LVDT Displacement Sensor Material Deformation Detection Principle Analysis

Key conclusions

LVDT (Linear Variable Differential Transformer) displacement sensors directly convert the micron-level deformation of materials into linear voltage signals by changing the position of the iron core in two sets of anti-phase series secondary coils. It is one of the contact-type solutions with the best overall performance in terms of accuracy and stability in material deformation detection.

Key points

● Non-contact magnetic coupling: There is no mechanical friction between the primary and secondary coils, and the theoretical lifespan is not limited by wear.

● Differential structure naturally suppresses temperature drift: When the two sets of secondary voltages are subtracted, common-mode errors (such as those caused by coil thermal expansion) are partially offset.

● Strict linearity between output and displacement: Linearity can reach ±0.25%FS or even better within the effective range, depending on the coil winding process.

Detailed analysis

In terms of working principle, an audio excitation (commonly 2.5kHz~10kHz) is applied to the primary coil . Changes in the core position alter the mutual inductance coupling coefficient between the two sets of secondary coils. After phase-sensitive detection (PSD), a DC voltage corresponding to the direction and magnitude of the displacement is output. When used for material deformation detection, a probe (spring-loaded or pneumatically loaded) presses against the surface of the test sample, capturing the minute displacements of the sample during tension, compression, bending, or creep in real time. Compared to strain gauges, LVDTs do not rely on bonding processes, are not limited by the conductivity of the sample surface, and can be repeatedly disassembled and reassembled for batch testing. Compared to laser displacement gauges, LVDTs offer greater reliability in industrial environments such as humid, oily, and dusty conditions. Dongfang Measurement Instruments' LVDT displacement sensor series offers various ranges and probe loading methods for material deformation detection, adapting to different tooling interfaces such as tensile testing machines and compression testing benches.