| Boolean Logic
| A method of testing for desired outcomes or “states” by combining data, using operators such as AND, OR and NOT. Boolean logic is frequently used in PLCs to compare input data in order to generate outputs. |
| CRT
| Abbreviation for Cathode Ray Tube, or monitor. This has been the dominant luminous display technology until the late 1990’s, when flatpanel technology is starting to replace CRTs in popularity. |
| Cursor
| A visual indicator on display devices to call the operator’s attention to a particular location on the screen. Cursors may take many forms, from text underlines, to background shading, to enclosure boxes. |
| DDE/NetDDE
| Dynamic Data Exchange (Networked DDE). This is a software protocol, much like a PLC protocol, designed to transfer individual bytes of data between different programs either in the same computer (DDE), or through a network (NetDDE). |
| Dual-scan
| A type of color, liquid crystal, flatpanel display. Dual-scan displays are quite affordable, but they have somewhat limited luminosity and viewing angle. |
| Ethernet
| Ethernet is a local area network protocol that uses a bus physical connection and supports data transfers at 10/100 Mbps. The physical media consists of different types of copper cable dependant on the network distance required. Ethernet uses the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) method to handle simultaneous demands. It is one of the most widely implemented local area network standards. |
| Flatscreen, Flatpanel
| A generic name for several kinds of display technologies which are flat and shallow in depth. |
| HMI
| Abbreviation for Human Machine Interface. This is an abbreviation for an indistinctly defined category of electronic operator interfaces that normally provide high capacity and advanced features. |
| I/O
| Abbreviation for the concepts of input and output, as in the categories of devices managed by PLCs and other types of control equipment. |
| LCD
| Abbreviation for liquid crystal display, a type of backlit display technology. LCD displays are available in color, monochrome and grayscale, but all varieties have limitations in luminosity and viewing angle. |
| MMI
| Abbreviation for man-machine interface. This early abbreviation for any technology which provides a control and monitoring link between humans and machines or plant operations has more recently been replaced by the term Operator Interface, or OI. |
| NEMA Rating
| Abbreviation for National Equipment Manufacturer’s Association. The NEMA rating is a numeric assignment for machinery or equipment, corresponding to a well-defined set of abilities to withstand environmental conditions. |
| OI
| Abbreviation for operator interface. This is a more modern abbreviation for technology providing a control and monitoring link between humans and machines or plant operations. Often, the term OI is applied to interface devices at the simpler end of the spectrum of interface devices. |
| Object
| A visual element in a graphic display which is stored and manipulated independently of other graphical objects. In comparison to bitmapped images, objects:
- require a relatively small amount of memory for storage
- can easily be edited
- can be visually layered on top of each other to produce more complex and useful images
|
| Pixel
| Abbreviation for picture element. A pixel is the smallest controllable, addressable element that can be used to build visual images on a display screen. |
| PLC
| Abbreviation for programmable logic controller. The PLC is the dominant tool for plant-floor control, monitoring, and sequencing of events involving input devices and output devices. |
| SVGA
| Super Video Graphics Adapter, a display system designed to offer greater resolution than standard VGA. There are several varieties of SVGA: 800 pixels by 600 pixels; 1024 by 728; 1280 by 1024, and 1600 by 1200. All SVGA standards support 16 million colors, but the number of colors displayed simultaneously is limited by the memory in the computer system. |
| Tag Name
| Refers to any name used to represent a data point in control or operator interface software. This permits the assignment of meaningful “labels” for data. |
| TFT/Active Matrix
| Abbreviation for Thin Film Transistor--a type of flatpanel color display technology, which, although still somewhat costly, has good luminosity and viewability. |
| Template
| A standardized onscreen visual tool used in some OI devices to perform the same function as a type of hardwired control panel device. For example, a “readout” template on an OI screen can display numeric information in the same way as a gauge or dedicated numeric readout device. |
| Touchscreen
| Refers to technology which permits an operator to make a selection on a display screen by touching the screen with a finger. Touchscreens most often detect finger touches by sensing pressure or changes in electrical capacitance. |
| VGA
| Video Graphics Array, a graphics display system developed by IBM for personal computers. VGA has become one of the de facto standards for PC displays, providing a resolution of 720 pixels by 400 pixels. In graphics mode, the resolution is either 640 by 480 at 16 colors or 320 by 200 at 256 colors. |
| XGA
| Extended Video Graphics Array. XGA display systems provide a resolution ranging from 640 pixels by 480 pixels to 1024 by 768, all at 65,000 simultaneous colors. |
