Dry Tests of Vacuum Stability in Milking Machines with Conventional Regulators and Adjustable Speed Vacuum Pump Controllers – A. Pazzona, L. Murgia, L. Zanini, M. Capasso, D. J. Reinemann (presentation at the 2003 ASAE Annual International Meeting Sponsored by ASAE, Riviera Hotel and Convention Center, Las Vegas, Nevada, USA, 27- 30 July 2003)