Page 332 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Small neon lamps are most widely used as indicators in electronic equipment and appliances, due to their low
power consumption, long life, and ability to operate on mains power. It also can be used as night lamp. Neon
indicator lamps are normally orange, and are frequently used with a colored filter over them to improve contrast
and change their colour to red or a redder orange, or less often green

Neon sign tube
Neon sign tube is also a cold cathode light. It is a lighting display made of glass tubes that have been filled with
different gases at low pressure. These glass tube can be bent into the shape of letters or decorative designs, and
are mainly used for advertising and decorative purposes. Electrodes are made of iron or nickel, and arranged at
the end of glass tube. The tubes are supplied electric current through a step up transformer. When a high-voltage
is given to the tube, a discharge through the gas start, and the tubes emit light. For starting the discharge these
tubes require 900 to 1200V /m. Applied voltage depends upon the length of tube. A choke may be connected in
series with the primary winding which control the current after discharge takes place. A condenser is connected
across the transformer to improve the power factor of the circuit. Different colours are obtained several other
gases are also used by filling different gases, along with different tints and phosphorcoatings for the glass tubes.
Gas filled Colour of light
Neon Red
Neon and argon Reddish orange
Vapour of mercury Blue
Neon and helium Golden colour

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CITS : Power - Electrician & Wireman - Lesson 54-59