TEMPERATURE LIMIT VALUE SENSOR

Abstract

The present disclosure relates to a system for monitoring a predeterminable temperature comprising a monitoring unit comprising a reference element composed at least partially of a material in which a phase transformation occurs at a phase transformation temperature, which lies in the region of the predetermined temperature, in which phase transformation the material remains in the solid phase, and a detection unit embodied to detect the occurrence of the phase transformation based on an abrupt change at least one physical or chemical parameter characteristic for the reference element and to generate a report concerning ex- or subceeding of the predeterminable temperature. Furthermore, the present disclosure relates to a monitoring unit and to a detection unit for application in a system of the disclosure as well as to a method for monitoring the predeterminable temperature by means of a system of the disclosure.

Claims

1-16. (canceled)

17. A system for monitoring a predeterminable temperature, comprising: a monitoring unit including a reference element composed at least partially of a material in which a phase transformation occurs at a phase transformation temperature which lies in a region of the predeterminable temperature, in which phase transformation the material remains in the solid phase, and a detection unit which is embodied to detect an occurrence of a phase transformation based on an abrupt change of at least one physical or chemical parameter for the reference element and to generate a report concerning ex- or subceeding of the predeterminable temperature.

18. The system as claimed in claim 17, wherein the material is a ferroelectric material, a ferromagnetic material, a superconductor, or a high-temperature superconductor.

19. The system as claimed in claim 17, wherein the physical or chemical parameter is a dielectric, electrical, or magnetic property of the material.

20. The system as claimed in claim 17, wherein the reference element is a capacitor having a dielectric at least partially composed of the material in which the phase transformation occurs at the phase transformation temperature.

21. The system as claimed in claim 17, wherein the reference element is a coil arrangement having at least one coil and a magnetically conductive body, wherein the body is composed at least partially of the material in which the phase transformation occurs at the phase transformation temperature.

22. The system as claimed in claim 17, wherein the detecting unit includes a means for detecting a change of an electric or magnetic field leaving the reference element, and wherein the detecting unit is embodied to detect the ex- or subceeding of the predeterminable temperature based on the change of the electric or magnetic field.

23. The system as claimed in claim 22, wherein the means for detecting a change of the electric or magnetic field includes a means for detecting a force or a change of a force.

24. The system as claimed in claim 22, wherein the monitoring unit or the detection unit includes a means for applying an electric or magnetic field.

25. The system as claimed in claim 24, wherein the detection unit is embodied to detect the ex- or subceeding of the predeterminable temperature based on a hysteresis diagram or based on polarization.

26. The system as claimed in claim 17, wherein the reference element and at least one other component of the monitoring unit or the detection unit are, at least at times, part of an electrical oscillatory circuit, and wherein the detecting unit is embodied to detect the occurrence of the phase transformation by a change of a resonant frequency of the oscillatory circuit.

27. The system as claimed in claim 17, further comprising: an output unit which is embodied to display, to output, and to transmit into an external unit the ex- or subceeding of the predeterminable temperature.

28. The system as claimed in claim 27, further comprising: a transmission unit including an RFID- or a Bluetooth module which transmission unit is embodied for wireless transmission the ex- or subceeding of the predeterminable temperature.

29. The system as claimed in claim 17, further comprising: an energy supply unit for supplying electrical power to at least one component of the monitoring unit, the detection unit, the output unit, and the transmission unit.

30. A monitoring unit for application in a system for monitoring a predeterminable temperature, comprising: a reference element composed at least partially of a material in which a phase transformation occurs at a phase transformation temperature which lies in the region of the predeterminable temperature, in which phase transformation the material remains in the solid phase.

31. A detection unit for application in a system for monitoring a predeterminable temperature, wherein the detection unit is embodied to detect an occurrence of a phase transformation based on an abrupt change of at least one physical or chemical parameter for a reference element and to generate a report concerning ex- or subceeding of the predeterminable temperature.

32. A method for monitoring a predeterminable temperature, comprising: providing a system for monitoring the predeterminable temperature, including: a monitoring unit including a reference element composed at least partially of a material in which a phase transformation occurs at a phase transformation temperature which lies in a region of the predeterminable temperature, in which phase transformation the material remains in the solid phase; and a detection unit which is embodied to detect the occurrence of a phase transformation based on an abrupt change of at least one physical or chemical parameter for the reference element and to generate a report concerning ex- or subceeding of the predeterminable temperature; detecting a phase transformation based on an abrupt change of a physical or chemical parameter for the reference element, and generating a report concerning ex- or subceeding of the predeterminable temperature when a phase transformation is detected.

Description

[0040] The invention will now be explained in greater detail based on the appended drawing, the figures of which show as follows:

[0041] FIG. 1 a schematic representation of a system of the invention with a monitoring unit and detection unit, which a) are arranged together and b) separately from one another,

[0042] FIG. 2 a schematic representation of the line or curve as a function of time of a characteristic parameter as well as of temperature for illustrating detecting the phase transformation based on a change of the parameter,

[0043] FIG. 3 a schematic representation of an embodiment of the reference element as (a) capacitor element and (b) as a coil arrangement,

[0044] FIG. 4 detecting a phase transformation based on a change of the polarization of the material, of which the reference element is at least partially composed,

[0045] FIG. 5 detecting a phase transformation based on a hysteresis diagram, for the case of (a) a ferroelectric and (b) a ferromagnetic phase transformation, and

[0046] FIG. 6 detecting a phase transformation based on the resonant frequency of an oscillatory circuit with a reference element in the form of an (a) inductance and (b) capacitance.

[0047] In the figures, equal elements are provided, in each case, with equal reference characters.

[0048] FIG. 1 shows schematically, by way of example, two embodiments of systems 1 of the invention. Many other embodiments and arrangements of the individual components are possible and fall within the scope of the present invention. In each case, there is a monitoring unit 2, which has a reference element 3, which is at least partially composed of a material, in the case of which there occurs at a phase transformation temperature T.sub.ph, which lies in the region of the predetermined temperature T.sub.min/max, at least one phase transformation, in which the material remains in the solid phase. Furthermore, each system 1 includes a detection unit 4, with which the occurrence of the phase transformation is detected based on an, especially abrupt, change of at least one physical or chemical parameter characteristic for the reference element 3 and a report generated concerning ex- or subceeding of the predeterminable temperature T.sub.min/max. This report can, for example, be output by means of an output unit 5, and/or transmitted into an external unit 7.

[0049] Monitoring unit 2 and detection unit 4 can either be arranged together, as shown in FIG. 1 a, or embodied as separate units separated from one another, as shown in FIG. 1b. Communication between the monitoring unit 2 and the detection unit 4 can occur both by wire as well as also wirelessly.

[0050] FIG. 1a shows the monitoring unit 2 with the reference element 3 in direct contact with detection unit 4, which, in turn, is in direct contact with an output unit 5. By means of the output unit 5 in this example of an embodiment, a report concerning ex- or subceeding of the predeterminable temperature T.sub.min/max is transmitted by wire to the external unit 7. The system 1 of FIG. 1a is essentially embodied in the form of a single component.

[0051] In contrast, the sending of the ex- or subceeding of the predeterminable temperature T.sub.min/max to the external unit 7 in the embodiment of FIG. 1b occurs wirelessly by means of the transmission unit 6. Detection unit 4 in this embodiment is embodied as an independent unit 8. This unit 8 includes the detection unit 4, the output unit 5 and the transmission unit 6. Furthermore, unit 8 includes an energy supply unit 9, which supplies the detection unit 4, the output unit 5 and the transmission unit 6 with electrical energy. Unit 8 is correspondingly autarkically fed from an energy supply and can be applied in a mobile manner.

[0052] The occurrence of the at least one phase transformation of the invention is detected based on an, especially abrupt, change of at least one physical or chemical parameter characteristic for the reference element 3, as shown in FIG. 2. The upper graph shows the line or curve as a function of time of a characteristic physical or chemical variable G used for detecting the phase transformation. If a phase transformation occurs in the reference element 3, then there occurs in the illustrated example an abrupt change of the variable G. The point in time, at which the abrupt change of the variable is detected, is the phase transformation point in time t.sub.ph, at which the reference element 3 achieves the phase transformation temperature T.sub.ph.

[0053] Shown in the lower graph is temperature T as a function of time t. The material, in which the phase transformation occurs, is selected in such a manner that the phase transformation temperature T.sub.ph lies in the region of the monitored, predeterminable temperature T.sub.min/max. FIG. 2 is for the case, in which the predeterminable temperature T.sub.min/max should not be exceeded. In this case it is expedient to choose the material of the reference element 3 in such a manner that T.sub.ph<T.sub.min/max, wherein a suitable temperature separation between the phase transformation temperature T.sub.ph and the predeterminable temperature T.sub.min/max is selectable depending on the application. In the case of a heating procedure of the respective measured liquid, material or mixture of materials, or a particular item, for example, a part, or a component, to a first point in time t.sub.1 first the phase transformation temperature T.sub.ph is reached. For example, a report is generated and output concerning the reaching of the phase transformation temperature T.sub.ph. Upon additional heating to a second point in time t.sub.2, the predeterminable temperature T.sub.min/max reached. Since a predeterminable temperature separation between the phase transformation at n temperature T.sub.ph and the predeterminable temperature T.sub.min/max is selected, it can, for example, be assured that between the first t.sub.1 and second t.sub.2 points in time, especially also in the case of additional heating, enough time remains, in order to prevent exceeding the predeterminable temperature T.sub.min/max. For the case, in which the predeterminable temperature T.sub.min/max should not be subceeded, analogous ideas hold, so that such does not need to be detailed here. The temperature separation between the phase transformation temperature T.sub.ph and the predeterminable temperature T.sub.min/max can be selected, for example, with reference to expected heating- or cooling rates of a particular measured liquid, material or a mixture of materials, or a particular item, for example, a part, or a component. Alternatively, the material of the reference element 3 can also be selected in such a manner that the phase transformation temperature T.sub.ph and the predeterminable temperature T.sub.min/max essentially correspond. In this case, the predeterminable temperature separation is essentially zero.

[0054] Some possible embodiments for the reference element 3 are shown in FIG. 3 by way of example. Suited in the case of a ferroelectric material, for example, is an embodiment of the reference element 3 in the form of a capacitor element, as shown in FIG. 3a. The material 10, in which the phase transformation occurs, forms the dielectric in this case. The reference element 3 includes, furthermore, two electrodes 11a and 11b, which in the example shown here are arranged on two directly oppositely lying, lateral surfaces of the material 10, which is embodied as an essentially cuboidal body and electrically contacted by means of the two connection lines 12a and 12b, in order, for example, to detect the capacitance C of the reference element 3 and based on an, especially abrupt, change of capacitance C to detect the phase transformation. For other details of this embodiment of the reference element 3 in the form of a capacitor element, reference is made to Offenlegungsschrift DE102010040039A1.

[0055] In the case of a reference element 3 comprising a ferromagnetic material 15, beneficial is an embodiment in the form of a coil arrangement, such as shown, by way of example, in FIGS. 3b-3d. An opportunity for detecting a phase transformation in the case of such an embodiment of the reference element 3 lies in detecting a change of the inductance L of the arrangement. Upon a phase transformation from the ferromagnetic to the paramagnetic state, the magnetic resistance of the material 15, in which the phase transformation occurs, changes, and, thus, for example, also the inductance L of the arrangement.

[0056] In the embodiment of FIG. 3b, the reference element 3 includes a coil 13 with core 14, and a magnetically conductive body 15, which is composed of the ferromagnetic material. The magnetically conductive body 15 is arranged in such a manner that it is located at least partially in a magnetic field B emanating from the coil 13 with the core 14. The magnetic field is indicated by the sketched field lines. Upon a phase transformation in the magnetically conductive body 15, the magnetic field B changes, which is detectable, for example, based on a change of the inductance L of the arrangement.

[0057] It is to be noted that the use of a core 14 for the coil 13 is optional. Two possible embodiments of the reference element 3 as a coil arrangement without core are correspondingly shown in FIGS. 3b and 3c. Shown in FIG. 3d is, furthermore, by way of example, on the one hand, the magnetic field B.sub.1, which reigns, when the material 15 is located in the ferromagnetic state. Moreover, shown in dashed lines is the magnetic field B.sub.2, which reigns, when the material 15 is located in the paramagnetic state.

[0058] It is to be noted, furthermore, that the material 15, the coil 13 and the core 14 do not necessarily need to be arranged together within detecting unit 4. It is likewise an option that the coil 13 and/or the core 14 is/are part/parts of the transmission unit 6.

[0059] In the case, in which the particular system 1 includes a plurality of reference elements 3, the different reference elements 3 can be of equal construction or differently embodied. Preferably used are materials with phase transformations at different phase transformation temperatures T.sub.ph1, T.sub.ph2, . . . . For example, at least one of the reference elements 3 can be embodied in the form of a capacitor element and at least one further reference element in the form of a coil arrangement. For detecting the phase transformations of the different reference elements 3, the detection unit 4 can, furthermore, comprise either one or, however, a plurality of measuring circuits. For example, a plurality of reference elements 3 can be integrated in a single oscillatory circuit for detecting particular phase transformations.

[0060] For detecting the occurrence of a particular phase transformation, varied options are available, which all fall within the scope of the present invention. In the next figures, some especially preferred embodiments will be explained. The invention is, however, in no way limited to the described embodiments.

[0061] An opportunity for detecting the occurrence of a phase transformation is composed in detecting a change of the polarization of a particular material 10, or 15, in which the phase transformation occurs, such as illustrated in FIG. 4. During the occurrence of a phase transformation, for example, the polarization of the material 10, or 15, in which the phase transformation occurs, can change. A change of the polarization can be recognized, for example, in the case of a ferromagnetic material, based on a change of an inductance L, such as illustrated in FIGS. 4b and 4c, or, in the case of a ferroelectric material, based on a change of a capacitance C, such as shown in FIGS. 4d and 4e.

[0062] FIG. 4a shows temperature T as a function of time t. At a first point in time t.sub.1, a phase transformation occurs, wherein the polarization of the material 10, or 15 disappears, as shown in FIGS. 4c and 4e. Before the point in time t1, the material 10, or 15 in the case of FIG. 4c was in the ferromagnetic state and in the case of FIG. 4e in the ferroelectric state. Between the point in time t.sub.1 and a second point in time t.sub.2, at which anew a phase transformation occurs, the material in the case of FIG. 4c is located in the paramagnetic state and in the case of FIG. 4e in the paraelectric state. At the point in time t.sub.2, the material, in contrast, returns to a ferromagnetic (FIG. 4c), or a ferroelectric (FIG. 4e) state. In the paramagnetic, and in the paraelectric state, the polarization of the material disappears. As a consequence, the capacitance C of the reference element 3 in the case of a ferroelectric material (FIG. 4d), or the inductance L of the reference element 3 with a ferromagnetic material 10, experiences an abrupt change, which can easily be detected.

[0063] Another opportunity for detecting a phase transformation based on polarization is composed in considering a field emanating from the reference element 3, for example, the remanence of a material. A field emanating from a material, which, at the start, is located in a ferroelectric or ferromagnetic state with high polarization, will disappear after an exceeding of the phase transformation temperature T.sub.ph. A starting state of high polarization of the utilized ferroelectric or ferromagnetic material can be produced, for example, by applying an, especially external, electrical or magnetic field.

[0064] In this case, even after a return to the ferromagnetic state, or to the ferroelectric state, as the case may be, the polarization present, in each case, no longer corresponds to the polarization in the starting state, such as indicated in FIGS. 4c and 4e for the phase transformation at the second point in time t.sub.2.

[0065] In this regard, applications as follows are conceivable: certain items, for example, electronic assemblies, or foods, must not at any time during transport exceed a certain predeterminable temperature T.sub.min/max. For monitoring the predeterminable temperature, a monitoring unit 2 comprising a reference element 3 with a ferroelectric or ferromagnetic material is placed on the item or in its immediate vicinity. The reference element 3 can be polarized at the beginning, for example, by applying an electrical or magnetic field, especially an external, electrical or magnetic field, which passes, at least at times and/or partially, at least through the material having the phase transformation.

[0066] For this embodiment, the monitoring unit 2 and the detection unit 4 are advantageously embodied as separate units.

[0067] The polarization of an item can be detected during transport by means of the detection unit 4 either continuously or in predeterminable time intervals. The occurrence of a phase transformation can then be detected based on an, especially abrupt, change of the polarization in the material, of which the reference element is at least partially composed. Alternatively, the occurrence of a phase transformation can also be checked once, especially at the end of a procedure, for example, after transport. In this case, for example, the polarizations at the beginning, thus in the starting state, and at the end can be compared. If the polarizations at the beginning and at the end are essentially unequal, then it can be determined therefrom that at least at a time the predeterminable temperature T.sub.min/max was exceeded. For another application, the reference element 3 can be polarized anew by applying a suitable field. Corresponding means for applying a field can be implemented, for example, in the monitoring unit 2 or in detecting unit 4.

[0068] Similar ideas hold also for the case, in which a certain predeterminable temperature T.sub.min/max must not be subceeded. This example is therefore not explained here in detail.

[0069] A detecting of a particular polarization can occur by means of a suitably embodied detection unit 4, basically, for example, using remanence. The presence of a remanence, or a polarization, can be ascertained, in such case, for example, based on a change of capacitance or inductance, such as in FIGS. 4b and 4d. Alternatively, however, also a force measurement or a measurement of a hysteresis can be performed. This example is especially advantageous for the case, in which no continuous temperature monitoring should take place, but, the ex- or subceeding of the predeterminable temperature T.sub.min/max should be checked at predeterminable points in time.

[0070] In the case, in which the at least one phase transformation is detected based on a hysteresis diagram, for example, an embodiment of the reference element corresponding to one of the embodiments of FIG. 5 can be used. In the case of the embodiments shown in FIG. 5, the monitoring unit 2 and the detection unit are arranged together. The reference element 3 is, in such case, part of an electrical circuit of the detection unit 4.

[0071] For registering a hysteresis diagram, the change of the polarization of a particular material, in which the phase transformation occurs, is registered by applying a time dynamic voltage U.sub.dyn. The particular hysteresis diagram results from plotting voltage U.sub.1 as a function of U.sub.dyn. The occurrence of a phase transformation can be detected, for example, based on a change of the ratio of the voltages U.sub.dyn and U.sub.1.

[0072] For the embodiment of FIG. 5a, the reference element 3 is a capacitor element with the capacitance Clef, such as, for example, in FIG. 3a. Correspondingly, a phase transformation is from the ferroelectric into the paraelectric state or vice versa. In the case of the circuit, which comprises the detection unit 4, such is a so-called Sawyer-Tower circuit, which is per se well known from the state of the art and therefore is not described in detail here.

[0073] An electrical circuit for detecting a phase transformation in the case of a reference element 3 in the form of a coil arrangement with the inductance L.sub.ref, such as, for example, in one of the figures, FIG. 3b-FIG. 3d, each of which includes ferromagnetic material, is, in contrast, shown in FIG. 5b. The capacitance C.sub.1, as well as the resistances R.sub.1 and R.sub.2 are, in each case, matched to the applied reference element 3.

[0074] Finally, it is likewise possible to embody the reference element 3 as part of an oscillatory circuit, such as illustrated based on FIG. 6. In this case, the occurrence of the phase transformation is detected, for example, based on a change of a resonant frequency f.sub.0 of the oscillatory circuit. However, also other properties of the oscillatory circuit, such as, for example, an attenuation, an amplitude response, or a frequency response can be evaluated as regards the occurrence of a phase transformation.

[0075] Also in the case of the examples of embodiments in FIG. 6, the monitoring unit 2 and the detection unit 4 are arranged together, wherein the reference element 3 is part of an oscillatory circuit, which is integrated into the detection unit 4.

[0076] For the case of a reference element 3 formed as a capacitor element with capacitance Clef as shown in FIG. 6a, suited is an RC oscillatory circuit with the resistance R.sub.1, which is suitably selected as a function of the reference element 3. A transmission unit 6, which is, for example, an element of an RFID module, can, in this case, advantageously be integrated directly into the oscillatory circuit. The phase transformation is then detected based on a change of the resonant frequency f.sub.0 of the oscillatory circuit, which is transmitted directly by means of the transmission unit 6.

[0077] In the case of an embodiment of the reference element 3 as a coil arrangement with the inductance L.sub.ref, as shown in FIG. 6b, suited is an RCL oscillatory circuit with the resistance R.sub.1 and the capacitance C.sub.1, both of which are selected as a function of the reference element 3. Analogously to the previous embodiment, a transmission unit 6 is integrated into the oscillatory circuit.

LIST OF REFERENCE CHARACTERS

[0078] 1 system of the invention [0079] 2 monitoring unit [0080] 3 reference element [0081] 4 detection unit [0082] 5 output unit [0083] 6 transmission unit [0084] 7 external unit [0085] 8 detection unit, output unit and transmission unit as one unit [0086] 9 energy supply unit [0087] 10 ferroelectric material, dielectric [0088] 11a,11b electrodes [0089] 12a,12b connection lines [0090] 13 coil [0091] 14 core [0092] 15 magnetically conductive body, ferromagnetic material [0093] G characteristic parameter of the reference element [0094] T temperature [0095] t time [0096] T.sub.ph phase transformation temperature [0097] t.sub.ph phase transformation point in time t.sub.ph [0098] T.sub.min/max predeterminable temperature [0099] t.sub.1, t.sub.2 first, second points in time [0100] B, B.sub.1, B.sub.2 magnetic field [0101] C.sub.ref capacitance of the reference element [0102] L.sub.ref inductance of the reference element [0103] U.sub.dyn voltage, dynamic with time [0104] U.sub.1 voltage [0105] R.sub.1, R.sub.2 resistances [0106] C, C.sub.1 capacitance [0107] L, L.sub.1 inductance [0108] P magnetic or electrical polarization