What is cold cathode illumination?
A cold cathode fluorescent lamp (CCFL) is a type gas-discharge lamp similar to linear fluorescent or compact fluorescent lamps. CCFLs are used in a number of different specialty applications, such as cold-weather lighting, display back lighting, and signage.
What is the function of cold cathode?
A cold cathode is a cathode that is not electrically heated by a filament. A cathode may be considered “cold” if it emits more electrons than can be supplied by thermionic emission alone. It is used in gas-discharge lamps, such as neon lamps, discharge tubes, and some types of vacuum tube.
What do you mean by hot cathodes and cold cathodes?
In vacuum tubes and gas-filled tubes, a hot cathode or thermionic cathode is a cathode electrode which is heated to make it emit electrons due to thermionic emission. This is in contrast to a cold cathode, which does not have a heating element.
Which monitors typically use a cold cathode fluorescent bulb to provide light for the display?
The liquid crystal display (LCD) has become ubiquitous. The LCD utilizes a cold cathode fluorescent lamp as a light source to back light the display.
Which gauge is the cold cathode discharge type gauge?
cold cathode pressure gauge. A cold cathode pressure gauge ionizes the rest gas in the system and uses the ion current as a measure of the pressure. In contrast to a (hot) ion gauge, the electrons for the ionisation of the rest gas are not created by a hot filament but by a high voltage discharge.
Which is the cold cathode lamp answer?
A cold cathode fluorescent lamp (CCFL) is a lighting system that uses two phenomena: electron discharge and fluorescence. CCFLs are mainly used as light sources for backlights, because they are smaller and have longer lifetimes than ordinary fluorescent lamps.
What are the four types of fluorescent lamp?
Fluorescent circline tubes are typically 1 and 1/8 of an inch in diameter. Their outside diameter (which is measuring the circle from one end to the other) comes in four options – 6, 8, 12, and 16 inches.
How cold cathode gauges work?
A cold cathode ionization gauge measures vacuum pressure by first ionizing gas molecules inside the vacuum gauge and then measuring the resulting ion current. A large potential between the gauge anode and cathode will cause ionization to occur.
Which gauge should be used to measure fine vacuum?
Pirani gauges are a group of indirect measuring pressure gauges which measure the thermal conductivity of the gas sample. Pirani gauges are typically used in the fine vacuum range (1 torr – 10-3torr), as this is the range where they achieve the best accuracy.
Which is the cold cathode lamp * 2 points?
What are the standard sizes of fluorescent tubes?
While there are multiple types of LED and fluorescent tube lights, the three most common are T12, T8 and T5. The terminology comes from “T” for “tubular” and the diameter of the bulb in eighths of an inch, so “T8” represents a tube of 8/8ths of an inch, or 1 inch.
What is a cold cathode gauge?
Cold Cathode Gauges. Cold Cathode Ionization Gauge – Ionization gauges which operate with a cold cathode discharge are called cold cathode or Penning vacuum gauges. The discharge process in the gauge tube is in principle the same as in the electrode system of a sputter-ion pump.
What is the difference between ionization vacuum and cold cathode gauge?
In all Cold Cathode gauges there is considerable higher gas sorption than in the ionization vacuum gauge which operates with a hot cathode. A cold cathode gauge tube, there fore, pumps gases similarly to a sputter-ion pump (S = 10-2 ltr s-1).
What is the upper limit of the measuring region of cold cathode?
The upper limit of the measuring region is decided by the fact that slightly above 10-2 mbar the cold cathode discharge changes to a glow discharge with intense light output in which the current – at constant voltage depends only to a small extent on the pressure and is, therefore, not suitable for measurement purposes.
What are hot and cold cathode devices?
Hot cathode devices include common vacuum tubes, fluorescent lamps, high-pressure discharge lamps and vacuum fluorescent displays . The surface of cold cathodes can emit secondary electrons at a ratio greater than unity (breakdown).