SCADA systems, hardware and firmware

This chapter discusses various aspects of supervisory control and data acquisition (SCADA) systems, hardware, and firmware. A SCADA system means a system consisting of a number of remote terminal units (RTUs) collecting field data connected back to a master station using a communications system. The master station displays the acquired data and also allows the operator to perform remote control tasks. A successful SCADA installation depends on utilizing proven and reliable technology, with adequate and comprehensive training of all personnel in the operation of the system. Typical considerations when putting a SCADA system together includes overall control requirements, sequence logic, analog loop control, ratio and number of analog to digital points, and speed of control and data acquisition. A watchdog timer is also required to provide a check that the RTU program is regularly executing. The RTU program regularly resets the watchdog time. It is found that where low-level voltages need to be digitized, they must be amplified to match the input range of the board's A/D converter. The ideal differential input amplifier only responds to the voltage difference between its two input terminals regardless of what the voltage common to both the terminals is doing. The typical requirements for an RTU system should include minimization of power consumption, maximization of noise immunity, and clear indication of diagnostics.