire with a diameter 30 micron core. Microwire elements for EAS and authentication tags of the prior art are typically cut to lengths ranging from 15mm to 75mm.

The magnetic properties of the microwire and the resulting hysteresis loops can be controlled by varying the alloy composition and the glass-to-metal diameter ratio. FIG. 2 illustrates an idealized hysteresis loop magnetic response of a typical microwire 20 with a large Barkhausen discontinuity suitable for use in the present invention as described below. When such a microwire 20 is exposed to an external alternating magnetic field whose field strength, in the opposite direction to the

ES 2 672 995 T3 instantaneous magnetic polarization of the element, is greater than the coercive force Hc, which, in this case, is ideally shown to be less than 10 A / m, the re-magnetization process results in the generation of a Harmonic-rich impulse that is easily detected. Magnetic flux changes during the pulse give rise to a peak in the derivative of the flux with respect to time. Accordingly, a voltage spike will be observed in a receiving coil located in the vicinity of the element, and the reader can correlate the voltage spike with the presence of a microwire element in the field.

Prior art glass-coated amorphous microwires 20 produced by the Taylor method can be manufactured to exhibit very low coercivities (substantially less than 10 A / m), high relative permeabilities (substantially greater than 20,000), magnetostrictions of substantially zero or slightly positive value, and large Barkhausen discontinuities (which means that microwires exist essentially only in bimodal magnetic states).

The re-magnetization properties of the microwires 20 are also important, and differentiate these microwires from other types of magnetic elements of the prior art. Referring to Fig. 3C (see, US Patent No. 6,556,139), it will be seen that the width of the remagnetization peak (measured at the mid-amplitude level) was in the range of 25 to 80 microseconds for a glass-coated amorphous microwire. By contrast (see Fig. 3B), markers or labels commercially available from Sensormatic Co. comprise a water-molded amorphous wire with a large Barkhausen discontinuity, the peak width of which was in the range of about 200 to 500 microseconds or greater. Finally (see Fig. 3A), the peak width was approximately 1 to 2 milliseconds for amorphous strips typically used in anti-theft markers or labels, eg a 32 millimeter Meto GmbH marker or label. Thus, microwires of the type illustrated in Fig. 1 they have extremely short re-magnetization peaks that allow discrimination of the response of a microwire with respect to background noise, such as the corresponding one caused by the interaction of the field with other external objects.

Zhukov et al., J. Mater R. 15, No. 10 Oct. (2000) describe the production of multi-bit markers when multiple amorphous glass-coated metal wire segments are used, each exhibiting , a different dimension (length, gross diameter, etc.) or magnetic property (for example, coercive field). For example, if a plurality of magnetic microwire elements exhibit different coercivities, respectively, each of their unique re-magnetization peaks can be detected in each period of the magnetic field, and their pattern can be recognized, for example, through described methods in US Patent No. 4,203,544. US Patent No. 5,729,201 describes a method for differentiating said plurality of metallic wires, even if they have the same magnetic properties and dimensions. A permanent magnet polarization field element in the vicinity of the metallic wire serves to differentiate the amplitude of the external magnetic field generated by a reader, which is required to overcome the coercive force for the re-magnetization of each magnetic element, by means of its different proximity to each individual wire segment. This leads to a phase difference in the detected re-magnetization peaks, thus allowing the differentiation of the individual elements.

US Patent No. 4,134,538 describes multi-element labels (markers) made of magnetic elements, each characterized by a different coercive force and thus allowing the assignment to any fixed object , of a reference code with as many characters as the magnetic elements used. Each character of the reference code is thus assigned, respectively, to a magnetic element in the order of the values ​​of its respective coercive forces, so that the signals corresponding to each magnetic element then appear in the detection apparatus therein. offset order than the order of the coercive forces, and each of them with amplitudes corresponding to the values ​​assigned at the time of coding, thus reproducing the complete code in terms of layout and breadth.

US Patent No. 6,622,913 teaches that data information can be encoded in binary format using microwire elements of different diameters or permeabilities, such that they produce considerably different responses to an alternating magnetic field produced by a transmitter. Consequently, one type of microwire may have a binary "0" and the other a binary "1". For example, an array of four microwires, each with successively greater coercivities in such a way that they can be easily differentiated by their phase differences detected during a period of an incident alternating magnetic field, can be made to produce high and low amplitudes. , alternating, of field disturbances (and thus alternating high and low voltage amplitudes in the detector) so that they represent a binary pattern of 1010.

US Patent Application No. 2005/0109435 describes various magnetic and optical methods for encoding multi-bit information in a single microwire. The stress sensitivity of a microwire coated with ferromagnetic amorphous glass can be used advantageously as a physical basis for influencing the structure of the magnetic domain. Encoding with ferromagnetic amorphous glass coated microwires may be the result of a localized alteration of this domain structure. The alteration is easily accomplished by

ES 2 672 995 T3 by the imposition of localized stresses or by selective crystallization of the amorphous alloy. Such changes are affected by various means, including localized heating by means of a pulsed laser, chemical recessing of the glass coating, coatings on the glass, and the like. Localized modifications of the ferromagnetic amorphous glass coated microwire glass coating can be used to effectively produce controlled changes in the magnetic domain structure of the amorphous alloy cores, thus enabling their encoding. The preferred method is to use laser pulses to locally heat the glass or alloy (by selecting the wavelength independent heating can be achieved) which causes changes in the structure of one or both of the two, and therefore alters , the existing stress fields or the basic magnetic characteristics.

Typically, detection devices of prior art EAS or authentication systems used in combination with all types of magnetic elements used as magnetic markers use a field transmission unit and a magnetic field detection unit. The field transmitter generally has a frequency generator and a field generator coil (which together constitute a source of alternating magnetic field) to create the alternating magnetic field in the interrogation zone of the marker. Typically, the detection unit has a field receiver coil and a signal processing unit that typically activates an alarm device.

In prior art EAS systems, when a magnetic marker is located in the vicinity of the coils, the interrogating AC field causes the magnetization of the magnetic element to switch. Consequently, the field receiving coil receives very short pulses of magnetic field disturbances. These pulses are detected by the signal processing circuit, which produces an output to activate an alarm.

First embodiment: chemically modified microwires for the detection of Curie temperatures

The first embodiment of the invention comprises a magnetic microwire temperature sensor having at least one and usually a plurality of magnetically susceptible microwires, such that individual alloys of at least certain of the microwires exhibit modified chemistries and, consequently, different Curie temperatures, usually below about 400 ° C. Additionally, this embodiment includes a microwire reader or detector capable of decoding temperature information obtained from the sensor microwires.

The chemically modified individual microwires are preferably manufactured so that the modified microwires retain high Barkhausen discontinuities, extremely low coercivities, and extremely high permeabilities below their respective Curie temperatures (with resulting hysteresis behavior of the type depicted in Fig. 2). These modified microwires essentially lose their ferromagnetism above their Curie temperatures. Other microwires within the sensor array need not have modified chemistries, but may function as data elements according to any of the prior art single-bit or multi-bit encoding methods and that have been previously described.

The most preferred chemical modification of Fe-based and / or Co-based alloys that are used in amorphous microwires of the prior art is the adjustment of the atomic percentage of chromium present in them. The chromium in amorphous iron-based (Fe80-xCrx) (PC) alloys has a considerable effect on their magnetic properties. An increase in the percentage of Chromium causes the Curie temperatures, the mean hyperfine fields and their saturation magnetizations to decrease, and, on the other hand, causes their initial permeabilities to increase notably. For example, increasing the percentage of Chromium from 0% to 6.5% reduced the Curie temperature to between 330 ° C and 155 ° C in certain samples tested. See, for example, Magnetic Measurements of Iron-Rich Amorphous Alloys Containing Chromium: Moosbauer Study and BH Loops, by Henry et al., Journal of Materials Science 19: 1000-06 (1984); and Magnetic Properties of Metals-d-Elements, Alloys, and Compounds, by Wijn, Springer-Verlag, Berlin (1991).

Other mechanical changes on Fe-based and Co.-based alloys can also be used to alter the magnetic characteristics of amorphous microwire elements. For example, Co can replace Fe in certain FCZBN alloys, and the resulting Curie temperature exhibits a sinusoidal-type behavior with increasing Co content, and shows two maxima at 3 and 12.5 atomic% Co and a minimum of 7.5 atomic% Co (Co Dependence of Curie Temperature in Amorphous Fe Co Zr B Nb Alloys With High Glass Forming Ability, from Yao et al., Journal of Physical Science: Condensed Matter, Vol. 16 6325 -34 (2004). IEEE Transactions on Magnetics, Vol. 22, 1349-51 (1986) presents a process by which amorphous Co-P alloys with a high P content can be obtained electrolytically. The Curie temperature of these alloys exhibits a linear behavior in the Curie temperature relative to composition up to 28-29% P. For higher concentrations, a constant Curie temperature is observed.

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As explained above, the first embodiment preferably makes use of a plurality of magnetic microwire temperature sensing elements, the chemistries of which have been changed such that the microwires become paramagnetic at individual temperatures (typically 400 ° C or lower) within a specific design temperature range of the global temperature sensor. For example, Fig. 4 represents a temperature sensor 26 that has a total of four temperature sensor microwires 28-34 that form an array 36. Each of the microwires 28 to 34 has its chemistry modified using any of the above techniques, such as a Increasing atomic percentage of chromium, with the result that the Curie temperatures of the microwires are different, all of which are exceeded during the normal operating temperature range of the sensor 26. The remaining two microwires 38 and 40 are data items. An optional permanent magnetic bias field element 41 can also be used.

In the embodiment of Fig. 4, the microwires 28-34 are arranged in a parallel relationship where the spacing 42 equals the sum of the radii of each adjacent microwire (spacing 42 may be greater than the sum of spokes), and are held together by means of a thermally conductive adhesive (not shown) which also bonds the microwires to an object 44 of which the temperature is to be monitored.

In this exemplary embodiment, the magnetic coercivity of each microwire 28 to 34 and 38 to 40 is altered by appropriate chemical changes in their alloys, and specifically by the chromium content of each alloy, in order to ensure that each one of the six microwires is uniquely detectable within each period in its order of position within the total matrix. Obviously, other prior art approaches can also be used for this purpose to change alloy chemistry as well as to adjust coercivity. Additionally, each of the six microwires 28 to 34 and 38 to 40 has the same length (eg, 20mm) except for the microwire 38, which is significantly longer (eg, 40mm). This extra length of microwire 38 ensures that the re-magnetization peak detected from this data item microwire is greater in amplitude than all other re-magnetization peaks.

Fig. 10 illustrates an exemplary detector device 46 used to detect temperatures sensed by sensor 26, corresponding to the temperature of object 44. Detector 46 broadly includes an alternating magnetic field transmission unit in the form of a generator. frequency 48 coupled to a field generating coil 50, such that the transmission unit can function to create an alternating magnetic field in order to interrogate the sensor 26. The total device 46 further includes a field receiver coil 52 operatively coupled to a digital signal processing unit 54 and a temperature display module 56. As illustrated, the processing unit 54 is equipped with ports. communication ports 58 and 60, and may be operatively coupled to a frequency generator 48 via connection 62. Additionally, the frequency generator 48 may be equipped with an optional input 61 that allows remote control of the generator.

Signal processing unit 54 operates using a decoding algorithm having the ability to decode magnetic field disturbance information received upon interrogation of sensor 26. Preferably, the decoding algorithm is in the form of one or more look-up tables. for different sensors according to the invention, stored in memory associated with unit 54. In the case of a detector 46 specific to sensor 26, the temperature look-up table would have both the expected phase position (phase relationship with respect to the stop bit and / or one with respect to the other) for each of the four microwire elements temperature sensors 28 to 34, such as the temperatures to be reported for each of the acceptable detected bit codes from the array 36 of microwires 20 (some bit codes may be unacceptable as they do not make logical sense according to the Curie temperature order of the microwires in phase and are therefore the product of an erroneous reading by the detector 46).

As described, sensor 26 and sensing device 46 are in correlation such that device 46, by appropriate interrogation of sensor 26, can find out the temperature of object 44. Such correlation involves comparing the sensor's bit logic. 26 with the decoding algorithm (s), in this case, the temperature look-up table (s) stored in the signal processing unit memory 54. Those skilled in the art will appreciate that a wide variety of bit logic and corresponding algorithm tables can be provided. However, the following description provides an exemplary system in the context of sensor 26 and sensing device 46 of FIG. 10.

Referring back to FIG. 4, it is assumed that the least significant bit of the four temperature sensing element microwires 34 to 38 is microwire 28, which may be referred to as the "first" microwire. Thus, when the object 44 is below the Curie temperature of the first microwire 28, the microwire 28 will continue to produce its characteristic short re-magnetization pulse under the influence of the alternating magnetic field generated by the device 46. When the object 44 has a temperature above the Curie temperature of the first microwire 28, the microwire 28 will no longer produce its short remagnetization pulse under the influence of the applied alternating magnetic field, and therefore its bit (a value of "0") in the bit matrix of the detected temperature sensor elements.

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The remaining temperature sensing microwires 30 to 34 each have respective chemically modified alloys, such that the Curie temperatures of the microwires are, in successive and stepwise fashion, slightly higher than that of the first microwire 28. Thus, the "second" microwire 30 has a slightly higher Curie temperature than the first microwire 28, and the "third" and "fourth" microwires 32 and 34 each have successive Curie temperatures slightly higher than the lower order microwires. In this way, the remagnetization pulses (bits) of the microwires 30 to 34 will disappear (that is, they will become a value "0") under the influence of the magnetic field applied from the detector 46 at respective temperatures each one higher. than that of the first microwire 28 and all previous lower order microwires.

For example, if object 44 has a temperature below the Curie temperatures of both the first and second microwires 28 and 30, then device 46 will read all the bits from array 36 (that is, they will be converted to a value "1 ”). If the object 44 has a temperature above the Curie temperature of the first microwire 28, but below the Curie temperature of the second microwire 30, the first bit will have disappeared for the device 46 as a value "0", and the remaining bits corresponding to microwires 30 to 34 will be read as a value "1" by device 46.

As indicated above, device 46 contains algorithm (s) in the form of look-up table (s) that recognize that the disappearance of the first temperature bit and the appearance of the second and all temperature bits Higher mean that the object temperature 44 is somewhere between the first and second Curie temperatures of the first and second microwires (temperature bits) 28 and 30 (as used herein, Sensor or object temperature sensing or determination may refer to a single temperature or an approximate temperature within a range of temperatures). Thus, by reading the temperature detection bit data generated by matrix 36, and correlating the binary value of this data with the look-up table of interest, the temperature of object 44 can be determined within the temperature range defined by the constraint. between the Curie temperatures of the first and second microwires. Obviously, this logic applies to all four microwires 28 to 34 of the simple example of Fig. 4.

If the N temperature sensing microwires in a given temperature sensor of magnetic elements have identified Curie temperatures of known increasing sequential order, and these Curie temperatures are selected so that they are consistent, at least in part, with respect to their increments from one to the other, the sensor can detect temperatures from the first to the N^th Curie temperatures. The resolution of said sensor is the increment between sequential Curie temperatures. It will be appreciated that even if the sequential Curie temperatures are not exactly consistent, the relevant look-up table can be constructed, and the sensor can function properly.

The Curie temperatures of the microwire alloys in this embodiment can be quantified before or after the alloys have been processed into microwires. In this way, the entire microwire sensor can be calibrated for temperature detection. For a given temperature range to be measured, the greater the number of microwires whose Curie temperatures are quantified and are almost evenly spaced within the temperature range, the higher the resolution of the microwire temperature sensor. Preferably, the temperature sensors according to this embodiment have at least 20 temperature sensor microwires, each having sequentially higher Curie temperatures, and with a microwire number ranging from first to first. an N^th and with an increase between successive microwires not exceeding 5 ° C.

In cases where a certain temperature sensor microwire does not disappear in the correct sequence with the other microwires (due to an erroneous reading by the reader, a lack of thermal contact with the others, or another reason), the lack An acceptable value from the look-up table preferably causes the device's reader algorithm 46 to attempt to re-read sensor 26. If repeated and continuous readings show the same anomalous temperature data, the reader's algorithm can discard the temperature data, use the last measured temperature (or the last measured temperature plus a temperature increase that is based on a calculation involving the last measured rate of temperature change and the reading time interval), and then you can make a new attempt at the next planned reading interval. Preferably, measures are taken to ensure that all the microwires make good thermal contact with each other and with the object 44 whose temperature is to be measured. One such measure is to fix all the microwires to a thermally conductive thin substrate. Another measure is to use thermally conductive foaming or potting materials as described hereinafter.

It is known that, in a period, up to 40 microwires can be detected, and consequently a temperature sensor of magnetic elements in this embodiment can contain many more than four temperature sensing microwires 20 and many more than a data item (not counting the stop bit). Data items, especially if each of them is encoded with multi-bit data, can be used to store correlation information (such as linear or nonlinear relationship constants) that can

ES 2 672 995 T3 allow the detector algorithm to decode the "specific numerical value" (temperature bits) into its associated temperature value. This is particularly valuable when you are not using a query table method. Therefore, the magnetic element temperature sensor 26 can store, in its data elements, data such as a permanent ID code or an "object class" code. This ability to store an "object class" code allows a single reader algorithm to read several different types of microwire temperature sensors, each with its own unique look-up table, and still decoding the correct temperature.

It will be appreciated that, in sensor 26 and device 46, several different encoding / decoding strategies may be used without deviating from the scope of the present invention, provided that each temperature sensor microwire is designed to lose its pulse properties of re-magnetization under the influence of the alternating magnetic field generated by device 46 above its Curie temperature. One of the options would consist of the use of the polarization field element 41, which serves to differentiate the amplitude of the external magnetic field generated by the device 46 that is required to exceed the coercive force for the re-magnetization of each microwire, due to its different proximity to each individual microwire 28 to 34 and 38 to 40. This leads to a phase difference in the re-magnetization peaks detected by detector 46, thus facilitating the differentiation of the six individual microwires. Other variants would include, but are not limited to, means for determining a stop bit or "delineation" between temperature sensing elements and data elements, encoding and decoding of non-temperature data, and different lengths for part or all of the data. microwires in order to alter their magnetic responses. Additionally, changes in the magnetic properties at temperatures close to the Curie temperatures of the individual temperature sensor microwires can alter, but not completely eliminate, the detectable re-magnetization pulses thereof. Such altered re-magnetization pulses, which have predictable behaviors over specific temperature ranges below Curie temperatures, can also be used to decode temperature information. This can allow each temperature sensing microwire to accurately capture more than one temperature, for example, from a small range below Curie temperature to Curie temperature.

Microwires with ferromagnetic jackets for temperature detection

Another example comprises a magnetic element temperature sensor 64 having a plurality of composite temperature sensor microwires 66 each including a magnetically susceptible microwire of the prior art type previously described and showing no reduction. of its Curie temperature, such that it will retain its high Barkhausen discontinuity and other magnetic properties as depicted in Fig. two throughout the operating range of sensor 64. This microwire structure further includes a tubular, surrounding structure 68. The second assembly embodiment further includes a microwire temperature detector similar to detector 46, having algorithm ( s) stored (s) capable (s) of decoding the temperature information obtained from the interrogation of the sensor 64.

In particular, each of the composite microwires 66 has an internal alloy 70 surrounded by an intermediate glass coating 72, such that these interior parts of the composite microwires 66 are conceptually identical with respect to the microwires 20 of the prior art. described. Additionally, the structure 68 of the microwires 66 includes a tubular jacket 74 of ferromagnetic metal material or Ferrite (such as NiZn or MgZn) surrounding the coating 72, and an optional external glass coating 76 that surrounds the tubular jacket 74. Jacket 74 has a carefully selected Curie temperature so that the individual microwire inner alloy 70 will produce its distinctive disturbances (and thus re-magnetizing voltage pulses at the detector) only when the microwire is placed in the field. alternating magnetic generated by the detector, and then only above the Curie temperature (or above a certain temperature near the Curie temperature) of the ferromagnetic jacket 74. Thus, when the composite microwire 66 experiences a temperature below the Curie temperature of the ferromagnetic jacket 74 (or below a certain temperature close to this Curie temperature), jacket 74 is ferromagnetic, thus alternating the distinctive impulse of microwire 66. This may prevent a re-magnetization of the composite microwire 66 due to magnetic saturation caused by the jacket 74, or it may allow the resulting re-magnetization in the form of a polarized or "altered" signal from the composite microwire 66. For example, the re-magnetization pulse may be phase-shifted from its location above the Curie temperature of the jacket, or the polarizing effect of the jacket may allow altered re-magnetization responses below and above a plurality of different setpoint temperatures.

When composite microwire 66 experiences a temperature above the Curie temperature of jacket 74, the jacket becomes paramagnetic and therefore has no effect on the distinctive impulse of alloy 70. Therefore, above the individual Curie temperatures of the jackets 74 (or above certain temperatures close to these Curie temperatures), the composite microwires 66 act normally (that is, they cause the detector 46 to detect a voltage pulse as expected in phase, amplitude, or the like, as recorded in a look-up table or by some other algorithm

ES 2 672 995 T3 decoding). However, when the composite microhols 66 experience temperatures below the individual Curie temperatures of their jackets 74, they are either not detectable by the detector, or they are detectable but have altered magnetic properties, especially in relation to Distinctive pulses detected above Curie temperatures of their liners 74. Such altered magnetic properties would not match the parameters of the look-up table or other decoding algorithm, such as the phase relationship with respect to an alternating current of the frequency generator 48, or the duration of the pulses.

If the material constituting the tubular liner 74 is a ferromagnetic metal, the liner 74 can only be microns thick or the thickness that is required for saturation of the inner microwire alloy 70, and suitable for fabrication. A method of forming the ferromagnetic jacket 74 is described in US Patent No. 7,011,911, entitled "Amorphous Microwire and Method for Manufacture Thereot '. Other methods include flame spraying or sputtering. When these methods are used to create sleeve 74, there does not need to be an outer coating 76. A modified Taylor method can also be used, where an inner glass tube and an outer glass tube are aligned coaxially and telescopically, such that the inner glass tube resides within the walls of the outer glass tube. The alloy 70 is within the central glass tube in the form of an ingot (bar form) or constituent metal, while the material that constitutes the tubular jacket 74 is located between the glass tubes nested together. This jacket material can be in the form of an ingot (possibly several bars) or of constituent metal. The alloys are heated to melt by magnetic induction or other suitable means, and the resulting molten metal and glass are rapidly stretched to form a composite microwire 66.

Techniques for adjusting the Curie temperatures of ferromagnetic alloys by adding specific metal trace elements are known in the art. Thus, any number of alloys can be used to make tubular sleeves 74. Fig. 9 illustrates that small additions of certain metals (in this case Copper) to ferromagnetic metal elements (in this case, Nickel) to form a true alloy can alter the Curie temperature of the resulting ferromagnetic alloys in a predictable way. Furthermore, additions of small amounts of Chromium to Iron produce alloys whose Curie temperatures are predictable. For a description on modifying the Curie temperature of Nickel with Copper and Aluminum, see US Patent No. 5,954,989.

The Curie temperatures (or set temperatures close to the Curie temperatures) of the Ferrite alloys or materials used in the fabrication of the tubular sleeves 74 may have been quantified before or after the Ferrite alloys or materials have been processed to obtain tubular jackets 74. In this way, the magnetic element temperature detector 46 can be easily calibrated for temperature sensing. As before, for a given range of temperatures to be measured, the greater the number of composite temperature sensing microwires 66 whose jacket Curie temperatures are quantified and are almost evenly spaced within the temperature range, the greater the temperature sensor resolution. It is preferred to have at least 20 composite temperature sensing microwires 66, each exhibiting a sequentially higher jacket Curie temperature, at most 5 ° C above the next lower order jacket. Obviously, if the jacket 74 alters the re-magnetization pulse of the microwire 66 over a range of temperatures close to the Curie temperature of the jacket 74 (say, for example, by detectably shifting the phase of the re-magnetization pulse), it may be possible , for the detector, to detect and decode multiple temperatures for each microwire 66 within a certain interval, thus being necessary fewer microwires 66 to allow a sensor to accurately measure temperatures over a wide range.

If the material that makes up the tubular sleeves 74 is a ferrite or some mixture of materials with ferrite, then the sleeve can either be glued to the layer of glass 72, or to a separate cylindrical bead, or to another cylindrical object of Sintered ferrite with a central hole, such that alloy 70 and surrounding glass 72 can be placed there. Alternatively, the tubular jacket 74 could be formed as part of the glass layer 72 using a glass-ferrite material for the layer 72 instead of pure glass. US Patent No. 6,909,395, entitled "Radar Absorbing Coatings", describes a Ferrite / glass composite material that can be used either to adhere directly to a metallic wire or other metallic object, or it can be stick to a layer of pure glass that is already glued to the metal.

Referring now to FIG. 6, sensor 64 includes a plurality of microwires 20 presenting an array 78 of data elements, and a plurality of composite temperature sensor microwires 66 forming an array 80 thereof. Microwires 20 and composite microwires 66 are attached to a sensor or label substrate 82, which is as thin and thermally conductive as possible so that sensor 64 can be placed in intimate thermal contact with an object (not shown). in order to measure the temperature.

The microwires 20 that make up the matrix 78 exhibit chemistries that offer individual Curie temperatures above the planned operating temperature range typically below

ES 2 672 995 T3 about 400 ° C for sensor 64. Composite microwires 66 within array 80 are preferably separated from each other by a distance 84, such that the ferromagnetic or Ferrite tubular jacket 74 of each individual composite microwire 66 does not affect its neighboring composite microwire once the tubular jacket 74 of the individual microwire experiences a temperature above its Curie temperature.

In this simple embodiment, each data item in matrix 78 is assumed to be laser-coded to a logic state of "1" or "0". Also, each of the data items is assumed to be the same length (say, 20mm) except for terminal items 83 and 86, which are significantly longer (say, 40mm). This extra length ensures that the amplitude of the detected re-magnetization peaks of data items 83 and 86 is greater than that of the others. Finally, it is assumed that data item 83 is laser coded to a logic value "1" while data item 86 is laser coded to a logic value "0". As described in the first embodiment, each of the elements of both matrices 78 and 80 is made in such a way that the order of the detected phase coincides with the alignment order represented from top (microwire 83) to bottom ( composite microwire 88), the latter having the highest Curie temperature of the jacket, among the composite microwires of matrix 80. In such a case, the detector 46 assigns the first detected pulse (in phase relation) with the highest amplitude with a logic level "1" as the start bit (in this case, represented as microwire 83) and the last microwire data set 86 with the highest amplitude and with a logic level "0" as the stop bit. All of the data micro-wires between the start and stop bits 83 and 86 are detected by the micro-wire temperature reader as data bits. The intermediate data micro-threads can be used, as described in the first embodiment, for a variety of functions, such as a tag identification number and an "object class" code.

In order to decode the temperature information from sensor 64, it is assumed that there are "N" composite microwires of array 80 that have ferromagnetic jackets 74, such that all respective jackets 74 have Curie temperatures that are exceeded ( or have setpoint temperatures “close to” Curie temperatures) during the normal operating range of the sensor 64. The least significant bit of these N composite microwires 66, detected in phase relationship just after stop bit 86, and with a specified phase relationship relative to stop bit 86, is considered to be the "first" composite microwire 89. Thus, the first composite microwire 89 will begin to produce its normal short pulse disturbance only at temperatures above the Curie temperature of its 7 jacket 74, and therefore only then will detector 46 detect its voltage pulse (bit ). The first composite microwire 89 will not produce its normal short pulse disturbance below the Curie temperature of its jacket 74, and therefore either its bit will not be present in the bits detected by detector 46, or its pulse it will be altered so that it is clearly detectable by detector 46 as an "altered" microwire.

A "second" composite microwire 90 in phase relationship with respect to stop bit 86 (the next least significant bit) has a ferromagnetic jacket 74 of slightly higher Curie temperature than that of the first composite microwire 89. The composite microwire bit 90 will not be read by detector 46, or its voltage signal will be detected as "bumpy" at temperatures below this higher Curie temperature of the jacket (or higher temperature close to the Curie temperature of the jacket). shirt), but will still appear as expected for phase and duration at a temperature higher than that of the first composite microwire 89.

Thus, if sensor 64 is subjected to a temperature below that of the corresponding Curie temperatures (or designated temperatures below Curie temperatures) of both the first and second composite microwires 89 and 90, the detector 46 does not it will detect no composite microwires (assuming all subsequent higher order composite microwires in matrix 80 have jackets 74 with a higher Curie temperature). If the sensor 64 is subjected to a temperature above the Curie temperature of the jacket (or related temperature) of the first composite microwire 89, but below the Curie temperature (or related temperature) of the jacket of the second composite microwire 90, the first bit will be read by the detector 46 but the second bit will either remain unread by the detector 46 or will present an "altered" signal read by the detector. Finally, if sensor 64 is subjected to a temperature greater than the Curie temperature (or related temperature) of the jacket of both the first and second composite microwires 89 and 90, the detector 46 will read both the first and second composite microwires.

The detector 46 contains a decoding algorithm that recognizes the appearance of the first temperature bit of the first composite microwire 89, but the lack (or alteration) of the second temperature bit of the second composite microwire 90, and therefore signals by means of from the display module 56, that the sensor temperature is somewhere between the Curie temperature of the first jacket and the Curie temperature of the second jacket. Thus, if sensor 64 is brought into intimate thermal contact with an object whose temperature is of interest, then, by reading the bit output of the composite microwire array from sensor 64, detector 46 determines the temperature of the object within the temperature range defined by the boundary between the Curie temperatures of the first and second jackets (or between their respective temperatures close to their Curie temperatures).

ES 2 672 995 T3

If the number of compound microwires 66 in sensor 64 that have jacket Curie temperatures known to be in increasing sequential order is increased to "N" compound microwires, and these jacket Curie temperatures are selected so that they are at least partially consistent in their increments from one to the other, sensor 64 has a detectable range of temperatures from 1st to N.^esima jacket Curie temperatures, and has a temperature resolution defined by the increment between sequential jacket Curie temperatures.

More generally, the decoding algorithm of detector 46 is built to understand that the appearance of the temperature bits first at N-1^th generated by the corresponding composite microwires 66 in their normal pulse state, along with the missing temperature bit N^thcorresponding to composite microwire N^th 66 in its normal boost state, states that the sensor temperature is somewhere between the Curie temperature of the N-1 jacket^th and the Curie temperature of the jacket N^th (or between their respective temperatures close to the Curie temperatures of the shirts). Preferably, the detector algorithm reports that the temperature of this sensor is halfway between the Curie temperatures N-1^th and N^th.

Preferably, the acceptable bit patterns of the composite microwires and their corresponding sensor temperatures are stored in a look-up table within the memory of the detector 46. Thus, when the detector 46 detects an acceptable bit pattern from a correlated sensor 64, this pattern is compared to the look-up table to find the sensor temperature that is in correlation.

In the cases in which one or more composite microwires 66 of the matrix 80 do not appear in their normal state in the correct sequence with the others (due to an erroneous reading by the detector 46, to a lack of thermal contact with the others composite microthreads, or for some other reason), the detector algorithm preferably attempts to re-read sensor 64. If continuous repeated readings show the same anomalous bit pattern, the detector algorithm can discard the temperature data, use the last measured temperature (or the last measured temperature plus a temperature increase that is based on a calculation involving the last speed). temperature change measurement and the reading time interval), and then retry the next planned reading interval.

Microwires with independent yet adjacent ferromagnetic saturation elements for temperature sensing

Another possibility is conceptually very similar to the microwires with ferromagnetic jackets described above, and differs in the use of polarization or saturation elements of ferromagnetic jackets as independent entities that do not need to touch the surface of the adjacent temperature sensor microwires, as compared to sleeves 74 of the second embodiment that are attached, or otherwise attached, to the central microwire structure. Referring to Fig. 7, a combined microwire 92 is illustrated and includes a microwire 20 of the type previously described that does not exhibit any intentional reduction in its Curie temperature, such that it will retain its high Barkhausen discontinuity and other properties. magnetic as depicted in Fig. 2 throughout the sensor's operating range. In addition, the combined microwire 92 includes an adjacent ferromagnetic jacket 94. Jacket 94 is located close enough to associated microwire 20 to avoid magnetic saturation or polarization re-magnetization of microwire 20 and consequent generation of its distinctive disturbance until combined microwire 92 experiences a temperature above Curie temperature (or by above a certain temperature close to the Curie temperature) of jacket 94. Again, as in the case of the second embodiment, the sleeve 94 can be designed so that the associated microwire 20 exhibits a series of different re-magnetization responses below and above different setpoint temperatures below the set point temperature. Curie of the jacket, and, if desired, such multiple different responses can be used for temperature detection and determination.

In more detail, the sleeve 94 is preferably in the form of a thin, rectangular sheet of ferromagnetic metal whose size is not significantly larger than that of the associated microwire 20, and whose flat surface can be bent to obtain a semicircular profile ( or, in the case of Ferrite, it can be sintered obtaining a semicircular profile or in some other suitable way). The Curie temperature of the shield 94 is carefully selected so that the associated microwire 20 produces its signal disturbance (and thus a voltage re-magnetization pulse) when the combined microwire 92 is placed in an alternating magnetic field of the detector. 46, and only when the combined microwire 92 experiences a temperature above the Curie temperature (or above a certain fixed temperature close to the Curie temperature) of the jacket 94. The sleeves 94 are required to be only microns thick or a thickness necessary to saturate the associated microwire 20, and to facilitate their manufacture. In the manufacture of the sleeve 94, the same types of alloys or Ferrites described in connection with the second embodiment can be used. In addition, magnetic inks (which use either powder

ES 2 672 995 T3 ferromagnetic or ferrite powder), and they have the advantage of being able to be printed on a support substrate for the combined microwires 92.

Referring to Fig. 8, a temperature sensor 96 is illustrated that is identical, in all respects, to sensor 64, except for the use of combined microwires 92 in place of composite microwires 66. Accordingly, in Fig 8. Reference numerals equivalent to those in Fig. 6 are used to indicate identical components, and an "a" designation has been used to differentiate the combined microwires 92 from the composite microwires 66.

The operation of the sensor 96 is identical to that of the sensor 64 and makes use of a similar detector 46 that has suitable decoding algorithms (preferably look-up tables) correlated with the sensor 96. Therefore, a detailed description of this operation is not necessary. .

The embodiments described above, and indeed other embodiments within the scope of the present invention, can be varied in accordance with a number of different aspects. For example, Fig. 4A depicts an advantageous alternative arrangement for some product applications. Specifically, in Fig. 4A, a sensor 26a is provided in which the microwire data element 40 is attached to a first object 44a, while the remaining data microwire 38 and temperature sensing microwires 28 to 34, and the optional bias element 41 , are attached to a second object 44b. The bit logic of sensor 26a is identical to that of sensor 26, which means that even though the components of sensor 26a are separated into objects 44a and 44b, sensor 26a as a whole will only function when all components of the sensor are within the alternating magnetic field generated by detector 46. If this condition is not met, then no satisfactory reading can be produced using detector 46. This construction can be used, for example, to control the heating of a bipartite object by means of a heater, only if the detector of the heater detects the two parts of the sensor (and therefore the two objects 44a and 44b), and to correspondingly avoid any heating unless the two parts of the sensor are present and within the magnetic field of the detector 46. In such a case, the heater control would typically be coupled to the signal processing unit 54 of the detector 46.

Obviously, this same design concept can be used when more than two objects are present. Additionally, more sophisticated data encoding methods, such as those described above, can be used to correlate one or more components of the sensor 26a with corresponding components thereof. Such methods may include laser encoding the first data item 40, with a corresponding multi-bit code for the stop data bit 38.

Although the alternative of Fig. 4A has been described with reference to sensor 26 of the first embodiment, it will be appreciated that, if desired, the same modification may be used with sensors 64 and 96 of the second and third embodiments. realization.

The microwires that are part of the sensors 64 and 96, just as in the case of the microwires 20 of the sensor 26, can be attached to an object 44 or a thermally conductive substrate, such as substrate 82, using a suitable adhesive. In another alternative, the microwires 20, the composite microwires 66, and / or the combined microwires 92 can be embedded in a very thin, non-ferromagnetic, thermally conductive material, such as a graphite-filled polymeric material that is compression moldable or injection, such as one belonging to the family of materials marketed by SGL Carbon under the designation RIDURID®. Other usable high temperature resistant materials include ceramic potting materials available from Aremco under the designation Ceramamcast 510, or other flexible high temperature resistant polymers. With the use of materials of this type, the thickness and the overall thermal mass of the embedding material should be kept to a minimum value, in order to minimize the thermal delay between the object whose temperature is to be monitored and the alloyed materials. of the microwire core.

Additionally, the microwires of the described embodiments can be twisted into a strand or can be woven into the structure of an object whose temperature is to be monitored, if deemed appropriate. For example, microthreads can be woven into carbon fabric, provided that good thermal contact can be maintained and industry-appropriate means are used to distinguish each temperature-sensitive element from and to each other. clearly identified data items (to include a stop bit).

Closed loop feedback system for heating devices

The magnetic element temperature sensors and associated detectors of this invention can easily be used, in place, respectively, of the RFID tag and associated RFID reader, in closed-loop temperature-regulated induction heating systems. described in US Patent Nos. 6,320,169 and 6,953,919. Therefore, innumerable heating applications can be realized with an induction heating system with temperature-regulated magnetic element technology which is similar to previous RFID systems, but replacing the RFID components.

ES 2 672 995 T3 with the components of the present sensors and detectors. For example, according to the present invention a smart kitchen such as that described in US Patent No. 6,953,919, a thermal dispensing system as described in US Patent No. 6,822,204, a dispensing system can be modified. of elements as described in US patents 6,504,135, 6,444,961, 6,274,856, and 6,232,585, and various heating devices such as cups, bowls, refractory metal dishes, plates, ski boots and other items described in US Patent No. 5,594,984. Furthermore, the same components (sensor and detector) can be integrated into other types of closed-loop heating systems that are not based on inductive operation, such as resistive, halogen and infrared heating systems, with temperature controlled loop. closed.

Referring to FIG. 11, a closed loop induction heating system 98 includes a microwire detector 46 (see FIG. 10) incorporated into an induction heating device 100 in place of an RFID reader. Device 100 includes a control microprocessor 102 operatively coupled to detector 46, solid state inverter 104, and rectifier 106, as well as induction heating coil 108 coupled to inverter 104. An AC power supply 109 and a current sensor 109a are operatively coupled to the rectifier 106. The field generator and receiver coils 50 and 52 are integrated into a sensor component 110 located below a support member 112.

System 98 is designed to control the temperature of a graphite heating disk 114, as described in US Patent No. 6,657,170, having one or more built-in microwire sensors 116 of the present invention. Disc 114 has layers of graphite 118 above and below sensor 116 as shown. Obviously, instead of disk 114 any other induction heatable object can be controlled, such as a multi-layer cookware (eg, saucepan or frying pan) having one or more sensors 116 built into it. The feedback of temperature information from the sensor (s) 116 is detected by the detector 46, and this information can be used to control the induction heating of the disk 114 by means of the control microprocessor 102.

If desired, the microwire sensors and detectors of the invention can be used to control other types of heating devices, such as halogen or resistive heaters, or gas or electric ranges.