JP5387771B2 - Passive sensor, wireless sensor system, and measurement method using wireless sensor system - Google Patents

Description

  The present invention relates to a wireless sensor system that performs remote measurement by wirelessly communicating a master device that receives an operation input and a slave device that performs measurement, and a passive sensor used in the wireless sensor system. The present invention also relates to a measurement method using such a wireless sensor system.

  Conventionally, as a system for measuring a predetermined physical quantity (temperature, pressure, etc.), there is a system using a passive sensor such as a SAW resonator as shown in Patent Document 1. In such a system, the SAW resonator utilizes the fact that the resonance frequency changes with temperature and pressure.

Japanese translation of PCT publication No. 2003-508739

  However, since the resonance frequency of a sensor element such as a SAW resonator depends on the shape of the sensor element, in a measurement system using such a sensor element, the measurement accuracy depends on the formation accuracy of the sensor element.

  However, when the required measurement accuracy is high, it is not easy to manufacture the sensor element within the range of manufacturing variation that satisfies the measurement accuracy.

  Therefore, an object of the present invention is to realize a wireless sensor system capable of obtaining high measurement accuracy even when there is an individual difference due to manufacturing variations of sensor elements, and a passive sensor used in the wireless sensor system.

  The present invention relates to a passive sensor. This passive sensor includes a sensor element, an antenna, and identification information recording means. The sensor element outputs a resonance signal having a frequency corresponding to the physical quantity to be sensed by an external excitation signal. The antenna is connected to the sensor element, and transmits and receives an excitation signal and a resonance signal. The identification information recording means records identification information based on the frequency characteristic of the sensor element with respect to the physical quantity.

  In this configuration, even if there is an individual difference in the frequency characteristic for each sensor element with respect to the physical quantity to be measured, identification information that can identify the frequency characteristic is provided for each passive sensor. Thereby, if the said identification information is acquired and the calculation process according to a frequency characteristic is performed, the measurement error of the physical quantity by the individual difference of a sensor element can be suppressed.

  In the passive sensor of the present invention, the identification information recording means is composed of marks formed in a plane such as numerals, alphabets, symbols, colors, and barcodes.

  This configuration shows a specific configuration example of the identification information recording means, and the identification information recording means is realized by various two-dimensional marks. Thereby, identification information can be easily acquired by the user visually recognizing and inputting an operation or performing an image reading process.

  In the passive sensor of the present invention, the identification information recording means is an RFID-IC connected to an antenna.

  This configuration also shows a specific configuration example of the identification information recording means, and the identification information recording means is realized by RFID-IC. Thereby, identification information can be acquired by radio | wireless communication similarly to the excitation signal and resonance signal for a measurement.

  The present invention also relates to a wireless sensor system including a passive sensor and a parent device that performs wireless communication with the passive sensor.

  As an example, the base unit of the wireless sensor system includes a storage unit, a base unit side antenna, an identification information acquisition unit, and a measurement unit. The storage unit of the master unit classifies the frequency characteristics of the sensor elements with respect to the physical quantity according to the difference in the frequency characteristics, and stores them in association with the identification information. The base unit side antenna transmits and receives the excitation signal and the resonance signal by electromagnetic coupling or radio waves with the antenna of the passive sensor. The identification information acquisition unit reads a mark that is an identification information recording unit, and acquires identification information. The measurement unit calculates a physical quantity based on the resonance frequency of the resonance signal, the identification information acquired by the identification information acquisition unit, and the frequency characteristics for each identification information stored in the storage unit.

  This configuration shows a wireless sensor system using a passive sensor provided with identification information recording means using the above-described marks.

  As another example, the base unit of the wireless sensor system includes a storage unit, a request signal generation unit, a base unit side antenna, an identification information acquisition unit, and a measurement unit. Similar to the above-described configuration, the storage unit classifies the frequency characteristics of the sensor elements with respect to the physical quantity according to the difference in the frequency characteristics, and stores them in association with the identification information. The request signal generation unit generates a request signal to the RFID-IC. The base unit side antenna transmits and receives an excitation signal, a resonance signal, a request signal, and a response signal from the passive sensor to the request signal by electromagnetic coupling or radio wave with the antenna of the passive sensor. The identification information acquisition unit analyzes the response signal and acquires identification information. The measurement unit calculates a physical quantity based on the resonance frequency of the resonance signal, the identification information acquired by the identification information acquisition unit, and the frequency characteristics for each identification information stored in the storage unit.

  This configuration shows a wireless sensor system using a passive sensor provided with the above-described RFID-IC identification information recording means.

  And by setting it as these system structures, the main | base station can obtain identification information with the resonance signal according to the physical quantity from a passive sensor. At this time, since the frequency characteristics corresponding to the individual difference of the sensor element (passive sensor) and the identification information are stored in association with each other in the parent device, the associated information and the frequency of the acquired resonance signal are stored. By using the identification information, the physical quantity can be measured while suppressing the influence of individual differences of the sensor elements.

  In the wireless sensor system of the present invention, the resonance signal, the request signal, and the response signal are communicated using different channels in the same communication band.

  In this configuration, when the above-described RFID-IC is used, measurement and identification information acquisition can be communicated with a signal in the same frequency band. At this time, interference between these signals can be prevented by using different channels in the same frequency band.

  The present invention also relates to a wireless sensor system including a passive sensor and a parent device. The passive sensor includes a sensor element that outputs a resonance signal having a frequency corresponding to a physical quantity to be sensed by an excitation signal from the outside, and an antenna that is connected to the sensor element and that transmits and receives the excitation signal and the resonance signal. The parent device includes a parent device that wirelessly communicates with a passive sensor and detects a physical quantity based on a resonance signal. In addition, this wireless sensor system includes a packaging material that packages a plurality of passive sensors grouped based on frequency characteristics with respect to a physical quantity to be sensed for each group. This packing material is provided with identification information recording means for identifying a group. The master unit includes an identification information acquisition unit that acquires identification information from the identification information recording unit, a resonance frequency of the resonance signal, identification information acquired by the identification information acquisition unit, and frequency characteristics for each identification information stored in advance. And a measurement unit that calculates a physical quantity based on the above.

  In this configuration, the identification information recording means is provided for each packing material that includes a plurality of passive sensors. Thereby, it is not necessary to provide identification information recording means for each passive sensor.

  In addition, the present invention includes a sensor element that resonates at a frequency corresponding to a physical quantity to be sensed, receives a excitation signal from the master unit and transmits a resonance signal, and transmits an excitation signal and receives a resonance signal. Then, the present invention relates to a measurement method using a wireless sensor system including a master unit that calculates a physical quantity based on the frequency of the resonance signal. This measurement method has at least the following three steps. First, this measurement method includes a step of classifying passive sensors according to differences in frequency characteristics of sensor elements with respect to physical quantities, and recording them in association with identification information. This measurement method includes a step of detecting a physical quantity with a sensor element and outputting a resonance signal. This measurement method includes a step of calculating a physical quantity based on a resonance signal, identification information, and frequency characteristics for each identification information.

  According to the present invention, it is possible to realize a wireless sensor system that can suppress measurement errors due to individual differences of sensor elements and obtain high measurement accuracy, and a passive sensor used in the wireless sensor system.

1 is a block diagram illustrating a configuration of a wireless sensor system 1 according to a first embodiment. It is a figure for demonstrating the concept of a group classification | category and a measurement process. It is a flowchart which shows the pre-process of measurement which concerns on 1st Embodiment. It is a flowchart which shows the measurement process which concerns on 1st Embodiment. It is a figure for demonstrating the concept of the measurement process using group classification. It is a block diagram which shows the structure of 1 A of wireless type sensor systems which concern on 2nd Embodiment. It is a figure which shows the setting concept of the frequency band which concerns on 2nd Embodiment. It is a flowchart which shows the measurement process which concerns on 2nd Embodiment.

  A wireless sensor system according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a wireless sensor system 1 according to the present embodiment.

<Description of configuration>
The wireless sensor system 1 includes a passive sensor 10 and a parent device 20. Passive sensor 10 and base unit 20 perform communication by electromagnetic field coupling or radio wave transmission / reception. The communication mode is not limited to electromagnetic field coupling, but may be based on electromagnetic induction or radio wave radiation.

  The passive sensor 10 includes an antenna 11, a SAW resonator 12 corresponding to the “sensor element” of the present application, and an identification mark 13. In the present invention, a SAW resonator is used as the sensor element. However, the resonance frequency varies depending on the physical quantity (temperature, magnetic strength, etc.) to be detected, such as a piezoelectric resonator, a crystal resonator, or a tuning fork resonator. Others may be used as long as they change.

  The antenna 11 is realized by a coil electrode formed in a winding shape if the electromagnetic coupling method is used, and is realized by a dipole antenna, for example, if it is a radio wave transmission / reception method. In any method, the antenna 11 is formed in a shape (electrode length or the like) corresponding to a frequency band used for communication. The antenna 11 receives the excitation signal SpL from the base unit side antenna 24 of the base unit 20 and applies it to the SAW resonator 12. The antenna 11 radiates the resonance signal Sfp output from the SAW resonator 12 to the outside. The resonance signal Sfp is transmitted from the antenna 11 of the passive sensor 10 to the parent device side antenna 24 of the parent device 20 by receiving the radiated resonance signal Sfp by the parent device side antenna 24.

  As a schematic configuration, the SAW resonator 12 includes a piezoelectric substrate and an IDT electrode formed on the surface of the piezoelectric substrate. The resonance frequency is determined by the material of the piezoelectric substrate and the shape of the IDT electrode. For this reason, the SAW resonator 12 has individual differences in resonance frequency and frequency characteristics based on the formation accuracy in the manufacturing process. Such individual differences are completely unavoidable in the manufacturing process and affect measurement accuracy. However, in the present application, although specific contents will be described later, it is possible to suppress deterioration in measurement accuracy due to the individual difference.

  The SAW resonator 12 has a characteristic of sensing a predetermined physical quantity (in this embodiment, magnetic intensity is taken as an example) and being excited at a resonance frequency corresponding to the sensed magnetic intensity. Therefore, when the pulsed excitation signal SpL is received from the antenna 11, the SAW resonator 12 is excited at a resonance frequency corresponding to the sensed magnetic intensity and outputs the resonance signal Sfp. The resonance signal Sfp is output to the antenna 11.

  The identification mark 13 is a mark printed on a base material (for example, a base substrate) of the passive sensor 10 on which the antenna 11 and the SAW resonator 12 are disposed. Specifically, numerals, alphabets, other symbols, colors, barcodes, and the like are used for the marks, and conceptually, any information that can be visually identified may be used. This mark is set in advance based on the individual difference of the frequency characteristic for each SAW resonator described above, and the mark means the identification group information Gr for each identification group.

  The base unit 20 includes a control unit 21, a transmission signal generation unit 22, a transmission / reception unit 23, a base unit side antenna 24, a measurement unit 25, an identification information reading unit 26 corresponding to the “identification information acquisition unit” of the present application, and a display unit 27. Is provided.

  The control unit 21 performs overall control of the parent device 20, and performs transmission / reception control such as switching between transmission mode and reception mode, and identification information acquisition control. These controls are executed based on the operation input content from the operation unit 28, for example.

  The transmission signal generation unit 22 generates a pulsed excitation signal SpL in accordance with transmission mode start control from the control unit 21, and outputs it to the transmission / reception unit 23.

  The transmission / reception unit 23 outputs the excitation signal SpL from the transmission signal generation unit 22 to the parent device side antenna 24 and outputs the resonance signal Sfp from the parent device side antenna 24 to the measurement unit 25. Similar to the antenna 11 of the passive sensor 10, the parent device side antenna 24 is realized by an antenna using a flat coil electrode or a dipole antenna according to specifications.

  The measurement unit 25 includes a frequency conversion unit 251, a physical quantity detection unit 252, and a storage unit 252. The frequency conversion unit 251 analyzes the frequency of the resonance signal Sfp and detects the resonance frequency fp.

  The storage unit 253 stores identification group information Gr and frequency characteristics (magnetic intensity-frequency characteristics) with respect to the magnetic intensity associated with each identification group information Gr.

  The identification group information Gr is input from the identification information reading unit 26 to the physical quantity detection unit 252. Based on the identification group information Gr, the physical quantity detection unit 252 reads the magnetic intensity-frequency characteristics corresponding to the corresponding identification group information Gr from the storage unit 253. The physical quantity detection unit 252 compares the read magnetic strength-frequency characteristic with the resonance frequency from the frequency conversion unit 251, and calculates the magnetic strength by reading the magnetic strength corresponding to the resonance frequency.

  The identification information reading unit 26 includes an image reader or the like, reads the identification mark 13 of the passive sensor 10 and acquires identification group information Gr. Note that if the identification mark 13 can be easily recognized by a person such as a numeral or alphabet, the operation unit 28 can be used as an identification information reading unit. In this case, the identification group information Gr is acquired by an operation input from the user. Thus, the acquired identification group information Gr is given to the physical quantity detection unit 252 of the measurement unit 25 as described above.

  The display unit 27 includes a liquid crystal display or the like, and displays the magnetic intensity calculated by the measurement unit 25.

<Description of identification concept and identification process>
Next, the identification concept and identification process of group classification will be described. FIG. 2 is a diagram for explaining the concept of group classification. FIG. 3 is a flowchart showing pre-measurement processing including group classification.

  First, as shown in FIG. 2, an identification frequency width Δf is calculated from a required measurement error ΔER of magnetic strength and a theoretical magnetic strength-frequency characteristic serving as a reference characteristic (FIG. 3: S901). Thereby, the identification frequency width Δf according to the specification of the measurement error ΔER can be set.

  Next, the identification group information Gr is set for each band of the identification frequency width Δf with reference to the resonance frequency (reference frequency) Fo when no magnetic field is applied in the reference characteristics. Then, an upper limit frequency and a lower limit frequency, that is, a threshold frequency Thf is calculated for each identification group information Gr (FIG. 3: S902).

  For example, as shown in FIG. 2, the identification group information Gr4 is set between a frequency that is higher by Δf / 2 to the high frequency side and a frequency that is lower by Δf / 2 to the low frequency side, centered on the reference frequency Fo. To do. In other words, the frequency section from (Fo−Δf / 2) to (Fo + Δf / 2) is registered in the identification group information Gr4. The identification group information Gr4 is associated with a magnetic field strength-frequency characteristic that becomes the reference frequency Fo when no magnetic field is applied.

  Also, as shown in FIG. 2, the identification group information Gr3 is set between a frequency that is higher by Δf / 2 toward the high frequency side and a frequency that is lower by Δf / 2 toward the low frequency side, centered on the reference frequency Fo + Δf. To do. In other words, the frequency section from (Fo−Δf / 2) + Δf to (Fo + Δf / 2) + Δf is registered in the identification group information Gr3. The identification group information Gr3 is associated with a magnetic field strength-frequency characteristic that becomes the reference frequency Fo + Δf when no magnetic field is applied. Then, by performing such a shift process to the high frequency side, as shown in FIG. 2, the related information of the identification group information Gr2, Gr1 is set.

  Further, as shown in FIG. 2, the identification group information Gr5 is defined between a frequency that is higher by Δf / 2 to the high frequency side and a frequency that is lower by Δf / 2 to the low frequency side, centered on the reference frequency Fo−Δf. Set to. In other words, the frequency section from (Fo−Δf / 2) −Δf to (Fo + Δf / 2) −Δf is registered in the identification group information Gr5. The identification group information Gr5 is associated with a magnetic field strength-frequency characteristic that becomes the reference frequency Fo-Δf when no magnetic field is applied. Then, by performing such a shift process to the low frequency side, as shown in FIG. 2, the related information of the identification group information Gr6 is set.

  The number of identification group information Gr to be set is not limited to this, and may be set as appropriate based on the maximum frequency and the minimum frequency when no magnetic field is applied, which is caused by variations in the actual manufacturing process of the SAW resonator.

  Each identification group information set in this way and the magnetic intensity-frequency characteristics respectively associated with these identification group information are stored in the storage unit 253 of the measurement unit 25 of the parent device 20 (FIG. 3: S910). ).

  Next, based on the identification group information set in this way, the group classification of each manufactured SAW resonator 12 is performed.

  Specifically, each SAW resonator 12 is excited by applying a pulsed excitation signal SpL without applying a magnetic field, and the resonance frequency fp is experimentally measured. The identification group information Gr is determined by detecting which identification group information Gr1-6 the experimentally measured resonance frequency fp belongs to. For example, if the experimentally measured resonance frequency fp is between (Fo−Δf / 2) and (Fo + Δf / 2), the SAW resonator 12 is set in the identification group information Gr4 (FIG. 3: S903). ).

  After group classification in this way, the classified identification group information Gr is printed in the form of the identification mark 13 on the passive sensor 11 in which the SAW resonator 12 is disposed (FIG. 3: S904).

<Explanation of measurement concept and measurement process>
FIG. 4 is a flowchart illustrating a measurement process according to the embodiment. FIG. 5 is a diagram for explaining the concept of measurement processing using group classification.

  In the following description, the identification group information is acquired before acquiring the resonance signal, but the identification group information may be acquired after acquiring the resonance signal.

  First, base unit 20 starts the identification information acquisition mode (FIG. 4: S101). Thereby, the identification information reading part 26 of the main | base station 20 reads the identification mark 13 printed on the passive sensor 10 (FIG. 4: S102). The identification information reading unit 26 of the parent device 20 acquires identification group information Gr based on the identification mark 13 (FIG. 4: S103).

  Next, base unit 20 starts the transmission mode of the measurement mode (FIG. 4: S104). Base unit 20 transmits a pulsed excitation signal SpL (FIG. 4: S105). After transmitting excitation signal SpL, base unit 20 switches to reception mode (FIG. 4: S106).

  The passive sensor 10 receives the excitation signal SpL (FIG. 4: S201). The SAW resonator 12 of the passive sensor 10 is excited by the excitation signal SpL, resonates at a resonance frequency corresponding to the magnetic strength of the atmosphere, and outputs a resonance signal Sfp (FIG. 4: S202). The passive sensor 10 transmits a resonance signal Sfp (FIG. 4: S203).

  The base unit 20 receives the resonance signal Sfp (FIG. 4: S107), analyzes the frequency of the resonance signal Sfp, and detects the resonance frequency fp (FIG. 4: S108).

  Base unit 20 calculates the magnetic intensity based on the detected resonance frequency fp, the acquired identification group information Gr, and the magnetic intensity-frequency characteristics corresponding to the previously stored identification group information (FIG. 4: S109).

Specifically, the magnetic intensity is calculated using the concept as shown in FIG.
For example, when the identification group information of the SAW resonator 12 is Gr4, the magnetic intensity-frequency characteristic SP (G4) of the frequency (reference frequency) Fo when no magnetic field is applied is read. Then, the magnetic strength P4 is calculated by referring to the detected resonance frequency fp in the characteristic.

  For example, when the identification group information of the SAW resonator 12 is Gr1, the magnetic intensity-frequency characteristic SP (G1) of the frequency (Fo + 3Δf) when no magnetic field is applied is read. Then, the magnetic intensity P1 is calculated by referring to the detected resonance frequency fp in the characteristic.

  For example, when the identification group information of the SAW resonator 12 is Gr5, the magnetic intensity-frequency characteristic SP (G5) of the frequency (Fo−Δf) when no magnetic field is applied is read. Then, the magnetic intensity P5 is calculated by referring to the detected resonance frequency fp in the characteristic.

  By performing such processing, the measured value of the magnetic strength is within the range of the measurement error width ΔER of the identification group to which it belongs even if it is large, and the measurement error is a measurement error width ΔER corresponding to a preset specification. Become. That is, the magnetic intensity (physical quantity) can be reliably detected within a measurement error narrower than the measurement error that can be taken due to manufacturing variations of the SAW resonator 12.

  In other words, there is no need to adjust the manufacturing process, and only the SAW resonators having characteristics close to ideal characteristics are not selected and used, and measurement errors are suppressed as compared with a conventional system that does not perform identification. Can do.

  In addition, since it is not necessary to perform a selection process of SAW resonators close to ideal characteristics in this way, even a SAW resonator that could not be used conventionally can be measured with high accuracy. SAW resonators that could not be used conventionally can be used effectively. As a result, the yield can be improved and the passive sensor can be made inexpensive.

  As an example using such a group classification and another specific element for measurement using the group classification and another physical quantity, a 10.6 MHz crystal resonator as a reference frequency at a standard temperature is used as a sensor element. The case will be described.

  Such a crystal resonator has a temperature characteristic of a resonance frequency, and the resonance frequency and temperature have a linear relationship. The inclination, that is, the ratio of frequency change to temperature change is 947 Hz / ° C.

  Here, when a sensor element is manufactured using such a crystal resonator, the resonance frequency deviates from the reference frequency due to the thickness of the crystal resonator, the electrode thickness, or the like. Specifically, a variation of ± 100 ppm = ± 1060 Hz occurs due to the manufacturing process. Therefore, the temperature variation is 2120 Hz / (947 Hz / ° C.) = 2.239 ° C. In this state, the temperature measurement error is about ± 1.1 ° C.

  Therefore, the temperature measurement error (corresponding to ΔER) is set to 0.2 ° C. = ± 0.1 ° C. This corresponds to ± 94.7 Hz in terms of the identification frequency width Δf. Accordingly, the classification is performed in units of the identification frequency width Δf = ± 94.7 Hz around the reference frequency of 10.6 MHz, and is associated with the identification group information Gr.

  Here, for example, as a specific method for setting the group classification, a frequency range of about ± 1.06 MHz is set with 10.6 MHz as the center frequency (the above-described reference frequency Fo) based on the assumed variation in the above-described manufacturing process. Classification is performed using the identification frequency width Δf = ± 94.7 Hz. Specifically, for example, (10.6 MHz + 1231.1 Hz) to (10.6 MHz−1041.7 Hz) are classified by ± 94.7 Hz.

  Then, temperature-frequency characteristics are set and stored for each identification group information Gr.

  At the time of measurement, based on the acquired identification group information Gr, the temperature-frequency characteristics corresponding to the identification group information are read, and the detected resonance frequency fp is applied to calculate the temperature.

  By using such a method, it becomes possible to measure a temperature measurement error of ± 0.1 ° C.

  Next, a wireless sensor system according to a second embodiment will be described with reference to the drawings. FIG. 6 is a block diagram showing the configuration of the wireless sensor system 1A according to the present embodiment. FIG. 7 is a diagram showing a concept of setting a frequency band according to the present embodiment.

  The wireless sensor system 1A of the present embodiment is obtained by replacing the wireless sensor system 1 shown in the first embodiment with the identification mark 13 of the passive sensor 1 replaced with the RFID-IC 14 of the passive sensor 1A. is there. Along with this, the means for acquiring the identification information of the master unit 20A has been changed. Therefore, in the following, only differences from the first embodiment will be described in detail.

  The passive sensor 1A includes an RFID-IC 14. The RFID-IC 14 is connected to the antenna 11 similarly to the SAW resonator 12. The RFID-IC 14 stores the identification group information Gr described above. The RFID-IC 14 is activated by the request signal Srq from the parent device 20A, and generates a response signal San including the identification group information Gr. Response signal San is radiated from antenna 11 and transmitted to base unit 20A.

  Master device 20 </ b> A includes request signal generation unit 31 and identification information analysis unit 32 instead of identification information reading unit 26.

  When receiving the identification information acquisition control from the control unit 21A, the request signal generation unit 31 generates a request signal Srq having a predetermined frequency and outputs the request signal Srq to the transmission / reception unit 23A.

  The transmission / reception unit 23A is provided with a switch (SW) 231 and transmits a request signal Srq to the parent device side antenna 24 when acquiring identification information. Here, as shown in FIG. 8, the frequency frq of the request signal Srq and the frequency fan of the response signal San are set in the same frequency band as the resonance frequency of the SAW resonator 12, thereby obtaining identification information. Communication and communication for measurement can be realized by only a pair of parent device side antenna 24 and antenna 11. As a result, the passive sensor 10A and the parent device 20A can be downsized. Furthermore, as shown in FIG. 8, even if they are in the same frequency band, by using different channels (local bands), it is possible to prevent interference between the resonance signal Sfp, the request signal Srq, and the response signal San.

  In addition, the transmission / reception unit 23 </ b> A receives the response signal San when acquiring the identification information and outputs it to the identification information analysis unit 32.

  In the transmission mode, the transmission / reception unit 23A outputs the excitation signal SpL from the transmission signal generation unit 22 to the parent device side antenna 24 as described above, and the resonance signal Sfp from the parent device side antenna 24 to the measurement unit 25. Output.

  The identification information analysis unit 32 analyzes the response signal San and acquires identification group information Gr. The identification information analysis unit 32 outputs the identification group information to the physical quantity detection unit 252 of the measurement unit 25.

  Similar to the first embodiment, the measurement unit 25 calculates the magnetic strength using the identification group information Gr, the resonance frequency fp of the resonance signal Sfp, and the magnetic strength-frequency characteristics for each identification group.

  Next, a measurement method according to the configuration of the present embodiment will be described with reference to FIG. FIG. 8 is a flowchart showing measurement processing according to the present embodiment.

  First, the master unit 20A starts a measurement mode (S301), and transmits a pulsed excitation signal SpL (S302). After transmitting excitation signal SpL, base unit 20A switches to reception mode (S303).

  The passive sensor 10A receives the excitation signal SpL (S201). The SAW resonator 12 of the passive sensor 10A is excited by the excitation signal SpL, oscillates at a resonance frequency corresponding to the magnetic intensity of the atmosphere, and outputs a resonance signal Sfp (S202). The passive sensor 10A transmits a resonance signal Sfp (S203).

  Main unit 20A receives resonance signal Sfp (S304), performs frequency analysis of resonance signal Sfp, and detects resonance frequency fp (S305).

  Master unit 20A detects which channel in the used frequency band the resonance frequency fp corresponds to. Furthermore, base unit 20A senses the availability of other channels in the used frequency band (S306).

  Base unit 20A generates request signal Srq at the detected frequency of the vacant channel and transmits it from base unit side antenna 24 (S307).

  The passive sensor 10A receives the request signal Srq (S204). The RFID-IC 14 of the passive sensor 10A is activated by the request signal Srq, and generates a response signal San including its own identification group information Gr. The passive sensor 10A transmits a response signal San from the antenna 11 (S205).

  Main unit 20A receives response signal San (S308). Main unit 20A analyzes response signal San and acquires identification group information Gr (S309).

  Main unit 20A calculates the magnetic intensity based on the detected resonance frequency fp, the acquired identification group information Gr, and the magnetic intensity-frequency characteristics corresponding to the previously stored identification group information (S310).

  Even with such a configuration and method, the magnetic intensity can be measured with a small measurement error. Furthermore, if the configuration of the present embodiment is used, the external access means for acquiring the identification group information in the master unit and the external access means for measurement are only antennas, and the size can be reduced.

  In the first embodiment described above, an example in which the identification mark 13 is printed for each passive sensor 10 has been shown. However, the passive sensor 10 is packed for each identification group, packed in the same box, and packed when shipped. An identification mark may be printed on the box. In this case, base unit 20 may read the identification mark provided on the packing box. Thus, by providing the identification mark on the packing box, it is not necessary to provide the identification mark for each passive sensor 10. Therefore, the passive sensor 10 can be further downsized. This can be similarly applied to the RFID-IC shown in the second embodiment.

1,1A-wireless sensor system, 10,10A-passive sensor, 11-antenna, 12-SAW resonator, 13-identification mark, 14-RFID-IC,
20, 20A-base unit, 21, 21A-control unit, 22-transmission signal generation unit, 23, 23A-transmission / reception unit, 24-base unit side antenna, 25-measurement unit, 251-frequency conversion unit, 252-physical quantity detection Section, 253-storage section, 26-identification information reading section, 27-display section, 31-request signal generation section, 32-identification information analysis section

Claims (8)

A sensor element that outputs a resonance signal having a frequency corresponding to a physical quantity to be detected by an external excitation signal;
An antenna connected to the sensor element for transmitting and receiving the excitation signal and the resonance signal;
A passive sensor comprising: identification information recording means for recording identification information based on a frequency characteristic of the sensor element with respect to the physical quantity. The passive sensor according to claim 1,
The identification information recording means is a passive sensor composed of planarly formed marks such as numerals, alphabets, symbols, colors, and barcodes. The passive sensor according to claim 1,
The identification information recording means is a passive sensor that is an RFID-IC connected to the antenna. A wireless sensor system comprising the passive sensor according to any one of claims 1 and 2, and a master unit that performs wireless communication with the passive sensor,
The base unit is
A storage unit that classifies the frequency characteristics of the sensor element with respect to a physical quantity according to the difference in the frequency characteristics, and stores them in association with identification information;
A parent-side antenna that transmits and receives the excitation signal and the resonance signal by electromagnetic coupling or radio waves with the antenna of the passive sensor;
An identification information acquisition unit that reads the mark as the identification information recording means and acquires the identification information;
A measurement unit that calculates the physical quantity based on a resonance frequency of the resonance signal, the identification information acquired by the identification information acquisition unit, and the frequency characteristics for each of the identification information stored in the storage unit; With
Wireless sensor system. A wireless sensor system comprising the passive sensor according to claim 3 and a parent device that performs wireless communication with the passive sensor,
The base unit is
A storage unit that classifies the frequency characteristics of the sensor element with respect to a physical quantity according to the difference in the frequency characteristics, and stores them in association with identification information;
A request signal generator for generating a request signal to the RFID-IC;
A base-side antenna that transmits and receives the excitation signal, the resonance signal, the request signal, and a response signal from the passive sensor to the request signal by electromagnetic coupling or radio waves with the passive sensor antenna;
An identification information acquisition unit that analyzes the response signal and acquires the identification information;
A measurement unit that calculates the physical quantity based on a resonance frequency of the resonance signal, the identification information acquired by the identification information acquisition unit, and the frequency characteristics for each of the identification information stored in the storage unit; With
Wireless sensor system. The wireless sensor system according to claim 5,
A wireless sensor system that communicates the resonance signal, the request signal, and the response signal using different channels in the same communication band. A sensor element that outputs a resonance signal having a frequency corresponding to a physical quantity to be sensed by an excitation signal from outside, and a passive sensor that is connected to the sensor element and has an antenna that transmits and receives the excitation signal and the resonance signal When,
A wireless sensor system comprising: a base unit that wirelessly communicates with the passive sensor and detects the physical quantity based on the resonance signal;
A plurality of passive sensors grouped based on frequency characteristics with respect to a physical quantity to be sensed are provided with a packing material for packing each group, and the packing material is provided with identification information recording means for identifying the group. ,
The base unit is
An identification information acquisition unit for acquiring identification information from the identification information recording means;
A measurement unit that calculates the physical quantity based on a resonance frequency of the resonance signal, the identification information acquired by the identification information acquisition unit, and the frequency characteristics for each of the identification information stored in advance. The
Wireless sensor system. A passive sensor that includes a sensor element that resonates at a frequency according to a physical quantity to be sensed, receives an excitation signal from the parent device, and transmits a resonance signal;
A measurement method using a wireless sensor system comprising: a master unit that transmits the excitation signal, receives the resonance signal, and calculates the physical quantity based on a frequency of the resonance signal;
Classifying the passive sensor according to a difference in frequency characteristics of the sensor element with respect to a physical quantity, and recording it in association with identification information;
Detecting the physical quantity with the sensor element and outputting a resonance signal;
A measurement method using a wireless sensor system, comprising: calculating the physical quantity based on the resonance signal, the identification information, and the frequency characteristic for each stored identification information.

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