Wet leg refers to which definition?

• A. A sealed transfer line for gas samples
• B. A surface-mounted sensor for ambient pressure
• C. An impulse line filled with a fluid that is compatible with the pressure-measuring device
• D. A vent line that opens to atmosphere

Answer: (C)

A wet leg is an impulse line filled with a liquid that is compatible with the pressure-measuring device. This liquid creates a continuous column that transmits the process pressure to the sensor while avoiding air pockets and vapor formation in the line. Keeping the line liquid-filled ensures a stable, accurate pressure transmission because the pressure is carried as a hydrostatic head of the fluid, which reduces errors from gas compression, temperature swings, or vaporization. The liquid must be chosen to withstand the process conditions and not react with the measurement system.

The other descriptions don’t fit because they describe lines or sensors that aren’t used to convey process pressure through a liquid-filled column: a sealed gas transfer line is for moving gas samples, a surface-mounted ambient pressure sensor measures outside pressure, and a vent line opens to the atmosphere rather than transmitting process pressure to the transmitter.