Question 53General Subjects - Assistant Engineer

The correct answer is B) Differential pressure sensor. A differential pressure sensor is the most suitable liquid level sensor for measuring the liquid level in a pressure vessel, such as a water-tube boiler steam drum. This is because the differential pressure between the top and bottom of the vessel is directly proportional to the height of the liquid column, allowing for an accurate measurement of the liquid level. The other options are not as suitable - a capacitance probe (A) may be affected by the pressure and density of the liquid, a static pressure sensor (C) would only measure the pressure at one point, and a displacement float level sensor (D) could be affected by the vessel's internal pressure.