When I first went to my electronics lab during my engineering, I found a machine that has so many buttons. I was in fact a little worried about this box’s features. There were so many knobs and other button which I felt like some rocket science as I have never seen anything like this before. However after some time, I got familiar with that CRO box and finally my fear was gone. So, let’s see what this CRO thing is. Basics Of CRO are here.
CRO means Cathode Ray Oscilloscope. CRO mainly consists of CRT- Cathode Ray Tube. The main components of CRT are
Screen of CRO
Components Of Electron Gun : Basics Of CRO
Pre and post accelerating anodes
There are two types of deflecting plates
Horizontal deflecting plates
Vertical deflecting plates
Heating element is used to heat up the element of cathode. It requires voltage 6.3 volt and current around 600 mA. Electronic focusing system used in CRO is quite straight forward.
CRT of TV uses electromagnetic focusing system. Its resolution is more than that of electromagnetic focusing system. In computing CRO, electromagnetic focusing system is used.
The cathode is in cylindrical shape at the end of which a layer of barium oxide BaO or stronsium oxide SrO is deposited in order to have high emission of electrons at moderate temperature.
Control grid which is in cylindrical shape , is used to control the intensity of electron beam. For that it is given to negative potential which is prepared by Nickel material.
Pre And Post Accelerating Anodes
These are the anodes responsible for injecting the acceleration to the electron beam in order to maintain constant velocity. For that these anodes are held at 1500volts.
In case of high frequency CROs, post accelerating anode is used to increase the brightness of the trace.
These are the anodes responsible for electrostatic focusing system. For that this anode is held at 500 volts. CRT of CRO uses electrostatic focusing system whereas CRT of TV picture tube uses electromagnetic focusing system which has more resolution.
In the normal CROs we use electrostatic focusing system, less resolution which are used in labs for scientific measurements.
In the focusing system , “Astigmatism” is used which is an additional focus control in which a small DC potential is applied to the deflecting plates by disconnecting the actual supply.
These are the plates responsible for getting the motion of electrones, horizontal as well as vertical. There are two types of deflecting plates available.