Level gauge

This question measures the liquid level using a single-chamber balance system with a negative pressure tap and a condenser. In this measurement method, the negative pressure transducer tube is exposed to the atmospheric environment, and the density of the condensate water in it changes due to variations in the atmospheric conditions, which results in instability in the pressure of the condensate water within the negative pressure transducer tube. Do not underestimate the pressure changes caused by slight variations in ambient temperature. Since the liquid level measured in the drum is generally low, usually within a range of around 0.8 meters, even minor changes in density can result in significant pressure differences, thereby causing the liquid level to deviate considerably from its actual value. As required by the problem, the density of the condensate is taken to be the same as that of the boiler water (g=10 m/s2). The gauge range is ΔP = ρgH = 7.9 Kpa. In the diagram, the differential pressure transmitter exhibits negative drift; the amount of this drift is A = ρgh1 – ρg(h1 + H) = –ρgH = –7.9 Kpa. Therefore, the lower and upper limits of this differential pressure transmitter are –7.9 Kpa and 0 Kpa, respectively.