Vacuum controllers monitor and control vacuum levels for process equipment such as vacuum furnaces, autoclaves, and coating machines. They provide stable and repeatable control of process chamber pressure for applications such as etching and thin-film deposition. A throttle valve and integral electronics control the pumping speed and provide consistent down-stream pressure control. The user interface consists of a digital front panel with a menu or keypad, or analog components such as knobs and switches. Computer-programmable, web-enabled, and network-ready vacuum controllers are also available. Often, these vacuum controls include a microprocessor or programmable logic controller (PLC). Vacuum controllers that interface to personal computers (PC) may include human machine interface (HMI) software or provide supervisory data acquisition and control functionality (HMI). A vacuum control that sends and receive commands via an industrial fieldbus protocol may use CANbus, SERCOS, or PROFIBUS® (PROFIBUS International).