An apparatus for exchanging a first gas contained in a sealed container for a second gas. The apparatus comprises a vacuum chamber for receiving the container and for maintaining a controlled pressure about the container, a gas exchange head for exchanging gas in the container while maintaining a seal between the container and the chamber, and a vacuum source coupled to the gas exchange head and to the vacuum chamber for evacuating the first gas from the container and air from the chamber. The apparatus further has a gas source for supplying the second gas, the gas source being coupled to the gas exchange head for supplying the second gas to the container, and a sensor for monitoring the pressure in the container during gas exchange. The present invention further provides for a controller for adjusting the rate with which the first gas is removed from the container and the rate at which the chamber is evacuated such that the container is not damaged, and the controller can adjust the rate at which gas is supplied to the container and the rate with which the chamber is pressurized so as not to damage said container.
A vacuum packaging apparatus is disclosed having a novel vacuum sensor system. The vacuum sensor system includes first and second sensors in communication with a control circuit, which sensors are provided to detect first and second preset vacuum levels as a container is being evacuated. The control circuit further includes a timer for measuring the elapsed time between detection of the first and second preset vacuum levels. The control circuit computes an additional time period necessary to reach a target vacuum level after reaching the second preset vacuum level by multiplying the elapsed time between the first and second preset vacuum levels by an algorithmic factor stored in the control circuit. The algorithmic factor is a numerical constant that is derived for a particular pump type, and is based on the pump characteristics and selected values for the first and second preset vacuum levels and the target vacuum level. The control of the vacuum level is self regulating, and compensates for atmospheric conditions, altitudes or pumping capacities.
A pirani absolute pressure sensor for sensing absolute pressure in a load lock in a range from 100 to 10.sup.-4 torr and a differential pressure sensor for sensing a pressure difference between ambient atmospheric pressure and pressure in the load lock chamber are combined together in a module with a manifold and common circuit components to provide a pressure transducer that is capable of producing not only analog output for absolute pressure measurements, but also control signals at settable absolute and differential pressure values for opening interior and exterior doors of a load lock used to shuttle wafers and other devices into and out of a vacuum processing chamber. The transducer can also produce signals to control transition from slow to fast vacuum pumping of the load lock chamber at a settable threshold pressure.
