#Gamma control interface full
A simple thought experiment proves this: imagine a vessel partially full of liquid, with a pressure transmitter attached to the bottom to measure hydrostatic pressure. It should be noted, though, that changes in liquid density will have absolutely no effect on hydrostatic measurement of liquid mass, so long as the vessel has a constant cross-sectional area throughout its entire height. If liquid density is subject to random change, the accuracy of any hydrostatic pressure-based level or volume instrument will be correspondingly unreliable. This means liquid density is a critically important factor for volumetric measurement when using hydrostatic pressure-sensing instruments. Pressure measured at the bottom of a vessel can give us a proportional indication of liquid height if and only if the density of that liquid is known and constant. So long as the vessel’s cross-sectional area is constant throughout its height, liquid height will be directly proportional to stored liquid volume. In most level-measurement applications, we are concerned with knowing the volume of the liquid contained within a vessel, and we infer this volume by using instruments to sense the height of the fluid column. In the following photograph, you see a Rosemount model 1151 pressure transmitter being used to measure the height of colored water inside a clear plastic tube: \[P_\) density for water).Īny type of pressure-sensing instrument may be used as a liquid level transmitter by means of this principle. \(h\) = Height of vertical fluid column above point of pressure measurementįor example, the pressure generated by a column of oil 12 feet high (\(h\)) having a weight density of 40 pounds per cubic foot (\(\gamma\)) is: \(\gamma\) = Weight density of fluid in newtons per cubic meter (metric) or pounds per cubic foot (British) \(\rho\) = Mass density of fluid in kilograms per cubic meter (metric) or slugs per cubic foot (British) The mathematical relationship between liquid column height and pressure is as follows: This principle makes it possible to infer the height of liquid in a vessel by measuring the pressure generated at the bottom: The relationship between column height and fluid pressure at the bottom of the column is constant for any particular fluid (density) regardless of vessel width or shape. Pressure of a fluid columnĪ vertical column of fluid exerts a pressure due to the column’s weight. This principle allows us to infer the level (height) of liquid in a vessel by pressure measurement.
The greater the vertical height of the fluid, the greater the pressure, all other factors being equal. A vertical column of fluid generates a pressure at the bottom of the column owing to the action of gravity on that fluid.
0 kommentar(er)
