Certified Pulmonary Function Technologist (CPFT) Practice Exam

What does a rotameter primarily measure?

1. Temperature

2. Pressure

3. Flow

4. Volume

The correct answer is: Flow

A rotameter is an instrument specifically designed to measure the flow rate of liquids or gases. It operates on the principle of variable area flow measurement, where the fluid flows through a tapered tube. As the flow rate increases, the fluid lifts a float within the tube to a height that corresponds to the flow rate. The position of the float can be read on a calibrated scale, which indicates the flow. While other measurements like temperature, pressure, and volume are essential in various contexts, they do not directly relate to the primary function of a rotameter. Temperature measurement usually involves different types of sensors or thermometers, pressure is monitored with manometers or pressure gauges, and volume often requires volumetric flasks or graduated cylinders. Therefore, the correct focus for a rotameter is on its ability to provide accurate readings of flow, making flow measurement its primary capability.