Single electromagnetic force sensor for electronic balance

Abstract

The utility model provides a monomer electromagnetic force sensor for an electronic balance, which relates to the technical field of electronic balances, and comprises a weighing monomer with an integrated structure, the weighing monomer comprises a weighing wall, a micro electromagnetic force balancing unit, a permanent magnet cylinder body and a weighing machine body, and further comprises a composite shielding layer arranged on the periphery of the permanent magnet cylinder body, a thermistor is further installed in the weighing single body, the thermistor is connected with a measuring circuit of the sensor, and the composite shielding layer is composed of a copper outer layer and a permalloy inner layer. According to the utility model, the thermistor is arranged, and the resistance value of the thermistor is obviously changed along with the temperature change, so that the thermistor is reasonably connected with the measuring circuit of the sensor, and the output change of the sensor caused by the temperature change is counteracted by the resistance value change; the temperature compensation mechanism can effectively improve the measurement precision and stability of the sensor in different temperature environments.

Description

TECHNICAL FIELD

[0001] The utility model relates to electronic balance technical field especially point to a kind of single electromagnetic force sensor for electronic balance. BACKGROUND

[0002] As the core instrument in modern precision measurement field, the single electromagnetic force sensor is the heart of this precision weighing instrument. The core component converts the physical quantity of mass into quantifiable current or voltage signal by constructing dynamic balance system of electromagnetic force and the gravity of measured object. When the measured object is placed on the scale pan, the coil in the sensor produces displacement in the constant magnetic field, triggering the feedback circuit to generate reverse electromagnetic force rapidly, until the object gravity is completely offset. At this time, the electrical signal output by the circuit is converted into digital form after analog-digital conversion, and the measurement result accurate to one ten-thousandth of a gram or even higher order is presented in real time.

[0003] In the patent with application number 202420388114.7, a micro electromagnetic force single weighing sensor is disclosed. The weighing single is designed as an integrated structure, which reduces the number of components, the difficulty of processing, and the assembly error between components, improves production efficiency, and reduces production cost. On the other hand, the overall structure is uniform in material, and the thermal expansion and contraction effect of the overall structure is consistent under the influence of temperature changes, avoiding inaccurate weighing caused by assembly error, increasing the stability and reliability of the overall structure, and improving the measurement accuracy and reliability. However, the electromagnetic force generated by the sensor lacks effective shielding protection structure, such as signal radiation of nearby wireless communication equipment, which can break the electromagnetic balance inside the sensor. This interference is particularly evident when the electronic balance is used for micro weighing. Even a small electromagnetic disturbance can cause the output electrical signal of the sensor to deviate, resulting in an error in the weighing result that cannot be ignored, affecting the accuracy and reliability of the measurement. In addition, the influence of temperature changes on measurement accuracy cannot be ignored. When the single electromagnetic force sensor works in different temperature environments, the change in temperature will also affect the magnetic permeability of the magnetic material, causing the electromagnetic force generated by the sensor to fluctuate. For example, when the temperature rises, the magnetic properties of the magnetic material may decrease, causing the electromagnetic force to decrease. When the temperature decreases, the rigidity of the material may increase, affecting the dynamic response characteristics of the sensor, making the measurement results under different temperature conditions lack consistency. Therefore, a single electromagnetic force sensor for electronic balance is proposed. UTILITY MODEL CONTENTS

[0004] To solve the above problems of the prior art, the utility model provides a single electromagnetic force sensor for electronic balance.

[0005] The utility model discloses a technical scheme is as follows: A kind of single electromagnetic force sensor for electronic balance, including integrated structure's weighing single body, the weighing single body includes weighing wall, micro electromagnetic force balance unit, permanent magnetic cylinder and weighing machine body, still including composite shielding layer, the composite shielding layer is located at the periphery of permanent magnetic cylinder, and composite shielding layer and permanent magnetic cylinder are connected with insulating connecting piece, and the inside of the weighing single body is also installed with thermistor, the thermistor is connected with the measurement circuit of the sensor.

[0006] Preferably, the composite shielding layer is composed of a copper outer layer and a permalloy inner layer, and an insulating layer is arranged between the copper outer layer and the permalloy inner layer.

[0007] Preferably, the purity of copper in the copper outer layer is greater than or equal to 99.9%, and a 0.01-0.03 mm nickel layer is arranged on the surface of the copper outer layer.

[0008] Preferably, the insulating layer is a polytetrafluoroethylene film layer, and the copper outer layer and the insulating layer and the insulating layer and the permalloy inner layer are all bonded by non-conductive adhesive, and the thickness of the adhesive layer is not more than 0.05 mm.

[0009] Preferably, the thermistor is a negative temperature coefficient thermistor.

[0010] Preferably, a force transmission spring is arranged in the inside of the weighing single body, and a reinforcing rod is further arranged on both sides of the inside of the weighing single body.

[0011] Compared with the prior art, the utility model has the following beneficial effects:

[0012] 1. The utility model discloses a thermistor, which can effectively improve the measurement accuracy and stability of the sensor in different temperature environments.

[0013] 2. The utility model discloses a composite shielding layer composed of a copper outer layer, an insulating layer and a permalloy inner layer, which can effectively shield external electromagnetic interference and provide a stable electromagnetic environment for the permanent magnetic cylinder. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical scheme in the embodiments of the utility model or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the utility model, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0015] Fig. 1 Figure 1 is a structural schematic diagram of the utility model;

[0016] Fig. 2 Figure 2 is a structural schematic diagram of the utility model;

[0017] Fig. 3 Figure 3 is a structural schematic diagram of the composite shielding layer of the utility model.

[0018] In the figure: 1, weighing wall; 2, micro electromagnetic force balance unit; 3, permanent magnet cylinder body; 4, composite shielding layer; 41, copper outer layer; 42, insulating layer; 43, permalloy inner layer; 5, insulating connecting piece; 6, weighing machine body; 7, force transmission spring piece; 8, reinforcing rod; 9, thermistor. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the utility model.

[0020] The utility model provides a kind of Figs. 1-3The single electromagnetic force sensor for the electronic balance includes a weighing single body which is integrally cut from a whole piece of high-purity aluminum alloy on a high-precision machining center. The integrated machining process greatly reduces the assembly errors that may exist in the traditional assembly method, effectively improves the overall structural stability and precision of the sensor, and the consistency of the material of the weighing single body makes the sensor less affected by temperature changes and more stable. The weighing single body includes a weighing wall 1, a micro electromagnetic force balancing unit 2, a permanent magnet cylinder 3, and a weighing machine body 6. The permanent magnet cylinder 3 includes a permanent magnet and a cylinder body sleeved outside the permanent magnet. The permanent magnet and the cylinder body are coaxially arranged. The connecting end of the micro electromagnetic force balancing unit 2 is connected to the weighing wall 1, and the balancing end of the micro electromagnetic force balancing unit 2 extends above the permanent magnet cylinder 3. The micro electromagnetic force balancing unit 2 is connected to the weighing machine body 6 at the balance fulcrum. The weighing wall 1, the micro electromagnetic force balancing unit 2, and the permanent magnet cylinder 3 form a lever structure. The structure and principle are disclosed in the patent with application number 202420388114.7, so they are not described here. The inside of the weighing single body is provided with a force transmission spring 7 made of elastic material, which has excellent elastic properties and fatigue resistance and can accurately transmit the force signal during weighing to ensure the accuracy of the measurement. The inside of the weighing single body is also provided with a reinforcing rod 8, which further enhances the structural strength of the weighing single body, making it stable even under heavy weighing loads and less likely to deform, providing reliable protection for the long-term stable operation of the sensor. It also includes a composite shielding layer 4, which is arranged around the permanent magnet cylinder 3. An insulating connecting piece 5 is connected between the composite shielding layer 4 and the permanent magnet cylinder 3. The insulating connecting piece 5 is made of a material with excellent insulating properties, which can ensure the insulation between the composite shielding layer 4 and the permanent magnet cylinder 3 and prevent abnormal situations such as electric leakage. It also plays a supporting and fixing role, allowing the composite shielding layer 4 to be stably arranged around the permanent magnet cylinder 3. A thermistor 9 is also installed inside the weighing single body. The thermistor 9 is connected to the measurement circuit of the sensor. The thermistor 9 is an NTC (negative temperature coefficient) thermistor, whose resistance value changes significantly with temperature. By reasonably connecting the thermistor 9 to the measurement circuit of the sensor and using the resistance value change to offset the sensor output change caused by temperature changes, the measurement accuracy and stability of the sensor in different temperature environments can be improved, and the sensor can adapt to more complex working environments.

[0021] Referring to Fig. 3As shown, the composite shielding layer 4 is composed of a copper outer layer 41 and a permalloy inner layer 43, and an insulating layer 42 is arranged between the copper outer layer 41 and the permalloy inner layer 43, and the permalloy is an alloy mainly composed of nickel and iron, and has very high magnetic permeability and low coercivity, and this characteristic can effectively shield external electromagnetic interference and provide a stable electromagnetic environment for the permanent magnet cylinder body 3.

[0022] The purity of copper in the copper outer layer 41 is greater than or equal to 99.9%, and a 0.01-0.03mm nickel layer is arranged on the surface of the copper outer layer 41, the high-purity copper has good electrical conductivity and can effectively shield high-frequency electromagnetic interference, and the nickel layer on the surface of the copper outer layer 41 can be covered with a nanocrystalline nickel layer by electroplating or chemical plating, and the nickel layer can form a dense passivation film, which can significantly improve the oxidation resistance of the copper outer layer 41 and prolong the service life of the composite shielding layer 4, and also helps to maintain good shielding performance.

[0023] The insulating layer 42 is a polytetrafluoroethylene film layer, and the polytetrafluoroethylene film layer is selected to be a directional stretching PTFE film, which has a dielectric constant ε=2.1 and a loss tangent tan δ=0.0001 (1GHz test value), and the dielectric loss is further reduced compared with an undirectional film (tan δ=0.0002), and this characteristic enables the insulating layer 42 to play a good insulating role between the copper outer layer 41 and the permalloy inner layer 43, avoids the occurrence of conduction between the two, and also reduces the loss of electromagnetic energy between the layers and improves the overall performance of the composite shielding layer 4, and the copper outer layer 41 and the insulating layer 42 and the insulating layer 42 and the permalloy inner layer 43 are all bonded by non-conductive glue, and the thickness of the glue layer is not more than 0.05mm, and here, a silicone heat-conducting glue can be used to connect the layers, and the silicone heat-conducting glue not only has insulation and can ensure the insulation effect between the layers, but also has good heat-conducting performance and can dissipate the heat generated by the composite shielding layer 4 during operation in time, so as to avoid the influence of heat accumulation on the performance and service life.

[0024] The above only describes preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A single electromagnetic force sensor for an electronic balance, comprising an integrated weighing unit, said weighing unit including a weighing wall (1), a micro electromagnetic force balancing unit (2), a permanent magnet cylinder (3), and a weighing body (6), characterized in that: It also includes a composite shielding layer (4), which is located on the periphery of the permanent magnet cylinder (3), and an insulating connecting piece (5) is connected between the composite shielding layer (4) and the permanent magnet cylinder (3). Furthermore, a thermistor (9) is installed inside the weighing unit, and the thermistor (9) is connected to the measurement circuit of the sensor.

2. The single electromagnetic force sensor for an electronic balance according to claim 1, characterized in that: The composite shielding layer (4) consists of a copper outer layer (41) and a permalloy inner layer (43), with an insulating layer (42) provided between the copper outer layer (41) and the permalloy inner layer (43).

3. The single electromagnetic force sensor for an electronic balance according to claim 2, characterized in that: The copper in the outer copper layer (41) has a purity of ≥99.9%, and a nickel layer of 0.01 to 0.03 mm is provided on the surface of the outer copper layer (41).

4. The single electromagnetic force sensor for an electronic balance according to claim 2, characterized in that: The insulating layer (42) is a polytetrafluoroethylene film layer. The copper outer layer (41) and the insulating layer (42), as well as the insulating layer (42) and the permalloy inner layer (43), are all bonded together with non-conductive adhesive, and the adhesive layer thickness does not exceed 0.05 mm.

5. The single electromagnetic force sensor for an electronic balance according to claim 1, characterized in that: The thermistor (9) is a negative temperature coefficient thermistor.

6. The single electromagnetic force sensor for an electronic balance according to claim 1, characterized in that: The weighing unit is provided with a force transmission spring (7) inside, and reinforcing rods (8) are also provided on both sides inside the weighing unit.

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