PLCs, DCSs & Controllers


Temperature process controller has easy-to-read graphics display

June 2000 PLCs, DCSs & Controllers

Overview

The 2704 is a high accuracy, high stability temperature and process controller available in a single, dual or three-loop format. It has a bright 120 x 160 pixel dot matrix display on which all the process information is displayed. The user interface is menu-driven via the display and seven front panel keys, providing extreme flexibility and ease of operation.

The 2704 incorporates a self-correcting input circuit to preserve the instrument calibration accuracy. This maximises accuracy and performance during warm-up and changes in ambient temperature.

Eurotherm's advanced control algorithm gives stable straight line control. Automatic tuning simplifies the commissioning procedure by performing a one shot tune to calculate the optimum PID and cutback values for each loop. To further optimise each control loop, gain scheduling can be used to automatically transfer control between up to three sets of PID values.

Configuration is achieved either via front panel interface or by using iTools configuration package which runs under the Windows 95 or NT operating systems.

PV/SP trending

Trending enables the user to view both current and historical information on the process variable and setpoint of each loop. Both the measurement range and time frame may be modified.

Setpoint programmer

The 2704 can store 50 programs with a maximum of 500 segments, allowing control loop setpoints to follow a predetermined series of ramp and dwell segments. Each program may profile up to three separate variables with each connected to its own control loop. Alternatively, one profile may be assigned to more than one loop.

Program segments can trigger up to 16 digital events allowing dynamic interaction functions. Digital inputs can be assigned to different programmer functions, eg Run, Hold, Reset, Wait, etc.

A holdback function is used to ensure guaranteed dwell periods. It can be applied on a per program or per segment basis and can be active on a low, high or band deviation from the setpoint.

Program segments can trigger user defined patterns of digital values. Digital patterns consist of 16 outputs. This feature is particularly useful when a large number of events are used.

Toolkit blocks

Toolkit blocks allow the user to create custom solutions by internally wiring analog and digital operations together in flexible ways. Twenty-four analog and 32 digital operations are available.

Other functions are available, including pattern generators, timers and totalisers.

I/O expander

The 2000 I/O DIN rail mounting expander can increase the digital I/O capability by a maximum of 20 inputs and 20 outputs. This facility provides the option for greater remote operation of the programmer and expands the 2704 controller PLC logic capability. Communication to this unit is via a two-wire proprietary communication link.





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