Printer- a type of Output Device

Printers

The printer is a device that transfers the computer data on to paper. Usually a speed of printer is measured in ppm (Pages/min) or cps (Character/sec). The quality of output is measured in dpi (dots/inch).

The printer are classified as

1.                  Impact

2.                  Non-Impact

Impact

Impact printer use a print head which strike an inked ribbon placed in front of paper. The print head consists of number of metal pins or character molded onto it.

Since these  type of printer requires lots of movable mechanism to produce a print these type of printer are relatively noisier than its counterpart. The printing process is also relatively slow. The print produced by these type of printers are generally of low quality and are very cheap.

Dot matrix printer

These printer consists of 9 to 24 pin head which is used to produce print on the paper. Characters or images are formed by the combination of matrix of dots created by these heads. These printer can produce draft, standard and near letter quality print. Generally the print obtained is poor.

Daisy Wheel printer

These printers resemble very much to electronic typewriters. These printer consists of head in which characters to be printed are molded onto it. These head strike ribbon placed in front of paper and characters are produced similar to that by typewriter mechanism.

These printers cannot produce complex images and prints only standard fonts. To change font the whole wheel mechanism must be changed.

Non-impact Printers

These type of printers don not use mechanical printing parts that strike paper as in case of Impact printers. Because of this these printer produce vary less noise and the printing process is relatively fast. The quality of printing are also high and they can produce good resolution images but these type of printer are quite expensive.

Thermal Printer

These printers use special heat sensitive paper. These printers consist of heated elements on which required images or characters are formed by heating it. When the thermal paper comes into contact with these elements then character are transferred on the paper.

These thermal papers tend to darken over time due to exposure to sunlight and heat. The quality of the printing produced by these printers is not of good quality.

Inkjet Pinter

An inkjet printer is any printer that fires extremely small droplets of ink onto paper to create an image. If you ever look at a piece of paper that has come out of an ink jet printer, you know that:

·                     the dots are extremely small (between 10 and 30 dots per millimeter)

·                     the dots are positioned very precisely

·                     in color printers, the dots can have multiple colors

Ink jet printers are fairly inexpensive -- less expensive than laser printers, and much less expensive than color laser printers.

Different types of ink jet printers form their droplets of ink in different ways. There are several technologies used by printer manufacturers, but by far the most popular technique is the bubble jet. In a bubble jet printer, tiny resistors create heat, and this heat vaporizes ink to create a bubble. The expansion that creates the bubble causes a droplet to form and eject from the print head. A typical bubble jet print head has 64 or 128 tiny nozzles, and all of them can fire a droplet simultaneously.

Laser Printer

The primary principle at work in a laser printer is static electricity. Static electricity is simply an electrical charge built up on an insulated object, such as a balloon or your body.

These printers consist of a photoconductive drum. This drum assembly is made out of highly photoconductive material that is discharged by light photons. As the drum revolves, the printer shines a tiny laser beam across the surface to discharge certain points. In this way, the laser “draws” the letters and images to be printed, as a pattern of electrical charges (an electrostatic image). The drum also rolls over the black toner powers, which are attracted by the charged portion of the drum. Then these black toner powder stick to the paper, which is moving over the drum. Finally, the printer passes the paper though the fuser, a pair of heated rollers. As the paper passes through these rollers, the loose toner power melts, fusing with the fibers in the paper.