Description and operation

The structure of the cathodic tube drift directly from the cold cathode diode valve , in its turn derived from the tube of Crookes, to which covered screen of fluorescent material is added one, also called Tube of Brown. In 1922 the first version was developed trades them to hot cathode from part of J. B. Johnson and H. W. Weinhart, of the Electric Western.

The cathode is a small heated metallic element to the incandescence that emits electrons for termoelettronico effect. To the inside of the cathodic tube, in which it has been practiced an empty one pushed, these electrons come directed in a bundle (cathode rays) for means of one elevated potential difference them electrical worker between cathode and anode, with the aid of other magnetic electric fields or opportunely arranged in order to focus the bundle accurately. The beam (said also electronic paint-brush) comes deflected from the action of magnetic fields (Force of Lorentz) so as to to succeed in to hit a point any on the internal surface of the screen, the anode. This surface is covered of fluorescent material (sayings phosphorus, in kind metals of transition or rare-earths) that excited from the energy of electrons it emits light.

In the televisori and the monitor the surface scandita second a predefined matrix of successive lines, call raster, and the image is created modulating the intensity of the electronic bundle second the course of marks them video. The scansion is obtained having the bundle for means of the variable magnetic field generated from opportune fixed electromagnets on the "neck" of the tube (electromagnetic deflection), that they constitute the so-called one giogo of deflection. I affixed electronic circuits to you pilot the electromagnets of the giogo so as to to carry out one scansion in perfect synchrony.

Inthe oscilloscope instead the intensity of the electronic paint-brush he is constant, while the deflection comes carried out based on marks them arbitrary. Usually the horizontal deflection happens proportionally to the time, second a configurabile base from the customer, while the vertical one is proporziona them to marks them to analyze.

In these tubes, plus tight and long, the deflection comes orthogonally carried out for means of an electric field generated from plates disposed to the inside of the tube (electrostatic deflection). This technique is preferibile in the oscilloscope because fast one concurs a variation much of marks them of deflection, that instead it is limited within precise margins fromthe inductance of the electromagnets.