IEC 61227:2008 pdf free download

IEC 61227:2008 pdf free download Nuclear power plants – Control rooms – Operator controls
4.2 Types of HMI
The types of operator interface available for control may be classified into two groups,
a) discrete controls comprising dedicated systems / multiplexed conventional systems;
b) soft controls.
The groups have the following characteristics, and the task analysis described in 4.3 is used to determine the most appropriate type to use.
4.2.1 Discrete controls
Dedicated controls have the disadvantage of being present even when not wanted, thus increasing the size of the whole control desk and providing “clutter” when other controls are in use.
Dedicated controls are particularly suitable for controls in constant use, for example electrical output, or those whose immediate accessibility and reliability are of prime importance, for example an emergency trip button. Requirements for their layout are described in 5.1 .1 .
Multiplexed controls, a sub-set of discrete controls, use a single control for the same function on several equipments, thus reducing the number of controls on the desk or panel so that they can be made smaller and the controls can be brought closer to the operator. However, the operator has to make a selection, so the number of operations is increased and the chances of error and the operator response time may be increased.
Multiplexed controls shall be designed with good feedback to the operator for the function selected, to permit error recovery. They are particularly suitable for the control of seldom- used systems that are not required in a hurry, for example, tank filling, and for systems where the consequences of error are not serious and where time is available for correction in the event of error.
4.2.2 Soft controls
These controls are a type of multiplexed system where they can have different functions at different times. Typically, soft controls are implemented using one (or two) VDUs together with a pointing device (such as mouse, track ball light pen or touch capability), or a combination of a VDU with a set of dedicated controls. Control actions are performed in the following way:
– selection of the object to be controlled using the pointing device;
– presentation of the command options on the VDU as menu items or icons, e.g. in a pop- up-window or on a separate VDU;
– selection and activation of the command option to be executed, again using the pointing device.
These systems have many of the characteristics of conventional multiplexed systems, but make it possible to assemble controls related to specific tasks and not offer the operator controls that are invalid or inappropriate to that task, so guiding the operator to correct