When designing an automated leak testing station it is not always possible to have the leak tester located as close to the test part as one would like. Uson has produced an aplication note that describes how a remote sensor and valve can be used to minimize test volume and keep the leak test time fast.
To eliminate problems caused by connecting test instruments far from the product, Uson recommends mounting a remote sensor close to the test head. Because remote pressure sensors are mounted near test points, internal test volumes remain small and thus response time is very rapid: exactly what automated processes demand.A remote valve traps air between the product under test and the remote sensor. The 
remote sensor returns its signals to the tester over wires, which can be shielded inside cable or metal conduit.
Full details of how the equipment may be setup, the appropriate leak rate calculations and a circuit diagram my be downloaded at Uson's Literature Club at http://www.uson.com/uson-literature-club/ where registration is free and members gain access to all published application notes, white papers and product literature.