JP2005164527A - Temperature detection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature detection system in a simple structure at a low cost, by using a wireless tag. <P>SOLUTION: An IC chip 1 of the wireless tag T is internally provided with not only a wireless-communications interface, a modulation controller, a memory unit, but also a voltage measuring circuit of the electricity generated at a tag antenna, and a switching circuit for switching a circuit based on a measured voltage value. The tag antenna of the wireless tag T receives an inquiry signal from the detection device, and generates an induced electromotive force by electromagnetic induction. The voltage measuring circuit measures the voltage value of a rectifier circuit, the switching circuit switches a circuit, based on correlation with temperature, selects a memory unit having the temperature data corresponding to the measured voltage value from among two or more memory units, reads out the temperature data of the above memory unit, and transfers the temperature data to an answer signal. The temperature detection system reads out the temperature data together with the identifying signal of the wireless tag T, and performs temperature displaying, by sending the acquired information to a display, a computer, a communication line and the like. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a temperature detection system constructed using a wireless tag.

Conventionally, a temperature detection system using a wireless tag incorporating an IC chip and a detection device called a reader that performs non-contact information exchange and power supply using electromagnetic waves has been proposed. For example, Patent Document 1 describes a system in which a transponder (wireless tag) including a temperature sensor is attached to clothes and a person's body temperature and ambient temperature are measured. In Patent Document 2, a transponder (wireless tag) equipped with a temperature sensor is attached to the body of an inpatient, the response signals from the transponder are collected by a reader, and the result is sent to a monitoring device installed at a nurse center. System to manage. Further, Patent Document 3 describes a system for measuring the temperature of a vehicle tire with a transponder provided with a temperature sensor.
JP 2001-307268 A JP 2001-314378 A JP 2003-127628 A

  The conventional temperature detection systems described in Patent Documents 1 to 3 require a temperature sensor for detecting the temperature separately from the transponder (wireless tag), which increases the size and cost of the device. There were drawbacks.

  The features of the temperature detection system adopted by the present invention in order to solve the above-mentioned conventional problems include a detection device having a radio wave transmission / reception function and a response to an inquiry signal transmitted from the detection device to the detection device. A wireless tag that returns a response signal, the wireless tag comprising: means for measuring a physical quantity depending on physical characteristics of the tag antenna; means for generating temperature data based on the measured value; and And means for supplying the temperature data information to a response signal to be returned.

  Here, the wireless tag is one that generates power by using, for example, a radio wave transmitted from a detection device, modulates a received radio wave based on information stored in a storage unit, generates a response signal, and transmits the response signal. Usually, the response signal includes individual information, position information, and the like for identifying the target to which the wireless tag is attached. The means for measuring the physical quantity depending on the physical characteristics of the tag antenna provided in the wireless tag includes means for measuring the voltage value or current value depending on the electrical characteristics such as electric resistance, reactance, impedance, etc. of the tag antenna. It is done. The means for generating the temperature data based on the measured value is determined in advance from means for selecting predetermined data corresponding to the characteristic measurement value from a plurality of temperature data stored in advance in the storage unit, or from the characteristic measurement value. A means for calculating temperature data based on the relational expression is conceivable.

  The temperature detection system according to the present invention operates as follows, for example. The detection device always transmits an interrogation signal, and the wireless tag generates operating power based on the interrogation signal and returns a response signal. The wireless tag measures the voltage value or current value of the induced electromotive force generated in the tag antenna by electromagnetic induction when receiving the interrogation signal. By the way, the magnitude of the voltage value or current value for a certain radio wave energy increases or decreases depending on the electric resistance value of the tag antenna. The electrical resistance value correlates with temperature. That is, the temperature can be obtained from the voltage value or current value. Accordingly, by reading the corresponding temperature data from the storage unit based on the measured value of voltage or current, or setting the temperature data to be calculated from a predetermined calculation formula, supplying this temperature data to the response signal The required temperature information can be obtained.

  In the temperature detection system according to the present invention, the wireless tag includes means for measuring a voltage value of an electromotive force generated in the tag antenna when receiving an interrogation signal, and a plurality of storage units that hold different temperature data, Circuit switching means for selecting a storage unit for reading data based on the measured voltage value, and the circuit switching means switches the circuit based on the measured voltage value measured by the voltage value measuring means, and the plurality of storages It is possible to select a storage unit that holds the corresponding temperature data from among the units and set the temperature data to be read from the storage unit.

  Further, the wireless tag of the temperature detection system according to the present invention has the voltage value of both ends of the electromotive force generated in the tag antenna when the interrogation signal is received, and the voltage value of both ends of the fixed resistor provided in the circuit continuous to the tag antenna. It is also possible to have a means for measuring and a means for calculating temperature data, and it is possible to set so as to generate temperature data based on the two measured voltage values.

  Since the temperature detection system according to the present invention acquires temperature data from, for example, the measured value of the voltage across the tag antenna, there is no need to separately provide a temperature sensor as in the prior art. Therefore, it is easy to reduce the size and cost of the device.

  The temperature detection system according to claim 2 is preferably used when the reception energy of the interrogation signal received by the wireless tag from the detection device hardly fluctuates, and it is only necessary to include means for switching the circuit according to the measured value. Since a complicated arithmetic device is not required, the cost can be kept low.

  According to a third aspect of the temperature detection system of the present invention, the electrical resistance value of the tag antenna has a correlation with the temperature, and the ratio between the voltage of the electromotive force generated in the tag antenna and the voltage of electricity flowing through a separately provided fixed resistor. The temperature data is obtained from the comparison data between the voltage value at both ends of the tag antenna and the voltage value at both ends of the fixed resistor based on a certain relational expression. Therefore, the temperature detection system has an advantage that accurate temperature data can be obtained even when the reception energy of the interrogation signal received by the wireless tag from the detection device varies.

[First Embodiment]
As shown in FIG. 1, a temperature detection system S according to the present invention mainly includes one or a plurality of wireless tags T arranged at a desired location and a detection device 10 that communicates with the wireless tags T via radio signals. It is a component. Each of the wireless tag T and the detection device 10 includes a tag antenna 2 and a reader antenna 11 for radio communication. In addition, the detection system S can be connected to a display device, a computer, a communication line, or the like in order to perform a required work based on the detection result. The temperature detection system S can remotely know the ambient temperature of the location by simply placing the RFID tag T at the location where the temperature is to be detected. If the environment does not exceed the durability of the RFID tag T, Temperature detection at any location is possible.

  The wireless tag T can have various structures. In this example, as shown in FIG. 2, a configuration in which the IC chip 1 and the tag antenna 2 are arranged on the substrate 3 is adopted. The tag antenna 2 and the reader antenna 11 adopt a surface loop shape wound in a coil shape in a plane in order to efficiently receive radio waves transmitted from the detection device. However, the form of each antenna 2 and 11 can be changed based on the frequency, intensity, etc. of radio waves used for communication. For example, a bar shape, a patch shape (element shape), a composite patch shape, a surface shape, a slot shape, A spiral shape, a pattern shape, or the like can be appropriately employed depending on the situation. In addition to the illustrated plate shape, the wireless tag T may have a bar shape, a disk shape, a rectangular parallelepiped shape, or the like.

  The internal structure of the IC chip 1 in this example is as shown in FIG. In addition to the wireless communication interface to which the tag antenna is connected, the modulation controller that controls the modulation of radio waves, the non-volatile memory, etc., which constitutes the functional center of the wireless tag, the rectifier circuit using the electromotive force generated in the tag antenna A voltage measuring circuit for measuring the output voltage and a switching circuit as circuit switching means for switching the circuit based on the measured voltage value obtained by the voltage measuring circuit are provided. The wireless communication interface includes a modulation circuit, a clock generator, and a rectifier circuit, and has a radio wave transmission / reception function and a function of generating electric power using the received radio wave. The storage unit includes a counter, a row decoder, a column decoder, and a memory, and holds temperature data together with identification information of the wireless tag. In this example, a plurality of storage units A1, A2, A3, A4... For holding different temperature data are provided. Of course, the contents of the temperature data held in the storage unit can be appropriately changed according to the measurement object. The memory may be a read-only nonvolatile memory, but may be a rewritable memory such as an EEPROM if desired.

  The operation of the temperature detection system S will be described as follows. The detection device 10 constantly or intermittently transmits an interrogation signal toward the wireless tag T arranged at an appropriate position. The wireless tag T that has received the interrogation signal by the tag antenna 2 uses the energy to generate operating power, and the information stored in the storage unit is sent to the detection device 10 as a response signal obtained by modulating the received radio wave. Send back. That is, the radio tag T and the detection apparatus 10 are in a state where communication using radio wave signals is always performed.

  The tag antenna of the wireless tag T generates an induced electromotive force due to electromagnetic induction when receiving an interrogation signal from the detection device 10. At this time, the voltage measurement circuit built in the wireless tag T measures the voltage value of the rectifier circuit. By the way, if the energy given from the interrogation signal to the tag antenna is substantially constant, the electromotive force due to electromagnetic induction is also substantially constant. Therefore, the generated voltage value is considered to be determined by the electric resistance of the tag antenna. However, since the electric resistance of the tag antenna correlates with the temperature condition, the temperature can be known by measuring the voltage value. Based on this principle, the switching circuit switches the circuit based on the measured voltage value, and selects the storage unit that holds the temperature data corresponding to the measured voltage value from the plurality of storage units A1, A2, A3, A4. Then, the temperature data of the storage unit is read and supplied to the response signal. Upon receiving the response signal from the wireless tag T, the detection device 10 analyzes the response signal, reads the temperature data together with the identification signal of the wireless tag T, and sends the obtained information to a display device, a computer, a communication line, etc. The temperature display can be executed. The detection device 10 and the display device / computer / communication device may be integrated.

  It is possible to provide a very large number of storage units and display, for example, temperatures from 0 ° C. to 100 ° C. in increments of 1 ° C. However, each of the storage units A1, A2, A3, A4. When the temperature data of 35, 40, 45 ° C. is held and the measured voltage value corresponds to less than 30 ° C., the switching circuit selects the storage unit A1, and the measured voltage value corresponds to 30 to 35 ° C. When the storage unit A2 is selected, and when the measured voltage value corresponds to 35 to 40 ° C., the storage unit A3 is selected.

  By the way, in order to perform temperature detection at a plurality of locations, when a plurality of wireless tags T are arranged at different locations, different identification information is held respectively. In this case, it is necessary to identify a plurality of response signals. . For this purpose, a multi-access mode in which the anti-collision function of the wireless tag T is used and a single detection device 10 can simultaneously communicate with a plurality of wireless tags T may be adopted. Alternatively, a method may be considered in which a dedicated detection device 10 is prepared for each wireless tag T, and detection results of the detection devices 10 are aggregated and analyzed by a computer or the like.

[Second Embodiment]
The IC chip 1 of the wireless tag T used for constructing the temperature detection system according to the present invention can be configured as shown in FIG. The IC chip 1 has a storage unit that includes a wireless communication interface to which a tag antenna is connected, a modulation controller that controls modulation of radio waves, a nonvolatile memory, and the like, in common with the first embodiment shown in FIG. It is.

  The IC chip 1 of this example includes a voltage measuring circuit E1 that measures the voltage across the tag antenna, and a voltage that measures the voltage across the fixed resistor R connected to the rectifier circuit by the induced electromotive force generated in the tag antenna. The measurement circuit E2 is provided, and the voltage value V1 across the tag antenna measured by the former voltage measurement circuit E1 and the voltage value V2 across the fixed resistor R measured by the latter voltage measurement circuit E2 are stored in the storage unit. For example, it is input to a row / column decoder to constitute temperature data calculation means. A plurality of temperature data is stored in the memory of the storage unit.

  The IC chip 1 having such a configuration detects temperature based on the following principle. As described above, the electric resistance value of the tag antenna has a correlation with the temperature. In addition, the ratio between the voltage across the tag antenna when an induced electromotive force is generated in the tag antenna due to electromagnetic induction and the voltage across the fixed resistor R connected to the rectifier circuit varies when the electrical resistance of the tag antenna changes. . That is, the electrical resistance of the tag antenna can be obtained from the comparison data between the voltage value at both ends of the tag antenna and the voltage value at both ends of the fixed resistor, based on a certain relational expression, and temperature data can be obtained therefrom.

  In this example, the both-end voltage value V1 of the tag antenna measured by the voltage measurement circuit E1 is input to the row decoder of the storage unit, and the both-end voltage value V2 of the fixed resistor R measured by the voltage measurement circuit E2 is input to the column decoder of the storage unit. It was configured to be input. A correlation formula between the value of the ratio V2 / V1 of the voltage values V1 and V2 and the temperature is stored in advance in the memory. Accordingly, the corresponding temperature data can be read from the memory by the normal matrix decode signal output from the matrix decoder and the decoder signal based on the measured voltage values V1 and V2.

  The temperature detection system using the RFID tag T configured by the IC chip 1 is configured to read the temperature data based on the ratio between the voltage value V1 across the tag antenna and the voltage value V2 across the fixed resistor R. Does not depend on the strength of the interrogation signal received by the wireless tag. Therefore, the present embodiment has an advantage that accurate temperature data can be obtained even when the reception energy of the interrogation signal received by the wireless tag from the detection device varies.

  As long as the temperature detection system according to the present invention can be attached with a wireless tag, the temperature detection system can remotely execute the temperature detection. For example, if a wireless tag is arranged on the wall, ceiling, floor, etc. of a house, the detection and management of room temperature can be performed easily. If a wireless tag is placed in the bathtub in the bathroom, the temperature of the hot water can be detected or monitored. In addition, it can be applied to electric water heaters, water heaters, cooking utensils, lighting devices and their surroundings to monitor the temperature of these exothermic devices and prevent abnormal heating.

It is drawing which shows schematic structure of the example of utilization of the temperature detection system which concerns on this invention. 1 is a front view illustrating an example of a wireless tag, which relates to a temperature detection system according to the present invention. 1 is a block diagram schematically showing an internal structure of an IC chip in a wireless tag, relating to a first embodiment of a temperature detection system according to the present invention. FIG. FIG. 6 is a block diagram schematically illustrating an internal structure of an IC chip in a wireless tag, relating to a second embodiment of a temperature detection system according to the present invention.

Explanation of symbols

S ... temperature detection system T ... wireless tag 1 ... IC chip 2 ... tag antenna 3 ... substrate 10 ... detection device 11 ... reader antenna

Claims (3)

The detection device includes a radio wave transmission / reception function, and a wireless tag that returns a response signal to the detection device in response to an inquiry signal transmitted from the detection device, and the wireless tag depends on physical characteristics of the tag antenna. Temperature measuring means, means for generating temperature data based on the measured value, and means for supplying the temperature data to a response signal returned by the wireless tag. Detection system. The wireless tag includes means for measuring an electromotive force voltage generated in the tag antenna when receiving an interrogation signal, a plurality of storage units for holding different temperature data, and a storage unit for reading data based on the measured voltage values. A storage unit that holds the corresponding temperature data from the plurality of storage units by switching the circuit based on the measured voltage value measured by the voltage value measurement unit. The temperature detection system according to claim 1, wherein the temperature detection system is set to read out temperature data from the storage unit. The wireless tag has a means for measuring a voltage value between both ends of an electromotive force generated in the tag antenna when receiving an interrogation signal, a voltage value between both ends of a fixed resistor provided in a circuit continuous to the tag antenna, and a temperature data The temperature detection system according to claim 1, further comprising: a calculation unit configured to generate temperature data based on the two measured voltage values.