Selecting a built-in LVDT displacement sensor for a metallurgy hydraulic cylinder requires more than matching stroke and accuracy. The sensor must survive heat, vibration, contamination, pressure, and electromagnetic interference while providing reliable position feedback for critical control loops. First, define measuring range and mechanical interface. The LVDT core and coil assembly must fit the cylinder bore, rod, and mounting space without affecting stroke or sealing. Choose a design rated for working pressure and temperature, including radiant heat from molten metal. High-temperature coils, stable core materials, and heat-resistant cables are essential. Second, verify environmental protection. Metallurgy plants expose sensors to dust, water, steam, scale, and oil. Specify an IP-rated housing, robust sealing, and corrosion-resistant materials. Cable entry and connectors should resist pull, vibration, and washdown. For severe contamination, consider redundant sealing and guided core movement. Third, evaluate signal performance. A built-in LVDT should offer low hysteresis, good repeatability, and linearity across the full stroke. Select excitation frequency and output type to match the controller, such as 4–20 mA, 0–10 V, or digital communication. Shielded cables and proper grounding reduce EMI. Fourth, confirm installation and maintenance. The sensor should allow field calibration or easy replacement without damaging the cylinder. Ask for shock and vibration ratings, pressure test data, and material certificates. A supplier with metallurgy experience can recommend the right LVDT for reliable long-term position feedback.