A gravimeter range calibration device

Abstract

The present invention relates to a gravimeter range calibration device, comprising a counterweight ball protective cover, a counterweight ball, a support rod, a compression spring, a limiting cover, a soft magnetic metal block, and an electromagnet. When the electromagnet is energized, the lower end of the soft magnetic metal block engages with the upper end of the electromagnet, and the support rod moves downward to a position where its top rod section is located below the core detection module of the gravimeter. The counterweight ball falls to a position where it contacts the upper edge of the central through hole of the core detection module, placing the gravimeter in a range calibration state. When the electromagnet is de-energized, the compression spring acts to disengage the lower end of the soft magnetic metal block from the upper end of the electromagnet, and the support rod moves upward to a position where the upper end of its top rod section extends from the upper end of the central through hole of the core detection module. The counterweight ball is supported in an arc-shaped groove of the support rod and limited in a cylinder of the counterweight ball protective cover, placing the gravimeter in a normal working state. This device uses the method of adding counterweights to equivalently generate relative gravity changes, solving the problem of difficulty in generating 8000mGal gravity changes.

Description

Technical Field

[0001] The invention belongs to the field of gravity acceleration measuring instruments, and in particular relates to a gravimeter range calibration and testing structure. Background Art

[0002] Gravitational acceleration, g, is a fundamental geophysical constant, but it varies with factors such as topography, geology, altitude, and the position of the moon. Accurately measuring gravitational acceleration is crucial in fields such as Earth science, resource exploration, and even national defense. Gravimeters are specialized instruments used to measure gravitational acceleration, and are classified as either absolute or relative. Absolute gravimeters directly measure the absolute value of gravitational acceleration, but they are large, require long measurements, and require a high-quality test environment. They can typically only be used at locations with well-prepared foundations and a favorable test environment. Relative gravimeters measure the relative change in gravitational acceleration between two locations. Due to their small size, light weight, and short measurement times, they require a relatively low-quality test environment and can achieve high-precision gravity measurements in a variety of complex terrains and environments. Using a relative gravimeter in conjunction with an absolute gravimeter significantly expands the scope of gravitational acceleration measurement and is widely used in various gravitational acceleration measurement applications.

[0003] Relative gravimeters measure the relative change in gravitational acceleration. The relative change in gravitational acceleration worldwide is less than 7000 mGal (1 mGal ≈ 1×10 -6 g) The range of mainstream relative gravimeters, both internationally and domestically, is approximately 8000 mGal. Creating a relative gravity variation of approximately 8000 mGal to measure the instrument's range is a challenge during the manufacture, calibration, and testing of gravimeters. Because relative gravimeters must operate in a stationary, horizontal state, the commonly used methods of generating acceleration changes through movement and tilt are inapplicable. The relative gravity variation generated by the elevation differences of mountainous terrain or the Earth's latitude is insufficient to cover the full 8000 mGal range of a relative gravimeter, and the time and labor costs are prohibitive. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a gravimeter range calibration device that is simple to operate and reliable in operation.

[0005] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0006] A gravimeter range calibration device, characterized by comprising a weight ball protection cover, a weight ball, a support rod, a compression spring, a limit sleeve, a soft magnetic metal block, and an electromagnet;

[0007] The weighted ball protective cover is arranged above the core detection module of the gravimeter. The upper part of the protective cover is fixedly connected to the main structure of the gravimeter, and the lower part is a cylindrical structure. The inner diameter of the cylinder is larger than the outer diameter of the configuration ball, which is used to horizontally limit the weighted ball.

[0008] The balancing ball is arranged between the upper part of the core detection module of the gravimeter and the lower part of the balancing ball protective cover; the balancing ball is made of low-density material;

[0009] The support rod is arranged directly below the core detection module of the gravimeter in a manner that allows it to move up and down, and is composed of a top rod section, a retaining spring section, an intermediate rod section, and a bottom rod section; the top rod section is aligned with the central through hole provided on the core detection module, and the diameter of the top rod section is smaller than the diameter of the central through hole of the core detection module; an arc-shaped groove is provided at the top of the top rod section that matches the outer diameter of the counterweight ball; the diameter of the retaining spring section is larger than the diameter of the top rod section; the bottom rod section is an externally threaded rod section;

[0010] The limiting sleeve is sleeved on the outside of the middle rod section of the support rod in a clearance fit manner; the outer side of the middle portion of the limiting sleeve is fixedly connected to the main structure of the gravimeter;

[0011] The compression spring sleeve is arranged outside the matching portion of the support rod and the limiting sleeve, the upper end of the compression spring contacts the lower end of the retaining spring section of the support rod, and the lower end of the compression spring contacts the middle upper end of the limiting sleeve;

[0012] The soft magnetic metal block is arranged directly below the limiting sleeve, and a central threaded hole is provided on the soft magnetic metal block, which is threadedly connected to the lower rod section of the support rod;

[0013] The electromagnet is arranged directly below the soft magnetic metal block and is fixedly connected to the main structure of the gravimeter. The electromagnet adopts a conductive winding containing an iron core;

[0014] When the electromagnet is energized, the lower end of the soft magnetic metal block is attracted and connected to the upper end of the electromagnet, and the support rod moves downward to a position where its top rod section is located below the core detection module of the gravimeter; the counterweight ball falls to a position where it contacts the upper edge of the central through hole of the core detection module of the gravimeter, placing the gravimeter in a range calibration state;

[0015] When the electromagnet is powered off, under the action of the compression spring, the lower end of the soft magnetic metal block is out of contact with the upper end of the electromagnet, and the support rod moves upward to a position where the upper end of its top rod section extends from the upper end of the central through hole of the core detection module of the gravimeter. The counterweight ball is supported in the arc-shaped groove at the top of the support rod and is horizontally limited in the cylinder of the counterweight ball protective cover, so that the gravimeter is in normal working condition.

[0016] Furthermore: the counterweight ball is a hollow sphere made of thermoplastic plastic materials such as polypropylene (PP).

[0017] The present invention has the following advantages and positive effects:

[0018] 1. The present invention adopts the method of adding counterweight to generate equivalent relative gravity change, which solves the problem of difficulty in generating 8000mGal gravity change.

[0019] 2. The present invention adopts electromagnet drive, which is simple to operate and avoids the complicated structure caused by external drive and the hidden danger of air leakage in the core detection module of the gravimeter.

[0020] 3. The present invention uses electromagnetic force to drive the soft magnetic metal block instead of using electromagnetic force to directly adsorb the counterweight ball. The advantage is that if the electromagnetic force directly adsorbs the counterweight ball, the counterweight ball must be made of metal material, which will be difficult to process and use due to its high density. However, when the electromagnetic force adsorbs the soft magnetic metal block, there is no requirement for the material of the counterweight ball, and a low-density non-metallic material can be selected.

[0021] 4. The present invention uses an electromagnet and a compression spring in combination to prevent the electromagnet from being powered on for a long time and affecting the gravimeter test. It can also automatically lift the counterweight ball when the power is off, thus preventing the core detection module from being damaged by an accidental power outage of the gravimeter. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the gravimeter range calibration device of the present invention in a non-calibrated state;

[0023] Figure 2 It is a structural schematic diagram of the gravimeter range calibration device of the present invention in the calibration state. DETAILED DESCRIPTION

[0024] The structure of the present invention will be further described below with reference to the accompanying drawings and through examples. It should be noted that the present examples are descriptive rather than restrictive.

[0025] A gravimeter range calibration device, see Figure 1-2 The invention is to increase or decrease the mass of the core detection module of the gravimeter to achieve the purpose of generating equivalent gravity changes. The increase or decrease of mass is achieved by using a weighted ball. The principle analysis of the calibration is as follows:

[0026] Assume that the mass of the counterweight ball is Δm and the length of the lever arm is L b , the local gravity acceleration is g, then after placing the weight ball on the core detection module of the gravimeter, the additional torque ΔM=Δm·g·L b If the acceleration due to gravity changes by Δg, the same torque ΔM = m·Δg·L can be generated. m , where m is the quality of the core detection module, L m It is the lever arm of the core detection module.

[0027] Since the above two methods can produce the same effect, Δm·g·L b =m·Δg·L m , then the change in gravitational acceleration satisfies the following formula:

[0028]

[0029] If the counterweight ball lever arm is equal to the core detection module lever arm, it can be simplified to:

[0030]

[0031] From the above two equations, we can know that by selecting the appropriate mass of the counterweight ball, we can produce an equivalent effect of 8000mGal relative gravity change, which can be used to measure the range of the instrument. For example, if m = 20 grams, L b =L m , then when Δm = 0.16 grams and placed on the core detection module, this is equivalent to the effect of a relative gravity change of 8000 mGal on the core detection module. As long as the gravimeter output can reflect this change, it means that the gravimeter's range has reached 8000 mGal.

[0032] The balancing weight is a standard spherical shape, made of a low-density material to increase its volume for ease of processing and use. During normal operation, the balancing weight is held up by the support rod's ejector pins, maintaining contact with the core detection module and preventing any interference with gravimeter testing. During range calibration, the balancing weight detaches from the support rod and falls to a preset position within the core detection module, generating an equivalent relative gravity change of 8,000 mGal.

[0033] A gravimeter range calibration device includes a weight ball protection cover 1, a weight ball 2, a support rod 4, a compression spring 5, a limit sleeve 6, a soft magnetic metal block 7, and an electromagnet 8.

[0034] The balancing weight ball is a standard spherical shape. To facilitate processing and use, a low-density material is selected to increase the volume of the ball. The balancing weight ball is a hollow sphere made of thermoplastic plastic materials such as polypropylene (PP) (for example, a sphere with a diameter of 6mm does not weigh more than 0.1 grams). The quality of the balancing weight ball can be controlled by processing hollow polypropylene (PP) balls of different diameters to meet the range calibration requirements. When the gravimeter is operating normally, the balancing weight ball is held up by the top of the support rod and has no contact with the core detection module, which does not affect the gravimeter test. During range calibration, the balancing weight ball detaches from the support rod and falls to the preset position of the core detection module, generating an equivalent relative gravity change of 8000mGal.

[0035] The outer side of the upper part of the counterweight ball protective cover is fixedly connected to the main structure of the gravimeter, and the inner diameter of the lower end cylinder is slightly larger than the outer diameter of the counterweight ball, which is used to limit the horizontal position of the counterweight ball to prevent it from falling due to handling, transportation or accidental tipping, losing the range calibration function or damaging the core detection module.

[0036] The top of the support rod has an arc-shaped groove that matches the outer diameter of the counterweight ball, which can pass through the through hole of the core detection module to lift the counterweight ball and separate the counterweight ball from the core detection module; the middle part of the support rod is a smooth cylinder, which can only move up and down under the constraint of the limit sleeve; a screw connected to the soft magnetic metal block is left at the bottom of the support rod.

[0037] A through hole is opened on the core detection module 3 at a position corresponding to the top of the support rod, for the support rod to pass through and support the counterweight ball; the diameter of the through hole is smaller than the outer diameter of the counterweight ball, which can not only ensure that the counterweight ball cannot pass through the core detection module and fall, but also limit the position where the counterweight ball is placed on the core detection module, ensuring the consistency of the counterweight ball force arm when calibrating each time.

[0038] The outer side of the middle part of the limit sleeve is fixedly connected to the main structure of the gravimeter, constraining the support rod to only move up and down along the limit sleeve with a limited stroke, and will not fall out or hit the core detection module; a compression spring is installed between the support rod ejector pin and the limit sleeve to provide a continuous upward force for the support rod.

[0039] The soft magnetic metal block is threadedly connected to the bottom of the support rod, and can drive the support rod to move downward under the action of the electromagnet. After the electromagnet is turned off, it moves upward with the support rod under the force of the compression spring. The material used for the soft magnetic metal block is a soft magnetic alloy, which is easily magnetized by the electromagnet, and its own magnetic induction emphasis basically disappears after the electromagnetic magnetic field disappears.

[0040] The electromagnet is a conductive winding containing an iron core. When energized, it generates an electromagnetic force acting on the soft magnetic metal block. The electromagnet is mounted at a suitable position below the soft magnetic metal block and is fixed to the main structure of the gravimeter. Its power is designed so that the electromagnetic force it generates on the soft magnetic metal block is slightly greater than the elastic force of the compression spring.

[0041] The working principle of this gravimeter range calibration device:

[0042] When the gravimeter range needs to be calibrated, the electromagnet is energized, and the electromagnet generates an electromagnetic force acting on the soft magnetic metal block, causing the soft magnetic metal block and the support rod threadedly connected to it to move downward along the constraint direction of the limit sleeve. At this time, the compression spring is further compressed until the ejector pin on the upper part of the support rod contacts the top of the limit sleeve; due to the downward movement of the support rod, the counterweight ball falls into the preset through hole of the core detection module under the action of gravity and separates from the support rod; the core detection module with the counterweight ball placed is equivalent to generating an 8000mGal gravitational acceleration change, and the gravimeter output subsequently generates an 8000mGal output change, which means that the gravimeter range is not less than 8000mGal, and the range calibration is completed.

[0043] When the range calibration is completed, the electromagnet is de-energized, the electromagnetic force disappears, and the soft magnetic metal block and the support rod move upward along the constraint direction of the limit sleeve under the action of the restoring force of the compression spring until the soft magnetic metal block contacts the bottom of the limit sleeve; during the upward movement of the support rod, the groove on the top of the support rod lifts the counterweight ball to separate it from the core detection module, and the equivalent 8000mGal relative gravity change attached to the core detection module disappears, and the gravimeter returns to normal testing state.

[0044] Regardless of whether the range calibration is stopped manually or the gravimeter is accidentally powered off, when the electromagnet is no longer energized, the support rod automatically moves upward to lift the counterweight ball, avoiding damage to the core detection components and protecting the gravimeter.

[0045] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will understand that various replacements, changes and modifications are possible without departing from the spirit of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A gravimeter range calibration device, characterized by: Including a counterweight ball protective cover, a counterweight ball, a support rod, a compression spring, a limit sleeve, a soft magnetic metal block, and an electromagnet; The weighted ball protective cover is arranged above the core detection module of the gravimeter. The upper part of the protective cover is fixedly connected to the main structure of the gravimeter, and the lower part is a cylindrical structure. The inner diameter of the cylinder is larger than the outer diameter of the configuration ball, which is used to horizontally limit the weighted ball. The balancing ball is arranged between the upper part of the core detection module of the gravimeter and the lower part of the balancing ball protective cover; the balancing ball is made of low-density material; The support rod is arranged directly below the core detection module of the gravimeter in a manner that allows it to move up and down, and is composed of a top rod section, a retaining spring section, an intermediate rod section, and a bottom rod section; the top rod section is aligned with the central through hole provided on the core detection module, and the diameter of the top rod section is smaller than the diameter of the central through hole of the core detection module; an arc-shaped groove is provided at the top of the top rod section, which matches the outer diameter of the counterweight ball; the diameter of the retaining spring section is larger than the diameter of the top rod section; and the bottom rod section is an externally threaded rod section; The limiting sleeve is sleeved on the outside of the middle rod section of the support rod in a clearance fit manner; the outer side of the middle portion of the limiting sleeve is fixedly connected to the main structure of the gravimeter; The compression spring sleeve is arranged outside the matching portion of the support rod and the limiting sleeve, the upper end of the compression spring contacts the lower end of the retaining spring section of the support rod, and the lower end of the compression spring contacts the middle upper end of the limiting sleeve; The soft magnetic metal block is arranged directly below the limiting sleeve, and a central threaded hole is provided on the soft magnetic metal block, which is threadedly connected to the lower rod section of the support rod; The electromagnet is arranged directly below the soft magnetic metal block and is fixedly connected to the main structure of the gravimeter. The electromagnet adopts a conductive winding containing an iron core; When the electromagnet is energized, the lower end of the soft magnetic metal block is attracted and connected to the upper end of the electromagnet, and the support rod moves downward to a position where its top rod section is located below the core detection module of the gravimeter; the counterweight ball falls to a position where it contacts the upper edge of the central through hole of the core detection module of the gravimeter, placing the gravimeter in a range calibration state; When the electromagnet is powered off, under the action of the compression spring, the lower end of the soft magnetic metal block is out of contact with the upper end of the electromagnet, and the support rod moves upward to a position where the upper end of its top rod section extends from the upper end of the central through hole of the core detection module of the gravimeter. The counterweight ball is supported in the arc-shaped groove at the top of the support rod and is horizontally limited in the cylinder of the counterweight ball protective cover, so that the gravimeter is in normal working condition.

2. The gravimeter range calibration device according to claim 1, characterized in that: The counterweight ball is a hollow sphere made of polypropylene (PP) thermoplastic plastic material.

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