Voltage bias feedback zeroing circuit of high-precision spring type relative gravimeter

Abstract

The invention discloses a voltage bias feedback zeroing circuit of a high-precision spring type relative gravimeter, which comprises a lower fixed capacitor sheet and a capacitor moving sheet positioned between an upper fixed capacitor sheet and the lower fixed capacitor sheet, and is characterized in that a square wave generator generates a first square wave oscillation signal and a second square wave oscillation signal which are opposite in polarity; the second square wave oscillation signal is connected with the lower fixed capacitor plate, the voltage bias feedback unit adds the first square wave oscillation signal and the voltage bias and outputs the added signal to the upper fixed capacitor plate, and the induced voltage generated by the capacitor moving plate passes through the signal amplifier with the amplification factor of K0 to obtain the voltage bias. The device is only provided by an electronic system, and does not relate to a sensor mechanical structure, so that mechanical movement and oscillation are not generated, the stability of the whole mechanical structure can be ensured, and meanwhile, the influence of electrostatic force on the capacitor moving plate is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of the development of sub-modules of the electronic system of a high-precision spring-type relative gravimeter, and particularly relates to a voltage bias feedback zeroing circuit for a high-precision spring-type relative gravimeter. Background Art

[0002] The gravity of the earth is an important physical quantity in disciplines such as geodesy, geophysics, and metrology. Its magnitude is mainly affected by the earth's structure and shape.

[0003] High-precision spring-type relative gravimeters can play an important role in disciplines such as geophysics and metrology, as well as in national defense security. Since the static gravimeter has a high precision, reaching an accuracy better than 1 μGal, many useful information can be extracted from the observed gravity values.

[0004] At present, the microgravity-level gravimeters on the market are mainly zero-length spring fixed-point relative gravimeters imported from abroad, such as the gPhone gravimeter developed by Microg-Lacoste in the United States. Since the accuracy of the microgravity-level gravimeter reaches the order of magnitude of 10 to the power of negative eight, the requirements for the observation environment are also very high. Otherwise, the reliability of the observed data will be greatly reduced due to factors such as environmental temperature, humidity, and air pressure. Basically, all gravimeters are placed in special gravity observation stations for observation. For example, the gWave-II type microgravity-level gravimeter developed by the Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, is placed in the Wuhan National Geodetic Field Scientific Observation and Research Station under the Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, and conducts gravity observation tasks. There are special observation piers for installing precision geodetic instruments in the national field scientific observation and research station, with stable observation temperature and air pressure, and professional personnel are equipped to regularly maintain the instruments.

[0005] High-precision spring-type relative gravimeters generally use capacitive micrometering systems as gravity sensing units. Traditional spring-type relative gravimeter sensing systems adopt open-loop or electromagnetic feedback modes. During field observations, metal springs are greatly affected by environmental factors such as ambient temperature and ground tilt. Even with data compensation using temperature and tilt sensors in the open-loop mode, it is impossible to avoid excessive fluctuations exceeding the instrument's range. In the electromagnetic feedback mode, after the electromagnetic coil is energized, an electromagnetic force is generated in the magnetic field generated by the permanent magnet, and the sensor is fed back to the zero position. Although this method can ensure that the sensor is at the zero position and effectively increase the range, the magnetic force will affect the helical metal spring, causing it to oscillate in the magnetic field and significantly reducing the accuracy of the sensor. In addition, when the power supply in the field is limited, energizing the electromagnetic coil will increase power consumption and reduce the instrument's operating time. In this case, a feedback zeroing system that does not affect the metal spring and consumes less power is required so that high-precision spring-type relative gravimeters can perform normal observations in various environments. Summary of the Invention

[0006] The object of the present invention is to solve the problem that the data of high-precision spring-type relative gravimeters exceeds the range during field observations due to environmental influences, and that general feedback systems affect the instrument's accuracy and consume a large amount of power, and to provide a voltage bias feedback zeroing circuit for high-precision spring-type relative gravimeters.

[0007] The above object of the present invention is achieved by the following technical solutions:

[0008] A voltage bias feedback zeroing circuit for a high-precision spring-type relative gravimeter includes a lower fixed capacitor plate, and a movable capacitor plate located between the upper fixed capacitor plate and the lower fixed capacitor plate, and also includes a square wave generator.

[0009] The square wave generator generates a first square wave oscillation signal U 1 and a second square wave oscillation signal U 2 , the second square wave oscillation signal U 2 is connected to the lower fixed capacitor plate, and the voltage bias feedback unit adds the first square wave oscillation signal U 1 and the voltage bias K 0 U 0 and outputs the sum to the upper fixed capacitor plate, and the induced voltage U 0 generated by the movable capacitor plate is obtained as the voltage bias K 0 after passing through a signal amplifier with an amplification factor of K 0 U 0 .

[0010] The added signal U 1 obtained by adding the first square wave oscillation signal U 0 and the voltage bias K 0 U 1+k 0 U 0 It is also output to the AC - DC signal rectification unit.

[0011] The first square - wave oscillation signal U 1 and the second square - wave oscillation signal U 2 have the same amplitude and a duty cycle of 50%.

[0012] As described above, the induced voltage U generated by the moving plate of the capacitor 0 is 0 or less than the set threshold value.

[0013] As described above, the voltage bias feedback unit includes a first buffer A1 and a second buffer A2.

[0014] One end of the first resistor R1 and one end of the first capacitor C1 are respectively connected to the input port of the first buffer A1. The non - inverting output port of the first buffer A1 is respectively connected to the input port of the second buffer A2 and the other end of the first capacitor C1. The inverting output port of the first buffer A1 is connected to the other end of the first resistor R1.

[0015] The non - inverting output port of the second buffer A2 outputs the first square - wave oscillation signal U 1 The first square - wave oscillation signal U 1 and the feedback voltage signal k 0 U 0 are respectively input to the inverting adder for inverting summation and then output the added signal U 1 +k 0 U 0 .

[0016] As described above, the inverting adder includes a first operational amplifier. The first square - wave oscillation signal U 1 and the feedback voltage signal k 0 U 0 are respectively connected to the inverting terminal of the first operational amplifier A3 through the second resistor R2 and the third resistor R3. The inverting terminal of the first operational amplifier A3 is also connected to the output terminal of the first operational amplifier A3 through the fourth resistor R4. The non - inverting terminal of the first operational amplifier A3 is connected to electrical ground.

[0017] The present invention has the following beneficial effects compared with the prior art:

[0018] (1) The present invention is only provided by an electronic system and does not involve the mechanical structure of the sensor, so there will be no mechanical movement and oscillation, which can ensure the stability of the overall mechanical structure.

[0019] (2) The present invention does not use permanent magnets and electromagnetic coils, so it will not produce electromagnetic effects on the metal springs of the sensitive unit, thus ensuring the accuracy of the sensor.

[0020] (3) The present invention does not require energizing an electromagnetic coil to generate current, thus avoiding related power consumption and reducing the overall power consumption of the instrument. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the functional schematic diagram of the present invention;

[0022] Figure 2 is the circuit design diagram of the present invention;

[0023] Figure 3 is the circuit structure diagram of the voltage bias feedback unit of the present invention;

[0024] Figure 4 is the signal waveform diagram of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] In order to facilitate the understanding and implementation of the present invention by those of ordinary skill in the art, the present invention will be further described in detail below with reference to embodiments. It should be understood that the embodiments described herein are only for the purpose of illustrating and explaining the present invention and are not intended to limit the present invention.

[0026] Embodiment 1:

[0027] A voltage bias feedback zeroing circuit for a high-precision spring-type relative gravimeter

[0028] 1. Overall working mode of the capacitive sensor

[0029] As Figure 1 , the capacitive sensor includes an upper fixed capacitor plate, a movable capacitor plate, and a lower fixed capacitor plate. Among them, the upper fixed capacitor plate and the lower fixed capacitor plate are capacitor plates with fixed positions; the movable capacitor plate is connected to a vertically arranged metal spring, and the movable capacitor plate is suspended between the upper fixed capacitor plate and the lower fixed capacitor plate, and the upper fixed capacitor plate, the movable capacitor plate, and the lower fixed capacitor plate are parallel to each other.

[0030] The square wave generator generates two first square wave oscillation signals U 1 and a second square wave oscillation signal U 2 with the same amplitude, opposite polarities, and both duty cycles of 50%. The second square wave oscillation signal U 2 is connected to the lower fixed capacitor plate to directly provide a square wave oscillation signal for it; the first square wave oscillation signal U 1 is connected to the voltage bias feedback unit to provide a basic reverse square wave oscillation signal for it. The first square wave oscillation signal U 1 is superimposed with the voltage bias K 0 U 0 and then connected to the upper fixed capacitor plate to provide another reverse square wave oscillation signal for it.

[0031] A uniform electric field is generated between the upper fixed capacitor plate and the lower fixed capacitor plate. The capacitor moving plate moves to a certain position under the action of gravity, and a tiny induced voltage U is generated in the uniform electric field. 0 , the induced voltage U 0 The magnitude of is:

[0032]

[0033] Among them, ΔL is the distance that the middle capacitor plate deviates from the zero position in the middle of the upper fixed capacitor plate and the lower fixed capacitor plate.

[0034] The signal amplifier is connected to the middle capacitor plate and amplifies the tiny induced voltage U 0 into a relatively stable feedback voltage signal k 0 U 0 .

[0035] The voltage bias feedback unit is connected to the square wave generator and the signal amplifier. Its function is to add the first square wave oscillation signal U 1 generated by the square wave generator and the feedback voltage signal k 0 U 0 , and output the stable added signal U 1 +k 0 U 0 to the upper fixed capacitor plate, and finally make the absolute value of the induced voltage U 0 output by the middle capacitor plate be 0 or less than the set threshold.

[0036] The AC to DC signal rectification unit converts the added signal U 1 +k 0 U 0 into a DC voltage value U. This DC voltage U contains the information of the gravity change.

[0037] 2. Working mode of the voltage bias feedback unit

[0038] As Figure 2 , A1 and A2 are the first buffer and the second buffer respectively. A DC voltage is input to the input port, and a common-phase DC voltage and an inverted DC voltage are respectively output from the corresponding common-phase output port and inverted output port. The first buffer A1 and the second buffer A2 can use the CD4041 chip.

[0039] One end of the first resistor R1 and one end of the first capacitor C1 are respectively connected to the input port of the first buffer A1. The input port of the second buffer A2 and the other end of the first capacitor C1 are respectively connected to the common-phase output port of the first buffer A1. The inverted output port of the first buffer A1 is connected to the other end of the first resistor R1.

[0040] The first buffer A1, the first resistor R1, and the first capacitor C1 form an RC oscillation circuit to generate a square wave signal.

[0041] The non-inverting output port of the second buffer A2 outputs the first square wave oscillation signal U 1 , the first square wave oscillation signal U 1 and the feedback voltage signal k 0 U 0 are respectively input into the inverting adder for inverting summation and then output the added signal U 1 +k 0 U 0 . The added signal U 1 +k 0 U 0 is loaded on the upper fixed capacitor plate, and at the same time the added signal U 1 +k 0 U 0 is converted into a DC signal U by the alternating direct signal rectification unit, and the inverting output port of the second buffer A2 outputs the second square wave oscillation signal U 2 . The second square wave oscillation signal U 2 is loaded on the lower fixed capacitor plate.

[0042] Principle description:

[0043] 1. The reason for providing the upper fixed capacitor plate and the lower fixed capacitor plate with the first square wave oscillation signal U 1 and the second square wave oscillation signal U 2 with opposite phases instead of DC signals is to effectively reduce the electrostatic force on the movable capacitor plate. If the upper fixed capacitor plate and the lower fixed capacitor plate adopt DC signals with the same magnitude and opposite directions, the induced electromotive force generated by the middle movable capacitor plate will be fixed, and the polar movable capacitor plate will be affected by the electrostatic force in the uniform electric field. When using the first square wave oscillation signal U 1 and the second square wave oscillation signal U 2 with opposite phases, the induced electromotive force of the middle movable capacitor plate will change with the change of the magnetic field. At the moment of polarity switching, the charge polarity on the movable capacitor plate is opposite to the electric potential in the electric field, and a force moving towards the middle position will be generated, balancing the influence of the electrostatic force. At the same time, the frequency of this oscillation signal is about 10 kHz, and the polarity switching is frequent, which also effectively reduces the possibility of generating electrostatic force.

[0044] 2. The first resistor R1 and the first capacitor C1 of the first buffer A1 must use precision components, otherwise the generated square wave oscillation signal will have problems such as unstable duty cycle, affecting the zero adjustment effect of the feedback unit;

[0045] 3. The upper fixed capacitor plate, the movable capacitor plate, and the lower fixed capacitor plate must maintain a high degree of parallelism. Otherwise, the electric field generated between the upper fixed capacitor plate and the lower fixed capacitor plate is not a uniform electric field, and the induced voltage generated by the movable capacitor plate is neither accurate nor stable, greatly affecting the zero adjustment effect.

[0046] 4. The input impedance of the voltage bias feedback unit must be high enough. Otherwise, the signal terminal connected to the signal amplifier will be affected by the square wave oscillation signal and will not output a stable voltage signal, resulting in the failure of zero adjustment. Therefore, the voltage bias feedback unit is implemented by a first operational amplifier.

[0047] Embodiment 2:

[0048] Based on Embodiment 1, as Figure 3 shown, in the inverting adder, the first square wave oscillation signal U 1 and the feedback voltage signal k 0 U 0 are respectively connected to the inverting terminal of the first operational amplifier A3 through the second resistor R2 and the third resistor R3. The inverting terminal of the first operational amplifier A3 is also connected to the output terminal of the first operational amplifier A3 through the fourth resistor R4. The non-inverting terminal of the first operational amplifier A3 is connected to electrical ground. By selecting appropriate second resistor R2, third resistor R3, and fourth resistor R4, the signal output from the output terminal of the inverting adder is -(U 1 +k 0 U 0 ). The polarity of k 0 U 0 is opposite to that of U 1 .

[0049] It should be noted that the embodiments described in the present invention are only illustrative of the spirit of the present invention. Those skilled in the art of the present invention can make various modifications or supplements to the described embodiments or use similar methods for substitution, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A voltage bias feedback zeroing circuit for a high-precision spring-type relative gravimeter, comprising a lower fixed capacitor sheet and a capacitor moving sheet located between the upper fixed capacitor sheet and the lower fixed capacitor sheet, characterized in that: Also includes a square wave generator, The square wave generator generates a first square wave oscillation signal U1 and a second square wave oscillation signal U2 with opposite polarities. The second square wave oscillation signal U2 is connected to the lower fixed capacitor. The voltage bias feedback unit adds the first square wave oscillation signal U1 and the voltage bias K0U0 and outputs them to the upper fixed capacitor. The induced voltage U0 generated by the capacitor plate obtains the voltage bias K0U0 after passing through a signal amplifier with an amplification factor of K0.

2. The voltage bias feedback zeroing circuit of a high-precision spring-type relative gravimeter according to claim 1, characterized in that: The added signal U1+k0U0 ​​obtained by adding the first square wave oscillation signal U1 and the voltage bias K0U0 is also output to the alternating current signal rectifying unit.

3. The voltage bias feedback zeroing circuit of a high-precision spring-type relative gravimeter according to claim 1, characterized in that: The first square wave oscillation signal U1 and the second square wave oscillation signal U2 have the same amplitude and a duty cycle of 50%.

4. The voltage bias feedback zeroing circuit of a high-precision spring-type relative gravimeter according to claim 1, characterized in that: The induced voltage U0 generated by the capacitor rotor is 0 or less than a set threshold.

5. The voltage bias feedback zeroing circuit of a high-precision spring-type relative gravimeter according to claim 1, characterized in that: The voltage bias feedback unit includes a first buffer A1 and a second buffer A2. The input port of the first buffer A1 is connected to one end of the first resistor R1 and one end of the first capacitor C1 respectively, the in-phase output port of the first buffer A1 is connected to the input port of the second buffer A2 and the other end of the first capacitor C1 respectively, and the inverting output port of the first buffer A1 is connected to the other end of the first resistor R1. The in-phase output port of the second buffer A2 outputs the first square wave oscillation signal U1. The first square wave oscillation signal U1 and the feedback voltage signal k0U0 are respectively input into the inverting adder for inversion and summation, and then pass through the inverter to output the added signal U1+k0U0.

6. The voltage bias feedback zeroing circuit of a high-precision spring-type relative gravimeter according to claim 5, characterized in that: The inverting adder includes a first operational amplifier, the first square wave oscillation signal U1 and the feedback voltage signal k0U0 are respectively connected to the inverting end of the first operational amplifier A3 through the second resistor R2 and the third resistor R3, the inverting end of the first operational amplifier A3 is also connected to the output end of the first operational amplifier A3 through the fourth resistor R4, and the non-inverting end of the first operational amplifier A3 is connected to the electrical ground.

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