Key features of a counter object

$images\BTN_mini.gif$ How To See Also See Also

Introduction

A counter object provides a number of features and possibilities. This topic provides an overview of the counter-specific characteristics. For a definition of a counter object, click See Also.

Type-specific properties

Each object type has its own type-specific properties. The counter-specific properties can be viewed on the Counter tab in the object properties dialog box. The most important ones are:

Property	Description
Current count	Shows the current process value.
Limit	Check this box to enable alarm supervision so that an alarm will be generated when the value specified in the field to the right is exceeded.
Preset value	Enter the value you want to insert when the operator issues the Preset command.
Maximum value	Enter the maximum value for this object.

Beside the type-specific properties a number of properties which are common to all object types are available from the other tabs of the object properties dialog box.

Operator commands

The four option buttons on the Counter tab show the commands available to the operator during supervision.

When the operator activates one of the four commands, a bit combination is sent to the PLC. The PLC must then interpret the bit combination appropriately, that is, there are no fixed links between the sending of a command and what actually takes place in the PLC. An appropriate interpretation of the sending of, for example, a Preset command could be that the PLC program sets the counter value to the value in the address of the preset value.

Note: Seen from the point of view of the system designer, issuing any of the four commands corresponds to sending a specific bit combination to the PLC. The bit combinations for the four buttons are:

Start 1000

Stop 1001

Reset 1010

Preset 1011

PLC addresses

A counter command corresponds, therefore, completely to a digital command. When the addresses of the counter object are given, you must - just as with digital objects - be aware of the fact that out values must be separated from in values and that a whole word (16 bits) must be reserved for out values.

Both the limit and the preset value can be defined as in, out or i/o and can be linked to specific PLC addresses. They can both be activated from IGSS Supervise by indicating a random value, for example, 0, in the corresponding box.

If, for example, the preset value is defined as i/o, it is the PLC program’s job to transfer it to the counter value when the operator issues the Reset command.

Graphical display of counter objects

A counter object can be represented in multiple ways on a process diagram. Click here for details.

Using counter templates

If you have a number of very similar counter objects sharing multiple properties, you will find it useful to use a counter template. You will thus eliminate the need of entering the same information for many objects and obtain a better consistency in your configuration.

Click here for details.