Selector Switch Tags

Selector Switch tags provide the means to create multi-position switches that can be used to create on-off toggles, mode selectors, Hand-Off-Auto (H-O-A) switches, etc.

 

A selector switch can accept two types of feedback:  Equipment feedback indicates the current status or state of the equipment.  Switch Position feedback (an optional parameter that should be used when a second device is also controlling the equipment) drives the position of the selector switch tag.  Both feedbacks are assumed to come from the PLC operating the equipment.

 

Selector Switch Mismatch Conditions

The selector switch is designed to alert the operator to a mismatch condition by providing visual feedback through its native drawing methods.

There are two possible causes for a mismatch condition:

 

•    Position mismatch. The switch position as requested by the operator does not match the actual position as driven by the switch position feedback value. This can occur when there is a lag in response time from the equipment.

•    Value mismatch. The equipment feedback does not match the expected value for the requested or current position.  This type of mismatch can also be used to trigger an alarm.  The alarm must be enabled and the mismatch must exist for a set length of time before an alarm will become active.

 

The native drawing methods for the selector switch will use the following conventions to notify the operator of a mismatch or an alarm condition:

 

•    Alarm indicators take precedence. While an alarm indicator is active, no other mismatch indicator will be displayed. 

•    Alarms are normally indicated with red, and (if possible) will be shown on the requested or current position of the switch.

•    Alarm indicators are displayed until the alarm condition is cleared, regardless of whether the alarm has been acknowledged.

•    When a position mismatch occurs and no alarm state is active, then (if possible) the requested position will be indicated by the drawing method – often by blinking.

•    When a value mismatch occurs and the alarm is either disabled or has not yet triggered, an indication similar to a position mismatch will be displayed, if possible.

 

The characteristics of the selector switch are identified in the table below.

Selector Switch Characteristics

Tag Browser Name: Selector Switch

Database Table Name: SelectorSwitch

Type: Output Tag

Tag Group Memberships:  Numeric, Trenders

Log Enabled Variables: Value

Native Drawing Methods: Vertical Button Drawing Method, Horizontal Button Drawing Method, Toggle Switch Drawing Method, Selector Switch Drawing Method, Analog Output Tag Drawing Methods