GB1220313A - Method and apparatus for volume measurement - Google Patents

Abstract

1,220,313. Measuring volume. GEORGIA TECH RESEARCH INSTITUTE. June 12, 1969, No. 29769/69. Heading G1X. Apparatus for determining the volume of irregular bodies comprises a sealable system having a reference compartment 12 with a lid 16 through which a body under test may be introduced into the system, a valve 42 for establishing a predetermined constant gas pressure within the system e.g. by connection to a source of air at constant pressure, or to a source of inert gas such as helium, a pump 20 with a movable piston for varying the volume of the system and thus the gas pressure therein, a pressure detection mechanism 50 for recognizing the attainment of a known pressure in the system by operation of the pump, and an indicator e.g. a revolution counter 40 attached to the pump 20 to indicate the increase or decrease in volume to the presence or otherwise of the body under test in the compartment 12. The piston 26 comprises a nut member 34 co-operating with a screw 30 rotatable by a handwheel 38 to move the piston, and the pressure detection mechanism 50 includes a closed chamber containing a bellows which expands and contracts with pressure changes in the chamber and the movable end of which carries a contact closing the circuit to a lamp 82 on attainment of the known pressure in the system. In use with the lid 16 in place, the valve 42 is operated to fill the system with air at the predetermined pressure which may be atmospheric, the valve then being closed to seal the system. The piston is then moved to reduce the pressure allowing the bellows in the mechanism 50 to expand and close the circuit to the lamp 82. The reading on the counter 40 is then noted, and the process is repeated with the test body in place in the compartment 12. If the test body absorbs air then helium may be used after evacuation of the system by moving the valve 42 to connect with a vacuum pump. The difference in the readings of the counter 40 gives a measure of the volume of the test body related to the predetermined gas pressure at which the system was filled. If the system is calibrated using a body of known volume then it is not necessary to know the original predetermined pressure. The apparatus may also be used to determine the amount of gas absorbed by a test body by first measuring its volume using helium, which will not be absorbed and then repeating the measuring procedure using air or other gas which is absorbed. The apparatus may be modified by connecting the piping 52 leading to the mechanism 50 to the interior of the bellows. In this arrangement the pump 20 is used to increase the pressure in the system each time until the lamp 82 is illuminated.