Programmable logic controllers supplied by Omron are the focus of a major investment by Bristol Water. Over 100 pumping outstations are linked to a central control station via radio and wired modems. The PLCs, which replaced proprietary water industry controllers on valve actuators, had to be robust, operating in electrically and mechanically challenging environments where heat and vibration are normal. They also had to be able to communicate over radio links with the central computer using an existing Scada communications protocol, providing fail-safe two-way control and reporting procedures. The system had to be capable of expansion to meet future demand for clean water. Omron developed a single software program loaded on to the PLCs that enables them to communicate with both radio satellite and wired controller hubs. The latter proved troublesome because of the need to give hard-wired modems a ‘wake-up’ delayed handshake signal before transmitting data. Garbled data signals at the end of transmission also had to be dealt with. On the C200H-alpha PLC the fourth communications port can be used for security to log the identity of anyone working on the system. Operator control and feedback is provided locally at the PLC by Omron’s NT20S man-machine interface which handles alarms, I/O analysis, trending and pump management.
Pulsed Doppler signals similar to those used in police radar guns are being employed to good effect in the Flodar open channel flowmeter. It can measure the speed and depth of flow in a channel or part-filled pipe without being in contact with the liquid. Suitable for any size or shape channel or pipe from 100mm upwards, the meter can measure depths as shallow as 2mm.
Honeywell has brought out a Coriolis mass flowmeter said to improve process profitability by providing highly accurate measurement of mass or volume flow, density, temperature and percent solids. The SCM 3000 Plus combines a new sensor design and greater range of sizes and materials with a new transmitter option providing remote or integral configuration.The unit is available in eight sizes from 2mm to 80mm, handling mass flow measurement in the range of 0.1 to 200 tons per hour.
Eurotherm’s 2000i family of indicators measure and display temperature and other process variables and also provide alarm handling and advanced communication facilities, the company says. Developed for use with the Series 2000 PID controllers, there are four models catering for a range of applications from extrusions lines to engine test beds.