ROTAMETER

Typical Number in Hospital:

Cost Bands:

References: 2

This is a trade name which is commonly used for a type of flowmeter which is in widespread use for medical gases. It consists of a vertical glass or plastic tube which has an internal taper narrowing towards the bottom. Gases are fed in through a needle valve at the base and flow rate is metered as the height to which a bobbin rises up the tube. The bobbin is designed to rotate in the flowing gas so that it does not stick or oscillate and can be seen to be moving freely. Because of the different physical properties of each gas, a differently calibrated rotameter is required.

A continuous-flow anaesthetic machine has three, four, or five rotameters, and they are also found in the wards and clinics on oxygen therapy apparatus. To perform correctly they must be vertical in use. Errors can also arise due to static electricity on the glass, and they may stick if there is any dirt in the tube. Thus, servicing usually includes an annual cleaning and leak test.