As stated earlier, rotameters work best within applications where a low rate of flow is present, the reading is often done locally although the transmission of readings is an option in certain applications.

Rotameters - GPImeters.com

These flow meters are most commonly made from glass tubes that have markings along the sides in order to indicate the rate of flow visually. Metal rotameters are also available if that is something that your application requires.

As fluid enters the bottom of the rotameter, the float rises upwards within the tapered tube until gravitational force balances out. Typically, rotameters are read as a standard cubic feet per hour of air, this means that rotameres are not subject to constant restriction areas or variable pressure differentials because of the use of variable restriction and constant pressure differentials in order to measure the flow.

These flow meters can be used for a number of different applications as they can be designed to measure the flow rate of both single streams and also multiple streams of fluid or gases. The single flow meters are often mounted directly on the piping and are most commonly used in special conditions for measurements. Multiple tube rotameters are mounted onto a tripod base plate in order to level the system; they can also be mounted on a wall or even bench mounted.

Rotameters - GPImeters.com