JP2010261840A - Surface acoustic wave element, sensor, sensing system, and state detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave element that readily detects the response of a plurality of element parts, using a simple and small-sized circuit by utilizing a signal level detection system, and to provide a sensor, a sensing system and a state detection method. <P>SOLUTION: Since a first delay part 51, having a structure of a delay line is, included between an element part 19 for measurement and an element part 21 for reference, a signal outputted from the element part 19 for measurement can be delayed, with respect to a signal outputted from the element part 21 for reference. Namely, the signal outputted from the element part 19 for measurement can be made to deviate, in time from the signal outputted from the element part 21 for reference. Consequently, even when the signal outputted from the element part 19 for measurement and the signal outputted from the element part 21 for reference are transmitted by radio, an external device 3 which receives the signals can separate both signals, according to the deviation in time between both signals. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention uses surface acoustic waves (surface acoustic waves: SAW) to detect changes in various states (gas concentration, temperature, pressure, liquid viscosity, etc.) of a measurement object, and two or more elements Surface acoustic wave element provided with a portion (for example, a reference element portion, a measurement element portion), a sensor thereof, a sensing system including an external device that transmits and receives signals to and from the sensor, and a measurement target using the surface acoustic wave The present invention relates to a state detection method for detecting the state of the above.

  Conventionally, a sensing system that detects the gas concentration, temperature, pressure, liquid viscosity, etc. of the measurement object using the characteristics of surface acoustic waves has been developed. For example, a delay time or phase change by a delay line is used. A detection method and a detection method using a signal level change or a frequency change using a resonator are known.

Among these, as a method for detecting temperature and pressure based on a delay time using a delay line, a technique using a chirp signal has been proposed (see Patent Document 1).
In the case of detecting a measurement target gas, a resonance type sensor is known for the purpose of miniaturization and high sensitivity (see Patent Document 2).

  Furthermore, when detecting mechanical perturbations such as stress and pressure, the response due to the delay line is very small, on the order of nanometers. Therefore, sensors using resonators are the mainstream. A technique of detection, that is, a technique of detecting a signal wave transmitted wirelessly from a resonant sensor by a receiving circuit (resonant frequency detection) has already been studied (see Patent Documents 3 and 4).

JP 7-502613 A JP 2006-313092 A JP 2005-501235 A Special table 2007-52248 gazette

  Resonance frequency detection and signal level detection are known as detection methods when the above-described resonance type sensor is used. For example, an element unit including an electrode unit composed of a pair of comb electrodes and a reflector corresponding thereto. When a plurality of (for example, a measurement element part and a reference element part or a plurality of gas detection elements) are used and the detection is performed wirelessly, there are the following problems.

  In other words, in resonant frequency detection, by disposing elements with different resonant frequencies and using frequency modulation, components corresponding to each element part can be decomposed from the received signal, so that reflected signals are received simultaneously from multiple element parts. Even in such a case, separation / demodulation is possible, but for that purpose, a frequency synthesizer is required, and there is a problem that the circuit configuration becomes complicated and the size becomes large.

On the other hand, in the case of signal level detection, a simple circuit configuration is used. However, since reception signals are mixed, it is difficult to separate and detect signals from a plurality of element units.
SUMMARY OF THE INVENTION The present invention has been made in view of such problems. A surface acoustic wave element and a sensor that can employ a signal level detection method and can easily detect a response waveform composed of a plurality of elements with a simple and small circuit. It is an object to provide a sensing system and a state detection method.

  (1) In the invention of claim 1, one element portion having a pair of electrodes and a reflector on a piezoelectric substrate and a gas adsorber for adsorbing a measurement target gas, and a pair of electrodes and a reflector on the piezoelectric substrate are provided. A surface acoustic wave element having a frequency characteristic that changes in accordance with a calorific value or an increase in mass due to the measurement target gas adsorbed on the gas adsorbent. A first delay unit for delaying a signal of one element unit with respect to a signal of the other element unit is provided.

  In the present invention, the signal of one element part (for example, the element part for measurement provided with the gas adsorbent) is delayed from the signal of the other element part (for example, the element part for reference). Since the first delay unit (for example, constituted by a delay line) is provided, for example, the signal output from the measurement element unit and the signal output from the reference element unit are shifted in time. Can do.

  Therefore, for example, even when the signal output from the measurement element unit and the signal output from the reference element unit are transmitted wirelessly, the received device causes both signals Can be detected separately. Therefore, the signal level detection method is applied to each signal to grasp the signal state, and the state of the measurement target gas (for example, gas concentration) is easily grasped by performing a predetermined simple calculation. be able to.

  In other words, according to the present invention, a signal level detection method using a surface acoustic wave element including a measurement element section and a reference element section and transmitting a signal wirelessly can be achieved with a simple circuit configuration. The state of the measurement target gas can be easily detected.

(2) The invention of claim 2 is characterized in that the surface acoustic wave element can detect a gas concentration.
The present invention exemplifies the use of a surface acoustic wave device.

  (3) The invention of claim 3 has two or more element portions each including a pair of electrodes and a reflector on a piezoelectric substrate, and the frequency characteristics change according to perturbation applied to any of the element portions. A surface acoustic wave element, comprising: a measurement element unit that receives perturbation of a measurement target; and a reference element unit that is used to correct the output of the measurement element unit. A first delay unit for delaying a signal of the element unit with respect to a signal of the other element unit is provided.

  In the present invention, the first delay unit that delays the signal of one element unit from the element unit for measurement and the element unit for reference is provided with respect to the signal of the other element unit. The signal output from the element unit and the signal output from the reference element unit can be shifted in time.

  Therefore, even when the signal output from the measurement element unit and the signal output from the reference element unit are transmitted wirelessly, the receiving device separates both signals due to the time lag between both signals. And can be detected. Therefore, it is possible to easily grasp the state of the measurement object (pressure, etc.) by applying a signal level detection method to each signal to grasp the state of the signal and performing a predetermined simple calculation. it can.

  In other words, according to the present invention, a signal level detection method using a surface acoustic wave element including a measurement element section and a reference element section and transmitting a signal wirelessly can be achieved with a simple circuit configuration. The state of the measurement target can be easily detected.

  Here, as the element part for reference, an element part that does not receive the state change of the measurement object or receives a different degree can be adopted. Therefore, for example, a signal from a measurement element that receives a change (for example, pressure) of a measurement object and is influenced by other factors (for example, temperature), and a signal that does not receive a change (for example, pressure) of the measurement object By obtaining the difference between the signals from the reference element portion that is affected by the above factors (for example, temperature), the change (for example, pressure) of the measurement object can be measured.

(4) The invention of claim 4 is characterized in that the surface acoustic wave element is capable of detecting gas pressure.
The present invention exemplifies the use of a surface acoustic wave device.

(5) The invention of claim 5 is characterized in that a piezoelectric substrate that excites a surface acoustic wave that does not emit energy to the liquid is used as the piezoelectric substrate of the surface acoustic wave element.
In the present invention, for example, by selecting the material and cut angle of the piezoelectric substrate (for example, by adopting 36 ° YX-LiTaO ₃ ), surface acoustic waves that do not radiate energy to the liquid (for example, mainly SH waves and labs). (A transverse wave such as a wave) can be excited.

This makes it possible to detect the state of the liquid such as the physical property values (for example, viscosity, density, etc.) of the liquid.
(6) The invention of claim 6 is characterized in that the surface acoustic wave element can detect a physical property value of a liquid.

The present invention exemplifies the use of a surface acoustic wave device.
(7) In the invention according to claim 7, mutual signal interference occurs between the signal line connected to the other element part and the signal line of the one element part connected via the first delay part. It is characterized by being distributed so as not to.

In the present invention, since the signals flowing in the signal lines are separated by time delay, measurement can be performed without signal interference.
(8) The invention of claim 8 is characterized in that the first delay section is a delay line using sound waves.

The present invention exemplifies the characteristics of the first delay unit.
(9) The invention of claim 9 is characterized in that when there are a plurality of the first delay portions, at least one of the first delay portions is provided on the piezoelectric substrate.

Thereby, the structure of a surface acoustic wave element can be made compact.
(10) The invention of claim 10 further includes a temperature detecting element portion capable of detecting temperature independently.

Since the present invention includes a temperature detecting element, for example, pressure can be detected, and temperature can be detected with high accuracy.
If the environment in which the sensor is installed is an environment in which perturbations other than the measurement target and temperature do not occur, the reference element portion can be used as the temperature element portion. That is, since it is not necessary to install a temperature element again, the sensor can be manufactured in a small size and at low cost.

  (11) The invention of claim 11 applies pressure to the surface acoustic wave element according to any one of claims 3, 4, 7 to 10 and an element portion for measurement of the surface acoustic wave element. A pressure applying unit; an antenna that wirelessly transmits a signal corresponding to the change in the frequency characteristic of the surface acoustic wave element to an external device; and a housing that houses the surface acoustic wave element and the antenna. It is characterized by that.

The present invention exemplifies the configuration of a pressure sensor.
(12) The invention of claim 12 applies gas to the surface acoustic wave element according to any one of claims 1, 2, 7 to 10 and an element portion for measurement of the surface acoustic wave element. A gas adsorber, an antenna that wirelessly transmits a signal corresponding to the change in the frequency characteristics of the surface acoustic wave element to an external device, and a housing that houses the surface acoustic wave element and the antenna. It is characterized by that.

The present invention exemplifies the configuration of a gas sensor.
(13) A thirteenth aspect of the invention is to hold a liquid to be measured with respect to the surface acoustic wave element according to any one of the fifth to tenth aspects and a measurement element portion of the surface acoustic wave element. A liquid adding portion including an enclosure, an antenna that wirelessly transmits a signal corresponding to the change in the frequency characteristics of the surface acoustic wave element to an external device, and a housing that houses the surface acoustic wave element and the antenna And.

The present invention exemplifies the configuration of a liquid phase sensor.
(14) According to the fourteenth aspect of the present invention, there is provided a first method for preventing interference between a signal input from the external device and a signal output from the surface acoustic wave element between the surface acoustic wave element and the antenna. A two-delay unit is provided.

  In the present invention, since the second delay unit (for example, constituted by a delay line) is provided between the surface acoustic wave element and the antenna, the signal input from the external device and the surface acoustic wave element are output. It is possible to prevent interference with the signal.

  (15) The invention of claim 15 includes the sensor according to any one of claims 11 to 14 and an external device that wirelessly transmits and receives signals to and from the sensor. The state of the measurement object is detected by a level change of an output signal of the element unit with respect to an input signal having a specific frequency.

  The present invention is a sensing system that wirelessly transmits and receives signals between a sensor and an external device. In this sensing system, it is possible to easily detect the state of the measurement object based on the level change (change in signal strength) of the output signal of the element unit with respect to the input signal of a specific frequency from the external device to the element unit.

(16) The invention of claim 16 is characterized in that the sensor is arranged in a measurement space, a signal from the sensor is received by the external device, and a state in the measurement space is detected.
The present invention relates to a sensing system for detecting a state in a measurement space, specifically, for example, a sensing system for detecting a pressure in a tire by arranging a sensor in the tire, and a gas sensor in a closed space. A sensing system for measuring the gas concentration in the space is illustrated.

  (17) The invention of claim 17 is provided with a measurement element portion that is provided with a pair of electrodes, a reflector, and a gas adsorber that adsorbs a measurement target gas on a piezoelectric substrate, and is affected by the adsorption of the measurement target gas; A piezoelectric substrate having a pair of electrodes and a reflector, and a reference element portion used for correcting the output of the measurement element portion, and the gas to be measured is adsorbed to the gas adsorber A sensor having a surface acoustic wave element whose frequency characteristics change according to the amount of heat generated or the amount of increase in mass, and an external device that performs wireless communication with the sensor, and from the external device to the surface acoustic wave A state detection method for detecting a state of a gas to be measured based on a level change of an output signal (reflected signal) from the surface acoustic wave element with respect to an input signal having a specific frequency to the element. The signal of the element part of The signals of the two element units are temporally delayed to separate the signals of the two element units, and the state of the measurement object is detected based on the separated signals (by performing a predetermined calculation). It is characterized by that.

  In the present invention, among the element part for measurement of the surface acoustic wave element and the element part for reference, the signal of one element part is delayed in time with respect to the signal of the other element part, The signal is separated, and the state of the measurement target gas can be detected using the separated signal.

  That is, by delaying the signal of one element unit with respect to the signal of the other element unit, the signal output from the measurement element unit and the signal output from the reference element unit are temporally Can be shifted. Therefore, when the signal output from the measurement element unit and the signal output from the reference element unit are transmitted wirelessly, the receiving device separates both signals due to the time lag of both signals. can do. Therefore, it is possible to easily grasp the state of the measurement target gas by grasping the state of the signal by applying the signal level detection method to the separated signal.

  That is, according to the present invention, when a surface acoustic wave element including an element part for measurement and an element part for reference is used and a signal is transmitted wirelessly, a signal level detection method that requires a simple circuit configuration is used. The state of the measurement target gas can be easily detected.

  Note that the predetermined calculation is to extract only the response due to the measurement target (gas) by subtracting the response from the reference element from the response from the measurement element received separately ( For example, if the measurement element is a temperature element, the response from the temperature is extracted by subtracting the response from the reference element from the response from the temperature element) This is an operation to output a numerical value representing a state by fitting with a function or data that is a reference for quantity.

  (18) The invention of claim 18 is provided with a pair of electrodes and a reflector on a piezoelectric substrate, a measurement element portion that receives perturbation of a measurement target, a pair of electrodes and a reflector on the piezoelectric substrate, A surface acoustic wave element having a frequency characteristic that changes according to perturbation applied to the measurement element part, and a reference element part used for correcting the output of the measurement element part. A level change of an output signal (reflection signal) from the surface acoustic wave element with respect to an input signal of a specific frequency from the external apparatus to the surface acoustic wave element using a sensor and an external device that performs wireless communication with the sensor A state detection method for detecting a state of a measurement object by delaying a signal of one element part with respect to a signal of the other element part among the two element parts, Are separated from each other and based on the separated signals. Te (that performs a predetermined operation on) and detecting the state of the measurement target.

  In the present invention, among the element part for measurement of the surface acoustic wave element and the element part for reference, the signal of one element part is delayed in time with respect to the signal of the other element part, The signal can be separated, and the state of the measurement object can be detected using the separated signal.

  That is, by delaying the signal of one element unit with respect to the signal of the other element unit, the signal output from the measurement element unit and the signal output from the reference element unit are temporally Can be shifted. Therefore, when the signal output from the measurement element unit and the signal output from the reference element unit are transmitted wirelessly, the receiving device separates both signals due to the time lag of both signals. can do. Therefore, the state of the measurement target can be easily grasped by grasping the state of the signal by applying a signal level detection method to the separated signal.

  That is, according to the present invention, when a surface acoustic wave element including an element part for measurement and an element part for reference is used and a signal is transmitted wirelessly, a signal level detection method that requires a simple circuit configuration is used. The state of the measurement target can be easily detected.

  The predetermined calculation is to extract only the response due to the measurement target (for example, gas) by subtracting the response from the reference element from the response from the measurement element received separately. (For example, when the measurement element is a temperature element, only the response due to temperature is extracted by subtracting the response from the reference element from the response from the temperature). This is an operation to output a numerical value representing a state by fitting with a function or data that is a reference for quantity.

It is explanatory drawing which shows schematic structure of the sensing system in which the pressure sensor of Example 1 is used. It is explanatory drawing which shows schematic structure of the pressure sensor of Example 1. FIG. (A) is explanatory drawing which shows the surface where the surface acoustic wave element of a pressure sensor is affixed, (b) is sectional drawing which shows the state which fractured | ruptured the pressure sensor in the thickness direction. (A) is explanatory drawing which shows the basic structure of the resonance type surface acoustic wave element of the reference example 1, (b) is explanatory drawing which shows the basic operation | movement, (c) is a graph which shows the output characteristic. (A) is explanatory drawing which shows operation | movement of the surface acoustic wave element of the reference example 1, (b) is a graph which shows the measurement principle. (A) is explanatory drawing which shows the basic structure and operation | movement of the resonance type surface acoustic wave element of the reference example 2, (b) is explanatory drawing which shows the measurement principle. It is explanatory drawing which shows the electrical structure of the sensing system of Example 1. FIG. 3 is a timing chart of signals in the sensing system according to the first embodiment. It is explanatory drawing which shows schematic structure of the pressure sensor of Example 2. FIG. It is explanatory drawing which shows the electrical structure of the sensing system of Example 2. FIG. 6 is a signal timing chart in the sensing system according to the second embodiment. 6 is an explanatory view showing a hydrogen concentration sensor of Example 3. FIG. It is explanatory drawing which shows the other example of a hydrogen concentration sensor. It is explanatory drawing which shows a liquid phase sensor.

  Embodiments to which the present invention is applied will be described below with reference to the drawings.

In the present embodiment, for example, a pressure sensor used as a tire pressure sensor for detecting tire pressure will be described as an example.
As shown in FIG. 1, the pressure sensor 1 constitutes a sensing system that wirelessly transmits and receives signals to and from an external device (measuring device) 3, and a signal (high frequency signal) from the external device 3. In response, the response to the signal is transmitted to the external device 3, and the external device 3 determines the tire pressure.

  The pressure sensor 1 is attached to, for example, the inner surface of the tire 5, and the external device 3 is attached to, for example, a portion that does not rotate (for example, near the rim 7 or around the tire housing 9). Details will be described below.

a) First, the configuration of the pressure sensor 1 will be described.
As shown in FIG. 2, the pressure sensor 1 includes a surface acoustic wave element 11, a high frequency distributor / coupler 13, a delay unit (second delay unit) 15, and an antenna 17. I have.

Among these, the antenna 17 is an antenna for transmitting and receiving a high-frequency signal to and from the external device 3, and a tablet antenna, a patch antenna, or the like can be used.
The second delay unit 15 delays the propagation of the high-frequency signal. Here, in order to prevent the signal input from the external device 3 and the signal output from the surface acoustic wave element 11 from interfering with each other. The antenna 17 and the high-frequency distributor / coupler 13 are arranged. The second delay unit 15 is configured by a well-known delay line to be described later.

  The high-frequency distributor / coupler 13 distributes the high-frequency signal received from the external device 3 to different electrode parts (consisting of a pair of electrodes) and transmits them to the element parts 19, 21. In response to the response from 21, the electrodes are separated from each other so that the direction of signal transmission is given direction and signals from different electrodes are transmitted as one signal to the external device 3 side. Is. Therefore, it is not influenced by the high frequency signal transmitted / received in each electrode part between different electrode parts.

The surface acoustic wave element 11 includes a first converter (measuring element part) 19 and a second converter (reference element part) 21 that perform mechanical / electrical conversion between a surface acoustic wave and an electric signal. I have.
Specifically, the surface acoustic wave element 11 is configured such that the first electrode portion 25 (a pair of comb-shaped electrodes 27 and 29 of the measuring element portion 19 is fitted to each other on the same surface of the piezoelectric substrate 23. Electrode portion) and the second electrode portion 31 of the reference element portion 21 (the electrode portion formed by fitting a pair of comb-like electrodes 33 and 35 with each other) are separated in the left-right direction in FIG. Are arranged. One electrode 27 (upper side in the figure) of the first electrode part 25 and one electrode 33 (upper side in the figure) of the second electrode part 31 are electrically connected by the same first electrode pattern 37. .

  In addition, a strip-shaped reflector 39 that reflects the surface acoustic wave is provided on both sides of the first electrode portion 25 (both sides in the traveling direction of the surface acoustic wave: left and right in the figure) and both sides of the second electrode portion 31. 41, 43, 45 are arranged.

  Further, a delay unit (first delay unit) 51 including a pair of left and right third and fourth electrode units 47 and 49 is disposed between the measurement element unit 19 and the reference element unit 21. Similar to the first and second electrode portions 25 and 31, the third and fourth electrode portions 47 and 49 are configured by fitting a pair of comb-like electrodes 53, 55, 57, and 59 into each other. It is an electrode part.

  The first delay unit 51 delays the propagation of a signal from the fourth electrode unit 49 to the third electrode unit 47, and the third and fourth electrode units 47 and 49 perform the signal propagation in a predetermined manner. The delay line is delayed by the delay time. The third and fourth electrode portions 47 and 49 are bidirectional electrodes capable of transmitting signals on both the left and right sides of the figure, and between the measuring element portion 19 and the reference element portion 21. By being arranged adjacent to each other, the reflectors 41 and 43 of both element portions 19 and 21 can be used. For this reason, a small and low-loss delay line can be configured.

  That is, the surface acoustic wave excited by the fourth electrode portion 49 is determined by the interval between the third and fourth electrode portions 47 and 49 before being propagated from the fourth electrode portion 49 to the third electrode portion 47. Will be delayed. The second delay unit 15 has the same configuration.

  The one electrode 59 of the fourth electrode portion 49 and the one electrode 35 of the second electrode portion 31 are separated from each other in a spatially and electrically separated state so as not to interfere with each other. -It is connected to the coupler 13. Therefore, the high-frequency distributor / coupler 13 outputs a high-frequency signal separately to each of the fourth electrode portion 49 and the second electrode portion 31 (in another path indicated by the power transmission lines 14 and 16). In addition, the fourth electrode unit 49 and the second electrode unit 31 output high-frequency signals to the high-frequency distributor / coupler 13 separately (in different paths indicated by the power transmission lines 14 and 16).

Thereby, the signal (reflected signal) output from one element part can be prevented from flowing into the input signal of the other element part.
Furthermore, one electrode 29 of the first electrode portion 25 and one electrode 55 of the third electrode portion 47 are electrically connected by a second electrode pattern 61.

Here, the propagation path of the high frequency signal in the surface acoustic wave element 11 will be briefly described.
The reference element unit 21 converts a high-frequency signal supplied from the external device 3 into a surface acoustic wave, and converts an electrical signal into a surface acoustic wave by the inverse piezoelectric effect. That is, the high-frequency signal received by the antenna 17 and transmitted through the second delay unit 15 and the high-frequency distributor / coupler 13 is converted into a surface acoustic wave and perpendicular to the electrodes 33 and 35 of the second electrode unit 31. A surface acoustic wave is excited in the direction (left and right in the figure). The surface acoustic waves are reflected by the reflectors 43 and 45, received by the second electrode unit 31, and output to the high frequency distributor / coupler 13.

  On the other hand, the high-frequency signal output from the high-frequency distributor / coupler 13 to the fourth electrode portion 49 is converted into a surface acoustic wave, like the second electrode portion 31, and the surface acoustic wave is converted into a predetermined delay time, It propagates to the third electrode part 47 and is converted into a high frequency signal. Since the third electrode portion 47 is connected to the first electrode portion 25 by the second electrode pattern 61, a high frequency signal is transmitted from the third electrode portion 47 to the first electrode portion 25 of the measuring element portion 19. .

  The measurement element unit 19 converts a surface acoustic wave into an electric signal, like the reference element unit 21. As described above, since the first electrode portion 25 and the third electrode portion 47 are connected to the measuring element portion 19 (transmitted from the fourth electrode portion 49), the third electrode portion 47 The received delayed high-frequency signal is transmitted to the first electrode unit 25 and excites surface acoustic waves in the direction perpendicular to the electrodes 27 and 29 of the first electrode unit 25 (left and right in the figure). The surface acoustic waves are reflected by the reflectors 39 and 41 and received by the first electrode unit 25. Thereafter, the delayed high-frequency signal is output to the high-frequency distributor / coupler 13 through the third electrode portion 47 and the fourth electrode portion 49 along the reverse path of reception.

b) Next, a method for manufacturing the surface acoustic wave element 11 will be briefly described.
When the surface acoustic wave element 11 is manufactured, a metal (aluminum) film is formed on the piezoelectric substrate 23 by sputtering, masked by photolithography, and etched (shown in the gray portion) as shown in FIG. Patterning is performed so as to form a pattern such as an electrode.

The design values and materials of the surface acoustic wave element 11 of this example having a resonance frequency of 433 MHz are shown below.
・ Piezoelectric substrate: ST-X quartz substrate (single crystal), thickness 0.5mm
Surface = mirror finish, back = rough finish ・ Metal film: Aluminum, thickness 0.1μm
・ Electrode structure (shown schematically in FIG. 1 etc .: λ is wavelength)
Excitation electrode (first to fourth electrode parts)
Electrode width: 1 / 4λ (1.81 μm), electrode spacing: 1 / 4λ (1.81 μm), crossing width: 229.2 μm
Reflector electrode width: 1 / 4λ (1.81 μm), electrode spacing: 1 / 4λ (1.81 μm), number: 400 • excitation electrode-reflector distance: 3 / 8λ (2.657 μm)
Delay line propagation distance: 1500λ (4.735mm)
Element size: 16.463 mm x 1.997 mm
c) Next, the overall configuration of the pressure sensor 1 containing the surface acoustic wave element 11 will be described.

FIG. 3A shows the surface side of the substrate of the pressure sensor 1, and FIG. 3B shows a longitudinal section of the pressure sensor 1.
As shown in FIG. 3A, the surface acoustic wave element 11 is attached to a metal base 71 made of, for example, Kovar with an adhesive or the like.

  Specifically, as shown in FIG. 3B, the base 71 is provided with a recess 73 so that one end side (the measurement element portion 19 side) of the surface acoustic wave element 11 can be bent. The surface acoustic wave element 11 is arranged so that the measurement element portion 19 side projects above the recess 73, and the reference element portion 21 side is attached to the substrate surface.

  A cover 74 made of, for example, polycarbonate is covered on one side of the base 71 (the side where the surface acoustic wave element 11 is disposed) so as to cover the surface acoustic wave element 11 with a space therebetween.

  In addition, the cover 74 is provided with a circular opening 75 at a position facing the measurement element unit 19. The opening 75 has a metal disk (diaphragm) 77 made of, for example, stainless steel, and a rubber made part. An O-ring 79 is arranged, and a metal pressure transmission pin 81 that contacts the surface of the measuring element portion 19 is attached to the diaphragm 77.

  Accordingly, when the air pressure around the pressure sensor 1 increases, the diaphragm 77 is recessed and the pressure transmission pin 81 presses the vicinity of the measuring element portion 19, so that an output corresponding to this pressing force can be obtained.

  The electrodes and the like of the surface acoustic wave element 11 are connected to pins (not shown) penetrating a glass seal 83 provided on the base 71, and the electronic component installation substrate 82 in which the antenna 17 and the like are arranged via the pins. It is connected to the. Note that a housing 86 is constituted by a cover 84 and a lid 84 that covers the electronic component mounting substrate 82.

d) Next, the measurement principle of the pressure sensor 1 will be described together with a reference example.
4A shows the basic structure of the resonant surface acoustic wave element of Reference Example 1, FIG. 4B shows its basic operation, and FIG. 4C shows its output characteristics. FIG. 5A shows the operation of the surface acoustic wave element of Reference Example 1, and FIG. 5B shows the measurement principle. Similarly, FIG. 6A shows the basic structure and operation of the resonant surface acoustic wave device of Reference Example 2, and FIG. 6B shows the measurement principle.

  FIG. 4A shows the resonance type surface acoustic wave element 91 of Reference Example 1. This surface acoustic wave element 91 is formed from a pair of electrodes 95 and 97 that input and output a high-frequency signal in the center of the piezoelectric substrate 93. And the reflectors 101 and 103 are provided on both sides of the electrode part 99.

The surface acoustic wave element 91 utilizes a resonance wave obtained when each component is arranged so as to satisfy the Fabry-Perot resonance condition.
That is, when an electric signal (high frequency signal) is applied to the electrode part 99, it is converted into a surface acoustic wave having a frequency determined by the period of the electrodes 95 and 97 of the electrode part 99 due to the reverse voltage effect, as shown in FIG. Similarly, it propagates from the electrode part 99 in both the left and right directions in the figure (input). Thereafter, the surface acoustic waves reflected by the reflectors 101 and 103 reach the electrode portion 99 again while resonating, and are converted into an electric signal by the piezoelectric effect (output).

  Therefore, when the reflection characteristic (signal level) is observed using a measuring instrument such as a network analyzer, the signal level is minimized at the resonance point and increases as the distance from the resonance point is increased, as shown in FIG.

  As shown in FIG. 5A, when the surface acoustic wave element 91 of Reference Example 1 is subjected to a load (pressure, temperature, stress, etc.), the electrode portion 99 expands (shrinks) according to the load. As shown in FIG. 5B, the frequency characteristic changes. In order to detect this response, signal level change detection (detection method (1)) and resonance frequency change detection (detection method (2)) are known.

  Among these, in the signal level change detection method, the presence or absence of the load and the degree of load are detected from the change in the signal level (at the resonance point) that changes depending on the presence or absence of the load. In this embodiment, this detection method is used. Is adopted.

On the other hand, in the detection method of the resonance frequency change, the presence or absence of the load and the degree of the load are detected from the resonance frequency that changes depending on the presence or absence of the load.
The resonance type surface acoustic wave element 111 of Reference Example 2 shown in FIG. 6A is obtained by improving the surface acoustic wave element 91 of Reference Example 1 in order to detect a load with higher accuracy.

  When a load is detected by a sensor, an unnecessary response is generated depending on the installation environment of the sensor, so that correction is often required. As a countermeasure against this, the surface acoustic wave element 111 of Reference Example 2 in which element parts (measuring element part 113 and reference element part 115) having the same shape as the surface acoustic wave element 91 of Reference Example 1 are arranged on the left and right is developed. Has been.

  In the surface acoustic wave element 111, the measurement element portion 113 is an element portion (sensing) that receives a load to be measured, and the reference element portion 115 is an element portion (reference) that does not receive a load to be measured. As shown in b), by obtaining the operation output of each signal, it is possible to exclude the response due to the change in the measurement environment and extract only the response to be measured.

  For example, considering the case where the temperature changes when measuring the stress applied to the sensor, when the stress is applied to the sensor, the substrate is distorted, causing expansion / contraction. Further, thermal expansion / contraction of the substrate also occurs depending on the temperature. Therefore, in order to obtain a response of only the stress to be measured, only the temperature effect is applied to the reference element portion 115 without applying stress, and both the temperature and the stress are applied to the measurement element portion 113. Thus, by taking the difference between these element portions 113 and 115 (difference between sensing output and reference output), it is possible to detect only the stress to be measured.

The surface acoustic wave element 11 of this example is an improvement of the surface acoustic wave element 111 of the reference example 2 in order to detect a load with higher accuracy.
In other words, it is possible to detect the load by the signal level change detection method using the surface acoustic wave element 111 of Reference Example 2, but when the responses of the two element units 113 and 115 are transmitted wirelessly. The signals from both element parts 113 and 115 cannot be separated. In the case of the resonance frequency change detection method, it is possible to separate the signals, but in that case, a complicated circuit configuration is required.

Therefore, in this embodiment, the surface acoustic wave element 11 having the above-described configuration is used.
That is, as shown in FIG. 2, a first delay unit 51 that delays a high-frequency signal is provided between the measurement element unit 19 and the reference element unit 21, and the signal output from the measurement element unit 19 The signal output from the reference element unit 21 is shifted in time.

  In the present embodiment, the second delay unit 15 is provided between the antenna 17 and the surface acoustic wave element 11, and the signal input from the external device 3 and the signal output from the surface acoustic wave element 11 interfere with each other. To prevent that.

  Furthermore, in this embodiment, in order to prevent signal interference due to transmission of the reflected signal from the previous reference element unit 21 to the other measurement element unit 19, the antenna 17 and the second and fourth electrode units 31, 49 are used. The high-frequency distributor / coupler 13 is disposed between the two power transmission lines 14 and 16, that is, the power transmission line 14 and the fourth electrode section between the second electrode portion 31 and the high-frequency distributor / coupler 13. 49 and the power transmission line 16 between the high-frequency distributor / coupler 13 are provided with isolation (separation that does not cause mutual electrical interference).

e) Next, a sensing system using the pressure sensor 1 will be described together with its operation.
FIG. 7 shows a sensing system, and FIG. 8 shows signal timing in the sensing system.

Here, the signals shown in FIGS. 7 and 8 will be described together.
SPDT (Vcount): Signal transmitted from the external device SPDT (Tx): Switch signal when transmitted from the external device SPDT (Rx): Switch signal when received by the external device REF: Output of the reference element unit Signal Sensing: Output signal of measurement element unit Hold1: Signal for holding output signal of reference element unit Hold2: Signal for holding output signal of measurement element unit SDO: Signal output to controller tS: Signal length of the signal transmitted from the external device tSW: Time required for switching the transceiver of the external device tD: Delay time by the second delay unit tDET: Delay time by the first delay unit Note that, for example, tS = 1 us, tD = 2 us, tSW <0.1 us, tDEF = 3 us, and tHold = 0.1 us can be employed.

Since the delay time occurs in the forward and return paths of the signal, the delay time shown in FIG. 8 is the total.
First, as shown in FIG. 7, the external device 3 includes a controller 121, a phase synchronization IC (PLL IC) 123, and the like as its main parts.

  The phase synchronization IC 123 includes a phase synchronization circuit (PLL circuit) 125, and a signal from a reference frequency oscillator (TCXO) 127 and a signal from a voltage control oscillation circuit (VCO) 129 are input to the phase synchronization circuit 125. The phase synchronization circuit 125 outputs a signal to the outside of the phase synchronization IC 123 via a low pass filter (LPF) 131 that is a phase compensator and a voltage control transmission circuit 129. The controller 121 outputs a control signal (Enable) for controlling on / off of oscillation from the phase synchronization IC 123 to the phase synchronization IC 123.

  Therefore, the output of the signal oscillated from the phase synchronization IC 123 is reduced by the attenuator amplifier (ATT) 133, and the signal is switched via the bandpass filter (BPF) 135 and the power amplifier (PA) 136 to the switch (SPDT) 137. When the switch 137 is set to be capable of transmitting a signal, the signal is transmitted to the pressure sensor 1 via the antenna 139. This signal is a 433 MHz high frequency signal of 10 mW, for example, and is oscillated for tS (see FIG. 8).

  The operation of the switch 137 is controlled by a control signal (Select) output from the controller 121. The connection to the circuit side for transmission (signal Tx to be transmitted) and the connection to the circuit side for reception ( It is switched with the received signal Rx). Note that the period of tS shown in FIG. 8 is determined by the period of connection to the circuit side for transmission.

  Next, the signal transmitted from the external device 3 is received by the antenna 17 of the pressure sensor 1, and passes through the second delay unit (SAW DL) 15 and the high-frequency distributor / coupler (RF D · C) 13. It is transmitted to the surface acoustic wave element (SAW) 11. Details will be described below.

  As shown in FIG. 8, the signal received by the antenna 17 is delayed by the delay time tD by the second delay unit 15. This is to prevent interference between the input signal Tx and the signal (REF, Sensing) output from the pressure sensor 1 and received on the external device 3 side.

  Further, as described above, the signal delayed by the second delay unit 15 is supplied to the second electrode unit 31 of the reference element unit 21 and the fourth electrode of the first delay unit 51 via the high frequency distributor / coupler 13. Transmitted to the unit 49.

  Among these, the signal sent to the second electrode part 31 of the reference element part 21 is converted into a surface acoustic wave by the second electrode part 31, reflected by the reflectors 43, 45, and the second electrode part 31. And is converted into a high-frequency signal. This signal follows the reverse path, and is transmitted from the antenna 17 to the external device 3 via the high frequency distributor / coupler 13 and the second delay unit 15. As shown in REF, this signal is delayed by the delay time tD by the second delay unit 15.

  On the other hand, the signal transmitted to the fourth electrode unit 49 of the first delay unit 51 and delayed by a predetermined delay time by the first delay unit 51 is the first electrode unit 25 of the measuring element unit 19 as described above. Sent to. In the measurement element unit 19, the first electrode unit 25 converts it into a surface acoustic wave, the reflectors 39 and 41 reflect it, the first electrode unit 25 receives the signal and converts it into a high-frequency signal. This signal follows the reverse path, and is transmitted from the antenna 17 to the external device 3 via the high frequency distributor / coupler 13 and the second delay unit 15. As shown in Sensing, this signal is delayed by the delay time tDEF by the first delay unit 51 in addition to the delay time tD by the second delay unit 15.

  That is, in each element unit 19, 21, the signal for each element unit 19, 21 is separated by time. Communicating.

In the pressure sensor 1, the signals returned from the surface acoustic wave element 11 are again combined into one signal and transmitted from the antenna 17 to the external device 3.
As shown in FIG. 8, since the delay time tDEF is set sufficiently longer than the transmission signal length tS, the signal Tx transmitted from the external device 3 to the pressure sensor 1 and the pressure sensor 1 to the external device are set. The signals REF and Sensing returned to 3 can be separated by time.

  Next, in the external device 3 that has received the signal from the pressure sensor 1, the signal is amplified and noise-removed to a required level by the low noise amplifier (LNA) 141, and the log amplifier is passed through the band pass filter (BPF) 143. And a detector (DET) 145 comprising a diode.

  Thereafter, a signal is output from the detector 145 to two analog-digital converters (ADC) 147 and 149 for measurement and reference. Since this output (REF, Sensing) is shifted by the delay time tDET as shown in FIG. 8, the value of each output is held by the hold signal tHold output from the controller 121 at the time corresponding to each output. The value (SDO) is output to the controller 121.

Specifically, when detection of all signals for one cycle from transmission to reception is completed, the held value is read, and this is repeatedly measured at period T.
As a result, the controller 121 can obtain a reference signal for temperature only and a measurement signal for indicating pressure (tire pressure) and temperature in a state that is clearly separated in terms of time.

  Therefore, the controller 121 can extract only the signal corresponding to the pressure by taking the difference between the signal levels of the measurement signal and the reference signal, and therefore calculates the pressure value from the signal level corresponding to the pressure. be able to.

  That is, the air pressure (pressure) of the tire 5 is transmitted as strain to the measuring element unit 19 via the diaphragm 77 and the pressure transmission pin 81, and the signal intensity output from the pressure sensor 1 is increased by the strain amount of the measuring element unit 19. Change. Therefore, using the signal level detection method, the signal levels of the measurement signal and the reference signal can be obtained, and the difference between the two signal levels can be taken to extract only the signal corresponding to the pressure. On the other hand, since a linear relationship is established between the pressure and the response of the pressure sensor 1, the response amount to the pressure is mapped in advance, and the pressure in the tire 5 is determined by comparing with the measured value of the pressure. Can be identified.

  f) Thus, in this embodiment, the first delay unit 51 having the delay line structure is provided between the measurement element unit 19 and the reference element unit 21. The output signal can be delayed with respect to the signal output from the reference element unit 21.

  Thereby, since the signal output from the measurement element unit 19 and the signal output from the reference element unit 21 can be shifted in time, the signal output from the measurement element unit 19 and the reference element Even when the signal output from the unit 21 is transmitted wirelessly, the external device 3 that has received the signal can separate both signals due to the time lag between the two signals.

  Therefore, the signal state can be grasped by applying a signal level detection method to the separated signal. Then, using the signal after the level detection, from the signal corresponding to the pressure and temperature output from the measuring element unit 19 and the signal corresponding to the temperature output from the reference element unit 21, that is, the difference between both signals By taking this, it is possible to extract a signal indicating only the pressure.

  That is, according to the present embodiment, even when a surface acoustic wave element 11 including a measurement element unit 19 and a reference element unit 21 is used and a signal is transmitted wirelessly, signal level detection that requires a simple circuit configuration is possible. The pressure (air pressure) in the tire 5 can be easily detected by the method.

Next, the second embodiment will be described, but the description of the same contents as the first embodiment will be simplified.
a) First, the configuration of the pressure sensor of this embodiment will be described.
As shown in FIG. 9, the pressure sensor 151 of this embodiment includes a surface acoustic wave element 153, a high-frequency distributor / coupler 155, a second delay unit 157, and an antenna 159, as in the first embodiment. I have.

Similar to the first embodiment, the surface acoustic wave element 153 includes a measurement element unit 161, a reference element unit 163, and a first delay unit 165.
In particular, in this embodiment, a temperature measuring element portion 169 is provided on the opposite side of the first electrode pattern 167 from the measuring element portion 161 and the reference element portion 163.

The temperature measuring element unit 169 includes reflectors 177 and 181 on both sides of a fifth electrode unit 175 including a pair of electrodes 171 and 173.
One electrode 171 of the fifth electrode portion 175 is connected to the high frequency distributor / coupler 153. The fourth electrode unit 185 of the first delay unit 165 is connected to the high frequency distributor / coupler 153 via the third delay unit 187, and the second electrode unit 189 of the reference element unit 163 is connected to the fourth delay unit. It is connected to the high frequency distributor / coupler 153 via 191.

b) Next, a sensing system using the pressure sensor 151 will be described.
As shown in FIG. 10, the sensing system of this embodiment includes a pressure sensor 151 and an external device 201 as in the first embodiment.

  As in the first embodiment, the external device 201 includes a controller 203, a phase synchronization IC (PLL IC) 205, an attenuator amplifier (ATT) 207, a bandpass filter (BPF) 209, a power amplifier (PA) 211, a switch ( SPDT) 213, low noise amplifier (LNA) 215, band pass filter (BPF) 217, detector (DET) 219, antenna 221 and the like.

  In particular, in this embodiment, three analog-digital converters (ADC) 223, 225, and 227 for temperature measurement, reference, and measurement are provided corresponding to the three element portions 161, 163, and 169.

Therefore, in this embodiment, a signal as shown in FIG. 11 is obtained. This will be described in detail below with reference to FIGS.
The signal from the external device 201 to the pressure sensor 151 is the same as in the first embodiment.

  First, a signal (high-frequency signal) received from the external device 201 and input to the temperature measuring element unit 169 is converted into a surface acoustic wave by the fifth electrode unit 175 and is reflected on the reflectors 177 and 181 side. The surface acoustic wave transmitted and reflected here returns to the fifth electrode unit 175 again and is converted into a high-frequency signal. The signal output from the temperature measuring element unit 169 is delayed by the delay time tD by the first delay unit 155, received by the external device 201, and the value thereof is held by the signal tHold of Hold1.

  A similar signal generated by inputting / outputting to / from the reference electrode element unit 163 is delayed by the delay time tD by the first delay unit 155, and also delayed by the delay time tDEF by the fourth delay unit 191. The value is received by the device 201 and held by the signal tHold of Hold2.

  Further, a similar signal that is input / output to / from the measurement element unit 161 is delayed by the first delay unit 155 by the delay time tD, and is also delayed by the third delay unit 187 by the delay time tDEF. The delay unit 165 delays the delay time tDEF, and the external device 201 receives the signal. The value is held by the Hold3 signal tHold.

  Therefore, in addition to the reference signal for temperature only and the measurement signal indicating pressure (air pressure) and temperature, the controller 203 obtains a signal indicating a more accurate temperature in a state that is clearly separated in time. Will be.

  Therefore, since the controller 203 can extract only the signal corresponding to the pressure by taking the difference between the signal levels of the measurement signal and the reference signal, the pressure value can be obtained from the signal level corresponding to the pressure. it can. Further, the temperature can be obtained from the temperature measurement signal.

  In the present embodiment, the same effects as those of the first embodiment are provided, and the temperature measuring element unit 169 is provided, so that not only the pressure but also the temperature can be accurately detected.

Next, Example 3 will be described.
In this embodiment, a hydrogen concentration sensor 231 as shown in FIG. 12 is illustrated as a specific example of the gas concentration sensor.

  Similar to the first embodiment, the hydrogen concentration sensor 231 includes the piezoelectric substrate 233, the first electrode portion 235, the second electrode portion 237, the first delay portion 239, the reflector 241 and the like, and the measurement element portion 243. The reference element portion 245 is provided. In addition, description of the same part as the said Example 1 is abbreviate | omitted, and the element structure provided with the gas sensitive film | membrane (gas adsorption body) 247 of a different point and its reaction principle are demonstrated.

  In order for the characteristics of the surface acoustic wave element 249 to change depending only on the influence of hydrogen gas, a sensitive film (in this case, a gas adsorbent 247 that adsorbs hydrogen) on the surface acoustic wave propagation path is required. Become. The sensitive film 247 is formed of a thin film made of hydrogen storage alloy (Pd alloy or the like) having a thickness of several hundreds μm to several tens μm, and is disposed between the first electrode part 235 and the reflector 241, for example.

The surface acoustic wave response to hydrogen can be broadly classified into two types.
The first is a sensor that uses a hydrogen storage alloy, Pd—Ni alloy, or the like for the sensitive film 247 and utilizes changes due to heat of chemical reaction (heat generation amount) when hydrogen molecules are adsorbed on the film. In this type, the frequency characteristic shifts in accordance with the temperature characteristic of the substrate (when a quartz substrate is used, the change is a quadratic curve). Therefore, the shift amount is specified from the change amount of the signal level of the specific frequency, and the hydrogen concentration is specified.

  The second is a sensor that uses Pb or a Pb alloy for the sensitive film 247 and utilizes changes in mass load and elastic modulus due to adhesion of hydrogen molecules. The propagation speed of the surface acoustic wave changes due to the change in the elastic constant of the propagation surface of the surface acoustic wave and the mass load effect. Thereby, the shift of the frequency characteristic is specified from the change amount of the signal level of the specific frequency, and the hydrogen concentration is specified.

As shown in FIG. 13, as another hydrogen concentration sensor 251, an insulating protective film 261 such as SiO ₂ is loaded so as to cover each of the electrode portions 253 to 259, and then a sensitive film (gas adsorber). ) 263 may be provided.

  Although the sensor for detecting the hydrogen concentration has been described here, for other gases, a sensitive film that adsorbs the gas can be provided, and the gas concentration can be detected by the same principle.

Next, the fourth embodiment will be described, but the description of the same contents as the first embodiment will be simplified.
In this embodiment, as shown in FIG. 14, a sensor structure for liquid sensing (for example, a liquid phase sensor 271 capable of detecting various physical property values of a liquid) is illustrated. Note that parts that are the same as those in the other embodiments are omitted, and an electrode structure for liquid sensing and a reaction principle thereof are illustrated.

  In this example, the frequency characteristic changes (as when pressure is applied) by the liquid adhering to the piezoelectric substrate 275 of the surface acoustic wave element 273. Therefore, the physical property value of the liquid is determined from the change in the frequency characteristic. Can be detected.

Specifically, the viscosity, density, etc. of the liquid can be detected by using an element that excites a surface acoustic wave in a mode (SH, Love, etc.) in which wave energy is not radiated to the liquid.
The surface acoustic wave used for sensing liquid is a sliding shear wave (SH) type surface acoustic wave that has almost no longitudinal displacement component that radiates energy into the liquid and has only a lateral displacement component. The mode of the surface acoustic wave to be excited depends on the piezoelectric material (material type and cut angle) to be used. As a piezoelectric substrate material for exciting the SH type surface acoustic wave, the coupling coefficient is relatively high and the temperature coefficient is small. ° YX-LiTaO ₃ is known.

  The pattern of electrodes and reflectors is different from that of the first embodiment because it depends on substrate material constants (coupling coefficient, capacitance, etc.), but the design method is the same. Further, the distance between the excitation electrode and the reflector needs to be equal to or larger than the width (several mm) at which the surface of the surface acoustic wave propagates and the measurement solution are in contact with each other.

  On the piezoelectric substrate 275, for example, an enclosure (for example, a pool made of silicon or resin) 283 for holding liquid is provided between the first electrode portion 279 of the measuring element portion 277 and the reflector 281. It is preferable to provide it.

  In addition, in order to perform dip-type sensing in which the sensor is directly immersed in the liquid, it is necessary to prevent the excitation electrode and the reflector from getting wet. Therefore, a waterproof shield is formed on the sensor substrate so as to cover the electrode and the reflector. Epoxy resin is used for the waterproof shield material, and a minute air gap is provided between the electrode and reflector and the waterproof shield. Note that if the installation area between the waterproof shield and the sensor surface is large, the signal will be attenuated, so it is desirable to make the installation area as small as possible.

In addition, this invention is not limited to the said Example at all, As long as it belongs to the technical scope of this invention, it can take a various form.
(1) For example, the present invention is not limited to a pressure sensor such as a tire pressure sensor, and can be applied to various applications such as a stress sensor, a displacement sensor, and a temperature sensor.

(2) Further, in the gas sensor, various kinds of gas sensors can be used by using a specific gas sensitive film such as carbon monoxide such as synthetic jarosite MgFe ₃ (SO ₄ ) ₂ (OH) ₆ or hydrogen-containing iron oxide (III) FeOOH. It can also be applied to gas sensing.

DESCRIPTION OF SYMBOLS 1,151 ... Pressure sensor 3, 201 ... External device 11, 153, 249, 273 ... Surface acoustic wave element 15, 157 ... Second delay part 19, 161, 243, 277 ... Element part for measurement 21, 163, 245 ... Reference element portion 25, 235, 253, 265, 279 ... first electrode portion 31, 189, 237, 255 ... second electrode portion 39, 41, 43, 45, 177, 181, 241, 281 ... reflector 47, 257 ... third electrode part 49,259 ... fourth electrode part 51,165,239 ... first delay part 86 ... housing 169 ... temperature measuring element part 187 ... third delay part 191 ... fourth delay part 175 ... first 5 electrode parts 231, 251 ... hydrogen concentration sensor 247, 263 ... gas adsorbent 271 ... liquid phase sensor 283 ... enclosure

Claims (18)

One element portion having a pair of electrodes, a reflector, and a gas adsorber that adsorbs a measurement target gas on the piezoelectric substrate, and the other element portion having a pair of electrodes and a reflector on the piezoelectric substrate. A surface acoustic wave element having a frequency characteristic that changes according to an amount of heat generation or an increase in mass due to the gas to be measured adsorbed on the gas adsorbent,
A surface acoustic wave device comprising: a first delay unit that delays a signal of the one element unit in time with respect to a signal of the other element unit.   The surface acoustic wave element according to claim 1, wherein the surface acoustic wave element is capable of detecting a gas concentration. A surface acoustic wave device having two or more element portions each including a pair of electrodes and a reflector on a piezoelectric substrate, and having a frequency characteristic that changes according to a perturbation applied to any of the element portions,
A measurement element unit that receives perturbation of the measurement target, and a reference element unit used to correct the output of the measurement element unit,
A surface acoustic wave device comprising: a first delay unit that delays a signal of the one element unit in time with respect to a signal of the other element unit.   The surface acoustic wave element according to claim 3, wherein the surface acoustic wave element is capable of detecting gas pressure.   4. The surface acoustic wave device according to claim 3, wherein a piezoelectric substrate that excites a surface acoustic wave that does not emit energy to a liquid is used as the piezoelectric substrate of the surface acoustic wave device.   The surface acoustic wave element according to claim 5, wherein the surface acoustic wave element is capable of detecting a physical property value of a liquid.   The signal line connected to the other element part and the signal line of the one element part connected via the first delay part are distributed so that mutual signals do not interfere with each other. The surface acoustic wave device according to claim 1.   The surface acoustic wave device according to claim 1, wherein the first delay unit is a delay line using sound waves.   The surface acoustic wave device according to claim 1, wherein when there are a plurality of the first delay portions, at least one of the first delay portions is provided on the piezoelectric substrate.   The surface acoustic wave device according to any one of claims 1 to 9, further comprising a temperature detecting element portion capable of detecting temperature independently.   The surface acoustic wave element according to any one of claims 3, 4, 7 to 10, a pressure applying unit that applies pressure to an element unit for measurement of the surface acoustic wave element, and the surface acoustic wave element A sensor comprising: an antenna that wirelessly transmits a signal corresponding to a change in the frequency characteristic to an external device; and a housing that houses the surface acoustic wave element and the antenna.   The surface acoustic wave element according to any one of claims 1, 2, and 7 to 10, a gas adsorbent that applies gas to an element portion for measurement of the surface acoustic wave element, and the surface acoustic wave element A sensor comprising: an antenna that wirelessly transmits a signal corresponding to a change in the frequency characteristic to an external device; and a housing that houses the surface acoustic wave element and the antenna.   The surface acoustic wave element according to any one of claims 5 to 10, and a liquid addition unit including an enclosure for holding a liquid to be measured with respect to an element unit for measurement of the surface acoustic wave element, An antenna that wirelessly transmits a signal corresponding to a change in the frequency characteristic of the surface acoustic wave element to an external device, and a housing that houses the surface acoustic wave element and the antenna. Sensor.   A second delay unit for preventing interference between a signal input from the external device and a signal output from the surface acoustic wave element is provided between the surface acoustic wave element and the antenna. The sensor according to any one of claims 11 to 13. A sensor according to any one of claims 11 to 14, and an external device that wirelessly transmits and receives signals to and from the sensor,
A sensing system that detects a state of the measurement object based on a level change of an output signal of the element unit with respect to an input signal of a specific frequency from the external device to the element unit.   The sensing system according to claim 15, wherein the sensor is arranged in a measurement space, and a signal from the sensor is received by the external device to detect a state in the measurement space. A piezoelectric substrate is provided with a pair of electrodes, a reflector, and a gas adsorber that adsorbs a measurement target gas, a measurement element unit that is affected by the adsorption of the measurement target gas, a pair of electrodes and a reflector on the piezoelectric substrate, A reference element part used for correcting the output of the measurement element part, and a calorific value or an increase in mass due to the measurement target gas adsorbing to the gas adsorbent A sensor having a surface acoustic wave element whose frequency characteristics change according to the
An external device for wireless communication with the sensor;
A state detection method for detecting the state of a gas to be measured by a level change of an output signal from the surface acoustic wave element with respect to an input signal of a specific frequency from the external device to the surface acoustic wave element,
Of the two element parts, the signal of one element part is delayed in time with respect to the signal of the other element part, the signals of both element parts are separated, and the measurement object is based on the separated signals. The state detection method characterized by detecting the state of this. A piezoelectric substrate is provided with a pair of electrodes and a reflector, and a measurement element unit that receives perturbation of a measurement target, and a piezoelectric substrate is provided with a pair of electrodes and a reflector, and corrects the output of the measurement element unit. A sensor element including a surface acoustic wave element having a frequency characteristic that changes in response to a perturbation applied to the element part for measurement.
An external device for wireless communication with the sensor;
A state detection method for detecting a state of a measurement object by a level change of an output signal from the surface acoustic wave element with respect to an input signal of a specific frequency from the external device to the surface acoustic wave element,
Of the two element parts, the signal of one element part is delayed in time with respect to the signal of the other element part, the signals of both element parts are separated, and the measurement object is based on the separated signals. The state detection method characterized by detecting the state of this.