An inductive differential pressure sensor

Abstract

The utility model provides an inductive differential pressure sensor, including shield cover, be equipped with adjusting structure on shield cover, the utility model as an inductive differential pressure sensor, through adjusting structure, the core advantage of this scheme lies in the performance is improved significantly with differential measurement principle. When the diaphragm is offset by pressure difference, will cause two coil inductance value to have equal size, opposite direction change synchronously. The symmetrical change structure makes the sensor have three advantages: first, the detection sensitivity to small pressure change is improved through differential amplification effect, second, the nonlinearity error of two coils is compensated in differential output, the overall linearity is improved, third, the influence of temperature and other environmental factors on two coils is effectively eliminated in differential comparison, the stability and anti -interference ability of measurement are strengthened. This design improves product reliability while ensuring accuracy.

Description

Technical Field

[0001] This utility model relates to the field of differential pressure sensor technology, specifically to an inductive differential pressure sensor. Background Technology

[0002] Inductive displacement sensors, as precision measuring devices based on the principle of electromagnetic induction, consist of a core made of a highly permeable magnetic material and a precisely wound inductor coil. They can convert minute changes in the linear or angular displacement of the object being measured into precise changes in the coil's inductance. During operation, the number of coil turns and the permeability of the core material remain constant. The physical essence of the inductance change lies in the alteration of magnetic reluctance in the magnetic circuit caused by the measured displacement, leading to a change in the magnetic flux area or air gap length of the main magnetic flux path, ultimately achieving a linear conversion between displacement and inductance. When the coil is connected to a measuring bridge or oscillating circuit driven by an AC signal, the change in inductance is further converted into a voltage or current signal output proportional to the displacement, facilitating subsequent data acquisition and processing.

[0003] Current inductive differential pressure sensors have low sensitivity, resulting in insufficient ability to detect minute pressure changes. They also have a long settling time under step pressure signals, and their overall dynamic performance needs to be improved. Utility Model Content

[0004] In order to solve the above-mentioned problems in the existing technology, the purpose of this utility model is to provide an inductive differential pressure sensor.

[0005] The technical solution adopted in this utility model is as follows: An inductive differential pressure sensor includes a shielding cover with an adjustment structure. The adjustment structure includes a first sensor base and a second sensor base. The first sensor base contains a first E-type iron core, and the second sensor base contains a second E-type iron core. A diaphragm is provided between the first and second sensor bases. Cables are provided on both the first and second sensor bases. The first and second sensor bases are fixed together by bolts. A first PCB mounting plate is provided on the first sensor base, and a second PCB mounting plate is provided on the second sensor base. The first and second PCB mounting plates are fixed to the first and second sensor bases by screws. A differential pressure PCB is provided inside the shielding cover.

[0006] Preferably, the first E-type iron core and the second E-type iron core are fixed in the first sensor base and the second sensor base by hard sealant.

[0007] Preferably, there are four cables, arranged in pairs on the first sensor base and the second sensor base.

[0008] Preferably, the diaphragm is a stainless steel diaphragm.

[0009] Preferably, the diaphragm is welded to the first sensor base and the second sensor base.

[0010] Preferably, the bolt is provided with a washer.

[0011] Preferably, the screw opening is an internal hexagonal slot.

[0012] The beneficial effects of this invention are as follows: As an inductive differential pressure sensor, this invention, through structural adjustment, significantly improves performance by employing a differential measurement principle. When the pressure difference causes the diaphragm to shift, it simultaneously causes the inductance values ​​of the two coils to change in equal magnitude but opposite direction. This symmetrical change structure gives the sensor three advantages: first, it improves the detection sensitivity to minute pressure changes through differential amplification; second, the nonlinear errors of the two coils compensate for each other in the differential output, improving overall linearity; and third, the influence of environmental factors such as temperature on the two coils is effectively canceled out in the differential comparison, enhancing measurement stability and anti-interference capability. This design improves product reliability while ensuring accuracy. Attached Figure Description

[0013] The present invention will now be described in further detail with reference to the accompanying drawings and specific implementation methods.

[0014] Figure 1 This is an exploded structural diagram of an inductive differential pressure sensor according to the present invention. Figure 2 This is a schematic diagram of the overall structure of an inductive differential pressure sensor according to the present invention; Figure 3 This is a schematic diagram illustrating the principle and structure of an inductive differential pressure sensor according to the present invention. In the diagram: 1. Shielding cover, 2. First PCB mounting plate, 3. First sensor base, 4. First E-type iron core, 5. Diaphragm, 6. Second E-type iron core, 7. Second sensor base, 8. Second PCB mounting plate, 9. Cable, 10. Differential pressure PCB, 11. Bolt, 12. Screw. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present utility model and are not intended to limit the present utility model; that is, the described embodiments are only some embodiments of the present utility model, and not all embodiments. The components of the embodiments of the present utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0016] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0017] The following is combined with Figure 1-3This invention describes a specific embodiment of an inductive differential pressure sensor, comprising a shielding cover 1. The shielding cover 1 has an adjustment structure, which includes a first sensor base 3 and a second sensor base 7. The first sensor base 3 contains a first E-type iron core 4, and the second sensor base 7 contains a second E-type iron core 6. A diaphragm 5 is provided between the first sensor base 3 and the second sensor base 7. Cables 9 are provided on both the first sensor base 3 and the second sensor base 7. The first sensor base 3 and the second sensor base 7 are fixed by bolts 11. A first PCB fixing plate 2 is provided on the first sensor base 3, and a second PCB fixing plate 8 is provided on the second sensor base 7. The first PCB fixing plate 2 and the second PCB fixing plate 8 are fixed to the first sensor base 3 and the second sensor base 7 by screws 12. A differential pressure PCB 10 is provided inside the shielding cover 1. The working principle of this inductive differential pressure sensor is based on the coupling effect of electromagnetic induction and mechanical deformation. The core objective is to linearly convert the pressure difference (ΔP) between two pressure ports into a standard electrical signal output. The process begins with a pressure difference acting on the key component, diaphragm 5. Diaphragm 5 is made of stainless steel with good magnetic permeability and elasticity, and is welded to the first sensor base 3 and the second sensor base 7 to form two independent sealed chambers. However, under the pressure difference, the central region of diaphragm 5 can undergo micron-level elastic bending deformation. On both sides of diaphragm 5 are symmetrically distributed first E-type iron cores 4 and second E-type iron cores 6, each made of a highly permeable magnetic material with coils wound around it. The function of the first E-type iron cores 4 and second E-type iron cores 6 is to construct a concentrated and efficient magnetic circuit. When alternating current is applied to cable 9, an alternating magnetic field is generated in the magnetic circuit formed by the first E-type iron cores 4 and second E-type iron cores 6, the air gap, and diaphragm 5. In the initial equilibrium state, i.e., when the pressure on both sides is equal, diaphragm 5 is centered, the air gaps on both sides are equal, and the inductance values ​​of the two coils are the same. When a pressure difference exists, diaphragm 5 bulges towards the low-pressure side, causing the air gap on the high-pressure side to increase, resulting in increased magnetic reluctance and a decrease in the inductance of the coil on that side. Simultaneously, the air gap on the low-pressure side decreases, reducing magnetic reluctance and increasing the inductance of the coil on that side. These two coils are connected as the two arms of a differential bridge. The opposite changes in their inductance values ​​(one increasing, the other decreasing) disrupt the bridge's balance, resulting in an AC voltage signal proportional to the inductance difference. This weak differential signal is transmitted to the differential pressure PCB 10, where the circuitry powers the bridge and demodulates, amplifies, and normalizes the imbalance signal, ultimately outputting a standardized electrical signal such as 4-20mA or 0-5V. The entire sensing assembly is encapsulated within a sensor base and shielding cover 1. The base precisely fixes the position of the iron core and coils and shields against external electromagnetic interference; the shielding cover 1 further protects the internal components from stray magnetic fields.In summary, this sensor modulates the inductance of two coils by causing diaphragm 5 to deform due to pressure difference, thereby changing the air gap in the magnetic circuit. A bridge circuit is then used to detect this differential inductance change and convert it into a usable electrical signal, achieving accurate measurement from non-electrical quantities to electrical quantities. Its differential design significantly improves sensitivity, linearity, and temperature stability.

[0018] Advantageously, the first E-type iron core 4 and the second E-type iron core 6 are fixed within the first sensor base 3 and the second sensor base 7 using rigid sealant. The rigid sealant provides a stable mechanical fixation, ensuring that the positions of the first E-type iron core 4 and the second E-type iron core 6 relative to the first sensor base 3, the second sensor base 7, and the intermediate diaphragm 5 are precise and unchanging. The rigid sealant plays a crucial sealing and protective role. It fills all gaps between the iron core and the base mounting groove, forming a completely sealed cavity together with the welded diaphragm 5, effectively preventing contaminants such as moisture, oil, and dust from the external environment from entering and corroding the delicate iron core and coil. This protection is essential for ensuring the long-term reliable operation of the sensor in harsh industrial environments.

[0019] Advantageously, four cables 9 are provided, arranged in pairs on the first sensor base 3 and the second sensor base 7. The core of this design lies in independently leading out the two leads of each coil and connecting them in a specific manner to the bridge circuit on the differential pressure PCB 10, thereby constructing a complete differential measurement system. Its fundamental purpose is to achieve accurate differential signal detection and processing: when a pressure difference is applied, the inductance values ​​of the two coils will change in opposite directions and by the same amount. This change is transmitted to the bridge circuit by the independently led-out cables 9, and the bridge outputs a voltage signal that precisely corresponds to the pressure difference by detecting its imbalance state. This full-bridge architecture not only provides the necessary operating current path for the coils, but also significantly improves the sensitivity and linearity of the system through the differential principle. Simultaneously, it effectively suppresses common-mode interference such as temperature drift, ensuring the long-term measurement accuracy and stability of the sensor under complex operating conditions. This is a key design for achieving high-reliability differential pressure measurement.

[0020] Advantageously, the diaphragm 5 is made of stainless steel. Stainless steel possesses excellent mechanical strength and toughness, capable of withstanding repeated pressure cycles and potential overload impacts without plastic deformation or fatigue fracture, ensuring the long service life and measurement reliability of the sensor. Its excellent elastic properties allow the diaphragm 5 to produce precise and reproducible micron-level elastic deformation under pressure difference, and quickly return to its initial position after pressure recovery, which is the foundation for high-precision measurement. In terms of chemical stability, stainless steel has excellent corrosion resistance, resisting the erosion of water vapor, grease, and various chemical media commonly found in industrial environments. This, combined with the welded sealing structure, provides a robust barrier protection for the core inductive components. Furthermore, specific stainless steel grades possess sufficient magnetic permeability to efficiently conduct the magnetic circuit established by the E-type iron core and coil. Its magnetic permeability characteristics allow the minute displacement of the diaphragm 5 to effectively modulate the magnetic reluctance of the magnetic circuit, thereby causing a significant change in the coil inductance value, meeting the electromagnetic requirements for high-sensitivity conversion of pressure signals. Meanwhile, stainless steel maintains stable mechanical and magnetic properties over a wide temperature range, effectively suppressing measurement drift caused by thermal expansion or magnetic temperature coefficient. In summary, selecting the stainless steel diaphragm 5 is the optimal solution for achieving high accuracy, high reliability, long lifespan, and good environmental adaptability in this sensor. Its comprehensive performance perfectly meets the stringent requirements for core sensing elements in differential pressure measurement.

[0021] Advantageously, the diaphragm 5 is welded to the first sensor base 3 and the second sensor base 7. The metallurgical bond formed by metal welding creates a robust barrier with zero leakage between the diaphragm 5 and the first sensor base 3 and the second sensor base 7. This barrier can isolate moisture, oil, dust and other corrosive media in the external environment, ensuring that the internal precision inductor components (including the E-type iron core and coil) are free from contamination, oxidation or electrical short circuits in complex industrial environments, thereby guaranteeing the electromagnetic stability and measurement accuracy of its long-term operation. Secondly, the welded structure provides extremely high mechanical connection strength and rigidity. This robust connection not only withstands frequent pressure fluctuations and potential process pressure shocks, preventing loosening or displacement between the diaphragm 5 and the base due to mechanical fatigue, but more importantly, it solidifies the diaphragm 5, the base, and the internal magnetic circuit components into a dimensionally stable whole. This precisely locks the initial air gap distance between the first E-type iron core 4 and the second E-type iron core 6 and the diaphragm 5. This air gap is a core parameter determining the inductor's sensitivity and linearity; even a slight change in it can directly cause sensor performance drift. The welding process fundamentally reduces mechanical creep and parameter instability caused by vibration or temperature cycling. Furthermore, the rigid connection formed by welding ensures a direct and precise pressure transmission path. The differential pressure acting on the two pressure ports can be transmitted to the diaphragm 5 through the base without hysteresis or loss, driving it to produce a micron-level elastic deformation that strictly corresponds to the differential pressure, without signal attenuation or response lag caused by gaps or damping effects present in non-rigid connections. Finally, from a manufacturing process perspective, welding is a mature and controllable permanent connection technology. Through high-precision tooling and welding parameter control, the consistency of the size and sealing quality of each sensor cavity in mass production can be guaranteed, laying the technological foundation for product standardization and interchangeability. Therefore, the welding and encapsulation of diaphragm 5 is far from a simple connection; it is a comprehensive engineering technology solution integrating permanent sealing, mechanical holding, parameter stabilization, and precise pressure transmission. It is the cornerstone for building the long-term stability and accurate measurement capabilities of this sensor.

[0022] Advantageously, a washer is provided on the bolt 11, and the washer is located between the bolt 11 and the first sensor base 3 and the second sensor base 7. The washer is precisely positioned between the head of the bolt 11 and the contact surface of the base, and its core function is to establish an effective anti-loosening mechanism. Through the elastic deformation characteristics of the washer, it can continuously compensate for the preload decay caused by mechanical vibration, temperature cycling, or material creep, thereby maintaining the axial clamping force required by the bolt 11. This design not only effectively suppresses the rotational loosening tendency of the bolt 11 by increasing the friction of the contact surface, but also ensures that the compression between the two bases and the intermediate diaphragm 5 remains uniform and tight. The stability of this mechanical connection is directly related to the dimensional accuracy of the air gap in the internal magnetic circuit of the sensor, and is an important engineering technology measure to ensure that the sensor maintains structural integrity, sealing reliability, and final measurement accuracy under long-term dynamic loads.

[0023] Advantageously, the screw 12 has an internal hexagonal socket, which provides higher torque transmission efficiency and excellent anti-slip properties. When a tool (hexagonal wrench) engages with the socket, the force flow is evenly distributed along the socket wall, avoiding stress concentration and significantly reducing the risk of socket damage (i.e., "stripping") due to excessive torque or tool slippage. This structure ensures that the bolt 11 can be preloaded with precise and sufficient force during sensor assembly and maintenance, while maintaining the integrity of the interface itself.

[0024] Working principle of this utility model: First, when AC current is applied to cable 9, an alternating magnetic field is generated in the magnetic circuit formed by the first E-type iron core 4, the second E-type iron core 6, the air gap, and the diaphragm 5. In the initial equilibrium state, i.e., when the pressure on both sides is equal, the diaphragm 5 is centered, the air gaps on both sides are equal, and the inductance values ​​of the two coils are the same. When a pressure difference exists, the diaphragm 5 bulges towards the low-pressure side, causing the air gap on the high-pressure side to increase, and the magnetic reluctance to increase accordingly, resulting in a decrease in the inductance value of the coil on that side; simultaneously, the air gap on the low-pressure side decreases, the magnetic reluctance decreases, and the inductance value of the coil on that side increases. These two coils are connected as the two arms of a differential bridge, and their opposite changes in inductance value (one increasing and the other decreasing) disrupt the balance of the bridge, thereby outputting an AC voltage signal proportional to the inductance difference.

[0025] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0026] The above description is merely an example and illustration of the structure of this utility model. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the structure of the utility model or exceed the scope defined in the claims, they should all fall within the protection scope of this utility model.

Claims

1. An inductive differential pressure sensor, comprising a shielding cover, characterized in that, The shielding cover is equipped with an adjustment structure, which includes a first sensor base and a second sensor base. The first sensor base contains a first E-type iron core, and the second sensor base contains a second E-type iron core. A diaphragm is provided between the first sensor base and the second sensor base. Cables are provided on both the first sensor base and the second sensor base. The first sensor base and the second sensor base are fixed by bolts. A first PCB fixing plate is provided on the first sensor base, and a second PCB fixing plate is provided on the second sensor base. The first PCB fixing plate and the second PCB fixing plate are fixed to the first sensor base and the second sensor base by screws. A differential pressure PCB is provided inside the shielding cover.

2. The inductive differential pressure sensor according to claim 1, characterized in that, The first E-type iron core and the second E-type iron core are fixed in the first sensor base and the second sensor base by hard sealant.

3. An inductive differential pressure sensor according to claim 1, characterized in that, The cable is provided in four parts, with two parts each on the first sensor base and the second sensor base.

4. An inductive differential pressure sensor according to claim 1, characterized in that, The diaphragm is a stainless steel diaphragm.

5. An inductive differential pressure sensor according to claim 1, characterized in that, The diaphragm is welded to the first sensor base and the second sensor base.

6. An inductive differential pressure sensor according to claim 1, characterized in that, The bolt is equipped with a washer.

7. An inductive differential pressure sensor according to claim 1, characterized in that, The screw opening is an internal hexagonal socket.

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