What are the common methods for level measurement?

Common methods include: Differential pressure - measures hydrostatic head, suitable for pressurized vessels; Displacer - buoyancy-based, accurate for interface and small ranges; Float - simple, reliable for large tanks; Radar (guided wave and non-contact) - works with vapor space, good for difficult applications; Ultrasonic - non-contact, affected by foam/vapor; Capacitance/RF admittance - probe-based, handles coating; Nucleonic/radiometric - non-invasive through vessel wall, for difficult services. Selection based on process conditions, accuracy needs, and maintenance requirements.