Improvements in and relating to pressure difference gauges or manometers suitable for fluid velocity meters of the venturi and other pressure difference types

摘要

216,592. Hodgson, J. L. March 3, 1923. Liquid-level pressure gauges.- In a pressure-difference gauge of the type described in Specification 12255/13, the gauge tube G is made of celluloid, and is of rectangular cross-section. The back-plate W and sides are moulded in white celluloid, and the top of the lower side piece B is preferably painted black. The transparent front plate T is extended to form the surface on which the graduations are marked, and is secured by screws Q to the reservoir R. A plate of glass may be fixed to the front to strengthen the gauge tube. The reservoir R extends the whole length of the gauge, and is of large sectional area in order to avoid errors due to temperature changes. The instrument is provided with a screw-actuated displacer A for setting to zero an equalizing valve E, a spirit level L, and levelling screw Z. Paraffin may be used as the manometer liquid, and the liquid may be coloured. The dimensions may be selected so that the rise in the liquid level in the reservoir due to increase in temperature is equal to the fall of the level of the liquid in the gauge tube due to diminution of its surface tension so as to obtain a zero unaffected by moderate changes of temperature.