High Pressure Densometer - OpTest

 This machine has a configuration like the standard densometer, except that mercury is used instead of oil. The inner cylinder of a specified mass gradually moves downwards in the outer cylinder filled with a specified volume of mercury. The time necessary for a specified volume air pass through the specimen is measured. The high-pressure type is suitable for impermeable materials such as coated paper, which needs 60 to 75 seconds for making 100cc air pass through the specimen on the standard densometer. Higher air pressure shortens the measurement time.