Controller Designed for Harsh Water Environments

Typical programmable logic controllers (PLCs) are designed for factory automation and are not equipped to withstand the error-prone communications, temperature extremes, high humidity, poor quality power, and powerful lightning transients found in water and wastewater system applications.

Typical programmable logic controllers (PLCs) are designed for factory automation and are not equipped to withstand the error-prone communications, temperature extremes, high humidity, poor quality power, and powerful lightning transients found in water and wastewater system applications.

To provide the benefits of a PLC without the limitations, Control Microsystems has developed the SCADAPack programmable controller for use in harsh environments. It features a conformal coating for corrosion resistance, tolerates temperatures from minus 40 degrees F to 158 degrees F, and includes built-in transient protection on all I/O, power, and modem lines.

The same family of modules includes a nonstop power supply with battery charger and an isolated 24-volt output for current loops, and modems for radios, dedicated telephone lines, or dial-up telephone lines.

Compared to a factory PLC, the SCADAPack has significantly lower integration and installation costs. There is no need for ventilation or heating, and no need for additional transient protection. The modems and power supply are part of the same family of modules, which ensures compatibility.

The SCADAPack is programmable in Relay Ladder Logic, making it suitable for automation of pump stations, treatment plants, valve chambers, etc. Relay Ladder Logic programs are created on a personal computer using Windows™ 3.1, Windows 95 or Windows NT. The resulting program can be downloaded to the SCADAPack through a direct connection, or through the communication network, be it a data highway, radio, dedicated modem or dial-up modem. Any diagnostic function that can be performed on site can also be performed remotely, which reduces maintenance response time.

The SCADAPack is able to execute two programs at the same time: one written in “C” language and the other in Ladder Logic. With up to 900K of memory available to C, even the largest application can be achieved. Since the C program is independent of Ladder Logic, sensitive functions such as flow integration can continue while the Ladder Logic program is halted for maintenance.

The SCADAPack provides Modbus as its native protocol, making it compatible with all other Modbus devices and software. Other open protocols are also available. Up to four serial ports are provided, each of which can be used as a Modbus master or slave.

To simplify the system design, the SCADAPack provides a Store-and-Forward algorithm that allows the units to act as a digital repeater. Messages received by a suitably configured SCADAPack are retransmitted as required to more distant units. A further benefit of this technique is that only one radio frequency is required, which can overcome licensing issues in areas where available frequencies are limited.

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