SCADA Applications & Installations:
Control Manufacturing Co. Uses Lookout to Extend Useful Life of Tesco SCADA System
 Control Manufacturing Company, Inc. (CMC) in Napa, California has recently completed a project for the Lake Arrowhead Community Services District (LACSD) involving the integration of old technologies with new. The SCADA system upgrade project called for the replacement of LACSDs central computer and SCADA software with up-to-date Y2K-compliant hardware and software, without the replacement of the 43 existing Tesco LIQ-IVT controllers or the existing communications network.
The existing equipment consisted of two systems. The water SCADA system included an RS-485 network over copper wire to link 3 important sites to each other and to the central monitoring station at 4800 bps. This system also communicated over leased phone lines to 15 RTUs at 1200 bps. The waste water system, which had its central computer at the same location, communicated with 25 RTUs over leased lines at a baud rate of 300 bps.
The main goal of the project was to provide an open, user-friendly HMI SCADA master, which would allow the district to maintain their system in-house, and would allow for future expansion of their system using non-proprietary hardware and software. Ease-of-use was a key requirement as the district plans to maintain their system without complete reliance on the systems integrator, eliminating one of the problems with the original system.
The original setup relied on a combination of polling and report-by-exception protocol, which caused a number of problems with the 300-baud system. Since the district lies in the mountains of Southern California, there are often severe storms resulting in frequent power outages. With each power outage resulting in a large number of alarms in the field and a chorus of RTUs clamoring for attention, the system had to allow a great deal of delay between polling cycles to allow the system to keep up with exception reports. As a result, polling time had been slowed down to only a few polls per day. By taking advantage of National Instruments' Lookout HMI/SCADA software's exceptional flexibility in its polling configuration, Control Manufacturing was able to set up the system to poll for critical alarms at a rate of once every 3 minutes. Other alarms were polled every 15 minutes and poll for all other data at a rate of once every 30 minutes, thus improving the overall system turnaround time considerably. The improved polling configuration allowed the exception reporting to be deactivated at the RTUs, thus eliminating data overloads during system upsets.
The 1200 and 4800 baud portion of the system was also set up on a strictly polled basis without the need to use varying poll rates to have critical system alarms updated on a faster basis. The faster poll rates meant that there was no need for the flexibility of variable flow rates.
The installation and commissioning of the new system was completed in an orderly fashion, with little SCADA system downtime which allowed the district to remain fully operational, with only minor disruptions to their normal work.
According to CMC Project Engineer Doug Wirth, "The District now has a robust SCADA system with spare capacity to use additional drivers and modems to communicate to just about any type of equipment the District may install in the future."
For further information on this system, please contact Brian Smith, Engineering Manager at CMC at 707-258-8400.
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Trademark Acknowledgments: Windows 3.1, Windows 95, Window 98, and Windows NT are trademarks of Microsoft Corporation. Modbus is a trademark of AEG Modicon. Lookout is a trademark of National Instruments. TeleSAFE, Micro16, SCADAPack, and TelePACE are trademarks of Control Microsystems. HART is a trademark of the HART Comunication Foundation. LIQ-IV and LIQ-V are trademarks of Tesco Controls, Inc.
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