(under subclass 299) Gauges wherein means is provided for compressing or replenishing the fluid in the system between the reservoir and the pressure gauge, or means is provided for displacing or withdrawing fluid from the measuring system. The displacing or replenishing means may be, for example, an adjustable plug, a pump, a means to entrain air by sloshing of liquid in the tank, a vacuum feed tank in an internal combustion engine fuel feeding system, or other source of pressure or suction.
SEE OR SEARCH THIS CLASS, SUBCLASS:
439, for similar devices for determining specific gravity.
