Flow meter block with conductive Rotameter tubes
Date of manufacture:
For drainage reasons, many operating theatres have floors that slope towards a gutter at one end of the room. It follows that an anaesthetic machine within such a theatre will not be perfectly upright. Consequently, a bobbin rotating within a rotameter flowmeter tube may rub against the tube wall and the dissimilar materials can develop opposite electrostatic charge that can cause the bobbin to stick against the glass resulting in substantial errors in the reading. The Rotameter manufacturer has therefore provided for dissipation of these charges by depositing a monomolecular layer of tin on the insides of the tubes and finishing the ends of the tubes with gold flashing. The coating gives a smoky iridescent appearance to the tubes. The tubes are bedded in an antistatic rubber seal and a metal manifold.
The flowmeters are: oxygen 1 - 10 L/min., carbon dioxide 0 - 2 L/min., cyclopropane 0 - 1 L/min., and nitrous oxide 0 - 12 L/min. The provision of a needle valve for cyclopropane is not entirely necessary as the cylindre valve has a gradual flow characteristic. Several machines had cyclopropane flow meters but no needle valve.