What type of level measurement involves physical contact with the liquid?

Direct level measurement involves physical contact with the liquid being measured. This method typically uses devices such as floats, pressure transmitters, or other instruments that come into direct contact with the liquid. The readings obtained from direct level measurement are generally accurate and can provide immediate feedback about the level of the liquid in a vessel.

In contrast, indirect level measurement refers to techniques that do not involve physical interaction with the liquid, such as ultrasonic level sensors or radar level sensors, which determine the level based on calculations derived from sound waves or electromagnetic waves. Uncontacted level measurement is a specific subset of indirect measurement where there is no physical connection at all, typically relying on remote sensing technology. Continuous level measurement describes a system that provides ongoing measurements of the liquid level but does not specify whether it is direct or indirect; thus, it could include both types.

In summary, the essence of direct level measurement is that it interacts physically with the liquid, making it the right choice for this question.