What is the primary purpose of a rotameter?

A rotameter is a device specifically designed to measure the flow rate of gases or liquids. It operates on the principle of variable area flow measurement, which means that as the flow increases, a float inside a tapered tube rises to a position that indicates the flow rate.

The primary purpose of a rotameter being to measure the flow of gas aligns with its design and function, which is commonly used in various industries, including water treatment and chemical processing. Its accuracy and ability to provide a visual indication of flow make it essential for monitoring and controlling processes that require precise flow measurements.

In contrast, the other choices do not correctly represent the function of a rotameter. While measuring the speed of water flow might seem relevant, it specifically does not apply since rotameters are not calibrated solely for speed but rather for volumetric flow. Assessing chlorine levels and evaluating water temperature are functions that require entirely different instruments, such as colorimeters for chlorine concentration or thermometers for temperature measurements.