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Description
Some of the key system elements included a modular system design, easy to repair or replace components, the ability to quickly bypass a failed component, and a redundant design topology. The redundant design topology has been implemented with a two level design philosophy. The Low Level, or Level 2, Interlocks are critical motion control interlocks implemented completely in hardware. The High Level, or Level 1, Interlocks are complex interlocks implemented with an industry standard programmable logic controller and networked I/O sub-system. To assist the observers in determining the state of the interlock system a graphical display system has been developed in TCL/TK by Dennis Nicklaus and later upgraded by Robert Lupton. This allows the observers to check the real time interlock system status from any X-Terminal. The graphical display system, along with logic diagrams that are located in hard-copy form in a binder near the telescope, allow the observers to quickly identify problems and view the state of the system.
Motor capstan slip detection and telescope velocity limits remain to be installed and tested. The design is complete and printed circuit boards are being manufactured. Design testing at Fermilab is expected to begin in early May with installation at APO tentatively scheduled for mid-June. The hooks into the interlock system are complete and have been tested. Building motion interlocks have been implemented within the interlock system but have not been wired to the building. The connection of these interlocks is pending a lightning protection review. Instrument change interlocks have been installed to support manual instrument change operations. The hardware necessary for automatic instrument change operations has been installed. The configuration of the interlocks for automatic instrument change operations is expected by summer.
Review of Observing Systems and Survey Operations Apache Point Observatory April 25-27, 2000 |