CN210894735U - High-precision broadband gravimeter - Google Patents
High-precision broadband gravimeter Download PDFInfo
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- CN210894735U CN210894735U CN201921460702.2U CN201921460702U CN210894735U CN 210894735 U CN210894735 U CN 210894735U CN 201921460702 U CN201921460702 U CN 201921460702U CN 210894735 U CN210894735 U CN 210894735U
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Abstract
The utility model discloses a high accuracy broadband gravimeter relates to earthquake precursor early warning and solid tide observation technique. The gravity meter is as follows: from bottom to top, the chassis unit is connected with the constant temperature unit, a supporting unit is arranged in the constant temperature unit, and a capacitive displacement sensor, an elastic unit, a pendulum adjusting unit and a pendulum locking unit are respectively arranged on the supporting unit; the swing adjusting unit and the swing locking unit are respectively connected with the elastic unit; the elastic unit is connected with the capacitive displacement sensor; the capacitance displacement sensor is used for measuring the up-and-down change of the position of a moving plate in the elastic unit; the elastic unit is a precise spring; the constant temperature unit is a high-precision temperature control device. The constant temperature precision of the utility model is 0.0001 ℃; the capacitance sensor has high enough precision, and the measurement precision is 0.1 nanometer; the reasonable thermal structure is adopted, the sealing is good, the influence of temperature and air pressure is small, and a good observation result can be obtained even when the device works in an observation room without temperature control.
Description
Technical Field
The utility model relates to an earthquake precursor early warning and solid tide observation technique especially relate to a high accuracy broadband gravimeter.
Background
The high-precision broadband gravimeter capable of recording the solid tide at the earliest is a GS-type gravimeter invented by Graf in West Germany, which is widely popularized and used in Europe, America and China, and is not reproduced due to the fact that the Askania (Askania) is closed upside down; later in the united states Lacoste designed a Lacoste ET gravimeter, specifically designed to record solid tides; in the 80 s, the solid tide gravimeter was developed by our country and produced and popularized in China. The three gravimeters have different principles and great differences, and have the characteristics and advantages. But the difference in accuracy is not great.
The precision of solid tide is 1 micro gamma (about 10 mu gal)-9g) Therefore, the manufacturers capable of developing and producing the instrument have only three families at home and abroad.
Earthquake precursor prediction is one of the major topics of earthquake research work. The successful prediction of the time, location, magnitude of the earthquake is also a worldwide problem, and comprehensive, sufficient accuracy and quantity of information associated with the seismic precursor is largely unavailable.
At present, no high-precision broadband gravimeter exists at home and abroad.
SUMMERY OF THE UTILITY MODEL
The utility model discloses a shortcoming and not enough that prior art exists just aim at overcoming provides a high accuracy broadband gravimeter, both can improve the measurement accuracy and the long-term stability of high accuracy broadband gravimeter, has widened the measurement band again, can take notes more seismic information.
The purpose of the utility model is realized like this:
a) by adopting effective technical measures, the precision and the long-term stability of the output voltage of the high-precision broadband gravimeter are improved, so that the long-term change of the earth tidal factor can be detected, and the change of the tidal factor can be used for earthquake prediction;
b) because noise and frequency band are proportional, the utility model discloses with narrow band filtering and amplification, improve the SNR of the output voltage of high accuracy broadband gravimeter, available higher sensitivity detects the small vibrations information of earth inside.
c) The utility model discloses except that solid tide passageway observation record, still increased three passageway: high frequency channels (suitable for recording near earthquakes); low frequency channels (suitable for recording long ranges); the earth freely oscillates channels. (previous gravimeters only had solid tide channel recording, not these 3 seismic channels.)
Specifically, the high-precision broadband gravimeter comprises a capacitive displacement sensor, an elastic unit, a constant temperature unit, a pendulum adjusting unit, a pendulum locking unit, a supporting unit and a chassis unit;
the position and connection relation is as follows:
from bottom to top, the chassis unit is connected with the constant temperature unit, a supporting unit is arranged in the constant temperature unit, and a capacitive displacement sensor, an elastic unit, a pendulum adjusting unit and a pendulum locking unit are respectively arranged on the supporting unit;
the swing adjusting unit and the swing locking unit are respectively connected with the elastic unit; the elastic unit is connected with the capacitive displacement sensor;
the capacitance displacement sensor is used for measuring the up-and-down change of the position of a moving plate in the elastic unit;
the elastic unit is a precise spring;
the constant temperature unit is a high-precision temperature control device.
The utility model has the advantages of it is following and positive effect:
a) the high-precision temperature control system is adopted, the constant temperature precision of international similar instruments such as American lacosate and Germany GS gravimeters is 0.01 ℃, and the temperature compensation method is adopted to make up the deficiency of the temperature control precision due to the insufficient temperature control precision of foreign gravimeters; the constant temperature precision of the utility model is 0.0001 ℃, therefore, temperature compensation is not needed, the gravimeter with temperature compensation can compensate only at the best temperature point, and the working temperature of the high-precision broadband gravimeter of the utility model can be freely selected as long as the working temperature is higher than the highest ambient temperature;
b) because noise and frequency band are proportional, the utility model discloses with narrow band filtering and amplification, improve the SNR of the output voltage of high accuracy broadband gravimeter, available higher sensitivity detects the small vibrations information of earth inside.
c) The reasonable thermal structure is adopted, the sealing is good, the influence of temperature and air pressure is small, and a good observation result can be obtained even when the device works in an observation room without temperature control.
Drawings
FIG. 1 is a block diagram of the structure of a high-precision broadband gravimeter;
FIG. 2 is a schematic structural diagram of a high-precision broadband gravimeter;
FIG. 3 is a block diagram of a capacitive displacement sensor;
FIG. 4 is a schematic structural view of a spring unit;
FIG. 5 is a block diagram of the structure of a spring unit;
FIG. 6 is a block diagram showing the structure of a circuit of the thermostatic unit;
FIG. 7 is a block diagram showing the structure of a swing adjusting unit;
FIG. 8 is a block diagram showing the construction of a swing lock unit;
FIG. 9 is a circuit schematic of an oscillator;
FIG. 10 is a solid tide graph (2019-06-19);
FIG. 11 is a solid tide graph (2019-06-18);
FIG. 12 is a seismic trace of the high frequency channel (2019-06-18 days through 2019-06-26);
FIG. 13 is a seismic trace of the low frequency channel (2019-06-18 days through 2019-06-26).
In the figure:
1-a capacitive displacement sensor having a capacitive sensor,
111-moving plate, 112-upper fixed plate, 112-lower fixed plate,
121-oscillator, 122-inverter, 123-three stage amplifier, 124-lock-in amplifier,
125-solid tide channel, 126-earth free oscillation channel, 127-high frequency channel,
128-low frequency channel;
2-the elastic unit is arranged on the upper surface of the shell,
21-spring, 22-connecting piece, 23-flexible wire, 24-spring upper end fixing piece,
25-spring lower end fixing part, 26-flexible wire lower part, 27-swing (movable piece 111) and 28-leveling plate;
3-a constant temperature unit, wherein,
311-constant temperature thermistor bridge circuit, 312-constant temperature high gain amplifier,
313-an internal constant temperature power amplifier, 314-an internal constant temperature heating wire,
321-base constant temperature thermistor bridge circuit, 322-base constant temperature high gain amplifier,
323-base constant temperature power amplifier, 324-base constant temperature heating wire,
331-external constant temperature thermistor bridge circuit, 332-external constant temperature high gain amplifier
333-external constant temperature power amplifier, 334-external constant temperature heating wire;
4-pendulum adjustment unit
41-swing adjusting bracket, 42-swing adjusting motor bracket, 43-swing adjusting motor, 44-swing adjusting motor gear,
45-first-stage gear, 46-second-stage gear, 47-third-stage gear, 48-fourth-stage gear,
49-output gear, 410-pendulum adjusting circuit;
5-locking pendulum unit
51-locking swing motor, 52-locking swing motor support, 53-locking swing spring, 54-locking swing spring support,
55-lock pendulum upper limit, 56-lock pendulum lower limit, and 57-lock pendulum circuit;
6-a supporting unit for supporting the supporting unit,
61-support column, 62-support disk, 63-support seat, 64-support heat structure, 65-support cylinder;
7-a chassis unit, wherein the chassis unit,
71-chassis, 72-leveling screw rod nut, 73-foot cushion block, 74-chassis circuit box,
and 75, leveling the water bubbles.
Detailed Description
The following detailed description is made in conjunction with the accompanying drawings and examples.
Structure of high-precision broadband gravimeter
One) overall
As shown in fig. 1 and 2, the high-precision broadband gravimeter comprises a capacitive displacement sensor 1, an elastic unit 2, a constant temperature unit 3, a pendulum adjusting unit 4, a pendulum locking unit 5, a supporting unit 6 and a chassis unit 7;
the position and connection relation is as follows:
from bottom to top, the chassis unit 7 is connected with the constant temperature unit 3, a support unit 6 is arranged in the constant temperature unit 3, and the capacitive displacement sensor 1, the elastic unit 2, the pendulum adjusting unit 4 and the pendulum locking unit 5 are respectively arranged on the support unit 6;
the swing adjusting unit 4 and the swing locking unit 5 are respectively connected with the elastic unit 2; the elastic unit 2 is connected to the capacitive displacement sensor 1.
The mechanical parts of the capacitive displacement sensor 1, the elastic unit 2, the pendulum adjusting unit 4 and the pendulum locking unit 5 are arranged in the constant temperature unit 3, and the electronic parts of the capacitive displacement sensor are arranged outside the constant temperature unit 3;
capacitive displacement sensor 1: measuring the up-and-down change of the position of a moving plate 111 (pendulum) in the elastic unit 2, wherein the measuring precision is superior to 0.1 nanometer (nm);
the elastic unit 2: the spring 21 is a precise spring which is made of constant-elasticity alloy and is subjected to vacuum heat treatment, has high stability, has an elastic temperature coefficient of 10-5, has a daily drift requirement of less than 5 micro gamma (mu gal), is a core component of a high-precision broadband gravimeter, namely a sensor, and converts the gravity acceleration change into the change of the spring length;
a constant temperature unit 3: in order to ensure the stability of the elastic unit 2, the elastic unit 2 must be placed in a high-precision temperature environment;
the swing adjusting unit 4: the moving plate 111 (pendulum) of the capacitance type displacement sensor 1 is adjusted to be near zero, and the reduction ratio of a 5-stage gear system is required to be 5000 times as the adjustment precision requirement reaches 1 nanometer (nm);
the pendulum locking unit 5: in order to ensure the transportation safety and prevent the pendulum from colliding with other mechanical parts and being damaged, a pendulum locking unit is arranged.
The supporting unit 6: the device comprises a supporting capacitive displacement sensor 1, an elastic unit 2, a pendulum adjusting unit 4 and a pendulum locking unit 5.
The chassis unit 7: the horizontal arrangement of the output voltage of the high-precision broadband gravimeter is ensured.
The functional unit of the high-precision broadband gravimeter is introduced below
Two) functional unit
1. Capacitive displacement sensor 1
As shown in fig. 3, the capacitive displacement sensor 1 includes a rotor 111, an upper stator 112, a lower stator 113, an oscillator 121, an inverter 122, a three-stage amplifier 123, a lock-in amplifier 124, a solid tide measuring channel 125, an earth free oscillation channel 126, a high-frequency seismic channel 127, and a low-frequency seismic channel 128:
the connection relation is as follows:
the upper fixed plate 112 and the lower fixed plate 113 are arranged on the supporting unit 6, and the movable plate 111 is arranged between the upper fixed plate 112 and the lower fixed plate 113;
the oscillator 121 is respectively connected with the upper stator 112, the inverter 122 and the lock-in amplifier 124, the inverter 122 is connected with the lower stator 113, the rotor 111, the third-stage amplifier 123 and the lock-in amplifier 124 are sequentially connected, and the output end of the lock-in amplifier 124 is connected with 4 channels: a solid tide channel 125, an earth free oscillation channel 126, a high frequency channel 127 and a low frequency channel 128.
The working mechanism is as follows:
the oscillator 121 outputs signals to the upper stator 112 and the inverter 122, the inverter 122 outputs signals to the lower stator 113, the rotor 111 outputs signals to the three-stage amplifier 123, the oscillator 121 and the three-stage amplifier 123 provide signals to the lock-in amplifier 124, and the lock-in amplifier 124 outputs 4 channels, which are: a solid tide channel 125, an earth free oscillation channel 126, a high frequency channel 127 and a low frequency channel 128.
1) The moving plate 111: a metal wafer, the diameter is 40mm, and the thickness is 2 mm;
for flatness, the surface of the steel plate is plated with gold.
2) Upper stator plate 112: a metal wafer, the diameter is 40mm, and the thickness is 2 mm;
for flatness, the surface of the steel plate is plated with gold.
3) Lower stator plate 113: a metal wafer, the diameter is 40mm, and the thickness is 2 mm;
and machining the workpiece by using a precision grinding machine for flatness. And plating gold on the surface.
4) Oscillator 121
The oscillator 121 is a well-designed oscillator circuit.
As shown in fig. 9, the oscillator 121 includes an oscillation circuit 121A, a frequency dividing circuit 121B, and a shaping circuit 121C connected in this order;
4.1) Oscillator Circuit 121A
The oscillating circuit 121A is composed of a 1 st resistor R1, a 1 st capacitor C1 and a 1 st true-complement reverse buffer U1A;
one ends of a 1 st resistor R1 and a 1 st capacitor C1 are connected to the input end of the 1 st true complement reverse buffer U1A, and the other ends of the 1 st resistor R1 and the 1 st capacitor C1 are respectively connected with two output ends of the 1 st true complement reverse buffer U1A;
the 1 st true complement reverse buffer U1A is a four-way true complement reverse buffer 4041.
The working principle is as follows: the oscillation signal is generated by charging and discharging the 1 st resistor R1 and the 1 st capacitor C1 and amplifying the 1 st true complement reverse buffer U1A.
4.2) frequency divider circuit 121B
The frequency dividing circuit 121B is composed of 2 nd, 3 rd, 4 th and 5 th resistors R2, R3, R4 and R5, 2 nd, 3 rd and 4 th capacitors C2, C3 and C4, 1 st, 2 nd and 3 th diodes D1, D2 and D3, and 2 nd and 3 rd true complement reverse buffers U1B and U1C;
the 2 nd resistor R2 is connected with the 3 rd capacitor C3, and the 2 nd resistor R2 is connected with the 3 rd resistor R3;
one end of the 3 rd resistor R3 is connected with the output end 2 of the 2 nd true complement reverse buffer U1B, and the other end is connected with the input end 6 of the 3 rd true complement reverse buffer U1C;
one end of the 4 th resistor R4 is connected with the output end 3 of the 2 nd true-complement reverse buffer U1B; the other end is connected with the input end 3 end of a 3 rd true-complement reverse buffer U1C;
one end of the 2 nd diode D2 is connected to the 3 rd end of the 2 nd true-complement reverse buffer U1B, and the other end is connected to one end of the 2 nd resistor R2;
one end of the 2 nd diode D2 is connected to the 6 th end of the 3 rd true-complement reverse buffer U1C, and the other end is connected to one end of the 5 th resistor R5;
the 3 rd capacitor C3 is connected with one end of the 2 nd resistor R2, and the other end is connected with the 1 st diode D1;
the 4 th capacitor C4 is connected to one end of the 5 th resistor R5, and the other end is connected to the 1 st diode D1.
The working principle is as follows:
the 2 nd capacitor C2 is connected with the 1 st true complement reverse buffer U1A, the output of the 1 st true complement reverse buffer U1A is square wave, which is coupled by the 2 nd capacitor C2 and converted into negative pulse, the signal output by the 2 nd capacitor C2 is sent to the capacitor C3 and the 4 th capacitor C4, because one end of the bistable circuit is high level, and the other end is low level. Applied to both the 2 nd diode D2 and the 2 nd diode D3, the negative pulse is inactive only for low levels and active for high levels. The high level is pulled low after the negative pulse. Thereby causing the flip-flop to flip. The frequency oscillator 121 has a frequency half that of the frequency, thereby performing frequency division. After the oscillation signal is input into the two square waves, the output signal of the frequency dividing circuit becomes a square wave. The 1 pin of the frequency dividing circuit is sent to the stator 112, and the 5 pin is sent to the lower stator 122, because the short-term stability of the oscillator is very high, the short-term frequency stability of the oscillator can reach more than one ten-thousandth through testing by a digital frequency meter. The precision and the stability of the duty ratio after frequency division can be improved to one ten thousandth. And the error of the duty ratio of the square wave before frequency division reaches 2%.
4.3) shaping Circuit 121C
The shaping circuit 121C is composed of a 4 th true-complement inverting buffer U1C, and two square-wave signals with equal amplitude and opposite phases are output to the lock-in amplifier 124.
5) Inverter 122
Is a general inverter circuit. The zero drift of the operational amplifier is only required to be in the microvolt magnitude, the speed requirement is high, and the input resistor and the feedback resistor are all armored precise resistors of one ten thousandth. The armoured resistance has no parasitic inductance.
6) Three stage amplifier 123
Is a common three-stage amplifier circuit.
7) Phase lock amplifier 124
The phase-locked amplifier circuit is a universal precise single-frequency phase-locked amplifier circuit.
8) Solid tide measuring channel 125
Is a general active band-pass amplifying circuit.
9) Earth free oscillation channel 126
Is a general active band-pass amplifying circuit.
10) High frequency seismic channel 127
Is a general active band-pass amplifying circuit.
11) Low frequency seismic channel 128
Is a general active band-pass circuit.
The accuracy of the capacitive displacement sensor 1 depends on three aspects:
1. amplitude stability of the oscillator 121;
2. stability of the oscillator 121 duty cycle;
3. gain stability of the three stage amplifier 123 and gain and phase stability of the lock-in amplifier.
In order to improve the gain stability of the three-stage amplifier 123, all resistors adopt precision resistors with the precision of 0.0001; the resistor in the inverter 122 adopts a precision resistor of 0.0001 produced by 718 factories; the resistance of 0.001 is an armor resistance, and has no parasitic inductance; so that the inverter 122 does not produce an additional phase shift.
In the capacitive displacement sensor 1, a lock-in amplifier 124 is used; the lock-in amplifier 124 can effectively filter out the effects of interference and noise, thereby improving the measurement accuracy.
The capacitive displacement sensor 1 is shown in fig. 3.
Because the frequency band is narrower, and interference and noise are less, the utility model designs an enlarge and record passageway of 4 kinds of bandwidths:
the earth free oscillation channel 126 is used for recording earth free oscillation signals (the period of the earth free oscillation signals is 100-; the magnification of the earth free-running channel 126 is 150 ten thousand times.
The high-frequency earthquake channel 127 is used for recording near earthquakes, and when the earthquake source is close to the output voltage of the observation high-precision broadband gravimeter, earthquakes smaller than 0.1 level can be recorded; the high frequency seismic channel 127 has a magnification of 100 ten thousand times
The low frequency seismic channel 128 is used for recording long range earthquakes and can record seismic signals above 5 levels worldwide. The low frequency seismic channels 128 are at 100 ten thousand times magnification.
2. Elastic unit 2
As shown in fig. 4, the elastic unit 2 includes a moving plate 111, a spring 21, a connecting member 22, an upper flexible wire 23, a spring upper end fixing member 24, a spring lower end fixing member 25, a lower flexible wire 26, and a leveling plate 27:
the connection relation is as follows: from top to bottom, the connecting member 22, the upper flexible wire 23, the spring upper end fixing member 24, the spring 21, the spring lower end fixing member 25, the lower flexible wire 26, the moving plate 111 and the leveling plate 27 are connected in sequence.
1) Spring 21
The spring 21 is a key component of the high-precision broadband gravimeter, and the parameters of the spring 21 and the weight of the moving plate 111 (pendulum) must be properly selected, and the main factors causing the elastic change of the spring 21 include the following three factors: temperature effects, creep and elastic aftereffects; when designing a high-precision broadband gravimeter, the influence of the three factors is overcome as much as possible; in order to reduce the influence of temperature variation, the constant temperature precision can be improved; in order to reduce the creep of the spring, a method of reducing the load of the spring may be used, and the sensitivity of the spring is slightly lowered due to the reduction of the load, which requires higher accuracy and sensitivity of the elastic unit 2.
2) Connecting piece 22
Is a copper hook with the diameter of 10 mm.
3) Upper flexible wire 23
Is a 3J53 constant elasticity stainless steel wire with the diameter of 0.1 mm.
4) Spring upper end fixing member 24
Is a copper hook with the diameter of 10 mm.
5) Spring lower end fixing member 25
Is a stainless steel hook with the diameter of 10 mm.
6) Lower flexible wire 26
Is a 3J53 constant elasticity stainless steel wire with the diameter of 0.1 mm.
7) Leveling plate 27
The balance weight is a copper disk, i.e., a balance weight plate for adjusting the moving plate 111 to be strictly horizontal, and the moving plate 111 is strictly parallel to the upper and lower fixed plates 112 and 113.
3. Thermostatic unit 3
As shown in fig. 2 and 6, the constant temperature unit 3 comprises an outer constant temperature insulating layer 3A, an outer constant temperature cylinder 3B, a dewar flask 3C, an inner constant temperature cylinder 3D, a dewar flask seal 3E and a dewar flask mouth constant temperature controller 3F;
the constant temperature thermistor bridge circuit comprises an inner constant temperature thermistor bridge circuit 311, an inner constant temperature high-gain amplifier 312, an inner constant temperature power amplifier 313, an inner constant temperature heating wire 314, a base constant temperature thermistor bridge circuit 321, a base constant temperature high-gain amplifier 322, a base constant temperature power amplifier 323, a base constant temperature heating wire 324, an outer constant temperature thermistor bridge circuit 331, an outer constant temperature high-gain amplifier 332, an outer constant temperature power amplifier 333 and an outer constant temperature heating wire 334;
the position and connection relation is as follows:
an outer constant-temperature insulating layer 3A, an outer constant-temperature cylinder 3B, a Dewar flask 3C and a Dewar flask seal 3E are sequentially arranged from outside to inside, and an inner constant-temperature cylinder 3D and a Dewar flask mouth constant-temperature controller 3F are arranged in the Dewar flask 3C and the Dewar flask seal 3E;
the internal constant temperature thermistor bridge circuit 311, the internal constant temperature high-gain amplifier 312, the internal constant temperature power amplifier 313 and the internal constant temperature heating wire 314 are sequentially connected, and the internal constant temperature heating wire 314 is wound on the internal constant temperature barrel 3D;
the base constant-temperature thermistor bridge circuit 321, the base constant-temperature high-gain amplifier 322, the base constant-temperature power amplifier 323 and the base constant-temperature heating wire 324 are sequentially connected, and the base constant-temperature heating wire 324 is wound on the dewar bottle mouth constant-temperature controller 3F;
the outer constant temperature thermistor bridge circuit 331, the outer constant temperature high gain amplifier 332, the outer constant temperature power amplifier 333 and the outer constant temperature heating wire 334 are connected in sequence, and the outer constant temperature heating wire 334 is wound on the outer constant temperature barrel 3B.
The working mechanism is as follows:
the thermostatic control unit requires that the heating power is strictly equal to the heat dissipation power. If the heating power is greater than the heat dissipation power, the temperature in the temperature control unit rises, and if the heating power is less than the heat dissipation power, the temperature in the temperature control unit falls.
The inner constant temperature thermistor bridge circuit 311 outputs a signal to the inner constant temperature high gain amplifier 312, and the inner constant temperature high gain amplifier 312 supplies a power of an appropriate magnitude to the inner constant temperature heating wire 314 through the inner constant temperature power amplifier 313.
The base constant temperature thermistor bridge circuit 321 outputs a signal to the base temperature high gain amplifier 322, and the base temperature high gain amplifier 322 provides a proper amount of power to the base temperature heating wire 324 through the base temperature power amplifier 323.
The external temperature thermistor bridge circuit 331 outputs a signal to the external temperature high-gain amplifier 332, and the external temperature high-gain amplifier 332 provides power of a proper magnitude to the external temperature heater wire 334 through the external temperature power amplifier 333.
1) External constant temperature insulating layer 3A
The outer constant temperature insulating layer 3A comprises a cylinder made of a polypropylene material with better heat insulating property and a shell with an upper cover and a lower cover; its function is to preserve heat.
2) Outer constant temperature barrel 3B
The outer constant temperature cylinder 3B is a cylinder with an upper cover and a lower cover, is made of metal materials with good heat conductivity, has a diameter slightly smaller than the outer constant temperature insulating layer 3A, and is tightly matched with the outer constant temperature insulating layer; its functions are heating and temperature equalization.
3) Dewar flask 3C
The Dewar flask is a purchased part with vacuum degree less than 10-5Pa, it has good heat-insulating property.
4) Inner constant temperature barrel 3D
The same as the outer constant temperature cylinder 3B.
5) Dewar flask seal 3E
A cylindrical metal block fitted to the dewar 3C.
6) Dewar flask mouth constant temperature controller 3F
The structure of the dewar bottle mouth thermostatic controller 3F is as follows: the base constant-temperature thermistor bridge circuit 321, the base constant-temperature high-gain amplifier 322, the base constant-temperature power amplifier 323 and the base constant-temperature heating wire 324 are sequentially connected, and the base constant-temperature heating wire 324 is wound on the dewar bottle mouth constant-temperature controller 3F; its function is to prevent the change of the environmental temperature of the dewar mouth from affecting the temperature inside the dewar. The temperature control system increases the base for constant temperature, so that the precision of the whole constant temperature unit 3 is improved by more than 20 times, and the precision of the constant temperature unit 3 reaches ten thousandth.
The better the heat preservation performance of the heat preservation layer is, the smaller the required heating power is, and the higher the temperature control precision is. The better the heat conductivity of the heating cylinder, the smaller the thermal resistance, the smaller the temperature gradient of the heating cylinder, and the higher the temperature control precision.
1) Internal constant temperature thermistor bridge circuit 311
The bridge circuit consists of two high-precision thermistors and two precision resistors with precision better than one ten-thousandth.
2) Internal constant temperature high gain amplifier 312
The preamplifier is a general high-gain amplifying circuit, and in order to achieve one-ten-thousandth control precision, the preamplifier needs to adopt a low-drift operational amplifier, and the zero drift of the operational amplifier is less than 1 microvolt; it is also desirable that the open loop gain of the amplifier be greater than 108。
3) Internal constant temperature power amplifier 313
A power operational amplifier BUZ11 is adopted;
4) internal constant temperature heating wire 314
Is a copper enameled wire with the diameter of 0.15 mm.
In order to realize high-precision temperature control, several aspects must be achieved:
1. in the low-drift high-gain temperature control system, the drift of a preamplifier is less than 1 microvolt (mu V), and the loop gain needs to exceed 10 < -8 >.
2. A thermosensitive element with high stability. The utility model discloses tested a large amount of thermal element, only 44008 type thermistor of American production could satisfy the requirement of precision and time constant.
3. The design of a reasonable thermal structure requires that the thermal conductivity of the material is good and the thermal resistance is small in a temperature equalizing system; the heat insulation system requires good heat insulation performance and great heat resistance. In order to reach the temperature control precision of 0.0001 ℃, the utility model discloses three-layer accuse temperature has been made: the inner constant temperature, the outer constant temperature and the base constant temperature (constant temperature of the mouth of the Dewar bottle); a dewar flask is a good thermal insulation device; the problem is that the bottle mouth needs to dissipate heat. The change of the environmental temperature is transmitted to the inside of the output voltage of the high-precision broadband gravimeter through the bottle mouth; to overcome this phenomenon; the utility model adds a constant temperature control device at the mouth of the Dewar flask, so that the temperature of the mouth is kept constant; the measure finally improves the temperature control precision of the output voltage of the high-precision broadband gravimeter by 20 times. The design of the thermal structure is crucial to the accuracy of temperature control; the design of the thermal structure is shown in fig. 1; the elastic system is the most precise part of the output voltage of the high-precision broadband gravimeter. All enclosed in a temperature control system.
4. Pendulum adjustment unit 4
As shown in fig. 7, the swing adjusting unit 4 includes a swing adjusting bracket 41, a swing adjusting motor bracket 42, a swing adjusting motor 43, a swing adjusting motor gear 44, a primary gear 45, a secondary gear 46, a tertiary gear 47, a quaternary gear 48, an output gear 49, and a swing adjusting circuit 410;
the position and connection relation is as follows:
the swing adjusting bracket 41, the swing adjusting motor bracket 42 and the swing adjusting motor 43 are sequentially connected, the swing adjusting bracket 41 supports the swing adjusting motor bracket 42, and the swing adjusting motor bracket 42 supports the swing adjusting motor 43;
the swing adjusting circuit 410, the swing adjusting motor 43, the swing adjusting motor gear 44, the primary gear 45, the secondary gear 46, the tertiary gear 47, the quaternary gear 48 and the output gear 49 are sequentially connected, and the swing adjusting circuit 410 controls the swing adjusting motor 43 until the output gear 49.
The working mechanism is as follows:
the swing adjusting bracket 41 supports a swing adjusting motor bracket 42, the swing adjusting motor bracket 42 supports a swing adjusting motor 43, the swing adjusting motor 43 drives a swing adjusting motor gear 44, and the swing adjusting motor gear 44 drives a primary gear 45, a secondary gear 46, a tertiary gear 47, a quaternary gear 48 and an output gear 49 in series; the rotation direction of the swing motor 43 is controlled by the swing circuit 410.
1) Pendulum adjusting bracket 41
A support machined from copper.
2) Swing motor support 42
A support member machined from a soft magnetic alloy.
3) Pendulum adjusting motor 43
A hollow cup low-speed DC servo motor.
4) Adjustable pendulum motor gear 44
Motor gear with module 0.3.
5) First-stage gear 45
6) Two-stage gear 46
7) Three-stage gear 47
8) Four-stage gear 48
9) Output gear 49
10) Pendulum adjusting circuit 410
Is a simple automatic control circuit.
The functions are as follows: the motor controls the moving piece to move towards the zero position, and the motor automatically stops after the zero position is reached.
The output voltage of the high-precision broadband gravimeter has high precision and resolution, and the measuring range is small. The amplitude of each zeroing is not more than 0.2 mu m; a reduction ratio of 5000 gear systems is necessary.
5. Lock pendulum unit 5
As shown in fig. 7, the lock pendulum unit 5 includes a lock pendulum motor 51, a lock pendulum motor bracket 52, a lock pendulum spring 53, a lock pendulum spring bracket 54, a lock pendulum upper limit 55, a lock pendulum lower limit 56, and a lock pendulum circuit 57;
the position and connection relation is as follows:
the lock pendulum upper limit 55 and the lock pendulum lower limit 56 are respectively connected with the lock pendulum spring 53, so that the lock pendulum spring 53 is locked when contacting the lock pendulum upper limit 55, the motor stops, and the lock pendulum is completed; when the lock pendulum spring 53 contacts the lock pendulum lower limit 56, the lock pendulum spring is loosened, the motor stops, and the pendulum loosening is completed.
The lock swing motor bracket 52 is connected with the lock swing motor 51; the motor bracket 52 fixes the lock swing motor 51.
The lock pendulum spring holder 54 is connected to the lock pendulum spring 53, and the lock pendulum spring holder 54 fixes the lock pendulum spring 53.
The pendulum locking circuit 57 is connected to the pendulum locking spring 53, and the pendulum locking circuit 57 controls the pendulum locking spring 53 to rotate.
The working mechanism is as follows:
the lock pendulum motor bracket 52 supports the lock pendulum motor 51, the lock pendulum spring bracket 54 supports the lock pendulum spring 53, the lock pendulum motor 51 drives the lock pendulum spring 53, the rotation is stopped when the lock pendulum spring 53 reaches the lock pendulum upper limit 55, and the rotation is stopped when the lock pendulum spring 53 reaches the lock pendulum lower limit 56, and the rotation direction of the lock pendulum motor 51 is controlled by the lock pendulum circuit 57.
1) Lock pendulum motor 51
The lock swing motor is a DC servo motor, and is purchased from outsourcing.
2) Lock pendulum motor support 52
A support frame processed from soft magnetic alloy; not only supports the lock swing motor 51 but also shields the magnetic field of the lock swing motor 51.
3) Lock pendulum spring 53
The lock pendulum spring 53 is a leaf spring of constant elastic alloy.
4) Lock pendulum spring bracket 54
A support frame machined from copper;
5) lock pendulum upper limit 55
Is a copper-clad plate.
6) Lock pendulum lower limit 56
Is a copper-clad plate.
7) Pendulum locking circuit 57
The universal switching circuit is used for controlling the motor to rotate forward and loosen and rotate backward to lock and swing.
6. Support unit 6
As shown in fig. 1 and 2, the supporting unit 6 is a mechanical structure, and includes a supporting column, a supporting plate, a supporting seat and a supporting cylinder 65;
the device comprises a supporting capacitive displacement sensor 1, an elastic unit 2, a pendulum adjusting unit 4 and a pendulum locking unit 5.
7. Chassis unit 7
As shown in fig. 2, the chassis unit 7 includes a chassis 71, a leveling lead screw nut 72, a foot pad 73, and a leveling bubble 74;
the position and connection relation is as follows:
the chassis 71 is in an equilateral triangle shape, three top corners are respectively provided with a leveling screw nut 72, the bottom of the leveling screw nut 72 is connected with a foot pad 73, and two leveling blisters 74 which are perpendicular to each other are arranged on the chassis 71.
The working mechanism is as follows:
the chassis 71 supports downward an anchor nut 72, the anchor nut 72 supports an anchor screw 73, the anchor screw 73 is arranged on an anchor pad block 74, and the chassis 71 supports downward a chassis circuit box 75.
Measurement principle of high-precision broadband gravimeter
The utility model discloses it is 16KHz to produce oscillation frequency by the oscillator 121 of the steady amplitude of high accuracy, through the phase inverter 122 of high accuracy, with the range the same, two signals of opposite phase connect respectively to stator 112 and stator 113 down, the signal of telecommunication is responded to on rotor 111, through tertiary amplifier 123 and lock-in amplifier 124, solid tide measures behind passageway 125, earth free oscillation channel 126, high frequency earthquake passageway 127 and low frequency earthquake passageway 128, the output is enlargied to the direct current, the through-put is adopted from the automatic collection and is stored.
1. Spring elongation calculation and spring sensitivity
As is well known, the basic principle of the spring high-precision broadband gravimeter is to balance gravity by using the force of a spring, and the balance equation of the spring is as follows:
mg＝kx
where m is the mass of the pendulum, g is the gravitational acceleration, k is the elastic strength, and x is the spring elongation. Then
The sensitivity of the spring 21 is selected according to the precision required by the high-precision broadband gravimeter and the precision which can be achieved by displacement measurement; according to the experimental result, the accuracy dx of the capacitive displacement sensor 1 is 0.0001 μm, and the accuracy dg of the high-accuracy broadband gravimeter measurement is 1 μ Gal; the extension length of the spring
The sensitivity of the spring is
The measurement accuracy of the high-precision broadband gravimeter is 1 μ gal, so the measurement accuracy of the capacitive displacement sensor 1 must be better than 0.0001 μm.
2. Stiffness, effective turns, original length in spring parameters
Whether the parameter selection of the spring 21 is reasonable or not has great influence on the precision and the stability of the high-precision broadband gravimeter; in order to make the high-precision broadband gravimeter work stably, the stress of the working state of the spring 21 and the allowable stress of the prestress should be selected to be smaller; in this state, the spring 21 is less loaded and therefore less creeps, and a zero-length spring is used to reduce the size of the spring system.
The utility model discloses the spring material is Ni42CrTi, establishes spring wire footpath D ═ 0.45mm, well footpath Dm9.45mm, the shear modulus of the spring steel wire is 6600kg/mm3Number of turns N of coil springc(ii) a Having a stiffness of
The spring material selected by the utility model is a domestic 3J53 elastic steel wire (NiCrTi), and the shear elastic modulus of the material is G6600 kg/mm3The diameter d of the steel wire is 0.45mm, and the pitch diameter N of the spiral springcWhen the swing weight m is 30g, the number of turns of the spring is 128 turns.
The original length of the spring is then:
L＝Ncd
in order to ensure the stability of the spring, the prestress of the working state of the spring and the allowable stress tau of the prestress must be checked through calculation0Whether the design requirements of the spring are met.
In the formula kcIs coefficient of curvature
Wherein c is the winding ratio of the spring, and c is DmAnd d, substituting given values to obtain: tau is0＝10(kg/mm2)。
The allowable stress of the working state is smaller than 1/3-1/4 of the tensile strength, namely tau, according to the requirement of the stability of the spring0Theta (1/3-1/4). Due to the tensile strength limit theta of the spring wire used0＝120kg/mm2Therefore, the allowable stress of the spring is only 1/12 with tensile strength. Allowable stress tau of prestress according to design requirement of spring0Should be less than 1/10 to 1/20 of tensile strength, i.e.
I.e. tau0Less than or equal to (6-12) kg, so the allowable stress of the prestress can also meet the stability requirement of the spring.
3. Output voltage of high-precision broadband gravimeter
The mass m of the known moving piece 111, the increment Δ g of the gravity acceleration, the rigidity k of the spring, and the increment Δ x of the spring extension; the hooke theorem is:
mΔg＝kΔx
the distance between the moving plate 111 and the upper fixed plate 112 is d1(ii) a The distance from the moving plate 111 to the lower stator plate 113 is d2(ii) a The distance from the upper stator 112 to the lower stator 113 is d1+d22 d. Before calibration, automatic zero setting is performed, and the movable plate 111 is adjusted to be near the center of the upper fixed plate 112 and the lower fixed plate 113.
d1+d2＝2d
d2-d1＝2Δx
The voltage of the upper stator 112 is
The lower stator 113 voltage is-
The instantaneous value of the output voltage of the rotor 111 is
Amplification factor wire A of three-stage amplifierampsThe amplification factor of the lock-in amplifier is HLPAccording to the formula of phase-locked amplification, the input of the phase-locked amplification is alternating current, and the output of the phase-locked amplification is direct current; the output voltage of the high-precision wide-band gravimeter is
The formula is that the change of the gravity value causes the change of the output voltage of the high-precision broadband gravimeter.
Main technical indexes of high-precision wide-band gravimeter
Measurement range: greater than 10000 milli-gal (mgal) (applicable to the world)
Resolution: 0.1 micro-Gal (mu gal)
Direct measuring range: 2000 micro-gamma (mu gal)
Precision of the capacitive sensor: is better than 0.0001 micron (mum)
Temperature control precision: variation per quarter is less than 0.0001 DEG C
Rated power consumption: 18W
External voltage: 220V +/-10%/50 HZ
Observation result of high-precision broadband gravimeter
The high-precision broadband gravimeter completes the research work at the end of 2018, and is installed in a cave of the gravity center of science and technology university in Huazhong for observation after the laboratory is stabilized for 3 months. Through half a year observation, the precision, stability and function are obviously improved, and no fault occurs. Recent observations are as follows:
FIG. 10 is a solid tide curve, which shows that the solid tide curve is smooth, low in noise and high in resolution (the resolution can reach 0.1 μ gal through testing).
FIG. 11 is a comparison of solid tide curves and high frequency channel curves, from which it can be seen that the seismic information recorded by the high frequency channel is much richer than that recorded by the solid tide channels.
Fig. 12 is a seismic record diagram of high-frequency channels from 2019, 6, 18 and 2019, 6, 26, and a large amount of seismic information is recorded on the seismic record diagram, because there are few earthquakes in north of Hu, Wuhan, and the recorded earthquakes are all far earthquakes, and because the band-pass magnification of the high-precision broadband gravimeter can reach 60 to 100 ten thousand times, and the magnification is higher than that of the seismograph, the seismograph can record earthquakes smaller than that of the seismograph.
Fig. 13 is a seismic recording diagram of low-frequency channels from 18 days 6 and 2019 to 26 days 6 and 2019, and the low-frequency channels have large filter constants and small ground noise influence, so that the seismic recording method is suitable for recording the long-range earthquakes.
Claims (4)
1. The utility model provides a high accuracy broadband gravimeter which characterized in that:
the device comprises a capacitive displacement sensor (1), an elastic unit (2), a constant temperature unit (3), a pendulum adjusting unit (4), a pendulum locking unit (5), a supporting unit (6) and a chassis unit (7);
the position and connection relation is as follows:
from bottom to top, the chassis unit (7) is connected with the constant temperature unit (3), a support unit (6) is arranged in the constant temperature unit (3), and the support unit (6) is respectively provided with a capacitive displacement sensor (1), an elastic unit (2), a pendulum adjusting unit (4) and a pendulum locking unit (5);
the swing adjusting unit (4) and the swing locking unit (5) are respectively connected with the elastic unit (2); the elastic unit (2) is connected with the capacitive displacement sensor (1);
the capacitance displacement sensor (1) is used for measuring the vertical change of the position of a moving plate (111) in the elastic unit (2);
the elastic unit (2) is a precise spring (21);
the constant temperature unit (3) is a high-precision temperature control device.
2. A high precision broadband gravimeter according to claim 1, characterized in that:
the capacitance type displacement sensor (1) comprises a moving plate (111), an upper fixed plate (112), a lower fixed plate (113), an oscillator (121), an inverter (122), a three-stage amplifier (123), a phase-locked amplifier (124), a solid tide measuring channel (125), an earth free oscillation channel (126), a high-frequency seismic channel (127) and a low-frequency seismic channel (128):
the connection relation is as follows:
an upper fixed sheet (112) and a lower fixed sheet (113) are arranged on the supporting unit (6), and a movable sheet (111) is arranged between the upper fixed sheet (112) and the lower fixed sheet (113);
the oscillator (121) is respectively connected with an upper stator (112), an inverter (122) and a phase-locked amplifier (124), the inverter (122) is connected with a lower stator (113), the rotor (111), the three-stage amplifier (123) and the phase-locked amplifier (124) are sequentially connected, and the output end of the phase-locked amplifier (124) is connected with 4 channels: a solid tide measuring channel (125), an earth free oscillation channel (126), a high frequency seismic channel (127) and a low frequency seismic channel (128);
the oscillator (121) comprises an oscillating circuit (121A), a frequency dividing circuit (121B) and a shaping circuit (121C) which are connected in sequence;
the oscillation circuit (121A) is composed of a 1 st resistor (R1), a 1 st capacitor (C1) and a 1 st digital chip (U1A);
one ends of a 1 st resistor (R1) and a 1 st capacitor (C1) are connected to the input end of a 1 st digital chip (U1A), and the other ends of the 1 st resistor (R1) and the 1 st capacitor (C1) are respectively connected with two output ends of the 1 st digital chip (U1A); the 1 st digital chip (U1A) is a four-way true complement reverse buffer 4041;
the frequency division circuit (121B) is composed of 2 nd, 3 rd, 4 th and 5 th resistors (R2, R3, R4 and R5), 2 nd, 3 th and 4 th capacitors (C2, C3 and C4), 1 st, 2 nd and 3 th diodes (D1, D2 and D3) and 2 nd and 3 rd digital chips (U1B and U1C);
the 2 nd resistor (R2) is connected with the 3 rd capacitor (C3), and the 2 nd resistor (R2) is connected with the 3 rd resistor (R3);
one end of the 3 rd resistor (R3) is connected with the output end 2 of the 2 nd digital chip (U1B), and the other end is connected with the input end 6 of the 3 rd digital chip (U1C);
one end of the 4 th resistor (R4) is connected with the output end 3 end of the 2 nd digital chip (U1B); the other end is connected with the input end 3 end of a 3 rd digital chip (U1C);
one end of the 2 nd diode (D2) is connected with the 3 rd end of the 2 nd digital chip (U1B), and the other end is connected with one end of the 2 nd resistor (R2);
one end of the 2 nd diode (D2) is connected with the 6 th end of the 3 rd digital chip (U1C), and the other end is connected with one end of the 5 th resistor (R5);
the 3 rd capacitor (C3) is connected with one end of the 2 nd resistor (R2), and the other end of the 2 nd capacitor is connected with the 1 st diode (D1);
the 4 th capacitor (C4) is connected with one end of the 5 th resistor (R5), and the other end of the 4 th capacitor is connected with the 1 st diode (D1);
the shaping circuit (121C) is composed of a 4 th digital chip (U1D), and two square wave signals with equal amplitude and opposite phases are output to the phase-locked amplifier (124).
3. A high precision broadband gravimeter according to claim 1, characterized in that:
the elastic unit (2) comprises a moving plate (111), a spring (21), a connecting piece (22), an upper flexible wire (23), a spring upper end fixing piece (24), a spring lower end fixing piece (25), a lower flexible wire (26) and a leveling plate (27):
the connection relation is as follows: from top to bottom, connecting piece (22), upper flexible wire (23), spring upper end mounting (24), spring (21), spring lower extreme mounting (25), lower flexible wire (26), rotor (111) and leveling board 27 connect gradually.
4. A high precision broadband gravimeter according to claim 1, characterized in that:
the constant temperature unit (3) comprises an outer constant temperature insulating layer (3A), an outer constant temperature cylinder (3B), a Dewar flask (3C), an inner constant temperature cylinder (3D), a Dewar flask seal (3E) and a Dewar flask mouth constant temperature controller (3F);
the constant-temperature power amplifier further comprises an inner constant-temperature thermistor bridge circuit (311), an inner constant-temperature high-gain amplifier (312), an inner constant-temperature power amplifier (313), an inner constant-temperature heating wire (314), a base constant-temperature thermistor bridge circuit (321), a base constant-temperature high-gain amplifier (322), a base constant-temperature power amplifier (323), a base constant-temperature heating wire (324), an outer constant-temperature thermistor bridge circuit (331), an outer constant-temperature high-gain amplifier (332), an outer constant-temperature power amplifier (333) and an outer constant-temperature heating wire (334);
the position and connection relation is as follows:
an outer constant-temperature insulating layer (3A), an outer constant-temperature cylinder (3B), a Dewar flask (3C) and a Dewar flask seal (3E) are sequentially arranged from outside to inside, and an inner constant-temperature cylinder (3D) and a Dewar flask mouth constant-temperature controller (3F) are arranged in the Dewar flask (3C) and the Dewar flask seal (3E);
the internal constant temperature thermistor bridge circuit (311), the internal constant temperature high-gain amplifier (312), the internal constant temperature power amplifier (313) and the internal constant temperature heating wire (314) are sequentially connected, and the internal constant temperature heating wire (314) is wound on the internal constant temperature barrel (3D);
the base constant-temperature thermistor bridge circuit (321), the base constant-temperature high-gain amplifier (322), the base constant-temperature power amplifier (323) and the base constant-temperature heating wire (324) are sequentially connected, and the base constant-temperature heating wire (324) is wound on a constant-temperature controller (3F) at the mouth of the Dewar flask;
an external constant temperature thermistor bridge circuit (331), an external constant temperature high gain amplifier (332), an external constant temperature power amplifier (333)
And the outer constant temperature heating wire (334) is sequentially connected, and the outer constant temperature heating wire (334) is wound on the outer constant temperature barrel (3B).
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| CN110488369A (en) * | 2019-09-04 | 2019-11-22 | 武汉光演科学仪器有限公司 | High precision broad frequency gravimeter |
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