Hydrostatic Level vs. Ultrasonic Level for Tank Management, part 1of 2
The use of hydrostatic pressure to monitor the level/volume in storage tanks has many benefits over the more commonly used ultrasonic level instruments. Because a hydrostatic level sensor detects the pressure exerted on a column of fluid by the weight of the solutions above it, foam, vapors or process mixing do not interfere with the sensor's signal. Signet's custom tank program in the 8900 Multi-Parameter Controller and 8250 Level Transmitter can be used to accurately measure the fluid's level in uncommon, geometrically-shaped tanks.
Fig 1 shows a column of water in a tank. Physics dictates that the weight of the water exerts the same pressure in all directions no matter how large or small the diameter of the tank may be (.03 bars per 30.5 cm or .433 psi per foot).
The pressure of the fluid allows the 3-2450 Hydrostatic sensors to accurately measure the pressure exerted on the surface of the pressure/level sensor and translates this pressure in to a level measurement displayed in inches, feet, centimeters or meters on the instrument's display.
Disadvantages of ultrasonic level sensors:
Presence of foam: Because the ultrasonic sensor signal bounces off of a surface, the presence of foam could present a false surface from which the ultrasonic signal would bounce.
Position inside a tank: Ultrasonic sensors must be installed in a vertical position over the liquid. Any deviation could cause signal interference.
Vapor and gas interference: gas or vapors created by heated solutions can interfere with the ultrasonic signal
Turbulence or waves created by mixing motors or the filling process could cause inaccuracies.
Dust and air particles in open top tanks: Dust interferes with the ultrasonic signal.
The 3-2450 hydrostatic level sensor can be mounted through the side wall of a tank or assembled in a stand pipe configuration and suspended in the tank (pipe extension provided by customer).
