Printers: Character printers and graphic plotters are the two devices used to prepare a permanent (or hard copy) record of computer output. The basic difference between printers and plotters is that the former are de­vices whose purpose is to print letters, numbers and similar characters in text-readable form, while the latter print diagrams with continuous […]

Liquid Vapour Display

Liquid Vapour Display(LVD): Liquid Vapour Display are the latest in economical display technology. They employ a new reflective passive display principle and depend on the presence of ambient lights for their operation. Figure 2.25 gives the structure of a typical LVD cell. It consists of a transparent volatile liquid encased between two glass plates and side spacers. […]

Electrophoretic Image Display

Electrophoretic Image Display (EPID): Electrophoretic Image Display is the movement of charged pigment particles suspended in a liquid under the influence of an electric field. This pheonomenon has been uti­lised in electrophoretic image displays, as shown in Fig. 2.24. The basic principle; fabrication and operating characteristics of a reflective type Electrophoretic Image Display (EPID) panel […]

Incandescent Display

Incandescent Display: Incandescent Display has been a basic process of light generation for several decades. This process is now down in fully integrated electronic displays. Incandescent display using 16 segment as well as 5 x 7 dot matrix formats fabricated using thin film micro electronics are now available for alphanumeric characters. Such displays are characterized […]

Dot Matrix Displays

Dot Matrix Displays: Excellent alphanumeric characters can be displayed by using dot matrix LEDs with an LED at each dot location. Commonly used Dot Matrix Displays of prominent characters are 5 x 7, 5 x 8, and 7 x 9, of which 5 x 7 shown in Fig. 2.20 (a), is very popular due to […]

Segmental Displays using LEDs

Segmental Displays using LEDs: In Segmental Displays using LEDs, it is usual to employ a single LED for each segment. For conventional 7 segment LED displays (including the decimal point, i.e. the 8th segment), the wiring pattern is simplified by making one terminal common to all LEDs and other terminals corresponding to different segments. The […]

Segmented Gas Discharge Displays

Segmented Gas Discharge Displays: Segmented Gas Discharge Displays work on the principle of gas discharge glow, similar to the case of Nixie tubes. They are mostly available in 7 segment or 14 segment form, to display numeric and alphanumeric characters. Since these devices require high voltages, special ICs are developed to drive them. The construction […]

Gas Discharge Plasma Displays

Gas Discharge Plasma Displays: Gas Discharge Plasma Displays – These are the most well-known type of alphanumeric displays. Their operation is based on the emission of light in a cold cathode gas filled tube under break­down condition. These cold cathode numerical indicators are called Nixies (Numicators and Numbertrons). This Nixie tube is a numeric indi­cator […]

Liquid Crystal Display(LCD)

Liquid Crystal Display(LCD): Liquid Crystal Display(LCD) are passive displays characterised by very low power consumption and good contrast ratio. They have the following characteristics in common. They are light scattering. They can operate in a reflective or transmissive configuration. They do not actively generate light and depend for their operation on ambient or back lighting. […]

Light Emitting Diodes(LED)

Light Emitting Diodes(LED): The Light Emitting Diodes, Fig. 2.10 (a) is basically a semiconductor PN junction diode capable of emitting electromagnetic radiation under forward conductions. The radiation emitted by LEDs can be either in the visible spectrum or in the infrared region, depending on the type of the semiconductor material used. Generally, infra-red emitting LED’s […]

Digital Display System

Digital Display System: Digital Display System – The rapid growth of electronic handling of numerical data has bought with it a great demand for simple systems to display the data in a readily understandable form. Display devices provide a visual display of numbers, letters, and symbols in response to electrical input, and serve as constituents […]

Concentric Vane Repulsion Type Instrument

Concentric Vane Repulsion Type Instrument (Moving Iron Type): Concentric Vane Repulsion Type Instrument – A variation of the radial vane instrument is the concentric vane repulsion movement. The instrument has two concentric vanes. One vane is rigidly attached to the coil frame while the other can rotate coaxially inside the stationary vane, as shown in […]

Moving Iron Types Instrument

Moving Iron Types Instrument: Moving Iron Types Instrument can be classified into attraction and repulsion types. Repulsion type instruments are the most commonly used. Iron vane ammeters and voltmeters depend for their operations on the repul­sion that exists between two like magnetic poles. The movement consists of a stationary coil of many turns which carries […]


Electrodynamometer: Electrodynamometer – The D’Arsonval movement responds to the average or dc value of the current flowing through the coil. If ac current is sought to be measured, the current would flow through the coil with positive and negative half cycles, and hence the driving torque would be positive in one direction and negative in […]

Taut Band Instrument

Taut Band Instrument: The Taut Band Instrument utilizes the same principle as the D’Arsonval movable coil and fixed magnet. The primary difference between the two is the method of mounting the movable coil. The taut band movement has the advantage of eliminating the friction caused by a jewel-pivot suspension. The meter has a coil mounted […]

Practical PMMC Movement

Practical PMMC Movement: The basic Practical PMMC Movement (also called a D’Arsonval movement) offers the largest magnet in a given space, in the form of a horse-shoe, and is used when a large flux is required in the air gap. The D’Arsonval movement is based on the principle of a moving electromagnetic coil pivoted in […]