【文章內(nèi)容簡介】 of the 6th grade polynomial temperature conversion running at 1 Hz. The second one was the additional CPU load caused by the plex functionality of the existing D/3 system. Here it was underestimated that each digital and analog input and output channel had it?s own alarm limits in the D/3 system. In a SCADA like system as Cube the base functionality of a channel is to read the value and make it available to the system. Any additional functionality must be added. Last not least the load on the work for polling all the alarm limits – typically for a SCADA system – was also driving the work to it?s limits. Finally the contract with Orsi was cancelled and an upgrade of the D/3 system was the only possible solution. It was finally carried out in march 2021. In any case it should be mentioned that the Cube approach had the advantage of a homogeneous configuration environment (for the Cube front end controllers) – pared with heterogeneous environments for ?pure? SCADA systems. SCADA (PVSSII) The H1 experiment at the HERA accelerator decided to use PVSSII for an upgrade of their slow control systems[3]. The existing systems were developed by several members of the H1 collaboration and were difficult to maintain. The decision to use PVSS as a replacement was driven by the results of an extensive survey carried out at CERN by the Joint Controls Project [4]. PVSS is a ?pure? Supervisory And Data Acquisition System (SCADA). It provides a set of drivers for several field buses and generic socket libraries to implement munication over TCP/IP. The core element is the so called event manager. It collects the data (mostly by polling) from the I/O devices and provides an event service to the attached management services like: control manager, database manager, user interface, API manager and the built in HTTP server. The PVSS scripting library allows to implement plex sequences as well as plex graphics. Compared with other SCADA systems PVSS es with one basic feature: it provides a true object oriented API to the device?s data. One major disadvantage of SCADA systems is the fact that two databases, the one for the PLC and the one for the SCADA system must be maintained. Integrated environments try to overe this restriction. EPICS EPICS has emerged at DESY from a problem solver to a fully integrated control system. Starting from the data collector and number cruncher for the cryogenic control system, EPICS made it?s way to bee the core application for the DESY utility group. In addition it is used wherever data is available through VME boards or by means of Industry Pack (IP) modules. For those cryogenic systems which are not controlled by the D/3 system EPICS is used with it?s plete functionality. In total about 50 Input Output Controller (IOC) are operational processing about 25 thousand records. 1 EPICS as a SCADA System The utility group ( water, electrical power, pressed air, heating and air conditioning) is using a variety of PLC?s spread out over the whole DESY site. EPICS is used to collect the data from these PLC?s over Profibus (FMS and DP) and over Ether (Siemens H1 and TCP). The IOC?s provide the interfaces to the buses and collect the data. The built in alarm checking of the EPICS records is used to store and forward alarm states to the alarm handler (alh) of the EPICS toolkit. In addition tools like the channel archiver and the graphic display (dm2k) are used. The default name resolution (by UDP broadcast) and the directory server (name server) are used to connect client and server applications over TCP. All of these are basically SCADA functions. The textual representation of all configuration files ( for the IOC, the graphic tool, the alarm handler and the archiver) provides a flexible configuration scheme. At DESY the utility group has developed a set of tools to create IOC databases and alarm configuration files from Oracle. This way the controls group provides the service to maintain the EPICS tools and the IOC?s while the users can concentrate on the equipment being controlled. 2 EPICS as a DCS System Besides the basic ponents of a SCADA system EPICS also provides a full flavoured Input Output Controller (IOC). The IOC provides all of the function a DCS system requires, such as: a standard set of properties implemented in each record, built in alarm checking processed during the execution of each record。 control records like PID etc.。 configuration tools for the processing engine. The flexible naming scheme and the default display and alarm properties for each record ease the connection between the operator tools and the IOC?s. The flexible data acquisition supports the poll mode as well as the publish subscribe mode. The latter reduces the traffic drastically. PLC?s PLC?s provide nowadays the same rich functionality as it was known from stand alone control systems in the past. Besides the basic features like the periodic execution of a defined set of functions they also allow extensive munication over Ether including embedded servers and different sets of munication programs. Besides the munication processors, display processors can be linked to PLC?s to provide local displays which can be prised as touch panels for operator intervention and value settings. These kind of PLC?s are attractive for turn key systems which are missioned at the vendors site and later integrated into the customers control system. Intelligent I/O New developments in I/O devices allow to ?cluster? I/O in even smaller groups and connect theses clustered I/O channels directly to the control system. PLC?s are not any more necessary for distributed I/O. Simple munication processors for any kind of field buses or for Ether allow an easy integration into the existing controls infrastructure. Little local engines can run IEC 61131 p