Probes, floats and bubbler tubes are commonly used for which control?

• A. Level
• B. Temperature
• C. Flow
• D. Pressure

Answer: (A)

These devices measure how high the liquid is and feed that information to a control system to keep the liquid at a desired level. Probes detect the presence or absence of liquid at a chosen point, floats ride on the surface and change position with level, and bubbler tubes use the pressure of a trapped gas to infer the liquid height. Because their primary function is sensing and regulating liquid height, they are used for level control. Temperature, flow, and pressure control rely on sensors specifically designed for those quantities (temperature sensors, flow meters, and pressure transducers), not these level-sensing devices.