JP6850717B2 - Anomaly detection sensor and anomaly detection system - Google Patents

Description

The present invention relates to an abnormality detection sensor and an abnormality detection system that detect an abnormality of an object to be detected.

Anomaly detection sensors are cameras, contact sensors, and the like used for the purpose of detecting theft or anomalies of exhibits when displaying valuable exhibits in museums or the like. An abnormality detection system using a camera as an abnormality detection sensor is disclosed in, for example, Non-Patent Document 1. Further, an abnormality detection system using a contact sensor is disclosed in, for example, Non-Patent Document 2.

[Search on November 15, 2017], Internet <URL: http://www.sony.jp/snc/products/NSR-1100_01/alarm.html> [Search on November 15, 2017], Internet <URL: http://www.securityhouse.net/~shs-mk/jisya.htm>

However, in the technique shown in Non-Patent Document 1, light is required because a camera is used for the abnormality detection sensor. Therefore, there is a problem that an abnormality of an object such as an exhibit cannot be detected in a dark place. Further, in the technique shown in Non-Patent Document 2, since a contact sensor is used, it is not possible to distinguish whether the object to be monitored has been stolen or moved due to a violent shaking such as an earthquake. That is, there is a problem that the detection accuracy is not good.

The present invention has been made in view of these problems, and an object of the present invention is to provide an abnormality detection sensor and an abnormality detection system capable of accurately detecting an abnormality of an object such as an exhibit even in a dark place.

The abnormality detection sensor according to one aspect of the present embodiment is arranged at a position facing the first electrode on which the object to be detected is placed and the first electrode with an insulator in between, and is flatter than the first electrode. A second electrode having a large area, a signal source that generates a reference signal having a constant amplitude and frequency, and a resonance in which the reference signal is input to generate a resonance reactor that maximizes the terminal voltage of the first electrode. Reactance generation unit, a phase monitor unit that detects the terminal voltage of the first electrode and the in-phase component of the reference signal, and a determination unit that determines a change in the amplitude of the in-phase component and outputs a determination value obtained. The resonance reactor generation unit includes an inductor in which one end is connected to an input terminal via a first capacitor and the other end is connected to the first electrode, and a second capacitor in which one end is connected to the other end of the inductor. A variable capacitance diode that connects an anode electrode to one end of the inductor and a cathode electrode to the other end of the second capacitor, and a fixed voltage that applies a predetermined voltage to the anode electrode of the variable capacitance diode via a first resistor. When the source is connected to the cathode electrode of the variable capacitance diode via a third capacitor, an amplitude monitor unit that generates an amplitude signal corresponding to the amplitude of the terminal voltage of the first electrode, and the resonance reactor are generated. In addition, an adjustment unit that changes the magnitude of the control signal in one direction and outputs it until the amplitude signal is maximized, and an adjustment voltage corresponding to the magnitude of the control signal are generated, and the adjustment voltage is used as a second resistor. via an adjustment signal output unit to be applied to the cathode electrode of the variable capacitance diode and gist of Rukoto.

Further, the abnormality detection system according to one aspect of the present embodiment is an abnormality detection system composed of a sensor node, a network, and a server, and the sensor node includes the above-mentioned abnormality detection sensor and the above-mentioned abnormality detection sensor. A sensor control unit that transmits a switching signal instructing the start of generation of the resonance reactor and receives an adjustment completion signal indicating that the resonance reactor has been generated and the determination value, and the sensor control unit. It is a gist to include a transmission / reception unit that connects to the server via the network.

According to the present invention, it is possible to provide an abnormality detection sensor and an abnormality detection system that can accurately detect an abnormality of an object such as an exhibit even in a dark place.

It is a figure which shows the functional structure example of the abnormality detection sensor which concerns on embodiment of this invention. It is a figure for demonstrating the detection principle of the abnormality detection sensor shown in FIG. It is a figure which shows the state of the object detected by the abnormality detection sensor shown in FIG. 1, (a) is the reference state, (b) is the state which the object disappeared, (c) is the figure which shows the state which the object has fallen over. is there. It is a figure which shows the 1st Embodiment of the structural example of the reactance generation part for resonance of the abnormality detection sensor shown in FIG. It is a figure which shows typically the signal waveform of each part of the reactance generation part for resonance shown in FIG. It is a figure which shows the structural example of the phase monitor part of the abnormality detection sensor shown in FIG. It is a figure which shows the 2nd Embodiment of the structural example of the reactance generation part for resonance of the abnormality detection sensor shown in FIG. It is a schematic diagram explaining the operation of the reactance generation part for resonance shown in FIG. 7. It is a figure which shows the structural example of the abnormality detection system which concerns on embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same reference numerals are given to the same objects in a plurality of drawings, and the description is not repeated.

FIG. 1 is a diagram showing a functional configuration example of an abnormality detection sensor according to an embodiment of the present invention. The abnormality detection sensor 1 shown in FIG. 1 is a sensor that can detect the disappearance, fall, etc. of an object to be detected even in a dark place.

The abnormality detection sensor 1 includes a first electrode 10, a second electrode 20, an insulator 30, a signal source 40, a reactance generation unit 50 for resonance, a phase monitor unit 60, and a determination unit 70.

The first electrode 10 is a flat electrode on which an object to be detected is placed. The planar shape of the first electrode 10 is, for example, a rectangular shape. The planar shape of the first electrode 10 is not limited to a rectangular shape as long as it can carry an object to be detected. Further, the surface of the first electrode 10 may be either a conductor or an insulator.

The second electrode 20 is arranged at a position facing the first electrode 10 with the insulator 30 interposed therebetween, and has a larger flat area than the first electrode 10. The second electrode 20 is grounded, and a capacitance is formed between the second electrode 20 and the first electrode 10. The planar shape of the second electrode 20 is preferably the size of a range in which the object to be detected faces the overturned object via the insulator 30 when the object to be detected falls, for example.

The signal source 40 generates a reference signal having a constant amplitude and frequency. The reference signal is an AC signal having a constant amplitude and frequency.

The resonance reactance generation unit 50 generates a resonance reactance at which the reference signal generated by the signal source 40 is input and the terminal voltage of the first electrode 10 is maximized. Resonance reactance is generated when the switching signal input from the outside is, for example, a positive power supply potential. Hereinafter, the case where the reactance for resonance is generated is referred to as a reference search state.

On the other hand, when the switching signal has a negative power supply potential, it is referred to as an object detection state. For example, the value of the capacitive reactance of the reactance generating unit 50 for resonance in the object detection state is the value of the reactance for resonance generated in the reference search state.

The phase monitor unit 60 detects the terminal voltage of the first electrode and the in-phase component of the reference signal generated by the signal source 40. It is possible to detect the disappearance, fall, etc. of an object by changing the in-phase component. The principle of detection will be described later.

The determination unit 70 outputs a determination value obtained by determining the change in the amplitude of the in-phase component detected by the phase monitor unit 60. The amplitude of the in-phase component changes as the object disappears or falls. Therefore, the state of the object can be detected by determining the change in the amplitude of the in-phase component.

As described above, according to the abnormality detection sensor 1 according to the present embodiment, the state of the object is detected based on the change in the amplitude of the in-phase component detected by the phase monitor unit 60, so that the exhibit can be accurately exhibited even in a dark place. It is possible to detect anomalies in objects such as.

Next, the detection principle of the abnormality detection sensor 1 will be described with reference to FIGS. 2 and 3.

[Detection principle]
FIG. 2 shows a signal source 40, a reactance generator 50 for resonance, a capacitance Ce formed between the first electrode 10 and the second electrode 20, and an object A to be detected and the second electrode 20. It is a figure which shows typically the relationship with the stray capacitance Cb formed.

The signal source 40 is composed of an oscillator 41 that generates a reference signal Vs, and can be represented by a reference signal Vs and an output resistance Rs. The signal source 40 can be configured by a general oscillator.

The material of the object A may be either a conductor or a dielectric. When the object A is placed on the first electrode 10, a stray capacitance Cb is formed between the object A and the second electrode 20. When the object A is a dielectric material, a stray capacitance is also formed between the object A and the first electrode 10, but the stray capacitance will be omitted for the purpose of simplifying the explanation.

A capacitance Ce is formed between the first electrode 10 and the second electrode 20. In FIG. 2, the reactance component of the reactance generation unit 50 for resonance is represented by Xv.

The terminal voltage Vo of the first electrode 10 input to the phase monitor unit 60 is represented by the following equation from the circuit model shown in FIG.

Here, j is an imaginary unit, and f is the frequency of the reference signal Vs generated by the signal source 40. In order to make the numerator of equation (1) 1, multiplying the denominator and numerator by j (2πf) (Ce + Cb), equation (1) can be transformed as follows.

If the real part is a and the imaginary part is b, Vo can be expressed by the equation (5).

The absolute value of a in the formula (5) represents the magnitude of the terminal voltage Vo of the first electrode 10 having the same phase as the AC signal of the signal source Vs. The absolute value of b represents the magnitude of the terminal voltage Vo whose phase is delayed by 90 ° from the signal source Vs.

Focusing only on the in-phase component, it can be seen that a becomes positive when Cb becomes small and a becomes negative when Cb becomes large, based on Cb satisfying the equation (6).

FIG. 3 is a diagram schematically showing a state in which the magnitude of the stray capacitance Cb between the object A and the second electrode 20 changes. Cb0 shown in FIG. 3A represents a stray capacitance in a state where the object A is placed on the first electrode 10. Cb1 shown in FIG. 3B represents a stray capacitance in a state where the object A is separated from the first electrode 10. Cb2 shown in FIG. 3C represents a stray capacitance in a state where the object A has fallen.

Based on the stray capacitance Cb0 (nest 3 (a)), the stray capacitance Cb1 in a state where the object A is separated from the first electrode 10 is smaller than Cb0 (Cb1 <Cb0). On the other hand, the stray capacitance Cb2 in the state where the object A has fallen is larger than Cb0 (Cb2> Cb0).

Therefore, the value of the reactance Xv for resonance is searched so that the condition of the equation (6) is satisfied at a predetermined frequency f. After that, when the object A separates from the first electrode 10, the in-phase component becomes positive, and when the object A falls, the in-phase component becomes negative. Therefore, by evaluating the sign of the in-phase component, it is possible to detect whether the object A has disappeared from above the first electrode 10 or the object A has fallen.

The state of the object A on the first electrode 10 can be detected without changing the sign of the in-phase component. The change in the amplitude of the in-phase component may be determined. That is, the change in the state of the object A on the first electrode 10 can be detected by determining the change in the amplitude of the in-phase component. The change in the state of the object A may be detected by comparing the amplitude of the in-phase component with the threshold value.

The detection principle of the abnormality detection sensor 1 has been described above. Next, the reactance generation unit 50 for resonance that generates the reactance Xv for resonance will be described in detail.

[First Embodiment]
FIG. 4 is a diagram showing a functional configuration example of the reactance generating unit 50 for resonance according to the first embodiment of the present invention.

The reactance generating unit 50 for resonance includes a first capacitor C1, an inductor L, a second capacitor C2, a variable capacitance diode D, a fixed voltage source 51, a second resistor R2, a third capacitor C3, an amplitude monitoring unit 52, and an adjusting unit 53. And the adjustment signal output unit 54 is provided.

One end of the inductor L is connected to the input terminal via the first capacitor C1. A signal source 40 is connected to the input terminal, and a reference signal Vs is input. The other end of the inductor L is connected to the output terminal, and the output terminal is connected to the first electrode 10.

Anode over cathode electrode of the variable capacitance diode D is connected to one end of the inductor L. Cathodes when cathode electrode of the variable capacitance diode D is connected to the other end of the inductor L via a second capacitor C2. The second capacitor C2 is a DC cut capacitor. The second capacitor C2, an AC to shorting the cathode over cathode electrode of the other end and the variable capacitance diode D of the inductor L. The parallel connection of the inductor L and the variable capacitance diode D constitutes a reactance Xv for resonance.

The anode over cathode electrode of the variable capacitance diode D, a fixed voltage source 51 is connected via a first resistor R1. The fixed voltage source 51 outputs a constant voltage. The first resistor R1 acts so that the impedance seen from the input terminal (signal source 40) is not lowered by the fixed voltage source 51.

Cathodes when cathode electrode of the variable capacitance diode D is connected to the amplitude monitor unit 52 via the third capacitor C3. The input of the amplitude monitor unit 52 is connected to the other end (first electrode 10) of the inductor L via the third capacitor C3 and the second capacitor C2.

The amplitude monitor unit 52 receives the terminal voltage Vo of the first electrode 10 as an input, and generates an amplitude signal representing the amplitude of the terminal voltage Vo. The amplitude monitor unit 52 includes an A / D converter that converts the terminal voltage Vo of the first electrode 10 into, for example, a digital signal.

The second capacitor C2 and the third capacitor C3 are DC cut capacitors. The third capacitor C3 acts so that the adjustment voltage output by the adjustment signal output unit 54 is not input to the amplitude monitor unit 52.

The adjusting unit 53 uses the amplitude signal generated by the amplitude monitoring unit 52 as an input, and in the case of the reference search state (switching signal = positive power supply potential), the value of the control signal is obtained in order to obtain the control signal that maximizes the amplitude signal. Is swept in one direction to generate, and fixed to the value of the control signal that maximizes the amplitude signal. The value of the control signal is, for example, a digital value represented by a plurality of bits.

When fixing the control signal to a value that maximizes the amplitude signal, the adjustment unit 53 outputs an adjustment completion signal. The adjustment completion signal may be either a pulse signal or a fixed voltage signal.

The state in which the amplitude signal is maximized is the state in which the condition of Eq. (6) is satisfied. In the case of the object detection state (switching signal = negative power supply potential), the control signal that maximizes the amplitude signal is maintained.

Adjustment signal output unit 54 generates a regulated voltage having a one-to-one correspondence to the value of the control signal adjusting section 53 outputs, to the cathodes when cathode electrode of the variable capacitance diode D the regulated voltage via a second resistor R2 Apply. The adjustment signal output unit 54 can be configured by, for example, a D / A converter that converts a control signal, which is a digital signal, into an analog signal.

The second resistor R2 acts so that the impedance seen from the output terminal does not decrease by the adjustment signal output unit 54. Further, the second capacitor C2 short-circuits the inductor L and the variable capacitance diode D in an alternating current manner, and prevents the adjustment voltage output by the adjustment signal output unit 54 from leaking to the fixed voltage source 51 via the inductor L. ..

The operation of the abnormality detection sensor 1 including the reactance generating unit 50 for resonance described above will be described with reference to FIG. FIG. 5 is a schematic diagram illustrating the operation of each part of the reactance generating unit 50 for resonance.

FIG. 5A shows the relationship between the control voltage and the adjustment voltage, FIG. 5B shows the relationship between the adjustment voltage and the capacitance CD of the variable capacitance diode D, and FIG. 5C shows the capacitance CD of the variable capacitance diode D. The relationship between the terminal voltage of the first electrode 10 and the terminal voltage | Vo | is shown.

After placing the object A on the first electrode 10, the user of the abnormality detection sensor 1 presses an activation button (not shown) for activating the abnormality detection sensor 1. When the start button is pressed, the switching signal is in the reference search state (switching signal = positive power potential). The switching signal is generated by a sensor control unit (not shown). The sensor control unit will be described later.

The start signal (or reset signal, initialization signal) generated by pressing the start button may be input to each function component of the abnormality detection sensor 1. In FIGS. 1 and 4, the notation of the start signal is omitted.

The signal source 40 generates reference signals Vs. The reference signal Vs is supplied to the first electrode 10 via the reactance generating unit 50 for resonance.

When the switching signal is in the reference search state (switching signal = positive power supply potential), the adjusting unit 53 sequentially changes the control signal at regular intervals until the terminal voltage Vo of the first electrode 10 becomes maximum. The control signal is changed from a low voltage to a high voltage, for example, in steps.

The adjustment signal output unit 54 increases the adjustment voltage stepwise as shown in FIG. 5A in a one-to-one correspondence with the value of the control signal that changes stepwise. The horizontal axis of FIG. 5A is, for example, time, and the vertical axis is the adjustment voltage. The horizontal axis may be the value of the control signal.

The adjusting unit 53 stores the amplitude voltage of the terminal voltage Vo of the first electrode 10 output by the amplitude monitoring unit 52 during the time width of one step in which the adjusting voltage becomes constant.

When the adjustment voltage changes from a low voltage to a high voltage, the capacitance CD of the variable capacitance diode D decreases in inverse proportion to the adjustment voltage as shown in FIG. 5 (b). The adjustment voltage acts as a reverse bias voltage with respect to the variable capacitance diode D. The adjustment voltage may be changed from a high voltage to a low voltage. Moreover, the adjustment voltage may be changed at random. Since the value of the capacitance CD of the variable capacitance diode D does not change with respect to the adjustment voltage, it is possible to search for the control signal corresponding to the adjustment voltage that maximizes the amplitude of the terminal voltage Vo.

The horizontal axis of FIG. 5B is the adjusted voltage, and the vertical axis is the capacitance CD. When the adjustment voltage changes in a step-like manner, the capacitance CD also changes in a step-like manner, but in FIG. 5B, it is described in a gently changing form for the purpose of clearly indicating the direction of change.

FIG. 5C shows the relationship between the capacitance CD and the terminal voltage Vo. The horizontal axis of FIG. 5C is the capacitance CD, and the vertical axis is the terminal voltage Vo of the first electrode 10. By changing the capacitance CD of the variable capacitance diode D in this way, it is possible to search for the value of the capacitance CD that maximizes the terminal voltage Vo of the first electrode 10.

After storing the amplitude signals corresponding to all the control signals, the adjustment unit 53 stores the control signal that maximizes the amplitude signal and outputs the adjustment completion signal. The adjustment completion signal is input to the sensor control unit (not shown) and changes the switching signal to the object detection state (switching signal = negative power supply potential).

The adjusting unit 53 in the object detection state (switching signal = negative power supply potential) maintains a control signal that maximizes the amplitude signal. Therefore, the reactance Xv for resonance, which is composed of the inductor L and the variable capacitance diode D connected in parallel, is a value at which the terminal voltage Vo of the first electrode 10 is maximized in the order of control signal → adjustment voltage → capacitance CD. Is adjusted to.

After the switching signal changes to the object detection state (switching signal = negative power supply potential), the abnormality detection sensor 1 starts an operation of detecting the disappearance / fall of the object to be detected.

Next, the operation of the phase monitor unit 60 in the object detection state will be described.

[Phase monitor]
FIG. 6 is a diagram showing a functional configuration example of the phase monitor unit 60. The phase monitor unit 60 includes a multiplier 61 and a low-pass filter 62. The configuration of the phase monitor unit 60 is the same as that of a general lock-in amplifier.

The multiplier 61 multiplies the AC signal of the terminal voltage Vo of the first electrode 10 with the AC signal of the reference signal Vs. As a result, a component equal to the reference signal Vs (in-phase signal) included in the AC signal of the terminal voltage Vo of the first electrode 10 is converted into a DC signal.

The low-pass filter 62 passes a DC signal. Therefore, the phase monitor unit 60 can extract a signal component having the same phase as the reference signal Vs from the AC signal of the terminal voltage Vo.

The terminal voltage Vo of the first electrode 10 can be expressed by the following equation.

In the equation (7), it is assumed that only the reactance Xv for resonance is used as a variable, and the other parameters (capacitance Ce, stray capacitance Cb, output resistance Rs of the signal source) are constant. Under that assumption, when the reactance Xv for resonance resonates with the capacitance Ce and the stray capacitance Cb, the amplitude of the AC signal of the terminal voltage Vo becomes maximum.

In the object detection state, the value of the reactance Xv for resonance that maximizes the amplitude of the AC signal of the terminal voltage Vo has already been adjusted in the reference search state. Therefore, the phase monitor unit 60 extracts a signal component having the same phase as the reference signal Vs from the AC signal having the terminal voltage Vo having the maximum amplitude, and outputs a phase state signal representing the sign and amplitude of the in-phase component.

If the object A to be detected does not change from the state mounted on the first electrode 10, the condition of the equation (6) is satisfied, and the amplitude of the phase state signal is small. The amplitude of the phase state signal in this case is theoretically 0 (Equation (6)).

When the object A disappears from above the first electrode 10, the stray capacitance Cb between the object A and the second electrode 20 becomes smaller. As the stray capacitance Cb becomes smaller, the amplitude of the phase state signal increases in the positive direction.

On the other hand, when the object A falls on the first electrode 10, the stray capacitance Cb between the object A and the second electrode 20 becomes large. As the stray capacitance Cb increases, the amplitude of the phase state signal increases in the negative direction.

By detecting the change in the phase state signal, it is possible to detect the disappearance, overturning, etc. of the object A.

The determination unit 70 determines the change in the amplitude of the phase state signal output by the phase monitor unit 60 in consideration of the fluctuation of the reference signal Vs generated by the signal source 40, the fluctuation of the components constituting the phase monitor unit 60, and the like. The judgment value obtained by the above is output.

There are three types of determination values in this example: "the state of the object A does not change", "the object A disappears", and "the object A falls". The determination unit 70 can be easily realized by the conventional technique. Therefore, the description showing a specific example of the determination unit 70 will be omitted.

As described above, according to the abnormality detection sensor 1 according to the present embodiment, since the disappearance or fall of the object to be detected is detected by the change of the stray capacitance, the object such as an exhibit can be accurately detected even in a dark place. Abnormalities can be monitored.

Next, the reactance generation unit 52 for resonance according to the second embodiment of the present invention will be described.

[Second Embodiment]
FIG. 7 is a diagram showing a functional configuration example of the reactance generating unit 55 for resonance according to the second embodiment of the present invention. The reactance generation unit 55 for resonance constitutes the abnormality detection sensor 2. The abnormality detection sensor 2 replaces the resonance reactance generation unit 50 of the abnormality detection sensor 1 shown in FIG. 1 with the resonance reactance generation unit 55.

The reactance generation unit 55 for resonance includes a first switch SW1, a third resistor R3, a second switch SW2, a voltage monitor unit 56, and an adjustment unit 57 with respect to the reactance generation unit 50 (FIG. 4) for resonance. different.

The reactance generation unit 55 for resonance acquires the initial value of the adjustment voltage for searching the reactance Xv for resonance that resonates with the capacitance Ce and the stray capacitance Cb. Hereinafter, the phrase "resonates with the capacitance Ce and the stray capacitance Cb" is omitted, and is simply referred to as a reactance Xv for resonance.

The first switch SW1 connects the third resistor R3 in parallel with the variable capacitance diode D before searching for the reactance Xv for resonance. Here, before searching for the value of the capacitance CD constituting the reactance Xv for resonance, the start button is pressed, the switching signal is in the reference search state (switching signal = positive power supply potential), and the adjusting unit 57 This is until the first control signal is output. During this time, the adjustment voltage start signal is input from the sensor control unit (not shown) to the first switch SW1, the second switch SW2, and the adjustment unit 57.

The first switch SW1 is conducted (opened) when the adjustment voltage start signal is, for example, a positive power supply potential, before the search for the reactance Xv for resonance is started. In this state, when the reference signal Vs is input from the signal source 40, a direct current flows through the third resistor R3 due to the rectifying characteristics of the variable capacitance diode D, and a voltage drop Vdc occurs in the third resistor R3. The voltage drop Vdc acts as a reverse bias voltage Vdc with respect to the variable capacitance diode D.

The second switch SW2, the first switch SW1 is input when the voltage of the cathodes when cathode electrode of the variable capacitance diode D to the voltage monitor unit 56 to conduct. When the first switch SW1 is nonconductive, the cathodes when cathode electrode of the variable capacitance diode D, and applying an adjustment voltage adjustment signal output unit 54 via a second resistor R2 is output.

Voltage monitor section 56, the first switch SW1 is a voltage of the cathodes when cathode electrode of the variable capacitance diode D at the time of conducting the input signal, and inputs the adjustment unit 57 generates a voltage monitoring signal corresponding to the input signal. Voltage of cathodes when cathode electrode of the variable capacitance diode D at the time of the first switch SW1 is conducting, the reference signal Vs variable capacitance by the DC current Id flowing rectified by diode D occurs in the third resistor R3 voltage drop Vdc and a fixed voltage It is a voltage obtained by adding the output voltage of the source 51.

According to the configuration described above, the adjusting section 57 may be before searching the resonant reactance Xv, acquires a voltage monitor signal representative of the voltage of the cathodes when cathode electrode of the variable capacitance diode D.

The adjusting unit 57 inputs a control signal having the same value as the voltage monitor signal to the adjusting signal output unit 54. Adjustment signal output unit 54, when the search start the capacitance CD constituting the resonant reactance Xv, outputs an adjustment voltage having the same voltage as the voltage of the cathodes when cathode electrode of the variable capacitance diode D which the voltage monitoring unit 55 has acquired ..

As a result, the reactance generating unit 55 for resonance of the present embodiment can make the range in which the adjusted voltage is changed narrower than that of the reactance generating unit 50 for resonance (FIG. 4). As a result, the time for searching for the reactance Xv for resonance can be shortened.

The operation of the reactance generating unit 55 for resonance to find the control signal in the resonance state will be described with reference to FIG. FIG. 8 is a schematic diagram illustrating the operation of the reactance generating unit 55 for resonance.

FIG. 8A is a diagram showing the relationship between the voltage across the variable capacitance diode D | Vac | (horizontal axis) and the direct current Id (vertical axis) flowing through the variable capacitance diode D. Α to δ shown in FIG. 8A will be described later.

When an AC signal with an amplitude larger than the threshold value (forward voltage Vf) is applied to the variable capacitance diode D to which no DC voltage is applied, the variable capacitance diode D is larger than the threshold value in one cycle of the AC signal. A direct current Id is generated by the rectifying characteristics of the variable capacitance diode D during the period when the forward voltage is applied, that is, during the period when the variable capacitance diode D is short-circuited.

When a reverse bias voltage Vdc (voltage drop Vdc of the third resistor R3) occurs across the variable capacitance diode D, the period during which the forward voltage is applied, that is, the period during which the variable capacitance diode D is short-circuited becomes short. Therefore, the DC current Id becomes smaller for the same AC voltage | Vac |.

FIG. 8B is a diagram showing the relationship between the direct current Id (horizontal axis) and the voltage drop Vdc (vertical axis) generated in the third resistor R3. The reverse bias voltage Vdc of the variable capacitance diode D changes due to the flow of the direct current Id in this way.

FIG. 8C is a diagram showing the relationship between the reverse bias voltage Vdc (voltage drop Vdc of the third resistor R3) (horizontal axis) and the capacitance CD of the variable capacitance diode D. FIG. 8 (c) is the same diagram as in FIG. 5 (b). In this way, the value of the capacitance CD of the variable capacitance diode D changes depending on the reverse bias voltage Vdc.

FIG. 8D is a diagram showing the relationship between the capacitance CD (horizontal axis) of the variable capacitance diode D and the terminal voltage Vo of the first electrode 10. FIG. 8 (d) is the same as FIG. 5 (c).

Α to δ in FIG. 8 indicate changes in the respective currents and voltages after the reference signal Vs is input from the signal source 40 to the reactance generation unit 52 for resonance. The capacitance CD of the variable capacitance diode D has a value of C0 when the reverse bias voltage Vdc = 0. Further, the voltage across the variable capacitance diode D | Vac | is proportional to the terminal voltage | Vo | of the first electrode 10.

When the reference signal Vs is input from the signal source 40 while the first switch SW1 is conducting, the reference signal Vs is rectified by the variable capacitance diode D and a direct current Id flows (FIG. 8 (a)).
) Α).

When the direct current Id flows, a voltage drop Vdc is generated in the third resistor R3, and the same voltage becomes a reverse bias voltage and is applied to the variable capacitance diode D. As a result, the capacitance CD of the variable capacitance diode D decreases (α in FIG. 8C), and the terminal voltage | Vo | of the first electrode 10 becomes larger as it approaches the capacitance CD in which resonance occurs (FIG. 8 (C)). d) α).

Since the amplitude | Vac | of the reference signal Vs increases and the reverse bias voltage Vdc also increases, the relationship between the amplitude | Vac | of the reference signal Vs | Vac | and the DC current Id shifts to β in FIG. 8 (a).

After this, the capacitance CD decreases in the same manner, the amplitude | Vac | of the reference signal Vs increases and the voltage drop Vdc also increases, so that the amount of change in the DC current Id gradually decreases and converges to zero. .. When the amount of change in the DC current Id becomes zero, the voltage across the variable capacitance diode D | Vac | becomes constant (δ in FIG. 8A), and the terminal voltage | Vo | of the first electrode 10 becomes the amplitude at resonance. Approaching (δ in FIG. 8 (d)).

Through the processes of α to δ described above, the reactance generating unit 52 for resonance in the state where the first switch SW1 is conducting is the reverse bias voltage Vdc corresponding to δ in FIG. 8 (d) (FIG. 8 (a)). Δ) is obtained. Until the reverse bias voltage Vdc is acquired, the adjustment voltage start signal maintains the positive power supply potential through which the first switch SW1 conducts.

As described above, the resonance reactance generation unit 55 according to the present embodiment acquires an adjustment voltage for generating a resonance reactance close to the value of the resonance reactance Xv at the time of resonance immediately after the start button is pressed. .. Therefore, the search for the reactance Xv for resonance can be started from δ in FIG. 8 (d). Therefore, the search time can be shortened as compared with the resonance reactance generation unit 50 that starts the search from the capacitance C0 of the variable capacitance diode D when the reverse bias voltage Vdc = 0V.

[Anomaly detection system]
FIG. 9 is a diagram showing a configuration example of an abnormality detection system according to an embodiment of the present invention. The abnormality detection system 101 shown in FIG. 9 includes a sensor node 80, a network 90, and a server 1000.

The sensor node 80 includes the above-mentioned abnormality detection sensor 1 (FIG. 1), a sensor control unit 82, and a transmission / reception unit 81. The abnormality detection sensor 1 may be replaced with an abnormality detection sensor 2 provided with a reactance generating unit 52 for resonance.

The sensor control unit 82 transmits a switching signal instructing the abnormality detection sensor 1 to start searching for the capacitance CD constituting the reactance Xv for resonance, and adjusts to indicate that the search for the capacitance CD has been completed. The completion signal and the above-mentioned determination value are received from the abnormality detection sensor 1.

The transmission / reception unit 81 connects the sensor control unit 82 to the server 100 via the network 90.

According to the abnormality detection system 101 configured in this way, the server 100 detects three types of determination values: "the state of the object A does not change", "the object A disappears", and "the object A falls". can do. It is also possible to input the start signal (switching signal) generated by pressing the start button to the abnormality detection sensor 1 from the server 100.

As described above, according to the abnormality detection sensor 1 and the abnormality detection system 101 according to the present embodiment, the disappearance / fall of the object to be detected is detected by the change of the stray capacitance, so that the object can be displayed accurately even in a dark place. It is possible to monitor anomalies in objects such as objects.

The reactance Xv for resonance of the above-described embodiment has been described with an example in which the inductor L and the variable capacitance diode D are connected in parallel, but the present invention is not limited to this example. Another variable capacitance element may be used instead of the variable capacitance diode D. Further, the inductive reactance of the inductor L may be changed.

Further, although the example in which the adjustment voltage is changed in steps has been described, the adjustment voltage may be changed uniformly in one direction. Further, although the adjustment unit 53 has described an example of outputting the control signal that maximizes the amplitude signal after storing the amplitude signals corresponding to all the control signals, the control signal is changed in one direction and the amplitude signal is changed. It may be configured to stop the output of the control signal when it reaches the maximum.

Further, although the adjusting unit has been described with an example in which the amplitude signal and the control signal are configured by a digital circuit, the adjusting unit may be configured by an analog circuit. When the adjustment units 53 and 55 are composed of analog circuits, the amplitude monitor unit 21 and the voltage monitor unit 54 may be omitted.

As described above, the present invention is not limited to the above-described embodiment, and can be modified within the scope of the gist thereof.

1, 2: Abnormality detection sensor 10: First electrode 20: Second electrode 30: Insulator 40: Signal source 50, 55: Resonance reactor generation unit 51: Fixed voltage source 52: Amplitude monitor unit 53, 57: Adjustment unit 54: Adjustment signal output unit 56: Voltage monitor unit 60: Phase monitor unit 61: Multiplier 62: Low frequency pass filter 70: Judgment unit 80: Sensor node 81: Transmission / reception unit 82: Sensor control unit 90: Network 100: Server 101 : Abnormality detection system

Claims (3)

The first electrode on which the object to be detected is placed and
A second electrode, which is arranged at a position facing the first electrode with an insulator in between and has a larger flat area than the first electrode,
A signal source that produces a reference signal with constant amplitude and frequency,
A resonance reactance generating unit that generates a reactance for resonance in which the reference signal is input and the terminal voltage of the first electrode is maximized.
A phase monitor unit that detects in-phase components of the terminal voltage of the first electrode and the reference signal, and
It is provided with a determination unit that determines a change in the amplitude of the in-phase component and outputs a determination value obtained .
The reactance generator for resonance is
An inductor that connects one end to the input terminal via a first capacitor and the other end to the first electrode.
A second capacitor that connects one end to the other end of the inductor
A variable capacitance diode that connects an anode electrode to one end of the inductor and a cathode electrode to the other end of the second capacitor.
A fixed voltage source that applies a predetermined voltage to the anode electrode of the variable capacitance diode via the first resistor, and
An amplitude monitor unit that is connected to the cathode electrode of the variable capacitance diode via a third capacitor and generates an amplitude signal corresponding to the amplitude of the terminal voltage of the first electrode.
When generating the reactance for resonance, an adjusting unit that changes the magnitude of the control signal in one direction and outputs it until the amplitude signal is maximized, and
With an adjustment signal output unit that generates an adjustment voltage corresponding to the magnitude of the control signal and applies the adjustment voltage to the cathode electrode of the variable capacitance diode via a second resistor.
Abnormality detection sensor, wherein Rukoto equipped with. In the abnormality detection sensor according to claim 1,
The reactance generator for resonance is
Before starting the generation of the reactance for resonance, the first switch that connects the third resistor in parallel with the variable capacitance diode,
Wherein the first switch is input to the voltage monitor voltage of cathodes when cathode electrode of the variable capacity diode during conduction, the first switch is in an inactive state, via a second resistor to the cathodes when cathode electrode of the variable capacitance diode The second switch that applies the adjustment voltage and
Wherein the first switch is a voltage of the cathodes when cathode electrode of the variable capacity diode during conduction between the input voltage, and a said voltage monitor unit for generating a voltage monitor signal corresponding to the input voltage,
The adjusting unit is an abnormality detection sensor characterized in that a voltage value corresponding to the voltage monitor signal is used as an initial value of the adjusted voltage. An anomaly detection system consisting of a sensor node, a network, and a server.
The sensor node is
The abnormality detection sensor according to claim 1 or 2,
A sensor control unit that transmits a switching signal instructing the start of generation of the reactance for resonance to the abnormality detection sensor and receives an adjustment completion signal indicating that the reactance for resonance has been generated and the determination value.
An abnormality detection system including a transmission / reception unit that connects the sensor control unit to the server via the network.

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