Passive RFID temperature sensor based on temperature sensing material and test method thereof

Abstract

The invention discloses a passive RFID temperature sensor based on a temperature sensing material and a test method thereof, and relates to the technical field of temperature sensors, and the sensor comprises an RFID tag reference phase unit; the temperature measuring unit is arranged in parallel with the RFID tag reference phase unit; the lever deformation mechanism is made of a temperature sensing material, and the temperature sensing material is fixed on the substrate through a supporting shaft; the tail end of the lever deformation mechanism is connected with the adjustable capacitor assembly, and the adjustable capacitor assembly and the temperature measuring unit form capacitive coupling. When the temperature changes, after the deformation quantity generated by the temperature sensing material is amplified by the lever structure, the adjustable capacitor assembly is driven to generate a non-linearly amplified capacitance variable quantity; the phase response of the temperature measuring unit and the reference phase unit form a detectable phase difference value; and the RFID reader-writer is used for comparing the detected phase difference value with a pre-stored temperature calibration curve to obtain an absolute temperature value after the phase difference value is detected. The sensitivity of the temperature measurement chip and the label can be effectively improved.

Description

Technical Field

[0001] The present application relates to the technical field of temperature sensors, and in particular to a passive RFID temperature sensor based on temperature-sensitive materials and a testing method thereof. Background Art

[0002] As an indispensable basic component in the field of modern electronic technology and automatic control, temperature sensors have a wide range of backgrounds and applications, and play a vital role in many aspects such as industrial production, daily life, scientific research and even environmental protection. There are many types of temperature sensors on the market, which are mainly divided into contact temperature measurement and non-contact temperature measurement according to the contact method. Among them, for non-contact temperature measurement, the mainstream is infrared, laser, ultrasonic, microwave and other sensors. With the rapid development of the RFID industry, the use of RFID temperature measurement tags has emerged.

[0003] However, there are also serious problems in the actual application of RFID temperature measurement tags that restrict the development of the industry, such as the insufficient sensitivity of the tag chip, which needs to be solved. Summary of the invention

[0004] The purpose of this application is to provide a passive RFID temperature sensor based on temperature-sensitive materials and a testing method thereof, which can effectively improve the sensitivity of temperature measuring chips and tags.

[0005] To achieve the above objectives, this application provides the following solutions: In a first aspect, the present application provides a passive RFID temperature sensor based on a temperature-sensitive material, the passive RFID temperature sensor comprising: RFID tag reference phase unit.

[0006] A temperature measurement unit is arranged in parallel with the RFID tag reference phase unit.

[0007] A lever deformation mechanism is composed of a temperature-sensitive material, wherein the temperature-sensitive material is fixed on a substrate through a support shaft; the end of the lever deformation mechanism is connected to an adjustable capacitor component, and the adjustable capacitor component forms a capacitive coupling with a temperature measuring unit; when the temperature changes, the deformation generated by the temperature-sensitive material is amplified by the lever structure, and the adjustable capacitor component is driven to generate a nonlinearly amplified capacitance change; the phase response of the temperature measuring unit forms a detectable phase difference with the reference phase unit.

[0008] The RFID reader is used to compare the phase difference with a pre-stored temperature calibration curve to obtain an absolute temperature value after detecting the phase difference.

[0009] Optionally, the temperature sensing material adopts a bimetallic composite structure, and the bimetallic composite structure is composed of at least two layers of metal alloy layers whose linear expansion coefficient difference is greater than a set threshold.

[0010] Optionally, the lever deformation mechanism comprises: A deformable arm and a transmission arm; the deformable arm and the transmission arm form a mechanical amplification structure with a lever ratio of 3:1 to 8:1 through a support shaft; the deformable arm is fixedly connected to the bimetallic composite structure, and a displacement amplification protrusion is provided at the end of the transmission arm.

[0011] Optionally, the RFID tag reference phase unit adopts a single-chip multi-module structure, including: A reference capacitor module, a temperature compensation circuit and a phase locking module; the reference capacitor module, the temperature compensation circuit and the phase locking module are integrated on the same chip carrier.

[0012] Optionally, the nonlinear amplification relationship between the capacitance change rate of the adjustable capacitor component and the deformation rate of the temperature-sensitive material is specifically: ΔC / C0=K×(ΔL / L0)ⁿ.

[0013] Among them, n is a nonlinear index of 1.5-2.8, K is a structural amplification factor, ranging from 5 to 15, ΔC is the capacitance change rate of the adjustable capacitor component, C0 is the deformation rate of the temperature-sensitive material, ΔL is the deformation amount of the temperature-sensitive material at the initial length, and L0 is the initial length of the temperature-sensitive material.

[0014] Optionally, the RFID reader is a UHF band communication reader that complies with the ISO / IEC 18000-6C protocol, and the operating frequency range of the reader is 860-960 MHz.

[0015] Optionally, the adjustable capacitor component is formed by a metal sheet having a comb-shaped electrode structure, and the metal sheet and the radiator of the RFID antenna form a coupling capacitor with an adjustable spacing.

[0016] In a second aspect, the present application provides a testing method for a passive RFID temperature sensor based on a temperature-sensitive material, comprising: Step 1: Place the passive RFID temperature sensor to be tested in a preset temperature environment and record the current ambient temperature.

[0017] Step 2: Use the RFID reader to read the phase difference value of the passive RFID temperature sensor.

[0018] Step 3: Compare the read phase difference value with the pre-stored temperature calibration curve to obtain the corresponding absolute temperature value.

[0019] Optionally, it also includes: Tests were carried out under different temperature environments to obtain the performance evaluation results of the temperature sensor.

[0020] According to the comparison results between the absolute temperature values ​​obtained from multiple tests and the ambient temperature, an error curve is drawn.

[0021] According to the specific embodiments provided in this application, this application discloses the following technical effects: The present application provides a passive RFID temperature sensor based on temperature-sensitive materials and a test method thereof, wherein the temperature-sensitive material is formed of a lever deformation mechanism, and when the ambient temperature changes, the temperature-sensitive material will deform. Through the amplification effect of the lever structure, this tiny deformation is significantly amplified, and then converted into a capacitance change of the adjustable capacitor component. This nonlinear amplification mechanism allows even a small temperature change to cause a significant change in capacitance, thereby improving the sensitivity of temperature measurement. Secondly, the design of the temperature measurement unit and the reference phase unit enables a detectable phase difference to be formed between them. This phase difference has a direct relationship with the temperature change, and by measuring this phase difference, the temperature change can be indirectly known. Finally, the application of the RFID reader makes the entire temperature measurement process without the need for an external power supply, reducing the complexity and cost of the system. At the same time, the reader can accurately detect the phase difference and compare it with the pre-stored temperature calibration curve to obtain the absolute temperature value. This digital processing method further improves the accuracy and sensitivity of temperature measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 This is a schematic diagram of the structure of a passive RFID temperature sensor based on temperature-sensitive material in one embodiment of the present application.

[0024] Figure 2 A schematic diagram of a variable capacitor structure provided in one embodiment of the present application.

[0025] Figure 3 This is a schematic diagram of the structure of a temperature-sensitive bimetallic strip provided in one embodiment of the present application.

[0026] Figure 4 A schematic diagram of a single-chip multi-module structure provided in one embodiment of the present application.

[0027] Figure 5 A schematic diagram of the structure of a passive RFID temperature sensor provided in one embodiment of the present application.

[0028] Figure 6This is a schematic diagram of an example of a passive RFID temperature sensor provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0030] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0031] Embodiment 1 like Figure 1 As shown, this embodiment provides a passive RFID temperature sensor based on a temperature-sensitive material, and the passive RFID temperature sensor includes: RFID tag reference phase unit.

[0032] A temperature measurement unit is arranged in parallel with the RFID tag reference phase unit.

[0033] A lever deformation mechanism is composed of a temperature-sensitive material, wherein the temperature-sensitive material is fixed on a substrate through a support shaft; the end of the lever deformation mechanism is connected to an adjustable capacitor component, and the adjustable capacitor component forms a capacitive coupling with a temperature measuring unit; when the temperature changes, the deformation generated by the temperature-sensitive material is amplified by the lever structure, and the adjustable capacitor component is driven to generate a nonlinearly amplified capacitance change; the phase response of the temperature measuring unit forms a detectable phase difference with the reference phase unit.

[0034] The RFID reader is used to compare the phase difference with a pre-stored temperature calibration curve to obtain an absolute temperature value after detecting the phase difference.

[0035] This application cleverly forms a lever structure by configuring the temperature-sensitive material and the metal sheet, so that the metal sheet and the temperature measurement unit of the tag antenna form an adjustable capacitor, and the capacitance change rate is in a nonlinear amplification relationship with the deformation rate of the temperature-sensitive material. The adjustable capacitor is further logically coordinated with the reference module (single-chip multi-module) to form a stable phase (difference) output, thereby achieving temperature measurement by directly reading the RF parameters through general equipment.

[0036] In some embodiments, the temperature-sensitive material adopts a bimetallic composite structure, and the bimetallic composite structure is composed of at least two layers of metal alloy layers whose linear expansion coefficient difference is greater than a set threshold.

[0037] Specifically, the bimetallic composite structure (also known as thermal bimetallic strip) is a composite material composed of two or more layers of alloys with different linear expansion coefficients, which is used for temperature control, temperature compensation and other automatic control devices and thermal sensitive elements in instruments and meters. Generally, it has high thermal sensitivity and high resistivity, such as Figure 3 As shown, the bimetallic composite structure includes a low expansion layer and a high expansion layer. When the temperature changes, the low expansion layer and the high expansion layer will produce bending deformation due to the difference in linear expansion coefficient. This deformation is amplified by the lever deformation mechanism and converted into a capacitance change of the adjustable capacitor component. The high expansion layer expands more when heated, while the low expansion layer expands less. This difference causes the bending of the bimetallic composite structure, thereby providing a sensitive thermal response for the temperature sensor.

[0038] Among them, in some embodiments, the lever deformation mechanism includes: a deformation arm and a transmission arm; the deformation arm and the transmission arm form a mechanical amplification structure with a lever ratio of 3:1 to 8:1 through a support shaft; the deformation arm is fixedly connected to the bimetallic composite structure, and a displacement amplification protrusion is provided at the end of the transmission arm.

[0039] In some embodiments, the RFID tag reference phase unit adopts a single-chip multi-module structure, including: a reference capacitor module, a temperature compensation circuit and a phase locking module; the reference capacitor module, the temperature compensation circuit and the phase locking module are integrated on the same chip carrier.

[0040] like Figure 4 As shown: Two different modules A and B of the RFID chip are connected to the same antenna. Modules A and B share the power supply, memory, etc. of the chip, but can respond to different commands.

[0041] When these tags are affected by external factors (such as movement of objects around the tags, passing of people, changes in the medium, etc.), they will produce consistent phase changes because they use the same antenna. Subsequent temperature measurements can eliminate such uniform change values ​​through algorithms, thereby ensuring that the phase values ​​measured during the temperature detection process are stable and controllable (only the phase changes caused by temperature are different).

[0042] Among them, module A in the chip is used as a sensing branch mainly to sense temperature; module B is used as a phase reference branch and its main function is to compare with the actual measurement data of module A to ensure that the phase measured by temperature measurement branch A has a reference point.

[0043] The nonlinear amplification relationship between the capacitance change rate of the adjustable capacitor component and the deformation rate of the temperature-sensitive material is specifically as follows: ΔC / C0=K×(ΔL / L0)ⁿ.

[0044] Wherein, n is a nonlinear index of 1.5-2.8, K is a structural amplification factor, ranging from 5-15, ΔC is a capacitance change rate of the adjustable capacitor component, C0 is a deformation rate of the temperature-sensitive material, ΔL is a deformation amount of the temperature-sensitive material at an initial length, and L0 is an initial length of the temperature-sensitive material. The adjustable capacitor component is composed of a metal sheet with a comb-shaped electrode structure, and the metal sheet forms a coupling capacitor with an adjustable spacing with the radiator of the RFID antenna.

[0045] Specifically, Figure 1 and Figure 2 As shown, the fixed end of the temperature-sensitive material (bimetallic composite structure) is connected to the antenna, and the deformation end of the bimetallic composite structure forms a variable capacitor structure with a capacitor metal sheet connected to the antenna at one end.

[0046] When the temperature changes, the bimetallic composite structure bends. Since one end of the bimetallic composite structure is fixed, the bending causes a large deformation of one end, thereby changing the distance between the bimetallic composite structure and the independent metal.

[0047] The change in metal spacing results in different capacitance values. The change in capacitance values ​​causes modules A and B to obtain different phase values. The card reader can read the phase values ​​of A and B separately through different instructions.

[0048] According to the different phase values ​​(capacitance values) of modules A and B, the temperature vs phase calibration curve mapping is retrieved to obtain the accurate temperature value.

[0049] Wherein, the thermal sensitivity parameters of the bimetallic composite structure satisfy: dR / dT≥0.5Ω / ℃, and resistivity ρ≥2.5×10 -6 Ω·m.

[0050] In some embodiments, the RFID reader is a UHF band communication reader that complies with the ISO / IEC 18000-6C protocol, and the operating frequency range of the reader is 860-960 MHz.

[0051] In addition, in addition to the temperature-sensitive bimetallic strip, any material that will deform with temperature changes can be used as a component to adjust the capacitor (tripolar or bipolar). Most importantly, the temperature-sensitive material that serves as a support point can achieve a large change in the distance between the plates through the lever principle (adjusting the arm length L1 / L2 ratio at both ends of the support point), thereby completing the zero-power passive amplification of the sensing parameter (capacitance change rate). Figure 5 and Figure 6 Furthermore, the capacitor parameters can be configured more flexibly by adjusting the shape distribution of each plate of the capacitor.

[0052] Embodiment 2 This embodiment provides a test method for a passive RFID temperature sensor based on a temperature-sensitive material, including: Step 1: Place the passive RFID temperature sensor to be tested in a preset temperature environment and record the current ambient temperature.

[0053] Step 2: Use the RFID reader to read the phase difference value of the passive RFID temperature sensor.

[0054] Step 3: Compare the read phase difference value with the pre-stored temperature calibration curve to obtain the corresponding absolute temperature value.

[0055] In addition, the test method includes: Tests were carried out under different temperature environments to obtain the performance evaluation results of the temperature sensor.

[0056] According to the comparison results between the absolute temperature values ​​obtained from multiple tests and the ambient temperature, an error curve is drawn.

[0057] In summary, this application has the following technical effects: This application is based on temperature-sensitive materials and uses the lever principle to amplify the capacitance change rate. Then, through conventional radio frequency parameters that can be detected at a long distance, temperature measurement and data upload can be completed, which greatly simplifies the system difficulty. Most importantly, it does not increase the chip power consumption and can effectively improve the sensitivity (reading range) of the temperature measurement chip and tag.

[0058] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0059] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A passive RFID temperature sensor based on temperature-sensitive materials, characterized in that: The passive RFID temperature sensor comprises: RFID tag reference phase unit; A temperature measuring unit arranged in parallel with the RFID tag reference phase unit; A lever deformation mechanism composed of a temperature-sensitive material, wherein the temperature-sensitive material is fixed on a substrate through a support shaft; an adjustable capacitor component is connected to the end of the lever deformation mechanism, and the adjustable capacitor component forms a capacitive coupling with a temperature measuring unit; when the temperature changes, the deformation amount generated by the temperature-sensitive material is amplified by the lever structure, and the adjustable capacitor component is driven to generate a nonlinearly amplified capacitance change; the phase response of the temperature measuring unit forms a detectable phase difference with the reference phase unit; The RFID reader is used to compare the phase difference with a pre-stored temperature calibration curve to obtain an absolute temperature value after detecting the phase difference.

2. A passive RFID temperature sensor based on temperature-sensitive materials according to claim 1, characterized in that: The temperature sensing material adopts a bimetallic composite structure, and the bimetallic composite structure is composed of at least two layers of metal alloy layers whose linear expansion coefficient difference is greater than a set threshold.

3. The passive RFID temperature sensor based on temperature-sensitive material according to claim 2, characterized in that: The lever deformation mechanism comprises: A deformable arm and a transmission arm; the deformable arm and the transmission arm form a mechanical amplification structure with a lever ratio of 3:1 to 8:1 through a support shaft; the deformable arm is fixedly connected to the bimetallic composite structure, and a displacement amplification protrusion is provided at the end of the transmission arm.

4. The passive RFID temperature sensor based on temperature-sensitive material according to claim 1, characterized in that: The RFID tag reference phase unit adopts a single-chip multi-module structure, including: A reference capacitor module, a temperature compensation circuit and a phase locking module; the reference capacitor module, the temperature compensation circuit and the phase locking module are integrated on the same chip carrier.

5. The passive RFID temperature sensor based on temperature-sensitive material according to claim 1, characterized in that: The nonlinear amplification relationship between the capacitance change rate of the adjustable capacitor component and the deformation rate of the temperature-sensitive material is specifically as follows: ΔC / C0=K×(ΔL / L0)ⁿ; Among them, n is a nonlinear index of 1.5-2.8, K is a structural amplification factor, ranging from 5 to 15, ΔC is the capacitance change rate of the adjustable capacitor component, C0 is the deformation rate of the temperature-sensitive material, ΔL is the deformation amount of the temperature-sensitive material at the initial length, and L0 is the initial length of the temperature-sensitive material.

6. The passive RFID temperature sensor based on temperature-sensitive material according to claim 1, characterized in that: The RFID reader is a UHF frequency band communication reader that complies with the ISO / IEC 18000-6C protocol, and the operating frequency range of the reader is 860-960 MHz.

7. The passive RFID temperature sensor based on temperature-sensitive material according to claim 1, characterized in that: The adjustable capacitor component is composed of a metal sheet with a comb-shaped electrode structure, and the metal sheet and the radiator of the RFID antenna form a coupling capacitor with an adjustable spacing.

8. A method for testing a passive RFID temperature sensor based on a temperature-sensitive material according to any one of claims 1 to 7, characterized in that: include: Step 1: Place the passive RFID temperature sensor to be tested in a preset temperature environment and record the current ambient temperature; Step 2: Use the RFID reader to read the phase difference value of the passive RFID temperature sensor; Step 3: Compare the read phase difference value with the pre-stored temperature calibration curve to obtain the corresponding absolute temperature value.

9. The testing method according to claim 8, characterized in that: Also includes: Tests were conducted under different temperature environments to obtain performance evaluation results of the temperature sensor; According to the comparison results between the absolute temperature values ​​obtained from multiple tests and the ambient temperature, an error curve is drawn.

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