If the your AccuPyc 1330 has a 10cc standard sample chamber and you are using an insert to reduce the sample chamber volume to 1 cc, then there will be about 3 cc of dead space around the insert and pressure transducer. This space is necessary to allow free flow of gas around the insert and necessary clearance to allow the insert to be inserted and removed. Although the sample chamber cup size has been reduced to 1 cc by the insert, the total void volume remaining in the 10 cc sample chamber is larger and equals the 1 cc cup size plus the dead space. Your unit is responding normally.

Dead space offset always is associated with use of an insert, regardless of the size of the standard cell that came with the pycnometer. If you measure your chamber without an insert, then the result should be the size of the standard chamber. Only a 1 cc standard chamber is expected to measure 1 cc. ■