Computer Solutions
the practical limitation of only 12 devices a segment. Fieldbus was an ultra-expensive solution to the wiring problems of 4-20mA systems. Ethernet IP, HART, and wireless will replace fieldbus one of these days.” Caro rejoins: “There are no Ethernet IP process variable
transmitters yet, even from Endress+Hauser. They have not publicly announced any either. There are intrinsic safety and distance problems in taking Ethernet wiring to the field. Wireless can solve those problems, but Wi-Fi (IEEE 802.11) is not a low power technology yet, and there is no meshing protocol for it.” Before the days of desktop PCs, companies provided
their users with ‘dumb terminals’ connected to mainframe computers, while on the shop floor, equipment was controlled by relays, microcontrollers or dedicated industrial minicomputers. Today, companies want integrated control from the factory sensor/actuator to the boardroom and thin client has emerged as the technology of choice for companies around the world. Thin client is almost a throw back to the days of dumb
terminals. However, instead of having a large mainframe slicing up its processor time among a number of terminals, a central server containing several rack-mounted processor ‘blades’ apportions hardware and software resources via communications links to desktop users. The latter consists of
thin client PCs containing limited hardware resources like disk storage and memory, with the bulk of the software running on the server.
Fat clients
Rob Dinsmore, of HardwarePT, explains: “At present, businesses have to cope with increasingly powerful desktop PCs (fat clients) and the attendant problems of support, maintenance and security being spread throughout an organisation - which may be geographically dispersed across several locations or even several countries. “The concentration of resources at the client end opens up
the possibility of vulnerabilities should the hardware fail or be attacked deliberately. Thin client has revolutionised corporate IT and is now set to revolutionise industrial automation and processes. It cuts the amount of hardware needed at the operator’s end - the client end - and consumes less power.” The more bespoke applications that run on client
machines, the more difficult it is to get the client back up and running again in the event of failure, particularly if an engineer then has to go to the client location to fix the problem. If these applications run on a server instead, the measures would typically be in place to automatically restore the client session onto another blade processor with minimum disruption. ●
Fig. 5. HMI, PLC and servo technology have all been affected by fixed and wireless communications.
Photo courtesy: NASA.
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