An alarm device for monitoring helicopter mechanical failures through acoustic targets

Abstract

The present invention belongs to the technical field of helicopter fault diagnosis, and in particular relates to an alarm device for monitoring helicopter mechanical faults through acoustic target recognition. The alarm device comprises a fault sound pickup circuit, which comprises a signal acquisition and amplification circuit A1. The output of the signal acquisition and amplification circuit A1 is connected to a signal filtering circuit A2, the output of the signal filtering circuit A2 is connected to an effective value operation circuit A3, the output of the effective value operation circuit A3 is connected to an adjustment and holding circuit A4, and the output of the adjustment and holding circuit A4 is connected to a fault alarm circuit A5. The present invention solves the problem in the prior art that my country's technology for identifying faults through sound is still in its infancy, and there is still a lack of a fault noise identification and alarm device with strong integrity and accurate judgment.

Description

Technical Field

[0001] The invention belongs to the technical field of helicopter fault diagnosis, and in particular relates to an alarm device for monitoring helicopter mechanical faults through acoustic targets. Background Art

[0002] Warning systems are typically divided into visual, auditory, and tactile warnings. The combination of these warning methods allows operators to promptly identify and locate aircraft system or component faults, improving safety. For pilots, especially those with audible warnings, auditory warnings can heighten their awareness of dangerous situations and shorten their reaction time to abnormalities. However, existing technologies lack a robust and accurate fault noise recognition and warning device, as my country's technology for identifying faults through sound is still in its infancy. Summary of the Invention

[0003] The present invention provides an alarm device for monitoring helicopter mechanical failures through acoustic targets, so as to solve the problem in the prior art raised in the above background technology that my country's technology for identifying failures through sound is still in its infancy and lacks a fault noise identification and alarm device with strong integrity and accurate judgment.

[0004] The technical problem solved by the present invention is achieved by adopting the following technical solution: an alarm device for detecting helicopter mechanical failures through acoustic targets, including a fault sound pickup module, the fault sound pickup circuit including a signal acquisition and amplification circuit A1, the output of the signal acquisition and amplification circuit A1 is connected to a signal filtering circuit A2, the output of the signal filtering circuit A2 is connected to an effective value operation circuit A3, the output of the effective value operation circuit A3 is connected to an adjustment and holding circuit A4, and the output of the adjustment and holding circuit A4 is connected to a fault alarm circuit A5.

[0005] Furthermore, the signal acquisition and amplification circuit A1 includes an electret microphone T101, one end of the microphone T101 is connected to the power supply via a resistor R101, and is connected to one end of a capacitor C101, and the other end is grounded. The other end of the capacitor C101 is connected to one end of a resistor R102, and the other end of the resistor R102 is connected to the positive input end of the amplifier U101. The negative input end of the amplifier U101 is grounded, and the output of the amplifier U101 is connected to the input end of the signal filtering circuit A2.

[0006] Furthermore, the signal filtering circuit A2 includes a passive high-pass filtering circuit W1 and an active low-pass filtering circuit W2, and the output of the passive high-pass filtering circuit W1 is connected to the active low-pass filtering circuit W2.

[0007] Furthermore, the passive high-pass filter circuit W1 includes a capacitor C201, one end of which is connected to the output end of the amplifier U101 and grounded through a resistor R201, and the other end of which is connected to one end of a resistor R203 and grounded through a resistor R202.

[0008] Furthermore, the active low-pass filter circuit W2 includes a resistor R204, one end of which is connected to the other end of the resistor R203 and to one end of the feedback capacitor C202. The other end of the resistor R204 is connected to the positive input of the amplifier U201 and is grounded through the capacitor C203. The negative input of the amplifier U201 is grounded through the resistor R205 and is connected to the output of the amplifier U201 through the resistor R206. The output of the amplifier U201 is connected to the other end of the feedback capacitor C202.

[0009] Furthermore, the effective value operation circuit A3 includes an effective value DC converter U301, which is connected to the output end of the amplifier U201 and grounded through the integrating capacitor C301. The output of the effective value DC converter U301 is connected to the input end of the emitter follower U302, the output end of the emitter follower U302 is connected to the input end of the buffer U303, and the output end of the buffer U303 is connected to the input end of the adjustment and holding circuit A4.

[0010] Furthermore, the adjustment and holding circuit A4 includes an amplifier U401, the negative input terminal of the amplifier U401 is connected to the output terminal of the buffer U303 via a resistor R404 and is grounded via a resistor R406, the positive input terminal of the amplifier U101 is connected to the reference potential adjustment circuit W3, the output terminal of the amplifier U101 is connected to the positive input terminal of the amplifier U101 via a feedback resistor R405, and is connected to the positive electrode of the diode D401, the negative electrode of the diode D401 is grounded via C401, and is grounded via a button B401, and the output is connected to the fault alarm circuit A5.

[0011] Furthermore, the reference potential adjustment circuit W3 includes a resistor R401, one end of which is connected to the power supply, and the other end is connected to one end of the adjustable resistor VR401, the other end of which is connected to one end of the resistor R402, and the other end of the resistor R402 is grounded.

[0012] Furthermore, the fault alarm circuit A5 includes a controller U501, the input end of the controller U501 is connected to the cathode of the diode D401, the enable output port output is connected to the enable end of the voice chip U502, one trigger port is connected to the positive input end of the comparator U503 and is grounded via a resistor R501, the other trigger port is connected to the negative input end of the comparator U503 and is grounded via a resistor R502, and the output end of the comparator U503 is connected to the segment selection end of the voice chip U502.

[0013] Furthermore, the controller U501 is used to:

[0014] If multiple alarm signals appear, the voice information of the alarm signals will be output in order of priority according to the degree of danger to the helicopter safety and the alarm level;

[0015] The voice messages of the warning signals are output in order of priority according to the degree of danger to the helicopter safety and the warning level, including:

[0016] If a low-priority alarm is in progress and a high-priority alarm is triggered, the current voice alarm will be interrupted after the entire sentence is played, and at the same time, the high-priority voice alarm will be played until the high-priority voice alarm is finished playing.

[0017] Beneficial technical effects:

[0018] This patent adopts the signal acquisition and amplification circuit A1 output connected to the signal filtering circuit A2, the signal filtering circuit A2 output connected to the effective value operation circuit A3, the effective value operation circuit A3 output connected to the adjustment and holding circuit A4, and the adjustment and holding circuit A4 output connected to the fault alarm circuit A5. Since an electret microphone is used in the signal acquisition and amplification circuit, and an inverting amplifier is used to amplify the signal to a range suitable for processing, the signal filtering circuit well meets the sensitivity of the human ear to sounds of different frequencies. The effective value and its corresponding decibel value are easily obtained through the effective value operation circuit, avoiding the use of a single-chip microcomputer to perform large-scale logarithmic processing and improving the response speed; the adjustment circuit can determine the different required measurement zero points; finally, the fault alarm circuit performs priority control on the sound source and has issued an alarm sound source. This system has complete fault noise recognition and issues different alarm sounds through fault noise recognition. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a module circuit diagram of the alarm device of the present invention;

[0020] Figure 2 This is a circuit diagram of the signal acquisition and amplification circuit of the alarm device of the present invention;

[0021] Figure 3It is a circuit diagram of the signal filtering circuit of the alarm device of the present invention;

[0022] Figure 4 It is a circuit diagram of the effective value operation circuit of the alarm device of the present invention;

[0023] Figure 5 It is a circuit diagram of the adjustment and holding circuit of the alarm device of the present invention;

[0024] Figure 6 It is a circuit diagram of the fault alarm circuit of the alarm device of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings:

[0026] A1-Signal acquisition and amplification circuit, A2-Signal filtering circuit, A3-RMS operation circuit, A4-Adjustment and holding circuit, A5-Fault alarm circuit;

[0027] T101-electret microphone, R101-resistor, C101-capacitor, R102-resistor, U101-amplifier;

[0028] W1-passive high-pass filter circuit, W2-active low-pass filter circuit; C201-capacitor, R201-resistor, R203-resistor, R202-resistor, R204-resistor, R203-resistor, C202-feedback capacitor, C203-capacitor, U201-amplifier, R205-resistor, R206-resistor;

[0029] U301-RMS DC converter, integrating capacitor-C301, U302-emitter follower, U303-buffer;

[0030] U401-amplifier, R404-resistor, R405-feedback resistor, D401-diode, B401-button;

[0031] U501-controller, D401-diode, U502-voice chip, U503-comparator, R501-resistor, U503-comparator, R502-resistor.

[0032] Example 1:

[0033] This embodiment: Figure 1As shown, an alarm device for detecting helicopter mechanical failures through acoustic targets includes a fault sound pickup module. The fault sound pickup circuit includes a signal acquisition and amplification circuit A1. The output of the signal acquisition and amplification circuit A1 is connected to a signal filtering circuit A2. The output of the signal filtering circuit A2 is connected to an effective value operation circuit A3. The output of the effective value operation circuit A3 is connected to an adjustment and holding circuit A4. The output of the adjustment and holding circuit A4 is connected to a fault alarm circuit A5.

[0034] Since the output of the signal acquisition and amplification circuit A1 is connected to the signal filtering circuit A2, the output of the signal filtering circuit A2 is connected to the effective value operation circuit A3, the output of the effective value operation circuit A3 is connected to the adjustment and holding circuit A4, and the output of the adjustment and holding circuit A4 is connected to the fault alarm circuit A5, since an electret microphone is used in the signal acquisition and amplification circuit, and an inverting amplifier is used to amplify the signal to a range suitable for processing, the signal filtering circuit well meets the sensitivity of the human ear to sounds of different frequencies, and the effective value and its corresponding decibel value are easily obtained through the effective value operation circuit, avoiding the use of a single-chip microcomputer to perform large-scale logarithmic processing, thereby improving the response speed; the adjustment circuit can determine the different required measurement zero points; finally, the fault alarm circuit performs priority control on the sound source and has issued an alarm sound source. The system has complete fault noise recognition and issues different alarm sounds through fault noise recognition.

[0035] like Figure 2 As shown, the signal acquisition and amplification circuit A1 includes an electret microphone T101, one end of the microphone T101 is connected to the power supply via a resistor R101, and is connected to one end of a capacitor C101, and the other end is grounded. The other end of the capacitor C101 is connected to one end of a resistor R102, and the other end of the resistor R102 is connected to the positive input end of the amplifier U101. The negative input end of the amplifier U101 is grounded, and the output of the amplifier U101 is connected to the input end of the signal filtering circuit A2.

[0036] Since the signal acquisition and amplification circuit A1 includes an electret microphone T101, one end of the microphone T101 is connected to the power supply via a resistor R101 and to one end of a capacitor C101, and the other end is grounded. The other end of the capacitor C101 is connected to one end of a resistor R102, the other end of the resistor R102 is connected to the positive input of the amplifier U101, the negative input of the amplifier U101 is grounded, and the output of the amplifier U101 is connected to the input of the signal filtering circuit A2. Since the electret microphone is connected using a source-grounded, drain-output method, it has a wide dynamic range and high sensitivity. When driven by a voltage of VCC=9V, the dynamic range can reach -2 to +2V. After debugging, when the microphone voltage V1=VCC / 3, the microphone sensitivity reaches its maximum. In this circuit, the drain load resistor R1=18kΩ, the gain reaches A=2.55, and a standard voltage of 0 to 5V is output.

[0037] like Figure 3 As shown, the signal filtering circuit A2 includes a passive high-pass filtering circuit W1 and an active low-pass filtering circuit W2, and the output of the passive high-pass filtering circuit W1 is connected to the active low-pass filtering circuit W2.

[0038] Since the signal filtering circuit A2 includes a passive high-pass filtering circuit W1 and an active low-pass filtering circuit W2, the output of the passive high-pass filtering circuit W1 is connected to the active low-pass filtering circuit W2. The load of the active filtering circuit does not affect the filtering characteristics, and is therefore often used in situations where high signal processing requirements are required. The active filtering circuit is generally composed of an RC network and an integrated operational amplifier, and therefore must be used under the power supply of a suitable DC power supply. At the same time, amplification can also be performed. A passive high-pass filter, that is, a low-cutoff filter or a low-resistance filter, allows frequencies above a certain cutoff frequency to pass through, while greatly attenuating lower frequencies. It removes unnecessary low-frequency components in the signal or removes low-frequency interference. By combining the high-pass and low-pass filters, higher harmonics and low-frequency interference are filtered out.

[0039] The passive high-pass filter circuit W1 includes a capacitor C201 , one end of which is connected to the output end of the amplifier U101 and grounded via a resistor R201 , and the other end of which is connected to one end of a resistor R203 and grounded via a resistor R202 .

[0040] The active low-pass filter circuit W2 includes a resistor R204, one end of which is connected to the other end of the resistor R203 and to one end of the feedback capacitor C202. The other end of the resistor R204 is connected to the positive input end of the amplifier U201 and is grounded through the capacitor C203. The negative input end of the amplifier U201 is grounded through the resistor R205 and is connected to the output end of the amplifier U201 through the resistor R206. The output end of the amplifier U201 is connected to the other end of the feedback capacitor C202.

[0041] Since the passive high-pass filter circuit W1 includes a capacitor C201, one end of the capacitor C201 is connected to the output end of the amplifier U101 and is grounded through a resistor R201, and the other end is connected to one end of the resistor R203 and is grounded through a resistor R202, the active low-pass filter circuit W2 includes a resistor R204, one end of the resistor R204 is connected to the other end of the resistor R203 and is connected to one end of the feedback capacitor C202, the other end of the resistor R204 is connected to the positive input end of the amplifier U201 and is grounded through the capacitor C203, the negative input end of the amplifier U201 is grounded through a resistor R205 and is connected to the negative input end of the amplifier U201 through a resistor R206. The output end of the amplifier U201 is connected to the other end of the feedback capacitor C202. Since the weighting network consists of a passive high-pass filter and an active low-pass filter, the amplitude-frequency characteristic is close to the weighting curve by calculating and debugging the parameters of the relevant peripheral components. The corresponding parameters of the high-pass filter are C1 = 10μF. The corresponding parameters of the high-pass filter are calculated using the equation to obtain the rear-stage resistor R2 = 100Ω and the front-stage resistor R1 = 100kΩ to obtain a higher input impedance. The active filter circuit is calculated using a second-order Butterworth active filter circuit. Since the filter performance is sensitive to component errors, stable and precise resistors and capacitors should be selected in the circuit.

[0042] like Figure 4 As shown, the effective value operation circuit A3 includes an effective value DC converter U301, which is connected to the output end of the amplifier U201 and grounded through the integrating capacitor C301. The output of the effective value DC converter U301 is connected to the input end of the emitter follower U302, the output end of the emitter follower U302 is connected to the input end of the buffer U303, and the output end of the buffer U303 is connected to the input end of the adjustment and holding circuit A4.

[0043] Since the effective value operation circuit A3 includes an effective value DC converter U301, the effective value DC converter U301 is connected to the output end of the amplifier U201 and is grounded through the integrating capacitor C301, the output of the effective value DC converter U301 is connected to the input end of the emitter follower U302, the output end of the emitter follower U302 is connected to the input end of the buffer U303, and the output end of the buffer U303 is connected to the input end of the adjustment and holding circuit A4, since the effective value circuit adopts the true effective value / DC converter AD538, AD5 The performance of 38 is comparable to or even better than that of hybrid or analog-to-digital devices, but its price is much lower, and its connection is very simple. It only needs an external capacitor to set the average time constant. Here, the input time is taken as 0.3s. When the time constant of the low-pass filter formed with the input resistance of the signal is greater than the period of the signal, the effective value and logarithm can be well calculated. The voltage is buffered by the emitter follower and can be shifted by an external adjustment circuit. The voltage adjustment circuit is composed of the voltage regulator chip S580. The output of the buffer is cascaded with an amplifier with adjustable gain to change the step size.

[0044] like Figure 5 As shown, the adjustment and holding circuit A4 includes an amplifier U401, the negative input terminal of the amplifier U401 is connected to the output terminal of the buffer U303 through a resistor R404, and is grounded through a resistor R406, the positive input terminal of the amplifier U401 is connected to the reference potential adjustment circuit W3, the output terminal of the amplifier U401 is connected to the positive input terminal of the amplifier U101 through a feedback resistor R405, and is connected to the anode of the diode D401, the cathode of the diode D401 is grounded through C401, and is grounded through the button B401, and the output is connected to the fault alarm circuit A5.

[0045] The adjustment and hold circuit A4 includes an amplifier U101. Its negative input is connected to the output of buffer U303 via resistor R404 and to ground via resistor R406. Its positive input is connected to reference potential adjustment circuit W3. Its output is connected to the positive input of amplifier U101 via feedback resistor R405 and to the anode of diode D401. Diode D401's cathode is grounded via C401 and grounded via button B401. Its output is connected to fault alarm circuit A5. To continuously display the current maximum decibel value within the measurement period, a peak detection and hold circuit is required. A diode-capacitor detection circuit is used, with a 640μF capacitor, which has a short charging time constant and a long discharging time constant. The high input resistance and low output resistance of the op amp can also be utilized for optimization. When the power switch is set to "slow," the maximum sound level over a period of time can be measured; when set to "fast," ambient noise can be measured in real time.

[0046] like Figure 6 As shown, the reference potential adjustment circuit W3 includes a resistor R401, one end of the resistor R401 is connected to the power supply, and the other end is connected to one end of the adjustable resistor VR401, the other end of the adjustable resistor VR401 is connected to one end of the resistor R402, and the other end of the resistor R402 is grounded.

[0047] Since the fault alarm circuit A5 includes a controller U501, the input end of the controller U501 is connected to the cathode of the diode D401, the enable output port output is connected to the enable end of the voice chip U502, one trigger port is connected to the positive input end of the comparator U503 and grounded through the resistor R501, the other trigger port is connected to the negative input end of the comparator U503 and grounded through the resistor R502, and the output end of the comparator U503 is connected to the segment selection end of the voice chip U502. Since the alarm circuit is a comparison circuit, when the two input and output ports of the controller are connected to the two ends of the comparator, the comparator judges the levels of the two ports. If the positive input is higher than the negative input, a high level is output, otherwise a low level is output. By selecting the voice to be played, the chip select signal is provided to ensure that the alarm does not falsely alarm or miss alarms. At the same time, the controller performs internal calculations and analysis to obtain high priority and low priority, thereby controlling the levels of the two ports.

[0048] The fault alarm circuit A5 includes a controller U501, the input end of the controller U501 is connected to the cathode of the diode D401, the enable output port output is connected to the enable end of the voice chip U502, one trigger port is connected to the positive input end of the comparator U503 and is grounded via a resistor R501, the other trigger port is connected to the negative input end of the comparator U503 and is grounded via a resistor R502, and the output end of the comparator U503 is connected to the segment selection end of the voice chip U502.

[0049] The controller U501 is used to:

[0050] If multiple alarm signals appear, the voice information of the alarm signals will be output in order of priority according to the degree of danger to the helicopter safety and the alarm level;

[0051] The voice messages of the warning signals are output in order of priority according to the degree of danger to the helicopter safety and the warning level, including:

[0052] If a low-priority alarm is in progress and a high-priority alarm is triggered, the current voice alarm will be interrupted after the entire sentence is played, and at the same time, the high-priority voice alarm will be played until the high-priority voice alarm is finished playing.

[0053] Since, if multiple alarm signals appear, the voice information of the alarm signal is output in sequence according to the degree of endangerment to the safety of the helicopter and the alarm level according to the priority. Since, when multiple alarm signals appear at the same time, the alarm is issued one by one according to the degree of endangerment to the safety of the helicopter, that is, the alarm level, danger level, warning level, and attention level alarm. The alarm information is issued in sequence through the fault alarm circuit according to the alarm level, and the voice reminder of the alarm signal is output in sequence according to the priority. After the current voice alarm is played in one sentence, the current voice alarm is interrupted to play the priority alarm until the alarm playing is finished.

[0054] Working principle:

[0055] This patent provides an alarm device for detecting helicopter mechanical failures through acoustic targets. The output of the signal acquisition and amplification circuit A1 is connected to the signal filtering circuit A2, the output of the signal filtering circuit A2 is connected to the effective value calculation circuit A3, the output of the effective value calculation circuit A3 is connected to the adjustment and holding circuit A4, and the output of the adjustment and holding circuit A4 is connected to the fault alarm circuit A5. Because an electret microphone is used in the signal acquisition and amplification circuit, and an inverting amplifier is used to amplify the signal to a range suitable for processing, the signal filtering circuit effectively meets the sensitivity of the human ear to sounds of different frequencies. The effective value calculation circuit easily obtains the effective value and its corresponding decibel value, avoiding the need for large-scale logarithmic processing using a single-chip microcomputer and improving response speed. The adjustment circuit can determine the required different measurement zero points. Finally, the fault alarm circuit controls the priority of the sound source and issues an alarm sound source. This invention solves the problem of the existing technology that my country's current technology for identifying faults through sound is still in its infancy and lacks a complete and accurate fault noise identification and alarm device. It has the beneficial technical effect of complete fault noise identification and issuing different alarm sounds through fault noise identification.

[0056] Utilizing the technical solution of the present invention, or those skilled in the art designing similar technical solutions inspired by the technical solution of the present invention to achieve the above technical effects, all fall within the scope of protection of the present invention.

Claims

1. A warning device for detecting mechanical failure of a helicopter by means of an acoustic target, characterized in that: It includes a fault sound pickup module, which includes a signal acquisition and amplification circuit A1. The output of the signal acquisition and amplification circuit A1 is connected to a signal filtering circuit A2. The output of the signal filtering circuit A2 is connected to an effective value operation circuit A3. The output of the effective value operation circuit A3 is connected to an adjustment and holding circuit A4. The output of the adjustment and holding circuit A4 is connected to a fault alarm circuit A5. The adjustment and holding circuit A4 includes an amplifier U401. The negative input terminal of the amplifier U401 is connected to the output terminal of the buffer U303 via a resistor R404 and is grounded via a resistor R406. The positive input terminal of the amplifier U401 is connected to the reference potential adjustment circuit W3. The output terminal of the amplifier U401 is connected to the positive input terminal of the amplifier U101 via a feedback resistor R405 and is connected to the anode of the diode D401. The cathode of the diode D401 is grounded via C401 and is grounded via a button B401. The output of the diode D401 is connected to the fault alarm circuit A5. The button B401 acts as a power switch: If the weight switch is in the slow state, the adjustment and holding circuit A4 outputs a slow state signal to the fault alarm circuit A5. In response to the slow state signal, the fault alarm circuit A5 obtains the maximum sound level value within the effective measurement time range. If the weight switch is in the fast state, the adjustment and holding circuit A4 outputs a fast state signal to the fault alarm circuit A5. In response to the fast state signal, the fault alarm circuit A5 measures and obtains the environmental noise value in real time. The fault alarm circuit A5 includes a controller U501, an input end of the controller U501 is connected to the cathode of the diode D401, an enable output port output is connected to the enable end of the voice chip U502, a trigger port is connected to the positive input end of the comparator U503 and grounded via a resistor R501, another trigger port is connected to the negative input end of the comparator U503 and grounded via a resistor R502, and an output end of the comparator U503 is connected to the segment selection end of the voice chip U502; The controller U501 is used to: If multiple alarm signals appear, the voice information of the alarm signals will be output in order of priority according to the degree of danger to the helicopter safety and the alarm level; The voice messages of the warning signals are output in order of priority according to the degree of danger to the helicopter safety and the warning level, including: If a low-priority alarm is in progress and a high-priority alarm is triggered, the current voice alarm will be interrupted after playing the entire sentence, and at the same time, the high-priority voice alarm will be played until the high-priority voice alarm is finished playing; Among them, also include: When multiple alarm signals appear at the same time, alarms are issued in sequence according to the alarm levels of the degree of endangerment to the safety of the helicopter, wherein the alarm levels include danger level, warning level, and caution level alarms; The fault alarm circuit issues alarm information in sequence according to the alarm level, and outputs the voice reminder of the alarm signal in sequence according to the priority. After playing the entire sentence of the current voice alarm, the current voice alarm is interrupted to play the priority alarm until the alarm playback is completed.

2. The alarm device according to claim 1, characterized in that: The signal acquisition and amplification circuit A1 includes an electret microphone T101. One end of the microphone T101 is connected to a power supply via a resistor R101 and to one end of a capacitor C101, and the other end is grounded. The other end of the capacitor C101 is connected to one end of a resistor R102, and the other end of the resistor R102 is connected to the positive input end of the amplifier U101. The negative input end of the amplifier U101 is grounded, and the output of the amplifier U101 is connected to the input end of the signal filtering circuit A2.

3. The alarm device according to claim 1, characterized in that: The signal filtering circuit A2 includes a passive high-pass filtering circuit W1 and an active low-pass filtering circuit W2 , and the output of the passive high-pass filtering circuit W1 is connected to the active low-pass filtering circuit W2 .

4. The alarm device according to claim 3, characterized in that: The passive high-pass filter circuit W1 includes a capacitor C201 , one end of which is connected to the output end of the amplifier U101 and grounded via a resistor R201 , and the other end of which is connected to one end of a resistor R203 and grounded via a resistor R202 .

5. The alarm device according to claim 3, characterized in that: The active low-pass filter circuit W2 includes a resistor R204, one end of which is connected to the other end of the resistor R203 and to one end of the feedback capacitor C202. The other end of the resistor R204 is connected to the positive input end of the amplifier U201 and is grounded through the capacitor C203. The negative input end of the amplifier U201 is grounded through the resistor R205 and is connected to the output end of the amplifier U201 through the resistor R206. The output end of the amplifier U201 is connected to the other end of the feedback capacitor C202.

6. The alarm device according to any one of claims 1 to 3, characterized in that: The effective value operation circuit A3 includes an effective value DC converter U301, which is connected to the output end of the amplifier U201 and grounded through the integrating capacitor C301. The output of the effective value DC converter U301 is connected to the input end of the emitter follower U302, and the output end of the emitter follower U302 is connected to the input end of the buffer U303. The output end of the buffer U303 is connected to the input end of the adjustment and holding circuit A4.

7. The alarm device according to claim 1, characterized in that: The reference potential adjustment circuit W3 includes a resistor R401, one end of which is connected to a power supply, and the other end of which is connected to one end of an adjustable resistor VR401. The other end of the adjustable resistor VR401 is connected to one end of a resistor R402, and the other end of the resistor R402 is grounded.

Images