JP4433484B2 - Hydrogen sensor and ammonia sensor - Google Patents

Description

  The present invention relates to a hydrogen sensor and an ammonia sensor.

  The hydrogen sensor is a sensor necessary for ensuring the safety of a fuel cell system using hydrogen as a fuel source, and is expected to spread in the future. The hydrogen sensor is used to reliably detect hydrogen leakage at a low concentration stage, and to stop or warn the system. The hydrogen sensor employs various detection methods such as a catalytic combustion method, a semiconductor method, a thermoelectric method, and an optical fiber method, but all have problems in gas type selectivity, cost, and durability.

  In the contact combustion type hydrogen sensor, hydrogen is burned on a catalyst such as platinum, and the change in resistance value of the resistor due to the heat and heat is used. In this method, not only hydrogen but also hydrocarbons are combusted at the same time, so the selectivity of the gas species is poor. Moreover, it is necessary to use expensive materials such as platinum.

  In a semiconductor-type hydrogen sensor, a metal oxide semiconductor sintered body such as tin oxide is heated, and when it comes into contact with hydrogen, the electrical resistance of the semiconductor changes. The hydrogen concentration is calculated using this resistance value change. Even in this method, the same reaction occurs with hydrocarbons and carbon monoxide, so the selectivity of the gas species is poor. In addition, heating of the semiconductor with a heater is essential, and the cost is high. Furthermore, the life of the tin oxide is short because it deteriorates in the usage environment.

In addition, a hydrogen sensor using a crystal resonator with a palladium film has been proposed (Patent Document 1). Palladium has the property that hydrogen is occluded in the gaps between atoms. Since it is impossible for hydrocarbons and carbon monoxide to enter the gaps between the atoms, this hydrogen sensor has high gas species selectivity.
Japanese Patent Publication No. 3-40817

In addition, a sensor using a crystal resonator with a thin film containing zirconium phosphate has been proposed (Patent Document 2). Zirconium phosphate has the property of selectively adsorbing ammonia gas on its surface.
Utility Model Registration No. 3094415

  In the hydrogen sensor described in Patent Document 1, electrodes are provided on both sides of a quartz diaphragm, and a palladium film is formed so as to cover the electrodes. And an alternating voltage is supplied to an electrode and a diaphragm is vibrated. The vibration frequency at this time is determined by the natural resonance frequency of the diaphragm and the electrode. When hydrogen is adsorbed on the palladium film, the frequency of the diaphragm changes slightly, so the hydrogen concentration is calculated from this frequency change.

  However, in the hydrogen sensor described in Patent Document 1, the frequency change based on a very small amount of attached hydrogen is very small, and it is difficult to accurately detect the hydrogen concentration from this frequency change. Since hydrogen gas explodes in the atmosphere at a concentration of about 4%, it is necessary to detect it at the lowest possible concentration, and at least 0.1 to 1%. It is desirable that detection is possible at a concentration of about 100 ppm if possible.

  In the hydrogen sensor as described in Patent Document 1, in order to improve the hydrogen detection sensitivity, it is necessary to increase the amount of hydrogen adsorption per unit area. For this purpose, it is necessary to increase the thickness of the palladium film. is there. However, when the film thickness of the palladium film is increased, the amount of expensive palladium increases and the cost increases. In addition, since the time required for hydrogen to penetrate into the membrane becomes longer, the responsiveness to changes in hydrogen concentration becomes worse.

An object of the present invention is to provide a structure capable of improving the sensitivity of a hydrogen sensor using a piezoelectric vibrator.
Another object of the present invention is to provide a structure capable of improving the sensitivity of an ammonia sensor using a piezoelectric vibrator.

The present invention, vibrator, driving electrodes for exciting a fundamental vibration in this vibrator has a adsorption film having the adsorption ability of the detection electrode, and hydrogen to detect the vibration displacement caused by the vibration of the vibrator, the driving electrodes detection electrodes and are separated, when to measure the hydrogen concentration based on a difference between the detection value of the vibration displacement from the detection electrode during measurement and the detection value of the vibration displacement from the detection electrodes in the non-measurement mode,
Based on the signal voltage generated at the detection electrode due to the collapse of the line symmetry of the fundamental vibration with respect to the central axis due to hydrogen adhering to the adsorption film during measurement, the vibration displacement is substantially symmetric with respect to the central axis of the vibrator in the fundamental vibration. The mass of hydrogen adhering to the adsorption film is calculated .

Further, the present invention includes a vibrator, a drive electrode that excites fundamental vibration in the vibrator, a detection electrode that detects vibration displacement associated with the vibration of the vibrator , and an adsorption film having hydrogen adsorption ability. Using a hydrogen sensor in which the drive electrode and the detection electrode are separated,
In to measure the hydrogen concentration based on a difference between the detection value of the vibration displacement from the detection electrode during measurement and the detection value of the vibration displacement from the detection electrodes in the non-measurement mode, the oscillation center displacement of the vibrator in the fundamental vibration The mass of hydrogen adhering to the adsorption film is determined based on the signal voltage generated at the detection electrode due to the collapse of the line symmetry of the fundamental vibration with respect to the central axis due to hydrogen adhering to the adsorption film during measurement. The present invention relates to a method for measuring a hydrogen concentration, characterized in that it is calculated .

Further, the present invention, the vibrator, the driving electrodes for exciting a fundamental vibration in this vibrator has a adsorption film having the detection electrodes, and the ammonia adsorption capacity for detecting vibration displacement caused by the vibration of the vibrator, driving electrodes and the detection electrode and are separated, when the measured ammonia concentration based on a difference between the detection value of the vibration displacement from the detection electrode during measurement and the detection value of the vibration displacement from the detection electrodes in the non-measurement mode, Based on the signal voltage generated at the detection electrode due to the collapse of the line symmetry of the fundamental vibration with respect to the central axis due to ammonia adhering to the adsorption film during measurement, the vibration displacement is substantially symmetrical with respect to the central axis of the vibrator in the fundamental vibration. The present invention relates to an ammonia sensor, wherein the mass of ammonia attached to the adsorption film is calculated .

  According to the present invention, in the hydrogen (ammonia) sensor that measures the hydrogen and ammonia concentrations by utilizing the vibration state change caused by hydrogen adsorption on the adsorption film on the vibrator, the drive means and the detection means are separated, and the drive means Thus, the fundamental vibration was excited in the sensor, and the change of the vibration state due to hydrogen (ammonia) adsorption was detected by the detection means. By separating the drive means and the detection means in this way, it becomes easy to accurately detect a desired vibration that reflects the vibration state, and it is possible to provide the drive means and the detection means in the most effective parts. Become. As a result, the detection sensitivity of the hydrogen (ammonia) concentration in the sensor can be improved.

In the present invention, the fundamental vibration, the vibration displacement is substantially symmetrical with respect to the center axis of the vibrator. In a preferred embodiment, the detection value from the detection means is set to approximately 0 when not measuring. In this case, since the displacement from about 0 is detected, the measurement sensitivity is further improved and the influence of the environmental change can be reduced.

  In a preferred embodiment, the fundamental vibration is a torsional vibration mode in the thickness direction of the vibrator. By using a thickness torsional vibrator, it is possible in principle to detect hydrogen or ammonia at a hydrogen concentration equivalent to 1 ppm.

  1 to 6 relate to a hydrogen sensor (or ammonia sensor) using a thickness torsional vibration mode. FIG. 1 is a plan view schematically showing the sensor 1, FIG. 2 is a perspective view schematically showing the sensor 1, and FIG. 3 is a front view of the sensor 1. 4A is a plan view for explaining the thickness torsional vibration mode, FIG. 4B is a perspective view for explaining the thickness torsional vibration mode, and FIG. 5 shows a circuit example.

  As shown in FIGS. 1 and 2, the vibrator 2 of the sensor 1 has, for example, a square plate shape. Drive electrodes 3A, 3B and detection electrodes 4A are formed on the surface 2a of the vibrator 2, and drive electrodes 3C, 3D and detection electrodes 4B are formed on the surface 2b. An adsorption film 5 having hydrogen or ammonia adsorption ability is provided on the drive electrode 3A. 15 is a lead, and 16 is a lead terminal.

  By using the drive power supply 8 of the drive circuit unit 14 (see FIG. 5) and applying an AC voltage having a reverse phase between the drive electrodes 3A and 3C and between the drive electrodes 3B and 3D, respectively, FIG. a) Thickness shear vibration is generated as indicated by arrows A and B shown in FIG. D1 and D2 are AC voltage application terminals, and D1G and D2G are ground terminals. The drive vibrations A and B are substantially line symmetric with respect to the central axis D of the vibrator.

  When the vibrator 2 is displaced between the detection electrodes 4A and 4B, a voltage is generated between the terminal P and the ground terminal PG. This voltage difference is detected by the detection amplifier 9 of the signal processing unit 6, and phase detection is performed by the phase detection circuit 10 by driving vibration. Then, the vibration having the same phase as the drive vibration is passed through the low-pass filter 11 and output.

  Here, the detection signals at the center detection electrodes 4A and 4B are set to be substantially zero at the time of non-measurement. This is because the vibration displacements A and B of the drive vibration are substantially line symmetric with respect to the central axis D of the vibrator 2, so that the vibration displacement of the vibrator in the region between the detection electrodes 4 A and 4 B is almost zero. Because it becomes.

  If hydrogen or ammonia adheres to the adsorption film 5 during measurement, the mass of the adsorption film 5 increases, and the balance of the masses on the left and right of the central axis D of the vibrator 2 is lost. As a result, the line symmetry of the drive vibrations A and B with respect to the central axis D is lost, and a signal voltage in phase with the drive vibration is generated between the detection electrodes 4A and 4B. The mass is calculated based on this signal voltage.

  FIG. 6 is a front view schematically showing a sensor 1A according to another embodiment. The plan view and perspective view of this sensor are the same as the sensor shown in FIGS. Drive electrodes 3A and 3B and a detection electrode 4A are formed on the surface 2a of the vibrator 2, and a ground electrode 14 and a drive ground electrode 3D are formed on the surface 2b. An adsorption film 5 is provided on the drive electrode 3A.

  By using the drive power supply 8 of the drive circuit unit 14 and applying AC voltages of opposite phases between the drive electrodes 3B and 3D and between the drive electrode 3A and the ground electrode 14, respectively, FIG. As shown by arrows A and B shown in (b), thickness shear vibration is generated. D1 and D2 are AC voltage application terminals, and D2G and G are ground terminals. The drive vibrations A and B are substantially line symmetric with respect to the central axis D of the vibrator.

  When the transducer is displaced between the detection electrode 4A and the ground electrode 14, a voltage is generated between the terminal P and the ground terminal G. This voltage difference is detected by the detection amplifier 9 of the signal processing unit 6, and phase detection is performed by the phase detection circuit 10 by driving vibration. Then, the vibration having the same phase as the drive vibration is passed through the low-pass filter 11 and output. The detection signal at the center detection electrode 4A is set to substantially zero at the time of non-measurement. If a substance adheres to the adsorption film 5 at the time of measurement, the mass of the adsorption film 5 increases, and the balance between the masses on the left and right of the central axis D of the vibrator is lost. As a result, the line symmetry of the drive vibrations A and B with respect to the central axis D is lost, and a signal voltage in phase with the drive vibration is generated on the detection electrode 4A. The mass is calculated based on this signal voltage.

  In a preferred embodiment, the vibrator includes at least a pair of bending vibration pieces, and the basic vibration includes bending vibration of the bending vibration piece. Since such vibration can increase displacement, it is more effective in improving sensitivity. FIG. 7 is a plan view schematically showing the vibrator (before formation of the adsorption film) according to this embodiment, and FIG. 7 is a plan view schematically showing the vibrator 45 according to this embodiment.

  The transducer base 34 of the sensor 31 of this example has a substantially square shape that is four-fold symmetric about the center of gravity GO of the transducer 45. A pair of elongated support portions 35 extend substantially symmetrically with respect to the central axis D from the periphery of the base portion 34. A pair of drive vibrating pieces 36 </ b> A, 36 </ b> B, 36 </ b> C, 36 </ b> D extend substantially parallel to the central axis D from the respective tips of the support portions 35. A wide weight part or hammer head is provided at each tip of each of the drive vibrating pieces 36A to 36D, and a through hole is provided in each weight part. Drive electrodes 32, 33 </ b> A, and 33 </ b> B are formed on the side surface and main surface of each drive vibration piece.

  Elongated detection vibrating pieces 38A and 38B extend from the peripheral edge of the base 34 in the direction of the central axis D, respectively. A wide weight portion or a hammer head is provided at each end of each detection vibrating piece 38A, 38B, and a through hole is provided in each weight portion. Detection electrodes 40 and 39 are formed on the side surface and the main surface of each detection vibrating piece, respectively.

  In this example, adsorption films 41A and 41B are formed on the electrode 33A on the right drive vibrating piece in FIG. 7 (FIG. 8). As described above, the driving electrodes 36A, 36B, 36C, and 36D are flexibly vibrated around the tip of the support portion 35 as indicated by the arrow E using the driving electrodes. At this time, the vibrations of the bending vibration pieces 36 </ b> A and 36 </ b> B and the vibrations of the bending vibration pieces 36 </ b> C and 36 </ b> D are made substantially line symmetric with respect to the central axis D. As a result, the overall center of gravity GD of the drive vibration of the bending vibration pieces 36A, 36B, 36C, and 36D and the center of gravity GO of the vibrator are made to be substantially on the center axis D. In this state, the detection current at the detection electrodes 39 and 40 on the detection vibrating pieces 38A and 38B is adjusted to almost zero.

  If hydrogen or ammonia adheres to the adsorption films 41A and 41B at the time of measurement, the mass of each adsorption film increases, and the balance between the masses on the left and right of the center axis D of the vibrator is lost. As a result, the symmetry of the drive vibration E on the central axis D is lost, and a signal voltage in phase with the drive vibration is generated between the detection electrodes 39 and 40. The mass is calculated based on this signal voltage.

The material of the vibrator is not particularly limited. In one example, a piezoelectric single crystal or a piezoelectric ceramic can be used. Examples of the piezoelectric single crystal include quartz crystal, lithium niobate, lithium tantalate, lithium niobate-lithium tantalate solid solution (Li (Nb, Ta) O ₃ ) single crystal, lithium borate single crystal, and langasite single crystal. . Quartz production technology has been established, which can reduce the manufacturing cost of hydrogen sensors. Lithium niobate, lithium tantalate, and lithium niobate-lithium tantalate solid solutions have a high Curie point and can be used up to high temperatures. Examples of piezoelectric ceramics include lead zirconate titanate, lead titanate and so-called PZT-based piezoelectric ceramics with additives added thereto, barium titanate, strontium titanate, bismuth layered compounds, and the like.

Moreover, a vibrator made of AlN can be used. The AlN vibrator can operate up to about 1000 ° C. in a reducing atmosphere. Furthermore, a vibrator formed by silicon micromachining can be used.
Moreover, a vibrator made of Langasite can be used. The Langasite vibrator has a high melting point of 1470 ° C. and can operate up to about 1000 ° C.

The drive electrode and the detection electrode can be composed of a conductive film. Examples of such a conductive film include a gold film, a multilayer film of gold and chromium, a multilayer film of gold and titanium, a silver film, a multilayer film of silver and chromium, a multilayer film of silver and titanium, a lead film, and a platinum film. A metal oxide film such as TiO ₂ is preferable. Since the adhesion between the gold film and the oxide single crystal such as quartz is low, it is preferable to interpose an underlayer such as at least a chromium layer or a titanium layer between the gold film and the vibrating arm, particularly the quartz arm.
When operating at a high temperature, the electrode surface is preferably covered with platinum.

The material of the adsorption film having hydrogen adsorption capability is not particularly limited, and includes the following two types of materials.
(1) Hydrogen storage metal Nb, Pd, Ti, Zr, V, Ta, rare earth (Sc, Y, La), etc. have a strong affinity for hydrogen and have a hydrogen storage capacity. Alternatively, a metal alloy having hydrogen storage ability may be used. Examples of such alloys include TiFe, TiCr2, LaNi5, and MgNi.

(2) Metal that Adsorbs Hydrogen by Catalysis Catalytic metals such as platinum and palladium have the property of adsorbing and activating hydrogen. Chemosorption plays an important role in catalysis, and the hydrogen gas molecules are decomposed when the adsorption power of the catalytic metal and hydrogen is stronger than the binding force between hydrogen atoms in the hydrogen gas molecules. Thus, dissociative adsorption that is adsorbed to the metal occurs. The activation tendency of hydrogen gas differs depending on the catalyst metal, and therefore the adsorption ability of hydrogen is different.
(A) Metal having hydrogen adsorption ability Group 8 and Group 1B such as palladium, platinum, ruthenium, silver, cobalt, gold, nickel, copper (b) Metal having substantially no hydrogen adsorption ability Chromium, molybdenum, tungsten 6A group and 7A group such as manganese, technetium, rhenium

  As the material having hydrogen adsorption ability, palladium or palladium alloy is particularly preferable. Impurities may be contained in palladium. Examples of the metal constituting the palladium alloy include silver, platinum, gold, ruthenium, iron, molybdenum, cobalt, tin, copper, nickel, yttrium, rhodium, zinc, and vanadium.

  The thickness of the adsorption film is not particularly limited, but is preferably 90 angstroms or more, and more preferably 500 angstroms or more, from the viewpoint of further improving the detection sensitivity of the hydrogen sensor. In addition, if the adsorption film becomes too thick, the responsiveness of the sensor to changes in hydrogen concentration tends to decrease. From the viewpoint of responsiveness, the thickness of the adsorption film is preferably 5 microns or less. More preferably, it is as follows.

  The material of the adsorption film having ammonia adsorption ability is not particularly limited, but zirconium phosphate can be exemplified.

In the present invention, the drive electrode and the detection electrode need to be separated. In the present invention, a drive electrode and the detection electrode is sufficient if it is separated as a function, the drive electrode and the detection electrode is not required to be are electrically insulated. For example, it is not hindered that a certain conductive line or conductive pattern is continuous and electrically connected between the drive electrode and the detection electrode . Further, it is sufficient that at least one driving means and at least one detection electrode are separated. From the viewpoint of the present invention, the distance between the drive electrode and the detection electrode is preferably 1 micron or more, and more preferably 10 microns or more.

In the present invention, the physical quantity obtained from the detection electrode is vibration displacement.

Detection means of the vibration displacement is a detection electrode as described above.

  The hydrogen absorption amount of palladium varies depending on the environmental temperature. Such a change in the amount of absorbed hydrogen has little effect in applications for detecting leakage of hydrogen gas, but it is necessary to control the application where it is necessary to know the absolute value of the hydrogen concentration or the measured value of the hydrogen concentration. In use, it causes measurement errors. Therefore, in such a case, the change in the adsorption amount due to the temperature change can be corrected by the following method.

(1) The temperature of the vibrator is kept constant by adding a heater to the hydrogen sensor.
(2) Install a temperature sensor on or around the vibrator and measure the temperature. A calibration curve indicating the relationship between the temperature and the detected value of the physical quantity is stored in the control device. The physical value detected value is corrected by collating the measured value from the temperature sensor with the calibration curve.
(3) The resonance frequency of the vibrator changes according to the temperature change. Therefore, a calibration curve indicating the relationship between the resonance frequency of the vibrator and the detected value of the physical quantity is stored in the control device. The detected value of the physical quantity is corrected by collating the measured value of the resonance frequency obtained from the vibrator with the calibration curve. According to this method, since the temperature of the vibrator can be directly known, an error between the temperature of the temperature sensor and the temperature of the vibrator hardly occurs, and more accurate temperature correction is possible.

  In the embodiment of the present invention, each driving means 3E, 3F, 3G, and 3H includes a base film 20 and a surface film 21, respectively, as in the hydrogen sensor 1B shown in FIG. Each of the detection means 4C and 4D includes a base film 20 and a surface layer film 21, respectively. Examples of the material of the base film and the adsorption film have been described above. In addition, an adsorption film 5 made of a material having hydrogen adsorption ability is provided on the driving means 3E. The material having such hydrogen adsorption ability has been described above.

  However, it has been found that if a material having hydrogen adsorption capability, such as gold, is exposed on the surface of the drive means and the detection means, this will cause hydrogen to adsorb and cause an error in the measured value of the hydrogen concentration. . For this reason, in a preferred embodiment, at least the surfaces of the drive means and the detection means are made of a material that does not substantially have hydrogen adsorption ability.

  For example, in the hydrogen sensor 1C of FIG. 10, each driving means 3J, 3K, 3L, 3M is made of a material 23 that does not have hydrogen adsorption ability. An adsorption film 5 made of a material having hydrogen adsorption ability is provided on the driving means 3J. Such materials that do not have hydrogen adsorption ability and materials that have hydrogen adsorption ability have been described above.

Example 1
The hydrogen sensor 1 (1B) shown in FIGS. 1 to 5 and FIG. 9 was manufactured. The vibrator 2 was formed of an AT cut quartz plate. The width of the electrode portion was 5 mm, and the thickness of the vibrator 2 was 0.16 mm. For each electrode, a chromium film 20 / gold film 21 (thickness 500 angstrom) was used. The adsorption film 5 was a palladium film having a length of 2 mm, a width of 2 mm, and a thickness of 1000 angstroms, and was formed by vapor deposition. As a result, hydrogen having a concentration of 0.01% could be detected.

(Example 2)
The hydrogen sensor 1 (1C) shown in FIGS. 1 to 5 and 10 was manufactured. The vibrator 2 was formed of an AT cut quartz plate. The width of the electrode portion was 5 mm, and the thickness of the vibrator 2 was 0.16 mm. Each electrode used a chromium film 23. The adsorption film 5 was a palladium film having a length of 2 mm, a width of 2 mm, and a thickness of 1000 angstroms, and was formed by vapor deposition. As a result, hydrogen having a concentration of 0.01% could be detected.

A specific procedure for forming each film will be described.
The quartz substrate 2 having a length of 2 inches, a width of 2 inches, and a thickness of 0.16 mm was etched and washed with dilute hydrofluoric acid, and then dried by a spin dryer to clean both surfaces 2a and 2b of the quartz substrate 2. Using a sputtering apparatus, a 0.02 μm thick Cr film was formed as a base layer 20 on each surface 2a, 2b of the quartz substrate, and a 0.1 μm thick Pd film 5 was formed only on one surface.

  Photoresist was applied on the film formation surface of the quartz substrate to form a resist film having a thickness of 1 μm, and prebaked using an oven to remove the solvent component of the resist. Using an exposure apparatus capable of high-precision alignment of each surface and a photomask on which only an electrode etching pattern was drawn, the photomask pattern was transferred onto the resist film surface by an exposure apparatus to form a resist pattern. .

  Using this resist pattern as a mask, the Pd film formed on the quartz substrate is removed by etching with a mixed solution of nitric acid and hydrochloric acid, and the Cr film is removed by etching with ceric ammonium nitrate to obtain a multilayer of Pd and Cr. An etching mask pattern made of a film was formed. The remaining photoresist was dissolved and removed with acetone.

A photoresist was applied on the surface of the Pd film to form a resist film having a thickness of 1 μm, and pre-baked using an oven to remove the solvent component of the resist.
Using a photomask on which a Pd film formation pattern was drawn, the photomask pattern was transferred onto the resist film surface by an exposure apparatus by photolithography to form a resist pattern. Using the resist pattern as a mask, the Pd film formed on the quartz substrate was etched away with a mixed solution of nitric acid and hydrochloric acid to form an etching mask pattern. The remaining photoresist was dissolved and removed with acetone to form a Pd film 5.

It is a top view which shows the sensor 1 typically. 1 is a perspective view schematically showing a sensor 1. FIG. It is a front view which shows the sensor 1 typically. (A) is a top view for demonstrating the thickness shear vibration mode of the vibrator | oscillator 2, (b) is a schematic diagram which shows thickness shear vibration mode. It is a figure which shows the example of a circuit. It is a front view showing typically sensor 1A concerning other embodiments. It is a top view showing typically sensor vibrator 45 concerning other embodiments. FIG. 8 is a plan view schematically showing a state where an adsorption film is formed on the vibrator of FIG. 7. It is sectional drawing which shows the sensor 1B which concerns on other embodiment of this invention. It is sectional drawing which shows the sensor 1C which concerns on other embodiment of this invention, and the material which has hydrogen adsorption ability is not exposed among the surfaces of a drive means and a detection means.

Explanation of symbols

  1, 1A, 31 Sensor 2, 45 Vibrator 3A, 3B, 3C, 3D, 32, 33A, 33B Drive means 4A, 4B, 39 Detection means A, B Thickness shear vibration D Central axis E Basic vibration

Claims (15)

A vibrator, a drive electrode that excites fundamental vibration in the vibrator, a detection electrode that detects vibration displacement associated with the vibration of the vibrator , and an adsorption film that has an ability to adsorb hydrogen, the drive electrode and the detection The hydrogen concentration is measured based on the difference between the detected value of the vibration displacement from the detection electrode at the time of non-measurement and the detected value of the vibration displacement from the detection electrode at the time of measurement. In this case, in the fundamental vibration, the vibration displacement is substantially symmetric with respect to the central axis of the vibrator, and due to the collapse of the line symmetry of the basic vibration with respect to the central axis due to hydrogen adhering to the adsorption film at the time of measurement, A hydrogen sensor, wherein the mass of hydrogen adhering to the adsorption film is calculated based on a signal voltage generated at a detection electrode . 2. The hydrogen sensor according to claim 1, wherein the detection value from the detection electrode becomes substantially zero at the time of non-measurement. The fundamental vibration, characterized in that a thickness torsional vibration mode of the vibrator, the hydrogen sensor according to claim 1 or 2 wherein. The hydrogen sensor according to any one of claims 1 to 3 , wherein at least surfaces of the drive electrode and the detection electrode are made of a material that does not substantially have hydrogen adsorption ability. 5. The hydrogen sensor according to claim 4 , wherein the material having substantially no hydrogen adsorption ability is selected from the group consisting of groups 6A and 7A of the periodic table. A vibrator, a drive electrode that excites fundamental vibration in the vibrator, a detection electrode that detects vibration displacement associated with the vibration of the vibrator , and an adsorption film that has an ability to adsorb hydrogen, the drive electrode and the detection Using a hydrogen sensor that is separated from the electrode ,
In to measure the hydrogen concentration based on a difference between the detection value of the vibration displacement from the detection electrode during measurement and the detection value of the vibration displacement from the detection electrode in the non-measurement, the in the fundamental vibration The vibration displacement is substantially symmetric with respect to the central axis of the vibrator, and the signal voltage generated at the detection electrode due to the collapse of the line symmetry of the fundamental vibration with respect to the central axis due to hydrogen adhering to the adsorption film during measurement. Based on this, the mass of hydrogen adhering to the adsorption film is calculated . The method according to claim 6 , wherein the detection value from the detection electrode is substantially zero at the time of non-measurement. The method according to claim 6 , wherein the fundamental vibration is a thickness torsional vibration mode of the vibrator. The method according to claim 6 , wherein at least surfaces of the drive electrode and the detection electrode are made of a material that does not substantially have hydrogen adsorption ability. The method according to claim 9 , wherein the material substantially having no hydrogen adsorption ability is selected from the group consisting of groups 6A and 7A of the periodic table. A vibrator, a drive electrode that excites fundamental vibration in the vibrator, a detection electrode that detects vibration displacement associated with the vibration of the vibrator , and an adsorption film having ammonia adsorption ability, the drive electrode and the detection electrode And the ammonia concentration is measured based on the difference between the detected value of the vibration displacement from the detection electrode at the time of non-measurement and the detected value of the vibration displacement from the detection electrode at the time of measurement . At this time, in the fundamental vibration, the vibration displacement is substantially symmetric with respect to the central axis of the vibrator, and the detection is performed by breaking the line symmetry of the fundamental vibration with respect to the central axis due to ammonia adhering to the adsorption film at the time of measurement. An ammonia sensor , wherein the mass of ammonia adhering to the adsorption film is calculated based on a signal voltage generated at the electrode . The ammonia sensor according to claim 11, wherein the detection value from the detection electrode becomes substantially zero at the time of non-measurement. The ammonia sensor according to claim 11 or 12, wherein the fundamental vibration is a thickness torsional vibration mode of the vibrator. The ammonia sensor according to any one of claims 11 to 13, wherein at least surfaces of the drive electrode and the detection electrode are made of a material that does not substantially have an ammonia adsorption ability. 15. The ammonia sensor according to claim 14, wherein the material having substantially no ammonia adsorption ability is selected from the group consisting of groups 6A and 7A of the periodic table.

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