A recorder is a measuring instrument that display a time varying.Signal in a form easy to examine and re-examine,perhaps long after the original signal has ceased to exist.In other word a recorder is a device whose function is to record the value of quantity as it is being measured.Such device may include graphic recording devices,computer printers,tape recorders,or cathode ray tube.
Recording preserves the experimental data in a manageable and usable form.A recording system is very useful as (i)It preserves information which could be obtained at any instant from indicating instruments and (ii)It gives informations about waveforms and transient behaviour or phase relationship in different parts of a circuit.
A recorder records electrical and non-electrical quantities as a function of time or relates two signals to each other.Electrical quantities,such as current,voltage etc.,can be recorded directly while non-electrical quantities,such as pressure,temperature,speed,flow etc.,are recorded indirectly by first converting them into the form of electrical signal with the help of sensors or transducers.
Recording devices are of two types namely (i)analog recorders and (ii) digital recorders.
Gas disharge plasma displays 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 breaking down condition.These cold cathode numerical indicators are called Nixies.(Numicators and Numbertrons).
The Nixie tube is a numeric indicators based on glow disharge in cold cathode gas filled tubes.It is essenntially a multicathode tube filled with a gas such as Neon and having a single anode as shown in fig.
Each of the cathodes is made of a thin wire and is shaped in the form of characters to be displayed,for example,numerals 0 to 9.The anode is also in the form of a thin frame.In its normal operation ,the anode is returned to positive supply through a suitable current limiting resistor,the value of the supply being greater than the worst-case breakdown voltage of the gas within the tube.The gas in the vicinity of the appropriate cathode glows when the cathode is switched to ground potential.
Since 10 cathodes have to be associated with a single anode inside the glass bulb,they have necessarily to be stacked in differnt planes. This requires different voltages for differnt cathodes to enable the glow discharge.
Many Nixie tubes also possess dot-cathodes either on the left or right of the character to serve as decimal points.
For displaying large quantities of alphanumeric data,the readout system employed most commonly is a familiar CRT.CRTs form the basis of CROs and TV systems.To generate characters on the CRT,the generation system of characters on CRTs requires relatively simple electronic circuitry.
A typical CRT display has easy facilities for the control of digit size by controlling the deflections sensitivity of the system.The number of characters displayed can be changed with the help of time shared deflection and modulator circuits.
On a CRT display the intensity and brightness can be realized,with different gray scales,and the display can have different colour depending on the phosphor used in the screen.Generally the phosphor is chosen to be white or green.
Storage type CRTs facilities storing a stationary pattern on the screen without flickering display and it is possible to retain the pattern for a long time independent of the phospher persistence.