Multizone controller helps PLCs perform better

Edited by the Engineeringtalk editorial team Aug 13, 2004

The Mini8 controller offers a number of high performance control solutions for different applications at an affordable cost and in a compact mechanical form.

Designed to integrate seamlessly with programmable logic controllers and other supervisory control and monitoring systems, Eurotherm's latest controller, the Mini8, offers a number of high performance control solutions for different applications at an affordable cost and in a compact mechanical form.

The new controller offers outstanding modularity both in terms of hardware and software functions.

It has four plug-in slots which can accommodate a variety of IO modules, and its feature set enables it to handle a wide range of applications, from simple multiple loops and data acquisition up to complex strategies, including setpoint programming, mathematical and logical operations.

Eurotherm say that the Mini8 will be an ideal partner when used with a PLC in multiloop PID applications such as plastics extrusion and multizone furnaces.

By devolving loop control to the Mini8 the PLC can concentrate on providing fast and effective logic control without the burden of running complex control algorithms.

When used with a PLC in this way, overall system performance is not only improved, but additional advantages include easier configuration, deterministic response and the same autotune capability featured in Eurotherm's standard panel mount controllers.

Inputs and outputs are always updated at the same 110ms PV rate and, as with a PLC, are in no way dependent on the strategy being run.

Eurotherm's established open approach to datacommunications makes the new controller easy to interface both to PLCs and other intelligent masters.

Mini8 can multidrop on either Modbus RTU or Devicenet, offering a highly cost-effective alternative to performing analogue measurement or control loops within the PLC.

By implementing these functions remotely, PLC hardware cost is reduced and the device is relieved of the extra processing burden of analogue control.

The Mini8 can be used with a remote 5.7in operator touch-screen graphics terminal, the VT505, providing 128 user pages and recipes with 320 x 240 pixel resolution.

The VT505 technology provides an extremely easy and flexible interface, and standard screens enable "out of box" operation but still allow users to adapt screens, therefore enhancing visibility and ease of use, to suit their own process.

While the Mini8 will find many applications in use with PLCs, it is nevertheless a highly versatile eight-loop general purpose controller in its own right, providing performance equal to that normally reserved for conventional discrete controllers.

It uses the same analogue input circuitry and control features found in Eurotherm's latest panel mount controllers, and combines high quality multichannel analogue measurement with Eurotherm's proven PID algorithm.

It may be operated alone, or with other instruments as part of a wider data management system.

A wide range of toolkit functions, including maths and logic blocks, can be used to create custom solutions and small machine controllers.

Timing functions include timers, counters and totalisers as well as a nonvolatile real-time clock.

As a stand-alone setpoint programmer, setpoints can be programmed to follow a series of time based ramp and dwell segments.

Each Mini8 can store up to 50 programs with an overall total of 200 segments.

Digital events can be triggered in segments to interface to other parts of the control strategy or external devices.

When used in controlling plastics extrusion processes, the Mini8 is able to detect heater faults.

In this application, utilising a unique cycling algorithm and current transformer input module, the controller can automatically scan electrical heaters connected to its logic control outputs and indicate heater partial load failure, over current or SSR short and open circuit.

Heater current readings are also available within the controller to calculate power delivered to the load and make this information available to a supervisory system.

Heater failure detection is compatible with both single- and three-phase load installations.

If the controller's high density analogue inputs are combined with Eurotherm's 5000 Series recorders, the resulting solution provides outstanding local and network access to any process.

In this situation the 5000 Series offers remote viewing capability and acts as an HMI for the Mini8 using master communications.

The user can control and view information from the Mini8 from either the 5000 TFT touch screen display or from any remote PC connected to the network.