CN221227507U - Low-frequency charge amplifying circuit - Google Patents
Low-frequency charge amplifying circuit Download PDFInfo
- Publication number
- CN221227507U CN221227507U CN202322985865.5U CN202322985865U CN221227507U CN 221227507 U CN221227507 U CN 221227507U CN 202322985865 U CN202322985865 U CN 202322985865U CN 221227507 U CN221227507 U CN 221227507U
- Authority
- CN
- China
- Prior art keywords
- circuit
- frequency
- capacitance
- low
- sensor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 239000003990 capacitor Substances 0.000 claims abstract description 33
- 230000003321 amplification Effects 0.000 claims abstract description 11
- 238000003199 nucleic acid amplification method Methods 0.000 claims abstract description 11
- 238000011896 sensitive detection Methods 0.000 claims abstract description 11
- 230000010355 oscillation Effects 0.000 claims abstract description 5
- 238000001514 detection method Methods 0.000 claims description 22
- 238000001914 filtration Methods 0.000 claims description 3
- 239000000969 carrier Substances 0.000 claims description 2
- 238000010586 diagram Methods 0.000 description 8
- 230000005284 excitation Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009530 blood pressure measurement Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Landscapes
- Measuring Fluid Pressure (AREA)
Abstract
The utility model discloses a low-frequency charge amplifying circuit, which comprises an RC oscillating circuit, an LC bridge balancing circuit, a phase-sensitive detection circuit and an amplifying circuit which are connected in sequence; the RC oscillation circuit is used for generating a high-frequency carrier wave and loading the carrier wave to the sensor capacitor; the LC bridge balancing circuit is used for obtaining amplitude modulation waves which change along with the capacitance of the sensor; the phase sensitive detection circuit is used for obtaining a modulated low-frequency signal; an amplitude modulated output circuit is used to measure the slow change in capacitance of the sensor and a high frequency carrier is loaded onto the sensor capacitance. Charge amplification for a infrasound acoustic sensor of capacitive structure.
Description
Technical Field
The utility model relates to a low-frequency charge signal amplifying circuit which is mainly used for charge amplification and the like of a infrasound acoustic sensor with a capacitance structure, and belongs to the technical field of electricity.
Background
The lower the frequency of the electrical signal is, the larger the output impedance generated by the capacitor becomes, especially the sensitive capacitance of the infrasonic wave sensor is not more than 500pF, and the capacitance of the infrasonic wave sensor with high dynamic range is not more than 100pF; when the lower limit of the frequency of the electric signal is 0.001Hz, the generated output impedance is more than 10000G omega, and the input impedance of the general impedance conversion circuit can be up to about 1000G; the signal loss is larger at the lower limit frequency of the signal, and in addition, the lower the low-frequency 1/f noise frequency is, the larger the signal loss is, so that the signal-to-noise ratio is low, and the signal cannot be amplified.
At present, the acoustic microphone has high frequency requirements on sound pressure signals, and the measurement requirements of the frequency of 0.001Hz and below are difficult to achieve; therefore, it is difficult to satisfy the infrasonic wave frequency, especially the low frequency sound pressure measurement requirement in the prior art.
Disclosure of utility model
Aiming at the defects existing in the prior art, the utility model aims to provide a low-frequency charge amplifying circuit which solves the measuring requirement of infrasonic wave frequency, in particular to low-frequency sound pressure.
The utility model realizes the aim by adopting the following technical scheme:
the low-frequency charge amplifying circuit is characterized by comprising an RC oscillating circuit, an LC bridge balancing circuit, a phase-sensitive detection circuit and an amplifying circuit which are connected in sequence;
The RC oscillation circuit is used for generating a high-frequency carrier wave and loading the carrier wave to the sensor capacitor;
The LC bridge balancing circuit is used for obtaining amplitude modulation waves which change along with the capacitance of the sensor;
The phase sensitive detection circuit is used for obtaining a modulated low-frequency signal;
an amplitude modulated output circuit is used to measure the slow change in capacitance of the sensor and a high frequency carrier is loaded onto the sensor capacitance.
Further, the LC bridge balancing circuit includes coils of head capacitances S and C4, a calibration capacitance C3, and a multiplier T1; the calibration capacitor C3 and the capacitor C4 are connected in parallel, one end of the calibration capacitor C is connected with the end point of the multiplier T1, and the other end of the calibration capacitor C is connected with the capacitor S and the contact point; the other end of the joint capacitor S is connected with the other end of the multiplier T1;
When the inductance of the multiplier coil is completely equal (the inductances of the multiplier 34 and the end 45 are equal), and the head capacitance S has no capacitance difference, the output voltage of the bridge balance circuit is 0;
when the head capacitance S generates a capacitance difference, a high-frequency signal of a corresponding amplitude is output.
Further, the phase-sensitive detection circuit comprises a half-wave rectification circuit, a subtraction zeroing circuit and a detection circuit; the half-wave rectifying circuit is formed by a rectifier bridge by a detection diode 1N5817, becomes a unilateral high-frequency modulation wave and has a signal wave phase discrimination function; the subtracting zero-setting circuit consists of a variable resistor W1, a bridge balance circuit and a diode detection circuit, and the output voltage bias can be adjusted to eliminate the output bias voltage by adjusting the variable resistor W1; the detection circuit comprises detection capacitors C5 and R9 and is used for filtering high-frequency carriers to obtain modulated low-frequency signals.
Further, the detection capacitance C5 is 0.1uF.
The low-frequency charge amplification circuit is used for charge amplification of the infrasound acoustic sensor with a capacitance structure, such as an infrasound sensor/low-frequency amplification circuit based on the capacitance structure and the like. The principle of amplitude modulation is adopted, and the sensor capacitor is used as one arm of a capacitance bridge; when the head capacitance is not acted by the pressure wave signal, the bridge is in a balanced state; when the pressure wave signal acts on the head capacitance, the sensor capacitance changes, and the bridge balance changes; the output end of the bridge can obtain amplitude modulation wave which changes along with the capacitance, the amplitude modulation wave is amplified by voltage and demodulated by a demodulator, and then the voltage signal output of the infrasound frequency band can be obtained.
Compared with the prior art, the utility model has the following beneficial effects:
1. The utility model can pick up and amplify very low frequency signals, is especially suitable for capacitive sensors, and solves the problems that common impedance transformation circuits cannot amplify low frequency signals such as infrasonic waves and the like due to large low frequency output impedance.
2. The utility model can be applied to the amplification treatment of low-frequency signals below 0.001Hz by a capacitive sensor, thereby meeting the requirements of picking up low-frequency sound wave signals in the atmosphere and monitoring infrasonic waves generated by earthquakes and large-scale explosions, and further realizing early warning, emergency response and the like.
3. The circuit can also be applied to a capacitive sensor to realize displacement, static pressure and other measurement.
Drawings
FIG. 1 is a block diagram of an amplitude modulated phase demodulation circuit;
FIG. 2 is a schematic circuit diagram of an embodiment of an RC oscillator circuit of the present utility model;
FIG. 3 is a schematic circuit diagram of an embodiment of a bridge balancing circuit according to the present utility model;
FIG. 4 is a schematic circuit diagram of one embodiment of sensor detection demodulation in accordance with the present utility model;
fig. 5 is a schematic circuit diagram of an embodiment of a low frequency charge amplifying circuit according to the present utility model.
Detailed Description
The technical scheme of the utility model is clearly and completely described below with reference to the accompanying drawings and the embodiments of the utility model. It will be apparent that the described embodiments are some, but not all, embodiments of the utility model. The components of the embodiments of the present utility model generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the utility model, as presented in the figures, is not intended to limit the scope of the utility model, as claimed, but is merely representative of selected embodiments of the utility model. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures. In the description of the present utility model, it should be noted that, directions or positional relationships indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., are directions or positional relationships based on those shown in the drawings, or are directions or positional relationships conventionally put in use of the inventive product, are merely for convenience of describing the present utility model and simplifying the description, and are not indicative or implying that the apparatus or element to be referred to must have a specific direction, be constructed and operated in a specific direction, and thus should not be construed as limiting the present utility model. Furthermore, the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance. Furthermore, the terms "horizontal," "vertical," and the like do not denote a requirement that the component be absolutely horizontal or overhang, but rather may be slightly inclined. As "horizontal" merely means that its direction is more horizontal than "vertical", and does not mean that the structure must be perfectly horizontal, but may be slightly inclined. In the description of the present utility model, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present utility model will be understood in specific cases by those of ordinary skill in the art.
Referring to fig. 1, the utility model provides a low-frequency charge amplifying circuit, which mainly comprises an RC oscillating circuit, an LC bridge balancing circuit, a phase-sensitive detection circuit and an amplifying circuit. The utility model adopts an amplitude modulation type output circuit to measure the slow change of the capacitance of the sensor, loads a high-frequency carrier wave on the capacitance, uses the amplitude modulation principle, uses the capacitance as one arm of a capacitance bridge, and when the head capacitance is not acted by pressure wave signals, the bridge is in a balanced state; when the pressure wave signal acts on the head capacitance, the sensor capacitance changes, and the bridge balance changes; the output end of the bridge can obtain amplitude modulation wave which changes along with the capacitance, the amplitude modulation wave is amplified by voltage and demodulated by a demodulator, and then the voltage signal output of the infrasound frequency band can be obtained.
As shown in fig. 2, a schematic diagram of a specific RC oscillating circuit is shown. The RC oscillation circuit is used for generating a sine carrier excitation source, outputting a high-frequency carrier signal by adjusting the values of resistors R4 and R5 and capacitors C1 and C2 of the oscillation circuit, and requiring the carrier signal to output stable frequency and amplitude, wherein the frequency is set at a parallel resonance point of the capacitor bridge as much as possible; in addition, in order to ensure the consistency of the frequency of the excitation signal, the precision of the resistor and the capacitor is required to be 1 percent (the error of the selection capacitance is required to be within 1 percent), and the sine wave generating circuit is formed by using an operational amplifier, the distortion degree is less than 1 percent (the waveform distortion is less than 1 percent by adjusting the variable resistor R3), the stability of the sine wave frequency can be maintained, the stability to the temperature change is realized, and the influence of the sine wave generating circuit is controlled within a certain range.
As shown in fig. 3, a schematic diagram of a specific bridge balancing circuit is shown. In the figure, the head capacitors S and C4 and the coil of the multiplier T1 form an LC bridge type balance circuit, and C3 is a calibration capacitor. When the inductance of the coils of the multipliers is completely equal and the capacitance of the head capacitors is not equal, the output voltage of the bridge balance circuit is 0, and when the capacitance of the head capacitors is different, high-frequency signals with corresponding amplitude values are output. C3 is a calibration capacitor, the capacitance value of the LC bridge type balance capacitor arm is adjusted to be equal, zero drift is avoided, and meanwhile, the circuit head capacitors S and C4 and the calibration capacitor form a nonlinear correction circuit, so that output nonlinearity can be reduced. In addition, the circuit has the characteristics of low output impedance, larger output current and the like, and has better load capacity and anti-interference capacity. The instability factor and noise source of the circuit are leakage inductance of the multiplier T1, the leakage inductance and the capacitor form an LC series bridge, and the working carrier frequency is smaller than the resonance point frequency, so that the circuit noise and the working current of the circuit are reduced.
As shown in fig. 4, a schematic diagram of a phase sensitive detection circuit (sensor detection demodulation circuit) is shown. The circuit comprises three parts: the device comprises a half-wave rectifying circuit, a subtracting zero setting circuit and a detection circuit. The half-wave rectifying circuit is formed by a rectifier bridge by a detection diode 1N5817, becomes a unilateral high-frequency modulation wave and has a signal wave phase discrimination function; the subtracting zero-setting circuit is composed of a variable resistor W1, a bridge balance circuit and a diode detection circuit, and the voltage bias which is output can be adjusted by adjusting the size of the variable resistor W1 is used for eliminating the output bias voltage; the detection circuit comprises a detection capacitor C5 and a resistor R9 and is used for filtering high-frequency carrier waves to obtain modulated low-frequency signals. Among them, the detection capacitance C5 is preferably 0.1 uF.
The half-wave rectifying circuit is formed by a rectifier diode 1N5817, the voltage is opened by 0.2V, and meanwhile, small signals are allowed to pass through, and the rectifier diode has higher on-off working frequency, so that the impulse voltage introduced during turn-off is reduced, and the circuit noise is reduced. The signal passing through the rectifier bridge becomes single-side high-frequency modulation wave and has the phase discrimination function of the signal wave, and then the signal passes through a subtraction zeroing circuit to eliminate output bias voltage, enters a detection circuit and filters high-frequency carrier waves to obtain a modulated low-frequency signal. In order to obtain a modulated signal of a lower frequency, and a circuit having a larger input resistance than a bridge balance circuit, the detection capacitance is 0.1uF, and a smaller leakage current is required, thereby reducing the influence of low-frequency output noise.
As shown in FIG. 5, in a specific embodiment of the low-frequency charge amplifying circuit of the present utility model, the low-frequency charge amplifying circuit mainly comprises an RC oscillating circuit, an LC bridge balancing circuit, a phase sensitive detecting circuit and an amplifying circuit, wherein an amplitude modulation type output circuit is adopted to measure the slow change of the capacitance of a sensor, a high-frequency carrier is loaded on the capacitance, the capacitance is used as one arm of a capacitance bridge by using the amplitude modulation principle, and the bridge is in a balanced state when the head capacitance is not acted on by a pressure wave signal; when the pressure wave signal acts on the head capacitance, the sensor capacitance changes, and the bridge balance changes; the output end of the bridge can obtain amplitude modulation wave which changes along with the capacitance, the amplitude modulation wave is amplified by voltage and demodulated by a demodulator, and then the voltage signal output of the infrasound frequency band can be obtained.
The low-frequency charge amplification circuit can be mainly used for charge amplification of the infrasound acoustic sensor with the capacitance structure; specifically including infrasonic wave sensors/low frequency amplifying circuits based on capacitive structures, etc. The LC bridge circuit formed by the double capacitors amplifies the low-frequency signals in a phase-sensitive detection mode, the circuit theory can pick up and amplify DC signals, and the influence of common-mode interference signals can be eliminated.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present utility model and not for limiting the technical solution, and those skilled in the art should understand that modifications and equivalents may be made to the technical solution of the present utility model without departing from the spirit and scope of the present utility model, and all such modifications and equivalents are included in the scope of the claims.
Claims (4)
1. The low-frequency charge amplifying circuit is characterized by comprising an RC oscillating circuit, an LC bridge balancing circuit, a phase-sensitive detection circuit and an amplifying circuit which are connected in sequence;
The RC oscillation circuit is used for generating a high-frequency carrier wave and loading the carrier wave to the sensor capacitor;
The LC bridge balancing circuit is used for obtaining amplitude modulation waves which change along with the capacitance of the sensor;
The phase sensitive detection circuit is used for obtaining a modulated low-frequency signal;
an amplitude modulated output circuit is used to measure the slow change in capacitance of the sensor and a high frequency carrier is loaded onto the sensor capacitance.
2. The low frequency charge amplification circuit of claim 1, wherein the LC bridge balancing circuit comprises
Head capacitances S and C4, calibration capacitance C3, and the coil of multiplier T1; the calibration capacitor C3 and the capacitor C4 are connected in parallel, one end of the calibration capacitor C is connected with the end point of the multiplier T1, and the other end of the calibration capacitor C is connected with the capacitor S and the contact point; the other end of the joint capacitor S is connected with the other end of the multiplier T1;
When the inductance of the coils of the multipliers is completely equal and the head capacitance S has no capacitance difference, the output voltage of the bridge type balance circuit is 0;
when the head capacitance S generates a capacitance difference, a high-frequency signal of a corresponding amplitude is output.
3. The low-frequency charge amplification circuit of claim 1, wherein the phase-sensitive detection circuit comprises a half-wave rectification circuit, a subtraction zeroing circuit, and a detection circuit; the half-wave rectifying circuit is formed by a rectifier bridge by a detection diode 1N5817, becomes a unilateral high-frequency modulation wave and has a signal wave phase discrimination function; the subtraction zeroing circuit is composed of a variable resistor W1, a bridge balancing circuit and a diode detection circuit; by adjusting the variable resistor W1, the voltage bias of the output can be adjusted for canceling the output bias voltage; the detection circuit comprises detection capacitors C5 and R9 and is used for filtering high-frequency carriers to obtain modulated low-frequency signals.
4. A low-frequency charge amplification circuit according to claim 3, wherein the detection capacitance C5 is 0.1uF.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202322985865.5U CN221227507U (en) | 2023-11-06 | 2023-11-06 | Low-frequency charge amplifying circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202322985865.5U CN221227507U (en) | 2023-11-06 | 2023-11-06 | Low-frequency charge amplifying circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN221227507U true CN221227507U (en) | 2024-06-25 |
Family
ID=91569977
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202322985865.5U Active CN221227507U (en) | 2023-11-06 | 2023-11-06 | Low-frequency charge amplifying circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN221227507U (en) |
-
2023
- 2023-11-06 CN CN202322985865.5U patent/CN221227507U/en active Active
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN101551420A (en) | A weak capacitive detection circuit of MEMS device | |
| CN111623698B (en) | An Eddy Current Displacement Sensor Circuit with Nonlinear Correction Function | |
| CN108693486A (en) | A kind of faint low frequency magnetic signal detection method and system based on AMR sensor | |
| CN109150123A (en) | A kind of small-signal pre-amplification circuit of high-gain | |
| CN221227507U (en) | Low-frequency charge amplifying circuit | |
| CN216771595U (en) | Pre-processing circuit, pre-circuit board and eddy current sensor | |
| CN111505389A (en) | Differential capacitance detection circuit based on sampling holder demodulation | |
| CN107830851A (en) | Digital drive control integrated circuit for angular velocity sensor | |
| CN108562217B (en) | A Capacitive Displacement Sensor with Real-time Optimized Signal-to-Noise Ratio | |
| CN109030850B (en) | A driving device for stable modulation magnetic field of MHD angular velocity sensor | |
| CN112505436A (en) | Non-contact electrostatic field testing device and testing method | |
| CN105352584A (en) | Weak signal detection method based on capacitive sensor | |
| CN105004259A (en) | Capacitive MEMS sensor detection circuit | |
| CN204944423U (en) | A kind of capacitive MEMS sensor detection circuit | |
| CN109188509B (en) | Detector low-frequency compensation circuit, pre-amplification circuit and detector circuit thereof | |
| CN102494759B (en) | Interface circuit of differential capacitance micro vibrating sensor | |
| CN103592061B (en) | High precision silicon micro resonant pressure transducer interface circuit | |
| Barile et al. | A novel interface architecture for differential capacitive sensors | |
| CN221123301U (en) | Eddy current sensor | |
| CN208984657U (en) | A driving device for stable modulation magnetic field of MHD angular velocity sensor | |
| CN208282768U (en) | A kind of capacitance displacement sensor of real-time optimization signal-to-noise ratio | |
| CN107314799B (en) | A weak capacitance detection circuit for nanoliter liquid level sensor | |
| CN220084166U (en) | Digital high-precision low-frequency vibration sensor | |
| JPH04299607A (en) | Charge amplifier | |
| CN205642275U (en) | High dynamic response eddy current displacement sensor of wide range high accuracy |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| GR01 | Patent grant | ||
| GR01 | Patent grant |