Where should the ball on a rotameter be read for accurate measurements?

For accurate measurements on a rotameter, the reading should be taken at the middle of the ball. This is because the rotameter functions by allowing fluid to flow through a tapered vertical tube, with the ball inside rising to a point where the flow rate is in balance with the weight of the ball. The position of the ball is subject to the fluid's flow rate and can vary from the top to bottom, but the most accurate indication of the flow rate is determined at the midpoint of the ball's visible diameter, where it provides a stable and consistent reference. Reading at this point helps eliminate discrepancies caused by angle or light reflection, ensuring that the measurement reflects the actual flow rate.