PvPlot: A live software oscilloscope library for accelerator control systems

When operating a complex accelerator facility such as the Los Alamos Neutron Science Center (LANSCE), it is often necessary to observe live signal waveforms for various purposes. Traditionally, this has been done using dedicated physical oscilloscopes, whether permanently installed alongside equipment or temporarily deployed on rolling carts. At times, the screens of these oscilloscopes were even transmitted by video link over coaxial cable to secondary television monitors, which was a remarkable convenience at the time, but is considered cumbersome and limited today. With modern control system software and network infrastructure, the inconvenience of physical co-location and dedicated long-distance cabling with dedicated secondary equipment can be eliminated in favor of a flexible and dynamic distributed software approach which reduces complexity while adding significant capability. Here we present a solution using the Experimental Physics and Industrial Control System (EPICS) and Python as part of a comprehensive control system UI library that allows connection to arbitrary signal sources, simultaneous viewing from multiple remote networked locations, and instant reconfiguration or selection of alternate signal sources. Library architecture and various other available UI tools are also discussed.