WO2015113086A1 - Sensor for detecting when a temperature threshold has been temporarily exceeded a single time - Google Patents

Abstract

The invention relates to a sensor for detecting when a threshold temperature T_S has been temporarily exceeded a single time, comprising at least one sensor element (1) with a sensor material consisting of a magnetocaloric alloy. The sensor material of the sensor element (1) transitions from a first state into a second state when the threshold temperature T_S is exceeded, and the sensor material has a different magnetizability in the first state compared to the second state. A detection unit (5) is provided with which the transition of the sensor material of the sensor element (1) from the first state into the second state can be directly or indirectly detected.

Description

 Sensor for detecting the single temporary exceeding of a threshold temperature

The invention relates to a sensor for detecting the single temporary transgression of a threshold temperature Ts, according to the preamble of patent claim 1.

Temperature monitoring units according to the invention are used in particular for monitoring biological material or for monitoring cold chains of foods or medical products.

The uninterrupted monitoring of a cold chain along production, transport and storage processes is essential for ensuring product quality in many areas, such as the food and pharmaceutical industries, as well as in medicine. To ensure product quality, it must be ensured in most cases that the temperature of the goods to be cooled is within a narrow tolerance range around an optimum temperature and that the temperature of the goods does not leave this tolerance range along the entire process or transport path. A single temporary leaving this tolerance temperature range can already lead to sustained damage or loss of quality of the product or refrigerated goods. For example, for frozen foods (optimum temperature, for example -18 ° C), a single short thawing (temperature> 0 ° C) could lead to premature spoilage and thus a health risk to consumers. The situation is often much more critical in the field of the pharmaceutical industry (temperature-sensitive drugs or active substances) and medicine (for example blood preserves, biological materials). There is thus great interest in low-cost, seamless monitoring of cold chains in many industrial or market sectors.

In order to ensure complete monitoring of the cold chain, therefore, a cost-effective sensor is desirable, with the one-time and short-term interruption of the cold chain can be reliably detected already.

Particularly advantageous is the integration of a complete cold chain monitoring in RFID transponders, since in addition to the temperature monitoring, all other essential parameters and data for the supply chain or process chain management can be detected.

At present, RFID-based systems for seamless cold chain monitoring, consisting typically of a simple electronic circuit with a temperature sensor, which are connected to an RFID transponder or integrated into an RFID transponder, are known from the prior art. A practically significant problem of current systems is that this electronic circuit has a own power supply, usually a battery, needed to ensure the complete usually electronic temperature monitoring, eg a temperature monitoring in which the temperature is measured and stored in certain time intervals. This fact makes the transponder relatively expensive and therefore only limited for bulk goods used and as a long storage at low temperatures reduces the operating life of batteries, is usually necessary for long storage times, the batteries. Furthermore, battery-containing RFID transponders are also problematic with regard to their disposal.

Furthermore, alloys are known from the current state of materials engineering, e.g. magnetocaloric alloys or shape-memory alloys that change their magnetic properties when exceeding or falling below certain threshold temperatures. For example, certain Mn-Ni-Sn-Co alloys (and others, see EP2280262 AI), when passing a certain threshold temperature Ts, show a transition from the paramagnetic state (relative permeability ~ 1) to a ferromagnetic state (relative permeability »1) or vice versa. This change in magnetic material properties is due to first-order phase transitions in the alloy.

Patent specification EP 2280262 A1 describes a temperature monitor based on the abovementioned material properties. Specifically, this is a long-used by electronic article surveillance systems (EAS) akustomagnetisches principle recourse. This principle is based on the phenomenon of magnetostriction, i. that special materials undergo a change in length by magnetization, or vice versa, the mechanical vibrations of a magnetostrictive material generates an alternating magnetic field. A magnetostrictive resonator, e.g. a resonant-length material chip may therefore be excited to mechanical vibration by an external alternating magnetic field (at resonant frequency, e.g., 58 kHz).

As an advantage of the invention in EP 2280262 AI above all the low cost and thus the use in the mass market are cited. An obvious drawback from a practical point of view is that the arrangement described in EP 2280262 A1 is a parallel solution to established RFID methods, ie, the (acoustomagnetic) temperature monitor can not meaningfully be integrated into RFID transponders and requires a separate (acoustomagnetic) readout unit becomes. That is, in addition to the RFID technology already established in many transportation and production lines, the acoustomagnetic readout method must be installed and integrated into the logistics system.

The aim of the invention is therefore to produce a sensor which overcomes the disadvantages arising from the prior art. The invention solves this problem with a It is provided that the sensor for detecting the single temporary transgression of a threshold temperature Ts, at least one sensor element comprising a sensor material consisting of a magnetocaloric alloy, wherein the sensor material of the sensor element when exceeded the threshold temperature Ts passes from a first state to a second state and in the first state relative to the second state has different magnetizability, wherein a detection unit is provided, with the indirectly or directly the transition of the sensor material of the sensor element from the first state to the second state detectable is.

Particularly advantageous embodiments of the sensor for monitoring cold chains are defined by the features of the dependent claims:

The read-out of the states of the sensor and the sensor material is facilitated by the detection unit, in particular passive, RFID and / or NFC transponder for data transmission to an external data communication device, downstream of the respective state of the sensor element when activated by the external data communication device transmits the data communication device. The exceeding or falling short of the predetermined threshold temperatures can thus be detected directly via the RFID interface, without additional effort.

An advantageous embodiment of the sensor is provided if the sensor material of the sensor element has a first-order phase transition and is magnetic in at least one phase, and / or has a broad temperature hysteresis.

An easily implementable detection of the change in state of the sensor material of the sensor element is achieved in that the detection unit comprises at least one coil, wherein the sensor element is arranged in the field space of the coil and electrically insulated therefrom, and wherein the detection unit for measuring an inductance change of the coil with the coil electrically connected. In this case, the space requirement of the sensor is reduced when the sensor element is designed as the core of the coil and / or that the sensor element is designed as a carrier body of the coil.

The detection sensitivity can be increased by the sensor having two coils, namely a stimulator coil and a measuring coil, wherein the sensor element is designed as a magnetic coupling element and is preferably formed as a common core of the two coils or as a carrier material of the two coils and / or the sensor element is arranged between the two coils. An alternative sensor device according to an electromechanical principle is provided in that the sensor has an at least partially electrically conductive carrier part, two electrical contacts and a magnet, wherein the detection unit is designed to detect a conductive connection of the electrical contacts, wherein the sensor element on the carrier part is the magnet is arranged opposite, wherein the sensor element in the second state can be brought into interaction with the magnet and the carrier part connects the contacts.

An external cooling for activating the sensor element is omitted if the sensor has an activation unit for activating the sensor element comprising a soft magnetic material and a preferably mounted on the soft magnetic material coil and wherein the soft magnetic material is magnetizable through the coil, wherein the hysteresis curve and / or the threshold temperature Ts of the sensor element is displaceable by the magnetized soft magnetic material.

An activation of the sensor material of the sensor device is not required if the sensor has a base body made of non-electrically conductive material, a non-ferromagnetic carrier mounted on the base body, in particular rotatable, tiltable or translational, on which the sensor element is arranged, at least one on the Body arranged first permanent magnet and at least one arranged on the carrier permanent ferromagnetic first piece of material, wherein the first piece of material is disposed in the active region of the first permanent magnet, wherein the sensor element changes the position of the carrier when changing from the first state to the second state, wherein the detection unit is designed to measure the position of the carrier comprises.

A particularly flat sensor is provided when the carrier, in particular in the form of a cylindrical disk, is arranged rotatably on the base body and on the carrier a first sensor element with threshold temperature Tsi, a second sensor element with threshold temperature Ts ₂ and one to the second sensor element subsequently arranged permanently ferromagnetic material _piece is arranged, wherein the threshold temperature Tsi> Ts ₂ and / or Tui <T _u2 , on the base body of the first permanent magnet, a second permanent magnet and a third permanent magnet are arranged, wherein the third permanent magnet is formed and arranged that that the torque of the carrier caused by the magnetic interaction between the third permanent magnet, the permanent ferromagnetic piece of material and the sensor material located in the second state is greater than that torque caused by the magnetic interaction between the second permanent magnets, the permanent ferromagnetic material piece and the sensor material located in the second state is caused, and wherein the first sensor element is arranged on the carrier in the effective range of the first permanent magnet, and wherein the permanent ferromagnetic piece of material is arranged in the effective range of the second permanent magnet and the second sensor element is arranged in the effective range of the third permanent magnet, and / or in a starting position, the first sensor element is arranged on the carrier in the immediate vicinity of the first permanent magnet, the permanent ferromagnetic piece of material in the immediate Near the second permanent magnet and the second sensor element is arranged in the circumferential direction between the second permanent magnet and the third permanent magnet.

An alternative embodiment of the sensor device is achieved in that the carrier, in particular about its center, is arranged tiltably on the base body and at one end of the carrier a first sensor element with threshold temperature Tsi and on the first sensor element opposite end of the carrier second sensor element with threshold temperature Ts _2nd is arranged, wherein the threshold temperature Tsi> Ts ₂ and / or Tui <Tu ₂ , wherein on the base body, the first permanent magnet and a second permanent magnet are arranged, wherein a respective permanent magnet with respect to the first and second sensor element is arranged, wherein the first piece of material in Effective range of the first permanent magnet is arranged on the carrier and a second piece of material is arranged in the effective range of the second permanent magnet on the carrier.

The size of the sensor is further reduced if the carrier is arranged to be translationally movable on the base body between the first permanent magnet and a second permanent magnet, and at one end of the carrier a first sensor element with threshold temperature Tsi and on the first sensor element opposite end of the carrier second sensor element with threshold temperature Ts _{2 is} arranged, wherein the threshold temperature Tsi> Ts ₂ and / or Tui <Tu ₂ , wherein the first permanent magnet and the second permanent magnet are arranged on the base body, wherein a respective permanent magnet with respect to the first sensor element and the second sensor element is arranged wherein the first piece of material is arranged in the effective range of the first permanent magnet on the carrier and a second piece of material is arranged in the effective range of the second permanent magnet on the carrier.

Biological material, or chilled foods, can be monitored particularly well if Tu is between -100 ° and + 20 ° C and / or Ts between -30 ° C and + 100 ° C and / or the difference Ts - Tu = 5 to 80 ° C is.

The threshold temperature Ts and the operating temperature Ts-Tu can be set particularly well if the sensor element consists of one of the following alloys: Gd5 (SilxGex) 4, Ni-Mn, Ni-Mn-Ga, Ni-Mn-In ( Co), La-Fe-Si, La-Fe-Si-Co, La-Fe-Si-Co-B, La-Fe-Si-Cu, La-Fe-Si-Ga, La (Fe, Si, Co ), LaFexSil-x, La (Fe, Si) 13, RCo2 with R (R = Dy, Ho, Er), DyA12, DyNi2 Tb-Gd-Al, Gd-Ni, Mn-As-Sb, MnFe-P -as. A particularly suitable application of the sensor is provided if an RFID and / or NFC transponder comprising a sensor integrated in the RFID and / or NFC transponder according to one of the preceding claims.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

The invention is illustrated schematically below with reference to particularly advantageous, but not limiting exemplary embodiments in the drawings and is described by way of example with reference to the drawings:

Fig. 1 shows a first order phase transition of a magnetocaloric alloy. Fig. 2 shows hysteresis curves of magnetocaloric alloys. FIGS. 3a to 3c show three embodiments of the invention. 4 shows the structure of an RFID / NFC transponder according to the invention. 5a to 5c, 6 and 7 show further embodiments of the temperature sensor. Figures 8a and 8b show an embodiment with electromechanical detection. Fig. 9a shows an embodiment with activation unit. Fig. 9b shows a shift of a hysteresis curve by application of an external magnetic field. Fig. 10 shows hysteresis curves of sensor elements. FIGS. 11a to 11c show a further embodiment of the temperature monitor in the starting position. FIGS. 12a to 12c show the embodiment of the temperature monitor in the detection position shown in FIGS. 11a to 11c. 13a shows a further embodiment of the temperature monitor in the starting position. FIG. 13b shows the embodiment of the temperature monitor shown in FIG. 13a in the detection position. Fig. 14a shows a further embodiment of the temperature monitor in the starting position. FIG. 14b shows the embodiment of the temperature monitor shown in FIG. 14a in the detection position.

Fig. 1 shows so-called first-order phase transitions of a magnetocaloric alloy in which the material has a pronounced temperature hysteresis. The transition from the paramagnetic to the ferromagnetic state occurs at higher temperature Ts than the return from the ferromagnetic state to the paramagnetic state at the temperature Tu- The threshold temperature Ts for the phase transition, as well as the slope and the width of the temperature hysteresis curve can be determined by the alloy composition , adjust the manufacturing process of the alloy, as well as by thermal aftertreatment within certain limits. With currently available magnetocaloric materials hysteresis curves with widths of about 20-30 K at response temperatures in the range of about 120-600 K can be realized. In addition, materials with "erratic" changes from the paramagnetic to the ferromagnetic state without pronounced temperature hysteresis are also known Response temperatures Tu and Ts shift by impressing an external magnetic field. In Fig. 9b, such a hysteresis curve is shifted approximately along the temperature axis.

Furthermore, among the magnetocaloric materials and shape memory alloys, those are also known which show a so-called "virgin effect", ie the hysteresis curve and thus at least one Anp talk temperature looks different during the first cooling or where it is different than in the subsequent temperature cycles In the lower part of Fig. 2, for example, the solid curve shows the course of the magnetization during the first cooling, the dot-dash curve the course during reheating after the first cooling and finally the dashed curve the magnetization during the renewed cooling of the material ,

Finally, with many of these materials, it is also possible to trigger the transition from paramagnetic to ferromagnetic state and vice versa by mechanical stress.

A first embodiment of a sensor according to the invention is shown in FIGS. 3a to 3c. The sensor element 1, consisting of a magnetocaloric sensor material, is brought into the immediate vicinity of a coil 3. In the case of cylindrical coils, the sensor element 1 forms, for example, the carrier body of the coil winding or the coil core (FIG. 3 a). In an embodiment shown in Figs. 3b and 3c, the coil 3 is formed as a flat coil, e.g. in the form of printed or photolithographically produced flat coils. The sensor element 1 is applied to and / or below the coil 3 (FIGS. 3b and 3c). The coil 3 is electrically insulated from the sensor element 1 by a foil or an insulator attached to the coil windings 31.

Since the inductance L of a coil 3 generally depends on the magnetic permeability of the field space immediately surrounding the coil 3, a change in the inductance L of the coil 3 is to be expected on the transition of the sensor material of the sensor element 1 from the paramagnetic to the ferromagnetic state. This inductance change can be detected by a detection unit 5, as shown schematically in FIG. 4, with a simple electronic circuit.

The coil 3, the sensor element 1 and the detection unit 5 can, as shown in FIG. 4, be integrated into a low-cost, passive RFID and / or NFC transponder 4. The information about the magnetic state of the sensor material of the sensor element 1 and thus the information as to whether the temperature threshold Ts has ever been exceeded can be based on the RFID technology wirelessly through a transponder 4 with antenna 43 via an RFID / NFC radio link 45 to an external data communication device 44 are transmitted (Fig. 4). The detection of exceeding a predetermined threshold temperature Ts is based on a first-order phase transition of a magnetocaloric or shape memory alloy ("sensor element") .When a predetermined threshold temperature Ts is exceeded, the magnetic material properties of the sensor material of the sensor element 1 change from paramagnetic to ferromagnetic Sensor element 1 is integrated in an RFID transponder and the para- or ferromagnetic state of the sensor element lwird detected by means of an electronic circuit.

The detection of the magnetic state of the sensor element 1 and the associated change in the inductance of the coil 3 can be determined in various ways known from the prior art. These are in particular:

 • Measurement of the impedance of the coil 3 formed as a measuring coil and comparison with a predetermined impedance threshold

 Comparative measurement of the inductance of a reference coil and the inductance of the coil 3

• Determination of the resonant frequency of a resonant circuit containing the coil and comparison with a predetermined resonant frequency

 Comparative measurement of the resonant frequency of a resonant circuit containing the coil 3 with the resonant frequency of a reference resonant circuit

 • Measurement of voltage rise times on the coil 3 at a given current through the coil 3 and comparison with a predetermined threshold for the voltage rise time

 Comparative measurement of the voltage rise time at coil 3 and the voltage rise time at a reference coil at given currents through measuring coil and reference coil

Embodiments of the invention are shown in FIGS. 5a to 5c, in which the exceeding of a threshold temperature Ts is indicated by changing the magnetic coupling of two coils 3a and 3b through the sensor element 1. The sensor element 1 is brought as a magnetic coupling element in the immediate vicinity of the two coils (inductors). In the case of cylindrical coils, the sensor element 1 forms, for example, a common carrier body of the coil windings 31 or a common coil core (FIG. 5 a). For flat coils, e.g. In the form of printed or photolithographically produced coils 3, the sensor element 1 can be applied to and / or below the two coils 3 (FIG. 5b, FIG. 5c). One of the two coils serves as a commutator coil 3 a, the other as a measuring coil 3b. The magnetic coupling or the mutual inductance between stimulator 3a and measuring coil 3b thus significantly depends on the magnetic properties of the sensor material of the sensor element 1.

The transition of the sensor material from the paramagnetic to the ferromagnetic state also increases the magnetic coupling of exciter 3a and measuring coil 3b. An electrical current fed into the excitation coil 3a induces, in the case of the ferromagnetic state of the sensor material, a greater voltage in the measuring coil 3b than in the paramagnetic state of the sensor material. In this case, the detector unit 5 measures this voltage difference and forwards it to a communication controller 42 or compares it, for example, with a comparison value stored in a memory 41. The voltage change, a comparison value or a simple binary signal can then be transmitted on request of an external data communication device 44 by means of wireless RFID / NFC connection 45.

Accordingly, the voltage at the measuring coil 3b serves as an indicator for the magnetic state of the sensor material of the sensor element 1. The coil arrangement comprising the coils 3a and 3b and the sensor element 1 and the detection unit 5 can in turn be converted into a low-cost, passive RFID and / or or NFC transponder can be integrated, so that the information about the magnetic state of the sensor material and thus the information as to whether the temperature threshold Ts has ever been exceeded can be wirelessly transmitted to an external data communication device 44 on the basis of RFID technology (FIG. 6). ,

Alternatively, arrangements of coils 3 and sensor element 1 are possible in which the voltage induced in the measuring coil 3b is lower in the ferromagnetic state of the sensor element 1 than in the paramagnetic state of the sensor element 1. FIG. 7 shows such an alternative arrangement. The sensor element 1 is arranged between the two coils 3, whereby the voltage induced in the measuring coil 3b is increased or reduced.

Another embodiment of the invention is shown in Figs. 8a and 8b. The transition of the sensor material of the sensor element 1 into the ferromagnetic state can also be detected in an electromechanical manner, as shown schematically in FIGS. 8a and 8b. In this case, the sensor element 1 is applied to an elastic and non-ferromagnetic carrier 8 firmly clamped on one side and arranged at a small distance from a permanent magnet 9. At least one part 81 of the carrier is electrically conductive, so that when the carrier 8 is deflected in the direction of two contact springs 6 and 7 opposite the metallic carrier part 81, the two contact springs 6 and 7 are electrically conductively connected. During the transition of the sensor material in the ferromagnetic state, this is attracted to the permanent magnet 9, whereby the carrier 8 bends in the direction of the contact springs 6 and 7 and makes an electrical contact between the contact springs 6 and 7, which can be easily detected. In addition to the embodiment illustrated in FIGS. 8a and 8b, many other methods known from the prior art for detecting the position / position of the carrier 8 or of the sensor element 1 can also be used, for example capacitive proximity switches. With the arrangements described above, it is therefore possible to detect the one-time and temporary exceeding a predetermined upper threshold temperature Ts as long after the time of exceeding, as long as between the time of exceeding Ts and the detection time, the lower temperature threshold Tu was not exceeded this would bring the sensor material back to its original state. By arranging two different sensor elements, each with a corresponding coil arrangement with corresponding lower and upper threshold temperatures Tu, Ts, however, a possibly occurring "reset" can be reliably detected.

The embodiments described in FIGS. 3 to 8 can be integrated in thin RFID transponders constructed in the form of multi-layered foils, wherein in principle no restriction to a specific RFID technology is necessary. Naturally, preferred RFID frequency bands or technologies are those currently used in supply chain and process chain management, ie inductive coupling and load modulation based technologies in the frequency ranges 120-140 kHz, and 13-14 MHz, as well as on Backscatter coupling based RFID technologies in the UHF range of 800-1000 MHz and in the microwave range of 2.4-2.5 GHz. Using 13.56 MHz NFC-compatible RFID technology would not only provide manufacturers and suppliers with the ability to detect cold chain interruptions, but also consumers. Thus, any consumer equipped with an NFC-enabled mobile phone and associated application could check directly on site, for example in the grocery store or in the pharmacy, whether the frozen food or chilled goods selected by him were completely cooled below a predetermined critical threshold temperature Ts.

In the abovementioned embodiments described in FIGS. 3 to 8, activation, arming, of the sensor is necessary, which is explicitly necessary whenever the manufacturing or storage temperature of the sensor element 1 is above the upper temperature threshold Ts to be monitored. which is usually the case with sensors for monitoring cold chains. In this case, the sensor material of the sensor element 1 is already in the ferromagnetic state before attaching the sensor to the product to be monitored and must first be brought into the paramagnetic state. If this is possible with regard to the product to be monitored, this may be done by cooling the product with the sensor attached below Tu after attaching the sensor to the product. If this is not possible, then the previously activated sensor element 1 can be applied to the already cooled below Ts product immediately before mounting. Alternatively, the sensor may be attached to the product even at temperatures above Ts and cooled together with the product to the set temperature range between Tu and Ts. Subsequently, the sensor element 1 can be activated by local cooling below Tu. With a superficial arrangement of the sensor element 1 on the sensor, in particular in the case of a film-like sensor structure, the local cooling of the sensor element 1 required for activation can take place, for example, by targeted spraying with cold spray or by contact with a cold source.

Further possibilities for activation or "arming" of the sensor can be carried out in certain sensor materials of the sensor element 1 by a magnetization of the sensor material by permanently applying a magnetic field. This causes a shift of the hysteresis curve by the magnetic field. An example of a suitable arrangement is shown in FIG. 9a in a schematic side view. The embodiment described in FIG. 9 a has a similar construction to the embodiment described in FIG. 6. In addition to the detection unit 5, the exciting coil 3a, the measuring coil 3b, the communication controller 42, the memory 41 and the antenna 43, the sensor integrated in a transponder 4 has an activation unit 12 with soft magnetic material 14 and a coil 13 wound around it.

The soft magnetic material 14 is unmagnetized in the initial state, after mounting the sensor on already cooled product in the temperature range between the lower temperature threshold Tu and the threshold temperature Ts and has a remanent flux density of zero. Without magnetization by a permanent magnetic field, at least the transition temperature from the paramagnetic to ferromagnetic state of the sensor element 1 is above the storage temperature or production temperature Tp of the sensor (FIG. 9b) and thus at the same time very far above the temperature threshold Ts to be monitored. After attaching the sensor to the refrigerated goods and cooling to the target temperature T (Tu <T <Ts), the sensor is activated by magnetization of the soft magnetic material 14, by the activation unit 12 with coil 13, since thereby the remaining soft magnetic material 14 Remanenzflussdichte the sensor element 1 is magnetized so far that the hysteresis curve shifts into the area of application of the sensor (Tu <T <Ts). The magnetization of the soft magnetic material 14 may alternatively be done from the outside by a placed in the vicinity of the sensor element 1 permanent or electromagnet or via the external data communication device 44, as shown in Fig. 9, for example in the course of initialization / introduction into the RFID-monitored supply Chain Management System. On the basis of current materials research, it can also be assumed that sensor materials which themselves have suitable soft magnetic properties will also be available in the very near future, so that the soft magnetic material 14 shown in FIG. 9 can be dispensed with when using such materials. As an alternative to the described embodiments, monitoring of the undershooting of a threshold temperature Tu can also be used when selecting corresponding sensor materials of the sensor element 1, or the transition from magnetic to paramagnetic state can be detected and used to indicate that the temperature has fallen below a minimum.

FIGS. 11a to 14b show further embodiments of the invention. With these embodiments, sensors for detecting the one-time temporary overshoot of a threshold temperature Ts, without the need for an explicit activation of the sensor realized. The embodiment shown in FIGS. 11a to 11c comprises a main body 10 of non-electrically conductive and non-ferromagnetic material and a non-ferromagnetic carrier 11 which is rotatably mounted on the main body 10 and which is designed as a circular disk. On the support 11, a first sensor element 1a connected thereto is composed of a magnetocaloric sensor material with pronounced temperature hysteresis and transition from the ferromagnetic state to the paramagnetic state at the lower temperature threshold Tui and temperature threshold Tsi (FIG. 10) and a second sensor element 1b a magnetocaloric sensor material with very little or no temperature hysteresis and response temperature Ts ₂ slightly above Tui (Fig. 10) attached. On the support 11, a first permanent ferromagnetic piece of material Fl is further applied. The first sensor element 1a is arranged diametrically opposite the first permanent ferromagnetic material piece F1 on the circumference of the carrier 11, the second sensor element 1b likewise lies, like the first material piece F1, on the circumference of the carrier 11 and closes against the first permanent ferromagnetic material piece F1 at.

On the base body 10 is a, in each case fixedly connected to the base body 10, the first permanent magnet Ml, second permanent magnet M2 and third permanent magnet M3 mounted, wherein the third permanent magnet M3 stronger, a higher holding force or magnetization has or is greater than the second permanent magnet M2. The first permanent magnet Ml is arranged on the base body 10 with respect to the first sensor element 1a, or in its effective range. The second permanent magnet M2 is fastened to the first permanent ferromagnetic material piece F1, attracts it and aligns the carrier 11. The larger third permanent magnet M3 is arranged in the effective region of the second sensor element 1b and is spaced therefrom along the circumference of the carrier 11.

In order to determine the position or position of the carrier 11, contacts 6 and 7 are fastened with electrical conductor tracks to the detection unit 5 on the base body 10 and an electrically conductive surface 15 for the capacitive determination of the carrier position on the Bottom of the carrier 11 attached. However, all other methods known from the prior art for detecting the position of the carrier 11 are also usable.

11a to 11c show different views and illustrations of this embodiment of the invention in the starting position, which is produced in the production of the sensor device, it being assumed that an ambient temperature T> Tsi prevails in the production of the sensor (see FIG. , Both the sensor material of the first sensor element 1a and the sensor material of the second sensor element 1b are thus in the ferromagnetic state. If the first sensor element la supplied in the ferromagnetic state for sensor mounting, it is sufficient in the sensor mounting and an ambient temperature between Tui and Tsi. On the base body 10, the three permanent magnets Ml, M2 and M3 are arranged. On the opposite to the base body 10 rotatably mounted carrier 11 of electrically and magnetically non-conductive material, the first sensor element la and the first permanent magnet Ml are arranged such that the first sensor element la is held by the magnetic forces of the first permanent magnet Ml in its immediate vicinity and the first permanent-ferromagnetic piece of material Fl is held by the magnetic forces of the second permanent magnet M2 in its immediate vicinity. In addition, in addition to the third permanent magnet M3 in the direction of rotation to the third permanent magnet M3, the second sensor element lb. The ratios of the size and magnetic forces of the permanent magnets Ml, M2, M3 and the first piece of material Fl, and their arrangement, and the size and permeability of the first and second sensor elements la, lb, in the ferromagnetic state are coordinated such that the in Fig 11a to 11c can be produced during the sensor production and remains stable for T> Tui, the third permanent magnet M3 being made stronger / larger than the second permanent magnet M2. Although in the starting position of the carrier 11 there is a force on the second sensor element lb in the direction of the third permanent magnet M3, but by the attractive forces between the first sensor element la and the first permanent magnet Ml, as well as between the second permanent magnet M2 and the permanent-ferromagnetic piece of material Fl the approximation of the third permanent magnet M3 and the first sensor element lb, and thus prevents the rotation of the carrier 11 to the base body 10. In this initial position, the sensor can be mounted on the refrigerated goods even at temperatures> Tui. As a result of the following cooling process below Ts ₂ , first the sensor material of the second sensor element 1b loses its ferromagnetic properties, and immediately afterwards also the sensor material of the first sensor element 1a (see FIG. The carrier 11 is thereafter held exclusively in a position corresponding to the starting position by the magnetic forces exerted on the first permanent ferromagnetic material piece F1 by the second permanent magnet M2. The sensor is now activated or "armed" in this state If it is exceeded in this activated state the threshold temperature Ts ₂ , the sensor material of the second sensor element lb ferromagnetic and there is a resulting attractive force of the second sensor element lb in the direction of the stronger third permanent magnet M3. Due to the now lack of force between the first permanent magnet Ml and the first sensor element la, there is a rotational movement of the carrier 11, so that the second sensor element lb and the first permanent-ferromagnetic piece of material Fl come to lie in close proximity to the third permanent magnet M3. 12a to 12c show this "detection position", which is also approximately maintained stable.When the temperature Ts ₂ after the rotational movement again falls below this position is maintained, since the first permanent ferromagnetic material piece Fl held by the third permanent magnet M3 in position becomes.

With a suitable arrangement and tuning of the permanent magnets Ml, M2, M3 and permeabilities or sizes of the sensor materials of the sensor elements la, lb and the permanent ferromagnetic piece of material Fl, the detection position is maintained even if Tsi is exceeded and the first sensor element la changes to the ferromagnetic state ,

The determination of the position of the carrier 11 or the detection of the detection position can take place in various ways known from the prior art. In the embodiment illustrated in FIGS. 11a to 11c and 12a to 12c, this takes place on the basis of a change in the capacitance, conductivity or impedance between two electrodes 6 and 7 mounted or printed on the base body 10. This change results directly from the detection position over the electrodes 6 and 7 located metal surface 15, which is arranged on the underside of the carrier 11 at a corresponding location. The connection lines of the electrodes 6 and 7 are fed to a detection unit 5 integrated in an RFID transponder (compare FIGS. 4 and 6). Alternatively, of course, inductive methods according to the principles shown in FIGS. 3 and 5 as well as contact-based detection methods on (spring) contacts, position switches, etc. possible. In the manner described above, an automatically activating RFID compatible temperature monitor for cold chain monitoring can be realized.

An alternative and particularly simple embodiment of a self-activating temperature monitor based on magnetocaloric principles is shown in FIGS. 13a, 13b in a side view. On a base body 10, two permanent magnets Ml and M2 and a support 16 for a carrier 11 are attached in the form of a two-sided lever. The lever protrudes on each side in each case via one of the permanent magnets Ml or M2. At one end of the lever, in the region of the first permanent magnet M1, a first permanent ferromagnetic material or metal piece F1, as well as a first sensor element 1a are fastened. At the other end of the lever is a second permanent ferromagnetic material or metal piece F2 and a second one Sensor element lb in the region of the second permanent magnet M2. As part of the sensor production (both sensor materials ferromagnetic), the lever is positioned in the starting position. Due to the magnetic force effect, this starting position remains stable as long as the torque generated by the first permanent magnet M1, the first permanent ferromagnetic material piece F1 and the first sensor element 1a is greater than that by the second permanent magnet M2, the second permanent ferromagnetic material piece F2 and the second sensor element lb generated torque. The force ratios or torque ratios are adjustable by the choice and position of the permanent magnets Ml, M2, or the permeabilities of the sensor materials of the sensor elements la, lb and the permanent ferromagnetic materials Fl, F2 and their position along the lever. In the form / initial position shown in FIGS. 13a and 13b, the sensor can be mounted on the goods to be cooled (even at temperatures> Tsi). As a result of the cooling of the sensor below Tui, first the second sensor element 1b loses its ferromagnetic properties and immediately thereafter also the first sensor element 1a (see FIG. The carrier 11 is thereafter held in a position corresponding to the initial position exclusively by a resultant torque exerted by the permanent magnet first M1 and the first permanent ferromagnetic material piece F1. If the threshold temperature Ts ₂ is exceeded in this activated state, the second sensor element 1b becomes ferromagnetic and the torque ratios change as a result of the magnetic force now acting on the second permanent magnet With suitable dimensioning, a resulting torque occurs, so that the lever tilts in the direction of the second permanent magnet M2 into a detection position (FIG. 13b). With suitable dimensioning and positioning of the permanent ferromagnetic material pieces F1, F2 maintain this position of the lever stable, even if falls below Ts _2, the second sensor element lb again in the paramagnetic state.

Furthermore, by appropriate arrangement and tuning of the permanent magnets Ml, M2 and permeabilities or sizes of the sensor elements la, lb and the permanent ferromagnetic material pieces Fl, F2 the detection position can be maintained even if Tsi is exceeded and the first sensor element la changes into the ferromagnetic state ,

In order to detect the lever position, recourse can be had to conventional methods known from the prior art or to a method described in the preceding embodiments.

A further embodiment is shown in FIGS. 14a and 14b, in which case the desired functionality can be shown instead of that shown in FIGS. 13a and 13b Tilting mechanism also based on a purely translational movement, which allows a particularly flat design of the sensor.

On a base body 10, two permanent magnets Ml, M2 are attached. The region between the permanent magnets Ml and M2 serves as a sliding surface for a carrier 11. At one end of the carrier 11, the side facing the first permanent magnet Ml, a first permanent-ferromagnetic material piece Fl and the first sensor element la are attached. At the other end of the carrier 11, the second permanent magnet M2 side facing, is also a second permanent ferromagnetic piece of material F2 and a second sensor element lb. In the course of the sensor production - both sensor elements are ferromagnetic - the carrier 11 is positioned in the starting position (FIG. 14a). As a result of the magnetic force effect, this starting position remains stable as long as the force generated by the first permanent magnet M1, the first permanent ferromagnetic material piece F1 and the first sensor element 1a is greater than that by the second permanent magnet M2, the second permanent ferromagnetic material piece F1 and second sensor element lb generated force. The force ratios are adjustable by the choice and position of the permanent magnets Ml, M2, or the permeabilities of the sensor materials of the sensor elements la, lb and the permanent ferromagnetic materials Fl, F2, and their position along the carrier 11. In this initial position, the sensor can be mounted on the refrigerated goods even at temperatures> Tsi. As a result of the following cooling process below Tui, first the second sensor element 1b loses its ferromagnetic properties, and immediately afterwards also the first sensor element 1b (see FIG. The carrier 11 is then held in its position corresponding to the initial position exclusively by the resulting force exerted by the first permanent magnet M1 on the first permanent ferromagnetic material piece F1. If the threshold temperature Ts ₂ is exceeded in this activated state, the second sensor element 1b becomes ferromagnetic and the force relationships change as a result of the magnetic force of the second permanent magnet now becoming effective With suitable dimensioning, a resultant force is produced which pulls the carrier 11 in the direction of the second permanent magnet M2 into a detection position until it stops (FIG. 14b) Fl, F2 this position of the carrier 11 is stably maintained, even if falls below Ts _2, the second sensor element lb again in the paramagnetic state.

Furthermore, by suitable arrangement and matching of the permanent magnets M1, M2 and the permeabilities or sizes of the sensor materials of the sensor elements 1a, 1b and of the permanent ferromagnetic material pieces F1, F2, the detection position are maintained even when Tsi is exceeded and the first sensor element la changes to the ferromagnetic state.

In addition to the sliding of the carrier 11 on the base body 10, it is of course also possible to facilitate the movement of the carrier 11 on the base body 10 by means of rollers or ball bearings.

For detection of the carrier position, it is again possible to resort to common methods known from the prior art or to previously described methods.

Furthermore, by suitable arrangement and coordination of permanent magnets and permeabilities or sizes and properties of the sensor elements and the permanent ferromagnetic material pieces, a temperature monitor for falling below a predetermined threshold temperature can be realized.

Particularly suitable but non-limiting sensor materials are materials based on the following alloys: Gd5 (Sil-xGex) 4, Ni-Mn, Ni-Mn-Ga, Ni-Mn-In (Co), La-Fe-Si, La -Fe-Si-Co, La-Fe-Si-Co-B, La-Fe-Si-Cu, La-Fe-Si-Ga, La (Fe, Si, Co), LaFexSil-x, La (Fe, Si) 13, RCo2 with R (R = Dy, Ho, Er), DyA12, DyNi2 Tb-Gd-Al, Gd-Ni, Mn-As-Sb, MnFe-P-As.

Claims

claims 1. sensor for detecting the one-time temporary transgression of a threshold temperature Ts, comprising at least one sensor element (1) with a sensor material consisting of a magnetocaloric alloy,  wherein the sensor material of the sensor element (1) transitions from a first state to a second state when the threshold temperature Ts is exceeded and in the first state has different magnetizability compared to the second state,  - Wherein a detection unit (5) is provided, with the indirectly or directly, the transition of the sensor material of the sensor element (1) from the first state to the second state is detectable. 2. Sensor according to claim 1, characterized by one of the detection unit (5) downstream, in particular passive, RFID and / or NFC transponder (4) for data transmission to an external data communication device (44), which upon activation by the external data communication device ( 44) transmits the respective state of the sensor element (1) to the data communication device (44). 3. Sensor according to claim 1 or 2, characterized in that the sensor material of the sensor element (1) has a first-order phase transition and is magnetic in at least one phase, and / or having a wide temperature hysteresis. 4. Sensor according to one of the preceding claims, characterized in that the detection unit (5) comprises at least one coil (3),  - Wherein the sensor element (1) in the field space of the coil (3) is arranged and electrically isolated from this, and  - Wherein the detection unit (5) for measuring an inductance change of the coil (3) with the coil (3) is electrically connected. 5. Sensor according to claim 4, characterized in that the sensor element (1) as the core of the coil (3) is formed and / or that the sensor element (1) is designed as a carrier body of the coil (3). 6. Sensor according to one of the preceding claims, characterized in that the sensor comprises two coils (3), namely a stimulator coil (3a) and a measuring coil (3b), wherein the sensor element (1) is designed as a magnetic coupling element and preferably as common core of the two coils (3) or as a carrier material of the two coils (3a, 3b) is formed and / or the sensor element (1) between the two coils (3) is arranged. 7. Sensor according to one of claims 1 to 3, characterized in that the sensor comprises an at least partially electrically conductive carrier part (8), two electrical contacts (6, 7) and a magnet (9), wherein the detection unit (5) for Detection of a conductive connection of the electrical contacts (6, 7) is formed,  - wherein the sensor element (1) on the carrier part (8) the magnet (9) is arranged opposite,  - Wherein the sensor element (1) in the second state with the magnet (9) can be brought into interaction and the carrier part (8) connects the contacts (6,7). 8. Sensor according to one of the preceding claims, characterized in that the sensor has an activation unit (12) for activating the sensor element (1) comprising a soft magnetic material (14) and a preferably on the soft magnetic material (14) mounted coil ( 13) and wherein the soft magnetic material (14) is magnetizable by the coil (13), wherein the hysteresis curve and / or the threshold temperature Ts of the sensor element (1) by the magnetized soft magnetic material (14) is displaceable. 9. Sensor according to one of claims 1 to 3 comprising  a base body (10) of non-electrically conductive material,  a non-ferromagnetic support (11) mounted on the base body (10), in particular rotatable, tiltable or translatory, on which the sensor element (1) is arranged,  - At least one on the base body (10) arranged first permanent magnet (Ml) and at least one permanent ferromagnetic first piece of material (Fl) arranged on the carrier (11),  - Wherein the first piece of material (Fl) is arranged in the effective range of the first permanent magnet (Ml),  wherein the sensor element (1) changes the position of the carrier (11) when changing from the first state to the second state,  - Wherein the detection unit (5) for measuring the position of the carrier (11) is formed. 10. Sensor according to claim 9, characterized in that, in particular in the form of a cylindrical disc formed carrier (11) is rotatably mounted on the base body (10) and on the carrier (11) a first sensor element (la) with threshold temperature Tsi, a second sensor element (lb) with threshold temperature Ts ₂ and a second ferromagnetic material piece (Fl), which is subsequently arranged on the second sensor element (lb), is arranged the threshold temperature Tsi> Ts ₂ and / or Tui <T _u2 , - On the base body (10) of the first permanent magnet (Ml), a second permanent magnet (M2) and a third permanent magnet (M3) are arranged, - wherein the third permanent magnet (M3) is designed and arranged such that the torque of the carrier caused by the magnetic interaction between the third permanent magnet (M3), the permanent ferromagnetic piece of material (Fl) and the sensor material (lb) in the second state ( 11) is greater than the torque caused by the magnetic interaction between the second permanent magnet (M2), the permanent ferromagnetic material piece (Fl) and the second state sensor material (Ib), and  - The first sensor element (la) on the support (11) in the effective range of the first permanent magnet (Ml) is arranged, and wherein the permanent ferromagnetic piece of material (Fl) in the effective range of the second permanent magnet (M2) is arranged and the second sensor element (lb) is arranged in the effective range of the third permanent magnet (M3), and / or in an initial position, the first sensor element (la) is arranged on the carrier (11) in the immediate vicinity of the first permanent magnet (Ml), the permanent ferromagnetic material piece (Fl) in the immediate vicinity of the second permanent magnet (M2) and the second sensor element (lb) in the circumferential direction between the second permanent magnet (M2) and the third permanent magnet (M3) is arranged. 11. Sensor according to claim 9, characterized in that the carrier (11), in particular about its center, tiltable on the base body (10) is arranged and at one end of the carrier (11) a first sensor element (la) with threshold temperature Tsi and on the first sensor element (lb) opposite end of the carrier (11) second sensor element (lb) with threshold temperature Ts _{2 is} arranged, wherein the threshold temperature Tsi> Ts ₂ and / or Tui <T _u2 ,  - Wherein on the base body (10) of the first permanent magnet (Ml) and a second permanent magnet (M2) are arranged, wherein in each case a permanent magnet with respect to the first and second sensor element (la, lb) is arranged,  - Wherein the first piece of material (Fl) in the effective range of the first permanent magnet (Ml) on the support (11) is arranged and a second piece of material (F2) in the effective range of the second permanent magnet (M2) on the support (11) is arranged. 12. Sensor according to claim 9, characterized in that the carrier (11) on the base body (10) between the first permanent magnet (Ml) and a second permanent magnet (M2) is arranged translationally movable, and at one end of the carrier (11) a first sensor element (la) with threshold temperature Tsi and on the first sensor element (lb) opposite end of the carrier (11) second sensor element (lb) with threshold temperature Ts _{2 is} arranged, wherein the threshold temperature Tsi> Ts ₂ and / or Tui <T _u2 , - Wherein the first permanent magnet (Ml) and the second permanent magnet (M2) are arranged on the base body (10), wherein in each case a permanent magnet (Ml, M2) with respect to the first sensor element (la) and the second sensor element (lb) is arranged, - Wherein the first piece of material (Fl) in the effective range of the first permanent magnet (Ml) on the support (11) is arranged and a second piece of material (F2) in the effective range of the second permanent magnet (M2) on the support (11) is arranged. 13. Sensor according to one of the preceding claims, characterized in that Tu between -100 ° and + 20 ° C and / or T _s between -30 ° C and + 100 ° C and / or the difference T _s - Ύ _υ = 5 to 80 ° C is. 14. Sensor according to one of the preceding claims, characterized in that the sensor element (1) consists of one of the following alloys: Gd5 (Sil-xGex) 4, Ni-Mn, Ni-Mn-Ga, Ni-Mn-In ( Co), La-Fe-Si, La-Fe-Si-Co, La-Fe-Si-Co-B, La-Fe-Si-Cu, La-Fe-Si-Ga, La (Fe, Si, Co ), LaFexSil-x, La (Fe, Si) 13, RCo2 with R (R = Dy, Ho, Er), DyA12, DyNi2 Tb-Gd-Al, Gd-Ni, Mn-As-Sb, MnFe-P -as. 15. RFID and / or NFC transponder comprising a sensor integrated in the RFID and / or NFC transponder according to one of the preceding claims.