Overview of the DiscreteDevice object

The DiscreteDevice object is a general purpose ApplicationObject that represents a large class of physical equipment common in manufacturing, such as pumps, valves, motors, and conveyors. These devices have two or more discrete physical states (for example, Open, Closed, and Moving). The actual state of a device is monitored via a combination of discrete inputs, and a device can be optionally controlled using a combination of discrete outputs. For more information on states, see DiscreteDevice object states.

The state names are configurable and are mapped to both input and output Boolean combinations in truth-table form. The meaning of the states depends on the type of discrete device. For a pump, the states might be configured as "Off" and "On," while for a valve they might be configured as "Open," "Closed," and "Moving." Note that a control valve has a continuous position represented by an analog signal of 0 to 100% and is not properly represented with a discrete device. Control valves are best represented with the AnalogDevice object.

When a DiscreteDevice object is commanded to a new state, it sets the configured combination of discrete outputs for that state. When one or more of its monitored discrete inputs change, the DiscreteDevice object determines the new actual state of the equipment and sets the process value (PV) appropriately.

For more information, see Monitoring a DiscreteDevice object via inputs and Controlling a DiscreteDevice object via outputs.

Input and output states are totally independent of each other and can be configured as required by your application; however, the input and output states can be linked by alarms. This allows the object to detect a command timeout and uncommanded change alarms when devices unexpectedly change, or fail to change when commanded to do so. For more information, see DiscreteDevice object alarm capabilities.

Historization of key attributes including the current state (PV) and commanded state (Cmd) can also be configured.

Finally, the DiscreteDevice object supports a rich set of statistics reporting that you can enable during configuration. For more information, see DiscreteDevice object statistical features.

For general information on objects, including relationships, deployment, and alarm distribution, see the Integrated Development Environment (IDE) documentation.

For information on configuration options of object scripts, attributes, or features, click Attributes Help in the Help file header.