Bargraph Display


Operator Menu Location: Generic Hardware Operators Displays


Operator Bitmap:


Functional Description:
The Bargraph Display generic hardware operator provides access to a bargraph display resource in the physical hardware. When the generic operator is linked to a specific hardware resource, it will command that resource to indicate signal values on the display.


Bargraph hardware resources are a collection of LED elements used to visually represent a signal magnitude. The number of LED elements determine the resolution of the display. Typically, the number of elements illuminated is proportional to the signal value. Alternatively, bargraphs can be programmed to illuminate a variable-height band of LEDs above, below, or centered about the signal value of interest.
The number of LEDs illuminated on the bargraph hardware resource, , is proportional to input signal x2 ,

where is the total number of LED elements in the physical bargraph resource, is the minimum input signal value and is the maximum input signal value. (Parameters and are properties of this operator.) For example, if , , , and , 20 LED elements will be illuminated (half of the total elements in the display).


The example above demonstrates the typical configuration of the bargraph display operator. In certain applications however, the user may wish to activate a band of LEDs not necessarily anchored at the bottom reference point. The Bargraph Display operator allows the signal value ( ) to be displayed relative to a reference point input X1 . In fact, signal may be displayed above, below, or centered about the reference point X1 . (The alignment-above, center, or below-is a property of this operator.)
If the alignment property is set to Above, the number of LEDs that are illuminated is

The equation above indicates the following:
•No LEDs are illuminated if the reference point input X1 is above the maximum signal value.
•No LEDs are activated if the signal value is less than minimum signal value.
•The maximum number of LEDs that can be illuminated is

For example, if , , , and , the maximum number of LEDs that can be activated is 20.
•In general, the number of LEDs illuminated is

When the result of this formula is , LED elements are illuminated
Similarly, when the alignment property is set to Below, the number of LEDs that are illuminated is

When the alignment property is set to Center, the signal value is centered with respect to the reference point. The maximum number of LED elements that can be illuminated is

The number of LED elements illuminated is

Digital input controls the presentation of the signal on the display. If , the bargraph will flash; otherwise, if , the bargraph display will be steady. Flashing a bargraph display may be useful to indicate particular operating states. For instance, it could be used to indicate that a process is in Manual mode, or that some alarm condition has arisen.
Analog inputs and represent bargraph alarm limits.
When multiple generic Bargraph Display operators are linked to the same specific hardware resource (e.g., the same physical display), the display will cycle between each operator input value set. The digital output y of the operator is HIGH while the physical hardware is currently displaying its input value (e.g., while the operator is active). Digital output y is LOW while the operator is inactive. When a resource is shared between multiple operators, it is a good idea to indicate what value is currently being displayed. This can be done by connecting output y to an LED Display operator. For example, the same physical display can be used to indicate both a process variable and a process setpoint. In the schema diagram below, both process and setpoint values are displayed on the Chameleon PCM-1 top numeric display. The top LED is lit while the process variable is displayed and the second LED is lit when the process setpoint is displayed.


User-Defined Properties:
Object Name. A string label that identifies the operator
Alignment. This property determines how input signal is displayed relative to reference point X1 : Above, Centered, or Below.
Minimum. The minimum input signal value, . It corresponds to having no LED elements illuminated on the bargraph display.
Maximum. The maximum input signal value, . It corresponds to having all LED elements illuminated on the bargraph display.


Brightness. A brightness setting for the physical display in the range [0-15], with 15 indicating maximum brightness.
Active Period. The period of time (in milliseconds) that the physical display will show input of this operator if the resource is shared. This parameter has no effect if the resource is not shared.

Display Reference Input. This property determines if input pin X1 is visible in the schema diagram. Design Pad issues a warning upon processing the schema when the pin is visible but not connected. The warning message is not issued when the pin is not visible (when this property is not checked).

Display Blinking Input. This property determines if input pin X2 is visible in the schema diagram. Design Pad issues a warning upon processing the schema when the pin is visible but not connected. The warning message is not issued when the pin is not visible (when this property is not checked).

Display Output. This property determines if output pin y is visible in the schema diagram. Design Pad issues a warning upon processing the schema when the pin is visible but not connected. The warning message is not issued when the pin is not visible (when this property is not checked).
Display Low Alarm Input. This property determines if input pin is visible in the schema diagram. Design Pad issues a warning upon processing the schema when the pin is visible but not connected. The warning message is not issued when the pin is not visible (when this property is not checked).

Display High Alarm Input. This property determines if input pin X5 is visible in the schema diagram. Design Pad issues a warning upon processing the schema when the pin is visible but not connected. The warning message is not issued when the pin is not visible (when this property is not checked).

Comments:
•The minimum value must be greater than the maximum value .
•If input is not connected, Design Pad assumes that .
• Design Pad will issue an error on processing if an input pin is not connected.

See Also:
Numeric Display, Alpha-Numeric Display, LED Display