A corrosion-resistant LVDT displacement sensor is designed for wet, humid, and chemically exposed water conservancy sites. Its core is a linear variable differential transformer. A primary coil is excited by stable AC; two secondary coils are arranged symmetrically. A ferromagnetic core moves with the measured object, such as a gate, valve stem, or dam structure. The core changes magnetic coupling, so the secondary coils induce different voltages. The difference between these voltages indicates displacement. At the null position, outputs are nearly equal and cancel. As the core moves, output amplitude rises and phase changes according to direction. A demodulator converts this AC signal into a stable DC voltage or digital value proportional to position. For water conservancy, corrosion resistance is essential. The sensor uses 316L stainless steel, PTFE or PFA barriers, laser-welded seals, and IP68 housing. The coils and electronics are isolated from splashes, condensation, silt, and mild chemicals. Because the core does not touch the coils, the sensor has low wear and good repeatability. It supports gate opening monitoring, penstock valve position feedback, floodgate control, and structural displacement measurement. Proper shielding and temperature compensation keep signals reliable in damp control cabinets and outdoor chamber. Thus, the corrosion-resistant LVDT provides continuous, accurate displacement feedback for safe water infrastructure operation. This design ensures safe long-term use.