I.LVDT is a non-contact inductive precision displacement sensor that can convert the linear mechanical displacement of the measured object into an electrical signal that is strictly linearly proportional to the stroke and can be measured and transmitted. It is the core detection component in the field of industrial precision measurement and automated closed-loop control.

1. Core working principle The core structure of LVDT consists of three parts:

1 primary excitation coil, 2 symmetrical reverse series secondary induction coils, and 1 axially movable high magnetic permeability iron core (the iron core is rigidly/follow-uply connected to the object being measured). 1. Insert a high-frequency AC excitation signal into the primary coil, and an alternating magnetic field will be generated inside the coil;

2. When the iron core is at the zero point in the middle of the coil, the electromotive force induced by the two secondary coils is equal, and the differential output signal is 0 after reverse series connection; 3. When the iron core undergoes axial displacement with the measured object, the iron core deviates from the zero point, and the induced electromotive force of the two secondary coils differs. The amplitude and phase of the output differential AC signal are strictly linear with the displacement size and direction of the iron core. 4. The supporting signal processing circuit will demodulate and amplify the differential signal and convert it into a common industrial 4-20mA, 0-10V analog signal, or a digital signal such as RS485, which can be directly connected to the control system. The root of the core advantage: there is no physical contact between the iron core and the coil during the entire measurement process, and there is no mechanical friction, which in principle avoids the problems of wear, aging, and poor contact.

II. Core product advantages

1. Ultra-long service life, high reliability: non-contact measurement, no mechanical wear, no brush aging problem, service life of tens or even hundreds of millions of times, suitable for long-term continuous operation and high-frequency reciprocating motion scenarios.

2. Ultra-high measurement accuracy: the resolution can reach micron level or even sub-micron level, the linearity can reach up to 0.05% FS, the repeated positioning accuracy is excellent, the temperature drift is extremely small, there is no zero point drift, and the long-term working stability is extremely strong.

3. Adaptability to extreme environments: The fully sealed structure can achieve IP68 protection, with excellent resistance to vibration, impact, dust, oil, and strong electromagnetic interference. It can be customized for high temperature, high pressure, waterproof and explosion-proof models, and is suitable for harsh working conditions such as nuclear power, petrochemical industry, and underwater.

4. Fast response and good dynamic performance: The structural characteristics of no mechanical friction make it suitable for dynamic displacement measurement of high-frequency reciprocating motion without lag or jamming.

5. Wide range coverage and strong adaptability: The range coverage is extremely wide, ranging from micro-displacement measurement of ±1mm to large-stroke detection of more than 500mm. There are corresponding models, which can meet the needs of all scenarios from precision laboratories to heavy industrial sites.

III. Mainstream product classification (according to structure and adaptation scenarios) Product type Core structural features Core adaptation scenarios Rebound type (probe type) LVDT Built-in constant force return spring, the probe can automatically expand and contract without a rigid fixed connection, which can realize gap-free follow-up measurement Precision workpiece size/thickness/flatness detection, shaft part runout measurement, mold clamping detection, automation equipment limit detection, product online quality inspection Tie rod type (universal type) LVDT The iron core is rigidly connected to the object under test through a tie rod, with a stable structure and wide stroke coverage. Hydraulic cylinder/cylinder stroke feedback, valve opening control, lifting platform position monitoring, construction machinery displacement detection, machine tool equipment position closed-loop split LVDT The coil body and the iron core are designed separately, with flexible structure and compact size. Embedded scenarios with limited installation space, internal displacement detection in small cavities, special equipment customized installation for special working conditions. Customized high-temperature, high-pressure, waterproof and explosion-proof, radiation-resistant models. Petrochemical downhole equipment, nuclear power equipment monitoring, underwater operation equipment, wind power equipment, aerospace equipment

IV. and Core differences of resistive pull rod electronic ruler (potentiometer type) Comparison dimension LVDT displacement sensor Resistive pull rod electronic ruler Measurement principle Inductive differential transformer, non-contact measurement Resistive sliding potentiometer, contact measurement, service life without mechanical wear, extremely long life, almost no aging There is friction and wear between the brush and the resistor body, and poor contact is prone to occur after long-term use , Decreased accuracy, limited life. Measurement accuracy is ultra-high precision, micron/sub-micron level resolution, excellent linearity, minimal temperature drift. Conventional industrial accuracy, resolution is mostly 0.1% FS level, greatly affected by contact resistance and temperature. Environmental adaptability, anti-vibration, anti-dust and oil pollution, can adapt to extreme working conditions such as high temperature, high pressure, and explosion-proof. Sensitive to dust, oil pollution, strong vibration, It is easy to be damaged under harsh working conditions. It is only suitable for conventional industrial environments. The dynamic performance response speed is extremely fast. The dynamic measurement response speed that can be adapted to high-frequency reciprocating motion is slow. The wear and tear increases under high-frequency motion. It is not suitable for high-frequency dynamic scenarios. The cost and popularity cost are relatively high. It is mostly used for precision measurement and harsh working conditions. The cost is low and cost-effective. It is extremely popular in conventional automation scenarios.

V. Mainstream application scenarios

1. Precision manufacturing and quality inspection: online inspection of 3C product dimensions, precision mold clamping monitoring, circular runout/end face runout measurement of bearing/shaft parts, micro-displacement detection of material testing machines, precision positioning of semiconductor packaging equipment.

2. Industrial automation and engineering machinery: hydraulic cylinder/cylinder stroke closed-loop control, water gate/valve opening monitoring, shield machine/mining machinery displacement detection, lifting platform/elevator position monitoring, machine tool tool wear compensation.

3. Energy and high-end equipment: nuclear power equipment safety monitoring, petrochemical downhole instruments, wind power equipment blade gap monitoring, aerospace equipment attitude and displacement measurement, ship hydraulic system testing.

4. Scientific research and people's livelihood fields: fatigue testing of automobile parts, settlement/deformation monitoring of building structures, geological exploration equipment, biomedical precision instruments, and rail transit vehicle status detection.