Construction machinery hydraulic cylinders operate under vibration, dust, high pressure, and wide temperature changes. A magnetostrictive level gauge provides continuous oil level or piston position feedback by measuring the position of a magnetic float along a waveguide. The electronic head converts this position into analog or digital signals for control and monitoring. Model selection starts with installation style. Rod-style gauges suit compact cylinders; flexible-probe gauges fit long strokes; embedded high-pressure gauges are used where space is limited. A standard model code can be shown as MLG-HP-800-A4-M12. In this code, MLG is the gauge series, HP means high pressure, 800 is the measuring range in millimeters, A4 is 4–20 mA output, and M12 is the connector type. Buyers should confirm the code with the supplier before ordering. Key specifications include measuring range 50–2500 mm, pressure rating up to 40 MPa, repeatability ±0.05% FS, linearity ±0.1% FS, supply voltage 12–36 VDC, output 4–20 mA, 0–10 V, RS485, or CAN, operating temperature -40°C to +85°C, and protection class IP67 or IP69K. Probe and float materials must be compatible with hydraulic oil. Mounting threads, rod length, and cable exit direction also affect fit. Shielded cable and correct grounding reduce signal noise. For excavators, cranes, loaders, and other construction machinery, the correct model and specification improve accuracy, reduce downtime, and support predictive maintenance.