JP2013019827A - Sensor device - Google Patents

Abstract

Provided is a sensor device capable of measuring the state of an object to be measured while preventing deterioration of concrete quality, and utilizing information based on the measurement result for planned or preventive maintenance before corrosion of a reinforcing bar. To do.
A sensor device 1 according to the present invention includes a gap forming body 8 provided by forming a gap G between an electrical resistor 3 made of a metal material and a part of the surface of the electrical resistor 3. And a functional element having a function of measuring the resistance value of the electrical resistor 3, and configured to be able to measure the state of the measurement target part based on the resistance value measured by the functional element.
[Selection] Figure 4

Description

  The present invention relates to a sensor device.

As a sensor device, for example, a device that measures the corrosion state of a reinforcing bar in concrete is known (see, for example, Patent Document 1).
The concrete in the concrete structure immediately after construction usually exhibits strong alkalinity. Therefore, the reinforcing bars in the concrete structure immediately after construction are stable because a passive film is formed on the surface. However, in concrete structures that have been affected by acid rain or exhaust gas after construction, the concrete is gradually acidified, and the steel bars are corroded.

Therefore, for example, in the sensor device according to Patent Document 1, a thin wire made of the same kind of material as a reinforcing bar in a concrete structure is embedded in the concrete structure, and the presence or absence of breakage of the fine wire due to corrosion is detected. Predict the corrosion status of reinforcing bars.
In the sensor device according to Patent Document 1, it is possible to know the time when the corrosion of the reinforcing bars in the concrete structure has started, based on the timing at which the thin wire is cut. However, in the sensor device according to Patent Document 1, corrosion of the reinforcing bar progresses from when the fine wire starts to corrode until cutting, and preventive or planned maintenance cannot be performed before corrosion of the reinforcing bar. There was a problem.

Japanese Patent Laid-Open No. 11-153568

  An object of the present invention is to provide a sensor capable of measuring the state of an object to be measured while preventing deterioration in the quality of concrete and utilizing information based on the measurement result for planned or preventive maintenance before corrosion of a reinforcing bar. To provide an apparatus.

Such an object is achieved by the present invention described below.
The sensor device of the present invention includes an electric resistor made of a metal material,
A gap forming body arranged to form a gap with a part of the surface of the electric resistor;
A functional element having a function of measuring a resistance value of the electric resistor,
Based on the resistance value measured by the functional element, the state of the measurement target part can be measured.
According to the sensor device configured as described above, since a local gap is formed between the electric resistor and the gap forming body, the chloride ion concentration at the measurement target site is relatively low. However, the electric resistor can be corroded by crevice corrosion.
Therefore, even when the chloride ion concentration at the measurement target site is relatively low, the resistance value of the electrical resistor changes, and the entry of chloride ions can be detected based on the change.

In the sensor device according to the aspect of the invention, it is preferable that the electric resistor and the gap forming body each have a plate shape or a sheet shape and are disposed so as to overlap each other.
Thereby, a gap that can cause crevice corrosion of the electric resistor can be easily and reliably formed between the electric resistor and the gap forming body.
In the sensor device of the present invention, the electrical resistor has a long shape,
The gap forming body preferably forms the gap with a part of the surface in the longitudinal direction of the electric resistor.
Thereby, a gap that can cause crevice corrosion of the electric resistor can be easily and reliably formed between the electric resistor and the gap forming body.

In the sensor device of the present invention, it is preferable that the electric resistor has a surface area of a portion not covered with the gap forming body larger than a surface area of a portion covered with the gap forming body through the gap.
Thereby, crevice corrosion of an electrical resistor can be promoted.
In the sensor device of the present invention, it is preferable that the gap forming body is made of an insulating material.
Thereby, it can prevent that a clearance gap formation body functions as a part of electrical resistor. This facilitates the design of the electrical resistor and the gap forming body.

In the sensor device according to the aspect of the invention, it is preferable that the gap forming body is made of the same metal material as the metal material constituting the electric resistor.
Thereby, even if a clearance gap formation body and an electrical resistance body contact, corrosion of the electrical resistance body by the contact can be prevented.
In the sensor device of the present invention, it is preferable that the gap forming body is made of a material having alkali resistance.
Thereby, even if it is a case where a measurement object part is concrete, the endurance of a crevice formation object can be made excellent. Therefore, the state of concrete can be measured stably over a long period of time.

In the sensor device of the present invention, it is preferable that a distance between the gap forming body and the electric resistor in the gap is 1 μm or more and 100 μm or less.
Thereby, crevice corrosion of an electric resistor can be produced.
In the sensor device of the present invention, the metal material constituting the electrical resistor forms a passive film on the surface or disappears the passive film present on the surface in accordance with an environmental change of the measurement target site. It is preferable that it is a metal material to be made.
Thereby, a passive film is formed on the surface of the electrical resistor when the pH of the measurement target site is equal to or higher than a predetermined value.

Here, the passive film formed on the electric resistor is locally formed by chloride ions that have entered the gap between the electric resistor and the gap forming body even if the chloride ion concentration at the measurement target site is relatively low. Once a mechanical breakdown occurs, the concentration of metal ions (positive ions) eluted from the electrical resistor increases in the gap, and the concentration of chloride ions (negative ions) increases accordingly. The dynamic membrane is not regenerated. Therefore, when the pH of the measurement target site is equal to or higher than a predetermined value, even if the pH of the measurement target site fluctuates, when no chloride ion is present in the measurement target site, the electrical resistor does not corrode, Although the resistance value does not change, when chloride ions enter the measurement target site, crevice corrosion of the electrical resistor proceeds, and the resistance value of the electrical resistor increases.
For this reason, it is possible to detect with high accuracy that chloride ions have entered the measurement target site based on the resistance value of the electrical resistor.

In the sensor device according to the aspect of the invention, it is preferable that the metal material constituting the electric resistor is iron, nickel, or an alloy containing these.
These metals are relatively inexpensive and readily available. For example, when the sensor device is used for measuring the state of a concrete structure, the electric resistor can be made of the same material (or similar material) as the reinforcing bar in the concrete structure. It is possible to effectively detect the corrosion state of steel bars.

In the sensor device of the present invention, the sensor device has a porous electrical resistor that is provided apart from the electrical resistor and is composed of a porous material made of a metal material,
It is preferable that the functional element also has a function of measuring a resistance value of the porous electrical resistor.
As a result, even when the porous electrical resistor and the electrical resistor are installed in the same environment, the timing of the local corrosion by the chloride ion of the porous electrical resistor (that is, the increase in electrical resistance) It can be delayed from the start timing of local corrosion by chloride ions.

In addition, by making the metal material constituting the porous electric resistor the same type as the metal material constituting the electric resistor, the start timing of uniform corrosion due to acidification or neutralization of the porous electric resistor, and the electric resistance The start timing of the uniform corrosion due to the acidification or neutralization of the body can be matched or approximated.
Therefore, it is possible to measure the chloride ion concentration change in the measurement target portion separately from the pH change in the measurement target portion.

In addition, a large number of fine recesses are uniformly dispersed and formed on the surface of the porous electric resistor as a portion where corrosion easily occurs. Therefore, the surface of the porous electrical resistor is uniformly corroded in the presence of chloride ions, and local corrosion (pitting corrosion) is suppressed.
For this reason, the rate of corrosion of the porous electrical resistor by chloride ions can be reduced. Therefore, it is possible to measure the chloride ion concentration at the site to be measured over a long period of time.

In the sensor device of the present invention, the sensor device includes a dense electrical resistor that is provided apart from the electrical resistor and is configured of a dense material made of a metal material.
It is preferable that the functional element also has a function of measuring a resistance value of the dense electrical resistor.
As a result, even when the porous electrical resistor and the electrical resistor are installed in the same environment, the local corrosion start timing of the porous electrical resistor due to chloride ions It can be delayed from the start timing.

In addition, by making the metal material constituting the porous electric resistor the same type as the metal material constituting the electric resistor, the start timing of uniform corrosion due to acidification or neutralization of the porous electric resistor, and the electric resistance The start timing of the uniform corrosion due to the acidification or neutralization of the body can be matched or approximated.
Therefore, it is possible to measure the chloride ion concentration change in the measurement target portion separately from the pH change in the measurement target portion.

In addition, in the presence of chloride ions, the surface of the dense electric resistor is corroded most easily at the portion where corrosion is most likely to occur, and the portion where the corrosion first occurs is more easily corroded than at other portions. As a result, the local corrosion (pitting corrosion) occurs.
For this reason, although the rate of crevice corrosion of the electrical resistor is slower, the rate of local corrosion by chloride ions of the dense electrical resistor can be increased compared to the porous electrical resistor. Therefore, it is possible to measure the chloride ion concentration at the site to be measured over the medium term.

In the sensor device of the present invention, the functional element may also have a function of detecting whether the pH or chloride ion concentration of the measurement target site is equal to or lower than a set value based on a resistance value of the electrical resistor. preferable.
Thereby, the state change accompanying the pH change or chloride ion concentration change of a measuring object is detectable.
The sensor device of the present invention has an antenna and a communication circuit having a function of supplying power to the antenna,
It is preferable that the functional element also has a function of driving and controlling the communication circuit.
Thereby, a measurement result can be transmitted to the exterior of a measurement object by radio.

It is a figure which shows an example of the use condition of the sensor apparatus which concerns on 1st Embodiment of this invention. It is a block diagram which shows schematic structure of the sensor apparatus shown in FIG. It is a top view for demonstrating the electrical resistor and functional element shown in FIG. It is sectional drawing for demonstrating the electrical resistor shown in FIG. 2 (AA sectional view taken on the line in FIG. 3). It is a schematic diagram explaining the corrosion by the chloride ion of the electrical resistor shown in FIG. It is a top view which shows the sensor apparatus which concerns on 2nd Embodiment of this invention. It is sectional drawing for demonstrating the electrical resistor shown in FIG. 6 (AA sectional view taken on the line in FIG. 6). It is a figure which shows an example of the use condition of the sensor apparatus which concerns on 3rd Embodiment of this invention. It is an expanded sectional view for demonstrating the electrical resistor (porous electrical resistor) with which the sensor apparatus shown in FIG. 8 was equipped. It is a figure which shows an example of the use condition of the sensor apparatus which concerns on 4th Embodiment of this invention. It is a partial expansion perspective view which shows the sensor apparatus which concerns on 5th Embodiment of this invention. (A) is a top view which shows the electrical resistor with which the sensor apparatus shown in FIG. 11 was equipped, (b) is a side view which shows the electrical resistor with which the sensor apparatus shown in FIG. 11 was equipped.

Hereinafter, a preferred embodiment of a sensor device of the present invention will be described with reference to the accompanying drawings.
<First Embodiment>
First, a first embodiment of the present invention will be described.
1 is a diagram showing an example of a usage state of a sensor device according to a first embodiment of the present invention, FIG. 2 is a block diagram showing a schematic configuration of the sensor device shown in FIG. 1, and FIG. 3 is shown in FIG. FIG. 4 is a plan view for explaining the electric resistor and the functional element, FIG. 4 is a cross-sectional view for explaining the electric resistor shown in FIG. 2 (a cross-sectional view taken along the line AA in FIG. 3), and FIG. FIG. 3 is a schematic diagram for explaining corrosion of the electrical resistor shown in 2 by chloride ions.

In the following, a case where the sensor device of the present invention is used for quality measurement of a concrete structure will be described as an example.
A sensor device 1 shown in FIG. 1 measures the quality of a concrete structure 100.
The concrete structure 100 has a plurality of reinforcing bars 102 embedded in a concrete 101. The sensor device 1 is embedded in the vicinity of the reinforcing bar 102 in the concrete 101 of the concrete structure 100. When the concrete structure 100 is placed, the sensor device 1 may be fixed and embedded in a reinforcing bar before placing the concrete 101, or may be embedded in the concrete 101 hardened after placing.

The sensor device 1 includes a main body 2 and electrical resistors 3 and 4 exposed on the surface of the main body 2. In the present embodiment, the electric resistor 3 (first electric resistor) and the electric resistor 4 (second electric resistor) are located on the outer surface side of the concrete structure 100 with respect to the reinforcing bars 102, and the concrete structure 100. It is installed so that the distance from the outer surface of each other becomes equal. In addition, the electric resistor 3 and the electric resistor 4 are respectively installed so as to be parallel or substantially parallel to the outer surface of the concrete structure 100. And the electrical resistor 3 and the electrical resistor 4 are each comprised so that it may corrode by the acid or chloride ion of the measurement object site | part of the concrete 101, and may cut | disconnect. Although not shown in FIG. 1 for convenience of explanation, the sensor device 1 is provided with a gap forming body 8 provided with a gap between a part of the surface of the electrical resistor 3 and the sensor device 1. (See FIGS. 3 and 4). The electric resistor 3, the electric resistor 4, and the gap forming body 8 will be described in detail later.
Further, as shown in FIG. 2, the sensor device 1 includes an electric resistor 3 and a functional element 51 electrically connected to the electric resistor 4, a power source 52, a temperature sensor 53, a communication circuit 54, An antenna 55 and an oscillator 56 are provided, and these are housed in the main body 2.

Hereinafter, each part which comprises the sensor apparatus 1 is demonstrated sequentially.
(Body)
The main body 2 has a function of supporting the electric resistor 3, the electric resistor 4, the functional element 51, and the like.
As shown in FIGS. 3 and 4, the main body 2 has an electric resistor 3, an electric resistor 4, and a substrate 21 that supports the functional element 51. The substrate 21 also supports the power supply 52, the temperature sensor 53, the communication circuit 54, the antenna 55, and the oscillator 56. However, in FIGS. 3 and 4, for convenience of explanation, the power supply 52, the temperature sensor 53, and the communication circuit are used. 54, the antenna 55, and the oscillator 56 are not shown.

The substrate 21 has an insulating property. The substrate 21 is not particularly limited, and for example, an alumina substrate, a resin substrate, or the like can be used.
On this substrate 21, an insulating layer 23 made of an insulating resin composition such as a solder resist is provided. The electrical resistor 3, the electrical resistor 4, and the functional element 51 are mounted on the substrate 21 with the insulating layer 23 interposed therebetween.

As shown in FIG. 3, the conductor portions 61 and 62 (electrode pads) of the functional element 51 are electrically connected to both end portions of the electric resistor 3 through wirings 71 and 72, and the conductor portions 63 and 63 of the functional element 51 are connected. 64 (electrode pads) are electrically connected to both ends of the electric resistor 4 through wirings 73 and 74.
The main body 2 has a function of housing the functional element 51, the power source 52, the temperature sensor 53, the communication circuit 54, the antenna 55, and the oscillator 56.

In particular, the main body 2 is configured to store the functional element 51, the power source 52, the temperature sensor 53, the communication circuit 54, the antenna 55, and the oscillator 56 in a liquid-tight manner.
Specifically, as shown in FIGS. 3 and 4, the main body 2 has a sealing portion 24. The sealing unit 24 has a function of sealing the functional element 51, the power source 52, the temperature sensor 53, the communication circuit 54, the antenna 55, and the oscillator 56. Thereby, when the sensor apparatus 1 is installed in the presence of moisture or concrete, it is possible to prevent the functional element 51, the power source 52, the temperature sensor 53, the communication circuit 54, the antenna 55, and the oscillator 56 from being deteriorated.

  Here, the sealing portion 24 has an opening portion 241, and a part of the electric resistor 3 and the electric resistor 4 is exposed from the opening portion 241, and the portions other than the electric resistor 3 and the electric resistor 4 are exposed. It is provided so as to cover each part. Thereby, the sensor device 1 can perform the measurement while the sealing portion 24 prevents deterioration of each portion other than the electrical resistor 3 and the electrical resistor 4. Note that the opening 241 may be formed so as to expose at least a part of the electrical resistor 3 and at least a part of the electrical resistor 4.

Examples of the constituent material of the sealing portion 24 include thermoplastic resins such as acrylic resins, urethane resins, and olefin resins, epoxy resins, melamine resins, thermosetting resins such as phenol resins, and the like. Various resin materials etc. are mentioned, Among these, it can use combining 1 type (s) or 2 or more types.
In addition, the sealing part 24 should just be provided as needed, and can also be abbreviate | omitted.

(Electric resistor)
As shown in FIG. 4, the electrical resistor 3 and the electrical resistor 4 are respectively provided on the outer surface of the main body 2 described above (more specifically, on the substrate 21). In particular, the electrical resistor 3 and the electrical resistor 4 are provided on the same plane. Therefore, it is possible to prevent a difference in installation environment between the electrical resistor 3 and the electrical resistor 4.

In addition, the electric resistor 3 and the electric resistor 4 are separated to such an extent that they are not affected by the potential (for example, several mm).
These low electric resistances 3 and 4 are corroded by acid or chloride ions, respectively. Therefore, the electrical resistors 3 and 4 are cut by corrosion in an acid or chloride ion environment.

In addition, the outer shape of each of the electrical resistors 3 and 4 has a plate shape or a sheet shape. Further, each of the electrical resistors 3 and 4 has a long shape. That is, each of the electrical resistors 3 and 4 has a band shape. Thereby, the electrical resistors 3 and 4 can be easily cut by corrosion.
In addition, the electrical resistor 3 is longer than the electrical resistor 4. The relationship between the lengths of the electrical resistors 3 and 4 is not limited to this, and for example, the electrical resistor 4 may be longer than the electrical resistor 3, or the length of the electrical resistor and the electrical resistance The lengths of the resistors 4 may be equal.

The constituent material of such an electrical resistor 3 (first electrical resistor) is not particularly limited as long as it corrodes in the presence of acid or chloride ions, but with the environmental change of the measurement target site. It is preferable to use a metal material that forms a passive film on the surface or eliminates the passive film present on the surface.
As a result, a passive film is formed on the surface of the electrical resistor 3 when the pH of the site to be measured is a predetermined value or more.

Examples of the metal material (first metal material) forming such a passive film (first passive film) include Fe, Ni, Mg, Zn, and alloys containing these.
For example, Fe forms a passive film when the pH is greater than about 9. FeAl (Al 0.8%) carbon steel forms a passive film when the pH is higher than about 4. Ni forms a passive film when the pH is 8-14. Mg forms a passive film when the pH is higher than 10.5. Zn forms a passive film when the pH is 6-12.

Further, for example, in carbon steel (SD345), the passive film starts to break when the chloride ion concentration exceeds about 1.2 kg / m ³ .
Among them, the metal material constituting the electrical resistor 3 includes Fe or an alloy containing Fe (Fe-based alloy), that is, an iron-based material (specifically, carbon steel, alloy steel, SUS, etc.), nickel, or these. An alloy is preferred. These materials are inexpensive and easily available. Further, when the sensor device 1 is used for measuring the state of the concrete structure 100 as in the present embodiment, the constituent material of the electrical resistor 3 may be the same as or similar to the reinforcing bar 102 of the concrete structure 100. It is possible and the corrosive environment state of the reinforcing bar 102 can be detected effectively. For example, when the electrical resistor 3 is made of Fe, it can be determined whether the pH is 9 or more.

The electrical resistor 3 is preferably composed of a dense body made of the first metal material as described above. Thereby, the crevice corrosion mentioned later of electric resistor 3 can be made easy to occur.
On the other hand, the constituent material of the electric resistor 4 (second electric resistor) is not particularly limited as long as it corrodes in the presence of acid or chloride ions, as in the constituent material of the electric resistor 3. It is preferable to use a metal material (second metal material) for forming a passive film (second passive film), such as Fe, Ni, Mg, Zn, or an alloy containing these.

In addition, the constituent material of the electric resistor 4 may be the same as or different from the constituent material of the electric resistor 3 described above.
The electrical resistor 4 is provided so as not to cause crevice corrosion as will be described later of the electrical resistor 3. Therefore, even if the electrical resistor 3 and the electrical resistor 4 are installed in the same environment, the start timing of corrosion of the electrical resistor 4 by chloride ions is determined from the start timing of corrosion of the electrical resistors 3 by chloride ions. Can also be delayed.

Further, by making the metal material constituting the electric resistor 4 the same type as the metal material constituting the electric resistor 3, the corrosion start timing due to acidification or neutralization of the electric resistor 4, and the electric resistor 3 The start timing of corrosion due to acidification or neutralization can be made coincident or approximate.
Therefore, it is possible to measure the chloride ion concentration change in the measurement target portion separately from the pH change in the measurement target portion.

Moreover, the electrical resistor 4 may be comprised with the dense body comprised with the metal material, and may be comprised with the porous body comprised with the metal material.
When the electrical resistor 4 is a porous electrical resistor composed of a porous body made of a metal material, a large number of fine recesses are uniformly dispersed on the surface of the electrical resistor 4 as portions that are susceptible to corrosion. It is formed. Therefore, the surface of the electrical resistor 4 is uniformly corroded in the presence of chloride ions, and local corrosion (pitting corrosion) is suppressed.
For this reason, the rate of corrosion of the electrical resistor 4 by chloride ions can be reduced. Therefore, it is possible to measure the chloride ion concentration at the site to be measured over a long period of time.

On the other hand, when the electrical resistor 4 is a dense electrical resistor composed of a dense body made of a metal material, the surface of the electrical resistor 4 has a portion that is most susceptible to corrosion in the presence of chloride ions. Corrosion occurs first, and the corrosion resistance of the part where the corrosion first occurs is greater than that of other parts, so that local corrosion (pitting corrosion) occurs.
For this reason, although the rate of crevice corrosion of the electrical resistor 3 is slower, the rate of corrosion of the electrical resistor 4 by chloride ions can be increased. Therefore, it is possible to measure the chloride ion concentration at the site to be measured over the medium term.

Such electrical resistor 3 and electrical resistor 4 are not particularly limited, and can be formed using a film forming method.
The thicknesses of the electrical resistors 3 and 4 are not particularly limited, but are preferably 10 nm or more and 5 mm or less so that the change in electrical resistance due to corrosion is large and does not affect the concrete strength.

(Gap forming body)
The gap forming body 8 is disposed with a gap G formed between part of the surface of the electrical resistor 3. The gap G is locally formed with respect to the surface of the electrical resistor 3.
By forming such a gap G, the electrical resistor 3 can be corroded by gap corrosion even if the chloride ion concentration at the measurement target site is relatively low.
Therefore, even if the chloride ion concentration at the measurement target site is relatively low, the resistance value of the electrical resistor 3 changes, and the entry of chloride ions can be detected based on the change.

  In particular, when the electrical resistor 3 is made of a metal material that forms a passive film as described above, the passive film formed on the electrical resistor 3 has a relatively high chloride ion concentration at the site to be measured. Even if it is low, once local destruction occurs due to chloride ions that have entered the gap G between the electric resistor 3 and the gap forming body 8, the metal ions eluted from the electric resistor 3 in the gap G Since the concentration of (positive ions) increases and the concentration of chloride ions (negative ions) increases accordingly, it is not regenerated. Therefore, when the pH of the measurement target site is equal to or higher than a predetermined value, even if the pH of the measurement target site fluctuates, the electrical resistor 3 does not corrode when chloride ions are not present in the measurement target site. Although the resistance value of 3 does not change, if chloride ions enter the site to be measured, crevice corrosion of the electrical resistor 3 proceeds, and the resistance value of the electrical resistor 3 increases.

Therefore, it is possible to detect with high accuracy that chloride ions have entered the measurement target site based on the resistance value of the electrical resistor 3.
Hereinafter, based on FIG. 5, the corrosion (gap corrosion) by the chloride ions of the electrical resistor 3 in which the gap G is formed between the gap forming body 8 will be described in more detail.
When the electrical resistor 3 is in the presence of chloride ions (Cl ⁻ ), local destruction of the passive film formed on the surface of the electrical resistor 3 is temporarily caused by chloride ions that have entered the gap G. When it occurs, the first metal material constituting the electric resistor 3 is eluted into the gap G as metal ions (M ^{n +} ).

For example, when the first metal material is pure iron (Fe),
Fe → Fe ²⁺ + e
As a result of this reaction, Fe ²⁺ is eluted as a metal ion in the gap G.
Thus, the metal ions eluted in the gap G have a low diffusion rate and stay in the gap G. Thereby, the density | concentration of the metal ion in the clearance gap G increases.

Then, chloride ions migrate from the gap G to the gap G so that the electrical neutrality in the gap G is maintained, and the chloride ions concentrate in the gap G. Thereby, the density | concentration of the chloride ion in the clearance gap G also increases.
Therefore, the concentration of chloride ions in the gap G is higher than the concentration of chloride ions outside the gap G.

Further, in the gap G, hydrogen ions are generated by reaction of metal ions, chloride ions, and water, and the hydrogen ion concentration in the gap G increases, that is, the pH in the gap G decreases.
For example, when the first metal material is pure iron (Fe),
Fe ²⁺ + 2Cl ⁻ → FeCl ₂
FeCl ₂ + 2H ₂ O → Fe (OH) ₂ + HCl
Due to this reaction, the concentration of hydrogen ions in the gap G increases.

Therefore, the concentration of hydrogen ions in the gap G is higher than the concentration of hydrogen ions outside the gap G.
As described above, even if the concentration of chloride ions and hydrogen ions outside the gap G is relatively small, the chloride ion concentration and hydrogen ion concentration inside the gap G increase, and the crevice corrosion of the electrical resistor 3 proceeds. Will be.
Here, on the surface of the electrical resistor 3, a portion where crevice corrosion occurs is an anode region, and a portion exposed to the outside of the gap G is a cathode region.

For example, when the first metal material is pure iron (Fe),
In the anode region of the electrical resistor 3, an anodic reaction of Fe → Fe ²⁺ + 2e occurs,
In the cathode region of the electrical resistor 3, a cathode reaction of 1 / 2O ₂ + H ₂ O + 2e → 2OH− occurs.
Such a cathode reaction is promoted by increasing the cathode region of the electrical resistor 3. Therefore, by increasing the area of the portion exposed outside the gap G on the surface of the electrical resistor 3, crevice corrosion of the electrical resistor 3 occurs even when the concentration of chloride ions at the measurement target site is lower. Intrusion of chloride ions into the measurement target site can be detected with higher sensitivity.

In the present embodiment, the gap forming body 8 forms a gap G between the gap forming body 8 and a part of the surface in the longitudinal direction of the electric resistor 3. By configuring the gap forming body 8 in this way, the gap G that can cause gap corrosion of the electric resistor 3 can be easily and reliably formed between the electric resistor 3 and the gap forming body 8.
For example, after forming a sacrificial layer by forming a metal such as aluminum on the electric resistor 3 by electrolytic plating, the gap forming body 8 is formed on the sacrificial layer. It can be formed by a film method, and the sacrificial layer can be removed by dissolving with a strong alkaline solution.

The constituent material of the gap forming body 8 is not particularly limited, but for example, it is preferable to use an insulating material or a metal material of the same type as the first metal material constituting the electrical resistor 3.
When the gap forming body 8 is made of an insulating material, the gap forming body 8 can be prevented from functioning as a part of the electric resistor 3. Therefore, the electrical resistor 3 and the gap forming body 8 can be easily designed.

The insulating material is not particularly limited. For example, insulating ceramic materials such as SiO ₂ and Si ₃ N ₄ , PSF (polysulfone), PAI (preamidoimide), PTFE (polytetrafluoroethylene), PVDF ( Resin materials such as (polyvinylidene fluoride) and the like. Among them, in the present embodiment, those that can withstand the strong alkaline solution used for removing the sacrificial layer as described above are preferable.
Further, when the gap forming body 8 is made of the same metal material as the metal material constituting the electric resistor 3, even if the gap forming body 8 and the electric resistor 3 are in contact with each other, the electric resistor due to the contact is formed. 3 corrosion can be prevented.

Moreover, it is preferable that the clearance gap formation body 8 is comprised from the material which has alkali resistance. Thereby, even if it is a case where a measurement object part is concrete, the endurance of gap formation object 8 can be made excellent. Therefore, the state of concrete can be measured stably over a long period of time.
Further, the distance between the gap forming body 8 and the electric resistor 3 in the gap G (the distance in the thickness direction of the electric resistor 3) is preferably 1 μm or more and 100 μm or less, and is 10 μm or more and 80 μm or less. Is more preferably 20 μm or more and 60 μm or less. Thereby, crevice corrosion of the electrical resistor 3 can be caused.

(Functional element)
The functional element 51 is embedded in the main body 2 described above. The functional element 51 may be provided on the same surface as the electric resistor 3 and the electric resistor 4 with respect to the substrate 21 of the main body 2 described above or on the opposite side.
The functional element 51 has a function of measuring the resistance values of the electric resistor 3 and the electric resistor 4. Thereby, based on the resistance value of the electrical resistors 3 and 4, the state of a measurement object site | part can be measured.

Moreover, the functional element 51 is based on the resistance value of the electrical resistor 3 and the electrical resistor 4, and whether the pH or chloride ion concentration of the measurement object site | part of the concrete structure 100 which is a measurement object is below a setting value. It also has a function to detect. Thereby, the state change accompanying the pH change or chloride ion concentration change of the concrete structure 100 is detectable.
Such a functional element 51 is, for example, an integrated circuit. More specifically, the functional element 51 is, for example, an MCU (micro control unit), and includes a CPU 511, an A / D conversion circuit 512, and a measurement circuit 514 as shown in FIG.

The functional element 51 is activated by energization from the power source 52. The power source 52 is not particularly limited as long as it can supply power capable of operating the functional element 51. For example, the power source 52 may be a battery such as a button-type battery or has a power generation function such as a piezoelectric element. It may be a power source using an element.
The functional element 51 is configured to be able to acquire temperature information detected by the temperature sensor 53. Thereby, the information regarding the temperature of a measurement object site | part can also be obtained. By using such temperature-related information, it is possible to measure the state of the measurement target part more accurately or predict the change of the measurement target part with high accuracy.

The temperature sensor 53 has a function of detecting the temperature of the measurement target portion of the concrete structure 100 that is the measurement target. Such temperature sensor 53 is not particularly limited, and various types of known temperature sensors such as a thermistor and a thermocouple can be used, for example.
The functional element 51 also has a function of driving and controlling the communication circuit 54. For example, the functional element 51 relates to information on the resistance value of the electrical resistors 3 and 4 (hereinafter also simply referred to as “resistance value information”) and whether or not the pH or chloride ion concentration of the measurement target site is equal to or less than a set value. Information (hereinafter also simply referred to as “pH information”) is input to the communication circuit 54. The functional element 51 also inputs information related to the temperature detected by the temperature sensor 53 (hereinafter also simply referred to as “temperature information”) to the communication circuit 54.

The communication circuit 54 has a function of supplying power to the antenna 55 (transmission function). Thereby, the communication circuit 54 can wirelessly transmit the input information via the antenna 55. The transmitted information is received by a receiver (reader) provided outside the concrete structure 100.
The communication circuit 54 includes, for example, a transmission circuit for transmitting electromagnetic waves, a modulation circuit having a function of modulating a signal, and the like. Note that the communication circuit 54 receives a down-converter circuit having a function of converting a signal frequency to a low level, an up-converter circuit having a function of converting a signal frequency to a large level, an amplifier circuit having a function of amplifying a signal, and electromagnetic waves. And a demodulator circuit having a function of demodulating a signal.

The antenna 55 is not particularly limited, but is made of, for example, a metal material, carbon or the like, and has a form such as a winding or a thin film.
Further, the functional element 51 is configured to be able to acquire a clock signal from the oscillator 56. Thereby, each circuit can be synchronized and time information can be added to various information.

The oscillator 56 is not particularly limited. For example, the oscillator 56 includes an oscillation circuit using a crystal resonator.
In the measuring method using the sensor device 1 configured as described above, the electric resistor 3 and the electric resistor 4 are respectively embedded in the concrete structure 100 that is a measurement object, and the electric resistors 3, 4 are Based on the resistance value, the state of the concrete structure 100 is measured.

Hereinafter, the operation of the sensor device 1 will be described by taking as an example the case where the electrical resistors 3 and 4 are made of Fe (carbon steel).
In the concrete structure 100 immediately after placing, the concrete 101 exhibits strong alkalinity if it is properly placed. Therefore, at this time, each of the electrical resistor 3 and the electrical resistor 4 forms a stable passive film.
Thereafter, in the concrete structure 100, the pH of the concrete 101 gradually changes to the acidic side due to the influence of carbon dioxide, acid rain, exhaust gas, and the like.

If chloride ions enter the measurement target portion of the concrete 101 of the concrete structure 100 before the pH of the concrete 101 drops to about 9, the concentration of chloride ions corrodes carbon steel (about 1.2 kg). / M ³ ), the passive film formed on the electric resistor 4 does not corrode even in the presence of chloride ions, and the resistance value of the electric resistor 4 remains almost unchanged. Maintained. On the other hand, the passive film formed on the electric resistor 3 has a chloride ion concentration at a measurement target portion that does not reach a limit concentration that corrodes carbon steel (even if it is about 0.1 kg / m ^3). ), Crevice corrosion occurs due to the gap G in the presence of chloride ions, and the resistance value of the electrical resistor 3 increases.

And when the chloride ion concentration of a measurement object part reaches the limit concentration which corrodes carbon steel, the electrical resistor 4 will also corrode and the resistance value of the electrical resistor 4 will become large.
Based on the resistance values of the electrical resistors 3 and 4, it is possible to detect intrusion of chloride ions into the measurement target portion in a stepwise manner.
Further, even if chloride ions do not enter the measurement target portion of the concrete 101 of the concrete structure 100, when the pH of the concrete 101 falls to about 9, both the electrical resistors 3 and 4 corrode and the electrical resistance. Both the resistance values of the bodies 3 and 4 increase.

Based on such resistance values of the electrical resistors 3 and 4, it can be detected that the pH of the site to be measured has reached about 9.
By using such a detection result, it is possible to monitor a change with time in quality after placing the concrete structure 100. Therefore, deterioration (neutralization and salt intrusion) of the concrete 101 can be grasped before the reinforcing bar 102 corrodes. Thereby, before the reinforcing bar 102 corrodes, the concrete structure 100 can be repaired by painting, preservative-mixed mortar, or the like.

It can also be determined whether or not there was an abnormality when placing the concrete structure 100. Therefore, the initial trouble of the concrete structure 100 can be prevented and the quality of the concrete structure 100 can be improved.
As described above, according to the sensor device 1 of the first embodiment, since the local gap G is formed between the electric resistor 3 and the gap forming body 8, the chloride ion concentration at the measurement target site is formed. Even in a relatively low state, the electrical resistor 3 can be corroded by crevice corrosion.

Therefore, even if the chloride ion concentration at the measurement target site is relatively low, the resistance value of the electrical resistor 3 changes, and the entry of chloride ions can be detected based on the change.
In this embodiment, since the electrical resistor 4 that does not cause crevice corrosion is provided separately from the electrical resistor 3, the change in the chloride ion concentration at the measurement target site is compared with the pH change at the measurement target site. It can be measured separately.

Second Embodiment
Next, a second embodiment of the present invention will be described.
FIG. 6 is a plan view showing a sensor device according to the second embodiment of the present invention, and FIG. 7 is a cross-sectional view for explaining the electric resistor shown in FIG. 6 (cross-sectional view taken along line AA in FIG. 6). It is.
Hereinafter, the second embodiment will be described with a focus on differences from the above-described embodiment, and description of similar matters will be omitted.

The sensor device of the second embodiment is substantially the same as the sensor device of the first embodiment except that the shape and number of electric resistors are different and the configuration of the gap forming body is different. In addition, the same code | symbol is attached | subjected to the structure similar to embodiment mentioned above.
The sensor device 1A shown in FIG. 6 includes an electric resistor 3A provided on the main body 2 and a gap forming body 8A provided by forming a gap G between a part of the surface of the electric resistor 3A. Have.

The electric resistor 3 </ b> A includes two first portions 31 and 32 that are separated from each other, and a second portion 33 that is formed between the two first portions 31 and 32.
The first portions 31 and 32 each have a quadrangular shape in plan view.
The second portion 33 connects the first portion 31 and the first portion 32. In the present embodiment, the second portion 33 has an elongated shape, one end of which is connected to the first portion 31 and the other end is connected to the first portion 32.

  The area of the second portion 33 in plan view is smaller than the area of the first portion 31 in plan view and the area of the first portion 32 in plan view. That is, the area of the first portion 31 in plan view and the area of the first portion 32 in plan view are larger than the area of the second portion 33 in plan view, respectively. As a result, the surface area of the portion where the cathode reaction occurs at the time of crevice corrosion of the electrical resistor 3A can be increased. Moreover, the area of the cross section (cross section orthogonal to the direction in which the current flows) of the portion where the anode reaction occurs during the crevice corrosion of the electric resistor 3A can be reduced, and the electric resistor 3A can be easily cut by the crevice corrosion.

The gap forming body 8A is provided with gaps G formed between both side surfaces of the second portion 33 of the electrical resistor 3A described above. In the present embodiment, as shown in FIG. 7, the gap forming body 8 has a sheet shape or a plate shape, and is provided on the substrate 21.
Such a gap forming body 8A can be formed by a known film forming method.
According to such a sensor device 1A, the crevice corrosion of the second portion 33 of the electrical resistor 3A can be performed.

In particular, in the electrical resistor 3A, the surface area of the portion exposed outside the gap G is larger than the surface area of the portion exposed inside the gap G. That is, in the electrical resistor 3A, the surface area of the portion not covered with the gap forming body 8A is larger than the surface area of the portion covered with the gap forming body 8A via the gap G. Thereby, crevice corrosion of 3 A of electrical resistors can be accelerated | stimulated.
Even with the sensor device 1A according to the second embodiment as described above, the state of the measurement object is measured while preventing deterioration of the quality of the concrete 101, and information based on the measurement result is determined before the corrosion of the reinforcing bar 102. Can be used for environmental or preventive maintenance

<Third Embodiment>
Next, a third embodiment of the present invention will be described.
FIG. 8 is a view showing an example of a usage state of the sensor device according to the third embodiment of the present invention, and FIG. 9 is a diagram for explaining an electrical resistor (porous electrical resistor) provided in the sensor device shown in FIG. It is an expanded sectional view for doing.

Hereinafter, the third embodiment will be described with a focus on differences from the above-described embodiment, and description of similar matters will be omitted.
The sensor device of the third embodiment is substantially the same as the sensor device of the first embodiment except that the number of electrical resistors is different. In addition, the same code | symbol is attached | subjected to the structure similar to embodiment mentioned above.

A sensor device 1B shown in FIG. 8 includes electrical resistors 3, 4, and 9 provided on a main body 2B.
In the present embodiment, the electrical resistors 3, 4, and 9 have a distance from the outer surface of the concrete structure 100 so that the distance between the outer surface of the concrete structure 100 and the reinforcing bar 102 (that is, the covering depth of the reinforcing bar 102). ) To be almost equal.

The electrical resistors 3 and 4 are configured in the same manner as the electrical resistors 3 and 4 of the first embodiment described above. Although not shown in FIG. 8, the sensor device 1 </ b> B has a gap forming body provided by forming a gap in a part of the surface of the electrical resistor 3. Further, the electric resistor 4 is provided so as not to cause crevice corrosion.
In the present embodiment, the electrical resistor 4 is constituted by a dense body made of a metal material.

Further, the electrical resistor 9 is provided apart from the electrical resistors 3 and 4. And the electrical resistor 9 is comprised similarly to the electrical resistor 4 except being a porous electrical resistor comprised with the porous body which consists of metal materials.
Specifically, as shown in FIG. 9, the electrical resistor 9 is composed of a porous body 92 having a plurality of holes 91.

Moreover, the average diameter of the plurality of holes 91 is not particularly limited, but is preferably 2 nm or more and 50 nm or less, for example. That is, each of the holes 91 is preferably a meso hole.
Furthermore, the porosity of the electrical resistor 9 is not particularly limited, but is preferably 10% or more and 90% or less, for example.

Even if such electrical resistors 4 and 9 are installed in the same environment as the electrical resistor 3, the start timing of local corrosion by chloride ions of the electrical resistors 4 and 9 is determined based on the chloride of the electrical resistor 3. It can be delayed from the start timing of local corrosion by ions.
Further, by making the metal material constituting the electric resistors 4 and 9 the same type as the metal material constituting the electric resistor 3, the start timing of the uniform corrosion due to the acidification or neutralization of the electric resistors 4 and 9, The start timing of the uniform corrosion due to acidification or neutralization of the electrical resistor 3 can be made coincident or approximate.

Therefore, it is possible to measure the chloride ion concentration change in the measurement target portion separately from the pH change in the measurement target portion.
In addition, since the electrical resistor 9 is made of a porous material made of a metal material, a large number of fine recesses are uniformly dispersed on the surface of the electrical resistor 9 as a portion that is susceptible to corrosion. Therefore, chloride ions are also dispersed without locally collecting at one point. Therefore, the surface of the electrical resistor 9 is uniformly corroded in the presence of chloride ions, and local corrosion (pitting corrosion) is suppressed.

For this reason, the rate of corrosion of the electrical resistor 9 by chloride ions can be reduced. Therefore, it is possible to measure the chloride ion concentration at the site to be measured over a long period of time.
On the other hand, since the electric resistor 4 is composed of a dense body made of a metal material, the surface of the electric resistor 4 is corroded first in the presence of chloride ions. Local corrosion (pitting corrosion) occurs because the corrosion resistance of the portion where corrosion has occurred first is greater than that of other portions.

For this reason, although the rate of crevice corrosion of the electrical resistor 3 is slower, the rate of corrosion of the electrical resistor 4 by chloride ions is made faster than the rate of corrosion of the electrical resistor 9 by chloride ions. be able to. Therefore, it is possible to measure the chloride ion concentration at the site to be measured over the medium term.
Even with the sensor device 1B according to the third embodiment as described above, the state of the measurement object is measured while preventing the deterioration of the quality of the concrete 101, and information based on the measurement result is determined before the corrosion of the reinforcing bar 102. Can be used for environmental or preventive maintenance

<Fourth embodiment>
Next, a fourth embodiment of the present invention will be described.
FIG. 10 is a diagram illustrating an example of a usage state of the sensor device according to the fourth embodiment of the present invention.
Hereinafter, the fourth embodiment will be described with a focus on differences from the above-described embodiment, and description of similar matters will be omitted.

The sensor device of the fourth embodiment is substantially the same as the sensor device of the third embodiment, except that the usage state is different. In addition, the same code | symbol is attached | subjected to the structure similar to embodiment mentioned above.
In the sensor device 1 </ b> C shown in FIG. 10, the plurality of electrical resistors 3, 4, 9 are different from each other in distance from the outer surface of the concrete structure 100. Specifically, a plurality of electrical resistors 3, 4, 9 are provided in this order from the outer surface side of the concrete structure 100 to the inside. Intrusion prediction in the depth direction of neutralization (or salt damage) of the concrete structure 100 can be effectively performed.
Even with the sensor device 1C according to the fourth embodiment as described above, the state of the measurement object is measured while preventing the deterioration of the quality of the concrete 101, and information based on the measurement result is determined before the corrosion of the reinforcing bar 102. Can be used for environmental or preventive maintenance

<Fifth Embodiment>
Next, a fifth embodiment of the present invention will be described.
11 is a partially enlarged perspective view showing a sensor device according to a fifth embodiment of the present invention, FIG. 12A is a plan view showing an electric resistor provided in the sensor device shown in FIG. FIG. 12B is a side view showing the electrical resistor provided in the sensor device shown in FIG. 11.

Hereinafter, the fifth embodiment will be described with a focus on differences from the above-described embodiments, and description of similar matters will be omitted.
The sensor device of the fifth embodiment is substantially the same as the sensor device of the first embodiment, except that the configuration of the electrical resistor and the gap forming body for causing crevice corrosion is different.
A sensor device 1D shown in FIG. 11 is provided with a gap G formed between a main body 2D, an electric resistor 3D provided in the shape of the main body 2D, and a part of the surface of the electric resistor 3D. A gap forming body 8D.

In the present embodiment, the electrical resistor 3D and the gap forming body 8D each have a plate shape or a sheet shape, and are arranged so as to overlap each other. Thereby, the gap G that can cause the crevice corrosion of the electric resistor 3D can be easily and reliably formed between the electric resistor 3D and the gap forming body 8D.
More specifically, the electric resistor 3D and the gap forming body 8D are fixed to the electric resistor 3D by the fixing member 11 in a state where the electric resistor 3D and the gap forming body 8D are overlapped with each other.

The fixing member 11 includes a bolt 111, washers 112 and 113, and a nut 114.
The electrical resistor 3D and the gap forming body 8D are formed with a through-hole (not shown) penetrating both in a state of being overlapped with each other, and the through-hole is passed through a washer 112 from one side. The gap forming body 8D is fixed to the electric resistor 3D by the fixing member 11 by inserting the bolt 111 and screwing the nut 114 to the bolt 111 through the washer 113 from the other side.

Such bolts 111 and nuts 114 locally press the gap forming body 8D against the electrical resistor 3D, so that the portions other than the crimped portion of the gap forming body 8D are against the electrical resistor 3D. Slightly rises and a gap G is formed. The washers 112 and 113 may be omitted.
The distance between the electric resistor 3D and the gap forming body 8D in the gap G can be adjusted according to the tightening torque of the bolt 111 and the nut 114. Note that this distance is the same size as the distance between the electrical resistor 3 and the gap forming body 8 in the gap G in the first embodiment, that is, the magnitude that can cause crevice corrosion of the electrical resistor 3D. Should be set.

Also, minute protrusions corresponding to the size of the gap G may be formed on the surface of the gap forming body 8D on the electric resistor 3D side. In this case, the size of the gap G can be defined to a desired size regardless of the tightening torque of the bolt 111 and the nut 114.
The constituent materials of the bolt 111, the washers 112 and 113, and the nut 113 are not particularly limited, but it is preferable to use an insulating material and the same metal material as that of the electrical resistor 3D.

In the present embodiment, a through hole 34 is formed at the center of the electrical resistor 3D. As a result, the electrical resistor 3D includes two first portions 31D and 32D and two second portions 33D provided between the two first portions 31D and 32D.
The area of each second portion 33D in plan view is smaller than the area of the first portion 31D in plan view and the area of the first portion 32D in plan view.

Such a gap forming body 8D is provided with a gap G formed between the upper surface of each second portion 33D of the electric resistor 3D described above. Thereby, crevice corrosion of each 2nd part 33D of electrical resistor 3D can be carried out.
Even with the sensor device 1D according to the fifth embodiment as described above, the state of the measurement object is measured while preventing the deterioration of the quality of the concrete 101, and information based on the measurement result is determined before the corrosion of the reinforcing bar 102. As mentioned above, although the sensor apparatus of this invention was demonstrated based on embodiment of illustration, this invention is not limited to this.

For example, in the sensor device of the present invention, the configuration of each part can be replaced with any configuration that exhibits the same function, and any configuration can be added. In addition, for example, in the measurement method of the present invention, one or two or more optional steps may be added.
In the above-described embodiment, the case where the electrical resistors are provided on the substrate has been described as an example. However, the present invention is not limited to this. For example, the electrical resistor is, for example, a sealing resin for the main body of the sensor device. You may provide on the outer surface of the comprised part.

Also, the installation position, size (magnitude relationship), number, and the like of the electrical resistor are not limited to the above-described embodiment and can be arbitrary as long as the above-described measurement is possible.
In the above-described embodiment, the case where the functional element includes the CPU, the A / D conversion circuit, and the measurement circuit has been described as an example. However, the functional element is not limited thereto. For example, the functional element includes a ROM, a RAM, and various driving circuits. Such other circuits may be incorporated.

Further, in the above-described embodiment, the case where the information related to the resistance value of the electric resistor is transmitted to the outside of the sensor device by wireless transmission by active tag communication is described as an example. However, the present invention is not limited to this. The information may be transmitted to the outside of the sensor device, or the information may be transmitted to the outside of the sensor device by wire.
In the above-described embodiment, the functional element 51, the power source 52, the temperature sensor 53, the communication circuit 54, the antenna 55, and the oscillator 56 are accommodated in the main body 2, and these are measured together with the electric resistor 3 and the electric resistor 4. Although the case of embedding in the concrete structure 100, which is an object, has been described as an example, the functional element 51, the power source 52, the temperature sensor 53, the communication circuit 54, the antenna 55, and the oscillator 56 may be provided outside the measurement object. Good.

DESCRIPTION OF SYMBOLS 1 ... Sensor device 1A ... Sensor device 1B, 1C, 1D ... Sensor device 11 ... Fixing member 2 ... Main body 2A, 2B, 2D ... Main body 21, 21A ... Substrate 22a ... Conductor part 22b ... Conductor part 22c ... Conductor part 23, 23A ... Insulating layer 24, 24A ... Sealing part 25 ... Protective film 3, 3A, 3D ... Electric resistor 31, 32, 31D, 32D ... First part 33, 33D ... 2nd part 34 ... Through hole 4, 4A ... Electrical resistor 41, 41A ... Hole 51 ... Functional element 52 ... Power supply 53 ... Temperature sensor 54 ... Communication circuit 55 Antenna 56 Oscillator 61, 61A Conductor 62, 62A Conductor 63, 63A Conductor 64, 64A Conductor 71, 72, 73, 74, 75, 76, 71A, 72 A, 73A, 74A ··· Wiring 8, 81, 82, 83 · · · Electrical resistor 8A, 8D · · · Gap forming member 8c · · · Electrical resistor 9 · · · Electrical resistor 91 · · · Pore 92 · · · Porous Body 100 ... Concrete structure 101 ... Concrete 102 ... Reinforcing bars 111 ... Bolts 112, 113 ... Washers 114 ... Nuts 241 ... Openings 511 ... CPU 512 ... A / D conversion circuit 513 ... Board 514 ... Measuring circuit G ... Clearance

Claims (14)

An electrical resistor composed of a metal material;
A gap forming body arranged to form a gap with a part of the surface of the electric resistor;
A functional element having a function of measuring a resistance value of the electric resistor,
A sensor device configured to be able to measure a state of a measurement target part based on a resistance value measured by the functional element.   The sensor device according to claim 1, wherein each of the electric resistor and the gap forming body has a plate shape or a sheet shape, and is disposed so as to overlap each other. The electrical resistor has a long shape,
The sensor device according to claim 1, wherein the gap forming body forms the gap with a part of a surface in the longitudinal direction of the electric resistor.   4. The electric resistor according to claim 1, wherein a surface area of a portion not covered with the gap forming body is larger than a surface area of a portion covered with the gap forming body via the gap. Sensor device.   The sensor device according to claim 1, wherein the gap forming body is made of an insulating material.   5. The sensor device according to claim 1, wherein the gap forming body is made of the same metal material as that of the metal material constituting the electric resistor.   The sensor device according to claim 1, wherein the gap forming body is made of a material having alkali resistance.   The sensor device according to claim 1, wherein a distance between the gap forming body and the electric resistor in the gap is 1 μm or more and 100 μm or less.   The metal material that constitutes the electrical resistor is a metal material that forms a passive film on the surface in accordance with an environmental change of the measurement target site, or disappears the passive film present on the surface. The sensor device according to any one of 1 to 8.   The sensor device according to claim 9, wherein the metal material constituting the electrical resistor is iron, nickel, or an alloy containing these. A porous electrical resistor that is provided apart from the electrical resistor and is composed of a porous material made of a metal material;
The sensor device according to claim 1, wherein the functional element also has a function of measuring a resistance value of the porous electrical resistor. A dense electrical resistor formed of a dense body made of a metal material, spaced apart from the electrical resistor;
The sensor device according to claim 1, wherein the functional element also has a function of measuring a resistance value of the dense electric resistor.   13. The functional element according to claim 1, wherein the functional element also has a function of detecting whether the pH or chloride ion concentration of the measurement target site is equal to or lower than a set value based on a resistance value of the electric resistor. The sensor device described. An antenna and a communication circuit having a function of supplying power to the antenna;
The sensor device according to claim 1, wherein the functional element also has a function of driving and controlling the communication circuit.

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