Final answer:
Common pressure-sensing devices include manometers, which measure pressure based on the height of a fluid column, and mechanical pressure gauges like aneroid gauges that use bellows connected to an indicator.
Step-by-step explanation:
Two common pressure-sensing devices used in pressure controls are manometers and mechanical pressure gauges. Manometers use the property that pressure due to the weight of a fluid of constant density is given by the equation p = hpg, where p represents pressure, h is the height of the fluid column, ρ (rho) is the density of the fluid, and g is the acceleration due to gravity. Mechanical pressure gauges, such as aneroid gauges, convert pressure into a force that is then converted into some type of readout, often utilizing flexible bellows connected to a mechanical indicator.
Many pressure-sensing devices operate based on Pascal's principle, which states that a change in pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid and to the walls of its container. This principle allows for precise remote sensing of pressures, which is often more convenient than placing a measuring device directly into the system being monitored.