Plotters: Precision Instruments
Dot-matrix, page, and ink-jet printers are capable of producing page size graphic output, but are limited in their ability to generate high-quality, perfectly proportioned graphic output. For example, on a blueprint the sides of a 12-foot-square room must be exactly the same length. Architects, engineers, city planners, and others who routinely generate high-precision, hard-copy graphic output of widely varying sizes use another hard-copy alternative, plotters.
Types of Plotters:
Drum Plotters:
A drum plotter is also known as roller plotter. It consists of a drum or roller on which a paper is placed. Drum plotter also consists of mechanical device known as robotic drawing arm that holds a set of pens or pencils. The drum rotates back and forth to draw (or print) the graph on the paper. Drum plotter is used to produce continuous output such as to record earthquake readings.
Flatbed Plotters:
A flatbed plotter is also known as table plotter. It plots on paper that is
lying flat on a table-like surface. The flatbed plotter uses two robotic drawing
arms, each of which holds a set of pens. Most of the flatbed plotters have one
to four pens of different colors. These pens move across the paper to draw
charts or graphs on the paper. The movement of these pens is controlled by the
computer system.
Both have one or more pens that move over the paper under computer control to produce an image. Several pens are required to vary the width and color of the lines, and the computer selects and manipulates them. On the drum plotters, the pens and the drum move concurrently in different exes to produce the image. Drum plotters are used to produced continuous output, such as plotting earthquake activity, or ECG. On some flatbed plotters, the pen moves in both exes while the paper remains stationary. However, on most desktop plotters, both paper and pen move concurrently in much the same way as on drum plotters.
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