A method for manufacturing a variable range pendulous accelerometer differential capacitance measurement circuit

Abstract

The application discloses a manufacturing method of a variable-range pendulum accelerometer differential capacitance measurement circuit, and relates to the field of accelerometer circuit design.The manufacturing method comprises the following steps: step one, a controllable variable gain amplifier is combined with a reference source to generate a carrier with controllable amplitude; step two, the controllable amplitude carrier passes through a single-end or double-end driving circuit to generate a carrier and is connected to a plate; step three, before exciting the differential capacitance, a controllable amplitude carrier is connected to a carrier amplitude detection circuit, a synchronous phase signal is used for demodulation to obtain a carrier amplitude signal, the controllable variable gain amplifier is controlled by using the carrier amplitude signal, a closed loop negative feedback control is formed, and a carrier signal with controllable amplitude and stability is obtained; step four, a modulated differential capacitance signal flows into a differential preamplifier through the plate to obtain an amplified modulated differential capacitance signal; and step five, the modulated differential capacitance signal passes through a demodulation circuit to obtain a differential capacitance signal.The application has the effect of facilitating the measurement of a variable gain capacitance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of accelerometer circuit design, in particular to a manufacturing method of a variable range pendulum accelerometer differential capacitance measurement circuit. BACKGROUND

[0002] Accelerometers are widely used in aerospace, oil exploration, robots and other important military and civilian production fields, and have made important contributions to human scientific and technological development. Among them, the pendulum accelerometer represented by the quartz flexible acceleration is the most mature and widely used accelerometer. The sensitive body pendulum plate and the upper and lower plates inside the pendulum accelerometer form a differential capacitor, and the accelerometer mainly relies on the differential capacitor measurement circuit to obtain the position information of the pendulum plate. After the accelerometer obtains the position of the pendulum plate, the accelerometer controller and the torque output feedback torque to ensure that the pendulum plate remains at the zero position. At this time, the feedback torque of the accelerometer can be approximately equivalent to the measured acceleration.

[0003] Among them, the measurement signal of the differential capacitor can be linearly approximated as the position signal of the pendulum plate, so the measurement accuracy of the differential capacitor directly determines the measurement accuracy of the pendulum plate position. The measurement accuracy of the pendulum plate position directly affects the output of the accelerometer controller, and then affects the feedback torque, which ultimately affects the measurement accuracy of the accelerometer.

[0004] Generally, the higher the capacitance measurement accuracy of the accelerometer, the better, to avoid the influence of capacitance measurement noise on the measurement results of the accelerometer. At the same time, the larger the range of the capacitance measurement circuit without exceeding the distance between the upper and lower plates, the better, to ensure that the movement of the pendulum plate does not exceed the capacitance measurement range and cause the accelerometer control to fail.

[0005] However, due to the noise and dynamic range limitations of amplifiers and other components, in high dynamic or high disturbance measurement situations, the pendulum plate position of the accelerometer changes dramatically, so a larger capacitance measurement range is required; while in low dynamic or low disturbance measurement situations, the pendulum plate position of the accelerometer changes smoothly, and a higher measurement accuracy is required to improve the measurement accuracy of the accelerometer.

[0006] In the absence of breakthroughs in existing high-precision amplifiers and other key components, it is not easy to measure variable gain capacitance. SUMMARY

[0007] In order to facilitate the measurement of variable gain capacitance, the present application provides a manufacturing method of a variable range pendulum accelerometer differential capacitance measurement circuit.

[0008] The manufacturing method of a variable range pendulum accelerometer differential capacitance measurement circuit provided by the present application adopts the following technical scheme:

[0009] A manufacturing method of a variable range pendulum accelerometer differential capacitance measurement circuit, comprising the following steps:

[0010] Step one, using a reference source combined with a controllable variable gain amplifier to generate a controllable amplitude carrier;

[0011] Step two, the controllable amplitude carrier passes through a balanced transformer to generate a carrier and is connected to the plate;

[0012] Step three: the controllable amplitude carrier is divided into a path connected to the carrier amplitude detection circuit before exciting the differential capacitance, and the carrier amplitude signal is obtained by using the synchronous phase signal demodulation, and the controllable variable gain amplifier is controlled by using the carrier amplitude signal, forming a closed loop negative feedback control, to obtain a controllable amplitude and stable carrier signal;

[0013] Step four, the modulated differential capacitance signal flows into the differential preamplifier through the plate to obtain the amplified modulated differential capacitance signal;

[0014] Step five, the modulated differential capacitance signal is obtained through the demodulation circuit.

[0015] By adopting the above technical scheme, the controllable amplitude carrier is obtained through stable closed loop control, and the purpose of variable gain measurement of differential capacitance is achieved by relying on the change of carrier amplitude, so as to improve the test precision of the capacitance test circuit

[0016] Optionally, in step two, the balanced transformer adopts a double-path differential drive circuit to generate a double-ended carrier and connect to the upper and lower plates.

[0017] By adopting the above technical scheme, the double-ended carrier amplifies the controllable amplitude carrier into a differential inverted real carrier, and loads the carrier to the upper and lower plates of the differential capacitance structure, facilitating the subsequent signal input process.

[0018] Optionally, in step two, the balanced transformer adopts a single-path drive circuit to generate a single-ended carrier and connect to the central plate.

[0019] By adopting the above technical scheme, the single-ended carrier amplifies the controllable amplitude carrier into a real single-ended carrier, and loads the carrier to the central plate of the differential capacitance, facilitating the subsequent signal input process.

[0020] Optionally, in step three, in the case of a double-ended carrier, the modulated differential capacitance signal flows into the signal preamplifier through the central plate of the differential capacitance.

[0021] By adopting the above technical scheme, the double-ended carrier amplifies the controllable amplitude carrier into a differential inverted real carrier, and loads the carrier to the upper and lower plates of the differential capacitance structure, and then outputs the modulated differential capacitance signal through the central plate, completing the output of the modulated differential capacitance signal.

[0022] Optionally, in the single-ended carrier case, the modulated differential capacitor signal flows into the differential preamplifier through the upper and lower plates.

[0023] By adopting the above technical solution, the single-ended carrier amplifies the controllable amplitude carrier into a real single-ended carrier, loads the carrier to the central plate of the differential capacitor, and then outputs the modulated differential capacitor signal through the upper and lower plates, thereby completing the output of the modulated differential capacitor signal.

[0024] Optionally, in step one, when the reference source is an exogenous reference source, the carrier generated by the exogenous reference source is directly amplified by the controllable gain amplifier to generate a carrier with controllable amplitude; when the reference source is an endogenous reference source, the controllable variable gain amplifier is placed in the positive feedback of the self-oscillation circuit to generate a carrier with controllable amplitude.

[0025] By adopting the above technical solution, both kinds of reference sources can complete the test process, enhancing the universality of the test process and facilitating the test process.

[0026] Optionally, in step four, the differential preamplifier selects a low-noise, high-differential-mode impedance amplifier.

[0027] By adopting the above technical solution, the differential preamplifier selects a low-noise, high-differential-mode impedance amplifier, ensuring the high-impedance characteristics of the access end and ensuring that the subsequent demodulation circuit does not affect the signal of the differential capacitor.

[0028] Optionally, in step five, the phase signal used by the adjustment circuit is kept synchronous with the carrier phase in step one.

[0029] By adopting the above technical solution, the phase signal used by the adjustment circuit is kept synchronous with the carrier phase in step one, facilitating the test process.

[0030] In summary, the present application includes at least one of the following beneficial technical effects:

[0031] 1. The design method proposed by the present application is based on the basic principles and characteristics of the modulation and demodulation circuit, and obtains a controllable amplitude carrier through stable closed-loop control, and relies on the change of the amplitude of the carrier to achieve the purpose of variable gain measurement of the differential capacitor;

[0032] 2. The design method proposed by the present application reduces the requirement for the dynamic range of the preamplifier, and at the same time, the design sets the variable gain amplifier at the carrier source end instead of in the preamplifier module, which can pre-position the noise of the variable gain amplifier, reduces the influence of the noise of the variable gain amplifier on the circuit, realizes the variable gain measurement function without affecting the noise and dynamic range of the preamplifier, and realizes the purpose of large dynamic measurement of the accelerometer;

[0033] 3. The design method provided by the application realizes controllable amplitude carrier at the carrier source end, and in the case of using variable gain amplifier, can output standard carrier with approximately continuous change of amplitude, greatly reduces the risk of system out of control of the accelerometer closed loop system when switching the range, and improves the stability of the variable gain system.

[0034] 4. The design method provided by the application can resist the carrier amplitude drift caused by environmental factors (such as temperature) through the carrier amplitude closed loop, weaken the temperature drift of the capacitance measurement circuit to a certain extent, improve the stability and repeatability of the capacitance measurement, and finally achieve the purpose of improving the stability and repeatability of the accelerometer. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a functional block diagram of a variable range capacitance measurement circuit of a pendulum accelerometer according to the embodiment of the application;

[0036] Figure 2 is a controllable amplitude carrier source circuit diagram according to the embodiment of the application;

[0037] Figure 3 is a schematic diagram of a carrier modulation circuit and a gain control circuit according to the embodiment of the application;

[0038] Figure 4 is a schematic diagram of amplitude detection and carrier amplitude control closed loop according to the embodiment of the application;

[0039] Figure 5 is a schematic diagram of a modulation differential capacitance signal front-end amplification circuit according to the embodiment of the application;

[0040] Figure 6 is a schematic diagram of a demodulation circuit for the amplified modulation differential signal according to the embodiment of the application;

[0041] Figure 7 is a schematic diagram of an adjustable gain carrier source closed loop experiment according to the embodiment of the application;

[0042] Figure 8 is a schematic diagram of a demodulation of the amplified modulation signal according to the embodiment of the application; DETAILED DESCRIPTION

[0043] The following will be described in combination with the accompanying Figures 1-8 The application will be further described in detail.

[0044] The embodiment of the application discloses a manufacturing method of a variable range pendulum accelerometer differential capacitance measurement circuit, referring to Figures 1-8 , comprising the following steps:

[0045] Step one, using a reference source or self-oscillation circuit combined with a controllable variable gain amplifier to produce a controllable amplitude carrier;

[0046] Step two, controllable amplitude carrier through the balanced transformer to produce a carrier and access to the plate; balanced transformer using double differential drive circuit or single drive circuit, using double differential drive circuit to produce a double-ended carrier, access to both sides of the plate; using a single drive circuit to produce a single-ended carrier, access to the central plate; to achieve a variable amplitude high-frequency carrier process of differential capacitor;

[0047] Step three, controllable amplitude carrier before stimulating a differential capacitor access to a carrier amplitude detection circuit, using a synchronous phase signal demodulation to get the carrier amplitude signal, and using the carrier amplitude signal control the controllable variable gain amplifier described above, forming a closed-loop negative feedback control, ultimately get a controllable amplitude and stable carrier signal;

[0048] Step four, in the case of double-ended carrier, modulated differential capacitor signal through the central plate of the differential capacitor into the signal preamplifier, in the case of single-ended carrier, modulated differential capacitor signal through the upper and lower plate into the differential preamplifier, get amplified modulated differential capacitor signal;

[0049] Step five, get the amplified modulated differential capacitor signal, ultimately via a synchronous phase signal demodulation circuit to get the differential capacitor signal.

[0050] In step one, the reference source includes exogenous reference source and endogenous reference source, if using exogenous reference source to produce carrier, the carrier generated here is generally a sine wave, which can be directly amplified by a controllable gain amplifier to produce a controllable amplitude carrier; if using endogenous circuit to produce carrier, the controllable variable gain amplifier can be placed in the positive feedback of the self-oscillation circuit, which can also produce a controllable amplitude carrier.

[0051] In step two, the controllable amplitude carrier is modulated onto the differential capacitor through the modulation circuit. The modulation and demodulation technology of the accelerometer currently mainly has double-ended carrier and single-ended carrier. The double-ended carrier amplifies the controllable amplitude carrier into a differential anti-phase real carrier, and loads the carrier onto the upper and lower plates of the differential capacitor structure, and then outputs the modulated differential capacitor signal through the central plate, as shown in the double-ended carrier modulation circuit of Figure 3 The principle of single-ended carrier is also to amplify the controllable amplitude carrier into a real single-ended carrier, and load the carrier onto the central plate of the differential capacitor, and then output the modulated differential capacitor signal through the upper and lower plate, as shown in the single-ended carrier modulation circuit of Figure 3 In the double-ended carrier circuit, the resistance of R6 and R7 should be the same, and R4 / R5, R8 / R9 can be used to adjust the circuit amplification gain.

[0052] The double-ended carrier circuit and the single-ended carrier circuit built with the amplifier are typical forms of the circuit. Compared with the carrier form built with the amplifier, the double-ended carrier form built with the transformer can improve the carrier signal quality and reduce the carrier noise by the passive LC resonant circuit (composed of CF1, CF2 and T1 shown in Figure 3 The resonant frequency of the LC resonant circuit should be determined according to the required carrier frequency f In the real engineering, the carrier frequency of the LC resonant circuit can be adjusted by the parallel capacitor. The smaller the AC resistance R of the LC resonant circuit is, the higher the quality factor Q is, and the better the carrier quality is.

[0053] That is, the amplification gain of the differential capacitance modulation signal is changed by the controllable amplitude carrier instead of directly changing the gain of the amplifier (such as U4 and U17 shown in Figure 5 ) in the front-end amplification circuit to change the gain of the capacitance measurement capacitor. This is because the front-end amplifier is generally composed of a high-precision low-noise amplifier. If a variable gain amplifier is used as the front-end amplifier, the existing variable gain amplifier products are difficult to achieve the ideal noise level. Further, the dynamic range of the amplifier element is limited by the processing technology, and increasing the amplification gain will inevitably lead to an increase in the noise of the amplification circuit, which is obviously unacceptable for high-precision capacitance measurement circuits. The method of increasing the amplitude of the differential capacitance modulation signal by increasing the amplitude of the carrier can increase the amplification gain of the modulation differential capacitance signal without affecting the noise of the front-end circuit.

[0054] Taking the double-ended carrier variable gain scheme of the balanced transformer as an example, the problem of noise and modulation signal amplification can be better explained. Let the amplitude of the controllable sine carrier be A z Without loss of generality, the carrier signal can be represented as: Carrier = Az * sin(2πf) Signal At the same time, the angle signal of the swing plate as the measured signal can be represented as Mod_Signal = Az * sin(2πf) * Signal .

[0055] The modulation differential capacitance signal can be represented as Amp_Mod_Signal = K * Az * sin(2πf) * Signal Where * is the convolution operation.

[0056] Let the amplification gain of the subsequent front-end amplification circuit be K A Then the amplified modulation signal can be represented as Final_signal = K * Az * Signal Figure 1 A Figure 3

[0057] If an ideal top demodulation method is used, the swing plate angle signal finally demodulated is Figure 4 Figure 5 AFigure 7 Obviously, adjusting the amplitude of the controllable carrier can directly increase the gain of the demodulated wobble signal. And the measurement noise of the capacitance measurement circuit will not change due to the change of the gain.

[0058] In step three, the controllable amplitude carrier is connected to the carrier amplitude detection circuit before exciting the differential capacitance, and the carrier amplitude signal is obtained by using the synchronous phase signal demodulation, and the carrier amplitude signal is used to control the controllable variable gain amplifier described above to form a closed loop negative feedback control. The controller can use simple PID control, or advanced control algorithms such as fuzzy control, expert control, etc. And the controller can be composed of analog circuit or digital circuit, the specific form depends on whether the controllable gain amplifier is analog or digital. After the carrier amplitude forms a stable control loop, a carrier signal with controllable and stable amplitude is obtained at the carrier output end.

[0059] The digital variable resistance network in the digital variable gain amplifier can use a resistive digital-to-analog converter chip (D / A C). Only the reference end of the resistive digital-to-analog converter chip is connected as the access point of the carrier signal, and different feedback resistances are equivalent by digital signal control. The internal resistance network cooperates with the low-noise amplifier to realize the design of the digital variable gain amplifier; if it is used in the internal source controllable amplitude carrier source circuit, the digital variable gain amplifier can also constitute a controllable gain inverter for generating a controllable amplitude carrier signal.

[0060] The analog controllable gain inverter can adjust the gain of the amplifier by analog voltage adjustment method. The amplifier can be directly used as an inverter in the internal source self-oscillation circuit, or as an analog controllable gain amplifier in the external source controllable amplitude carrier source circuit.

[0061] It should be noted that the Schmidt trigger and the synchronous phase adjustment circuit (such as Figure 8 The essence of the Schmidt trigger and the synchronous phase adjustment circuit is to extract the phase of the carrier signal and add a certain delay to form the synchronous phase signal required by the system. The synchronous phase signal is finally used for demodulation of the modulated signal or the carrier signal.

[0062] Similarly, the digital chip and its auxiliary circuit used with the external source controllable amplitude carrier source circuit are used to provide the external source carrier signal and the synchronous phase signal. The above-mentioned circuits are mature technologies and have various styles, and are not within the protection features of this patent. In order to simplify the description of this patent, this patent does not provide specific circuit diagrams.

[0063] In step three, the carrier signal is obtained by ​The carrier signal output branch outputs the carrier signal output, and the carrier amplitude signal is obtained through an impedance isolation circuit and a phase synchronous demodulation circuit. The impedance isolation circuit is mainly used to ensure that the carrier amplitude detection circuit does not affect the carrier circuit, and the demodulation circuit can demodulate the carrier amplitude signal from the carrier. Obtaining the carrier amplitude signal is an important step of the carrier amplitude control loop, which provides a real-time amplitude signal for the amplitude control loop to facilitate comparison with the reference amplitude, and forms a closed-loop control effect through PID or other control methods. After the amplitude closed loop is established, a stable controllable carrier amplitude can be obtained, and the carrier amplitude can be arbitrarily adjusted through the reference signal. If a continuous variable reference signal is given, a carrier with continuously variable amplitude can be obtained.

[0064] In step three, considering that the variable gain carrier can also be realized in the form of a discrete amplitude carrier through switches and the like, the circuit structure can be regarded as a simplified version of the variable carrier amplitude circuit proposed in the patent. Compared with the switching scheme, the continuously variable carrier proposed in the patent has a significant advantage over the discrete amplitude carrier. The advantage mainly lies in that the continuously variable carrier provides the whole process of carrier amplitude variation. In contrast, the discrete amplitude carrier switches the gain through the on-off of the switch, so that the specific information of the carrier amplitude will be lost during the switching of the amplitude, resulting in unknown capacitance signal gain during the switching process, and the capacitance measurement result will be inaccurate during the switching process. In addition, switching the amplitude through a switch will inevitably bring unnecessary electrical signal jitter, which will cause noise and result in a temporary increase in noise in the circuit. The above two problems are unacceptable in precision circuits, and the continuously variable gain amplifier can well solve the above problems.

[0065] In step three, the scheme of forming a closed-loop control loop through the amplitude signal has another significant advantage, which is outstanding in resisting environmental disturbances. This is because the closed-loop circuit can resist the influence of the environment on the carrier. For example, the carrier driving circuit, transformer and other devices are affected by environmental factors such as temperature, resulting in a change in gain with the change in environment. This part of the drift will be coupled with the capacitance signal, resulting in temperature drift error in the capacitance measurement signal. The introduction of the amplitude closed loop can well suppress this problem, because when the circuit gain decreases (increases), the true carrier amplitude will decrease (increase), and the amplitude signal demodulated will decrease (increase). After passing through the negative feedback controller, the control signal will increase (decrease) the gain of the variable gain amplifier, so that the carrier signal with a larger (smaller) amplitude is generated, so that the final output carrier signal amplitude returns to the original set amplitude level. Through the closed-loop control loop, the capacitance measurement temperature drift caused by the carrier amplitude drift can be effectively suppressed, and a more accurate capacitance measurement signal can be obtained.

[0066] In step four, in the case of double-ended carrier, the modulated differential capacitance signal flows into the signal preamplifier through the central plate of the differential capacitor, and in the case of single-ended carrier, the modulated differential capacitance signal flows into the differential preamplifier through the upper and lower plates, obtaining the amplified modulated differential capacitance signal. In this step, the modulated differential capacitance signal is connected to the preamplifier and amplified. In this step, in order to ensure the high impedance characteristics of the connection end, a low-noise, high differential-mode impedance amplifier should be selected as much as possible, and a positive end amplification circuit should be selected to ensure that the subsequent demodulation circuit does not affect the differential capacitance signal.

[0067] In step four, the carrier amplitude can be mainly converted into a digital signal by an analog-to-digital converter chip (A / D C) and transmitted to a micro processing unit (MCU), and in the MCU, a PID control or even a more advanced control algorithm can be applied to control the amplitude of the carrier.

[0068] Correspondingly, the carrier amplitude signal can also use an analog amplitude control circuit to achieve equivalent proportional control, such as ​ analog amplitude control circuit in the analog scheme is relatively simple. The two forms have their own advantages, and the use of which form of control circuit mainly depends on the demand and cost of the project.

[0069] In step four, as shown in ​ , the double-ended carrier capacitance structure is modulated by the upper and lower plates of the carrier, and the modulated capacitance signal is output from the central swing plate electrode. The modulated differential capacitance signal will be amplified by the preamplifier U14, where R12 and R13 are used to adjust the gain of the preamplifier.

[0070] In the single-ended carrier capacitance structure, the carrier is modulated by the central plate and the corner signal, and the differential modulation signal is output from the upper and lower plates. The modulation signal will be amplified by U15, U16 and U17, where U17 is a more instrument amplifier, R16 can be used to adjust the gain of the instrument amplifier, and R14 and R15 can adjust the bias of the front-end amplifier and provide certain filtering effect

[0071] In step five, the modulated differential capacitance signal is input into the demodulation circuit to obtain the differential capacitance signal, where the phase signal used in the demodulation circuit should be synchronized with the carrier phase in step one.

[0072] In step five, the amplified modulated differential capacitance signal can be demodulated by a phase-synchronous demodulation circuit to obtain the required differential capacitance signal. The circuit capable of achieving demodulation function is not unique, and this type of circuit is relatively mature, so it is not listed here.

[0073] Taking the capacitance measurement circuit of a certain type of digital quartz flexible accelerometer as an example, the system adopts a differential capacitance measurement structure, and respectively adopts a digital external variable range capacitance measurement system scheme, a digital variable gain amplifier, a dual-ended carrier scheme based on a transformer, and a digital amplitude control closed loop.

[0074] In the above example, the debugging result is:

[0075] Step one, in order to realize the closed loop control of the carrier amplitude, a controllable amplitude carrier generation circuit is first needed. In feature one, we first give a certain digital gain signal (0-1, such as 0.2), and load an external oscillator, at this time a basically stable carrier can be obtained at the controllable amplitude output end, the sine carrier amplitude is about 0.5Vpp;

[0076] Step two, the controllable amplitude carrier is connected to the drive amplifier circuit, the LC resonant network composed of the drive amplifier and the differential capacitor is driven, and the differential carrier is loaded to the upper and lower plates of the differential capacitor at the same time. At this time, the carrier amplitude loaded on the plate is 1.8Vpp, and the carrier signal is output through the carrier signal output branch for measuring the amplitude of the carrier;

[0077] Step three, after the sine carrier is output through the carrier signal output branch, it is first impedance-isolated through a follower, and then demodulated by using a carrier signal of the same frequency to obtain a 0.9V DC signal. The DC signal is directly related to the carrier amplitude and is used to represent the carrier amplitude. The demodulation principle is the same as that of the demodulation circuit in feature five, which will not be described here. Then, the amplitude signal is sampled and quantized into a digital signal through an A / D C circuit and input into an MCU. For simplicity, a digital PID controller output described in feature one can be used to output the digital gain signal, and finally a control closed loop is formed. The control closed loop can be used to control and obtain a continuous carrier with varying amplitude. By setting different reference amplitude signals, carriers with different amplitudes can be obtained, and the experimental results are as follows ​ The carrier amplitude is set to vary in the range of 0Vpp-18Vpp, and the circuit design uses a 16-bit A / D C, so the carrier amplitude variation accuracy is 18 / 216 16 V≈0.27mV, by continuously adjusting the PID control loop, we can approximately obtain an accurate continuous variable amplitude carrier.

[0078] Step four, after the swing piece rotation signal is modulated with the carrier, the modulated differential capacitor signal will first enter the front-end amplifier for amplification to increase the signal gain for more accurate measurement. In this circuit design, the front-end gain amplification factor is set to 10 times.

[0079] In step five, the amplified modulated signal is demodulated by a demodulation circuit, and the demodulation process of the demodulated signal is as shown in the schematic diagram ​ The modulated signal is demodulated by convolution with the phase synchronization signal to obtain the low-noise amplified swing plate angle signal.

[0080] The implementation principle of the manufacturing method of the variable range pendulum accelerometer differential capacitance measurement circuit is as follows: a reference source or a self-oscillation circuit is used in combination with a controllable variable gain amplifier to generate a controllable amplitude carrier; the controllable amplitude carrier passes through a double-ended balanced transformer (a double-channel differential driving circuit or a single-channel driving circuit) to generate a double-ended carrier (a double-ended carrier or a single-ended carrier), and is connected to two side plates (two side plates or a central plate); the controllable amplitude carrier is divided into a path connected to a carrier amplitude detection circuit before exciting the differential capacitance, a carrier amplitude signal is obtained by using synchronous phase signal demodulation, and the controllable variable gain amplifier described above is controlled by using the carrier amplitude signal to form a closed-loop negative feedback control, so that a carrier signal with controllable amplitude and stability is finally obtained; in the case of a double-ended carrier, the modulated differential capacitance signal flows into a signal preamplifier through the central plate of the differential capacitance, and in the case of a single-ended carrier, the modulated differential capacitance signal flows into a differential preamplifier through the upper and lower plates, to obtain an amplified modulated differential capacitance signal; after obtaining the amplified modulated differential capacitance signal, a differential capacitance signal is finally obtained through a synchronous phase signal demodulation circuit; the circuit scheme can amplify the differential capacitance signal by different multiples without affecting the noise of the preamplifier, so that the accelerometer can obtain a high-precision capacitance measurement signal in a low disturbance condition, and the amplification multiple can be reduced in a high disturbance condition to expand the range and ensure that the control of the accelerometer does not fail, the capacitance measurement gain of the accelerometer is changed in different conditions, and finally the variable range measurement goal of the accelerometer is achieved; the application has been successfully applied to a digital quartz flexible accelerometer to realize the variable range measurement function of the accelerometer, and is suitable for an accelerometer system based on the capacitance measurement principle.

[0081] The above are preferred embodiments of the application, and do not limit the protection scope of the application, so that: equivalent changes made according to the structure, shape, principle of the application should be covered within the protection scope of the application.

Claims

1. A method for fabricating a differential capacitance measurement circuit for a variable-range pendulum accelerometer, characterized in that, The method comprises the following steps: Step one, using a reference source combined with a controllable variable gain amplifier to generate a controllable amplitude carrier; Step two, the controllable amplitude carrier passes through a balanced transformer to generate a carrier and is connected to the plate; Step three: the controllable amplitude carrier is divided into a path connected to a carrier amplitude detection circuit before exciting the differential capacitor, a synchronous phase signal is used for demodulation to obtain a carrier amplitude signal, and the controllable variable gain amplifier is controlled by using the carrier amplitude signal to form a closed-loop negative feedback control, thereby obtaining a controllable and stable carrier signal; Step four, the modulated differential capacitor signal flows into the differential preamplifier through the plate to obtain an amplified modulated differential capacitor signal; Step five, the modulated differential capacitor signal is demodulated by a demodulation circuit using a signal synchronized in phase with the carrier in step one to obtain a differential capacitor signal.

2. The method of claim 1, wherein: In step two, a balanced transformer or an amplifier element can be selected to form a double-path differential drive circuit to generate a double-ended carrier and connect it to the upper and lower plates.

3. The method of claim 1, wherein: In step two, a single-path drive circuit can be selected to generate a single-ended carrier and connect it to the central plate.

4. The method of claim 2, wherein: In step three, in the case of a double-ended carrier, the modulated differential capacitor signal flows into the signal preamplifier through the central plate of the differential capacitor.

5. The method of claim 3, wherein: In step three, in the case of a single-ended carrier, the modulated differential capacitor signal flows into the differential preamplifier through the upper and lower plates.

6. The method of claim 1, wherein: In step one, when the reference source is an exogenous reference source, the carrier generated by the exogenous reference source is directly amplified by the controllable gain amplifier to generate a controllable amplitude carrier; when the reference source is an endogenous reference source, the controllable variable gain amplifier is placed in the positive feedback of the self-oscillation circuit to generate a controllable amplitude carrier.

7. The method of claim 1, wherein: In step four, the differential preamplifier selects a low-noise, high-differential-mode impedance amplifier.

8. The method of claim 1, wherein: In steps three and five, the phase signal used by the demodulation circuit is synchronized in phase with the carrier in step one.

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