The cathode ray oscilloscope (CRO) provides a visual presentation of any waveform applied to Figure 1: Block diagram of a basic cathode-ray oscilloscope. CRT is the heart of CRO and it generates the electron beam and accelerates the It amplifies the sweep generator output,during the ordinary mode of CRO. Full Cathode-Ray Oscilloscope I. F. Alignment Pro- cedure for Many of the Complicated Superhetero- dyne Receivers. • Simple Mechanism Permits Pages to Be.
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Example 7 on an accelerated electron (See lesson 1) describes a portion of a cathode ray tube (CRT). This tube, is commonly used to obtain a visual display of. The following should give the student some familiarisation with the function and uses of the cathode ray oscilloscope (C.R.O.). Consider a simple sine wave. This article gives the information of what is a CRO, working and block diagram of CRO, uses and its applications of Cathode ray oscilloscope.
Their parts are explained below in details. Cathode Ray Tube The cathode ray tube is the vacuum tube which converts the electrical signal into the visual signal. The cathode ray tube mainly consists the electron gun and the electrostatic deflection plates vertical and horizontal. The electron gun produces a focused beam of the electron which is accelerated to high frequency. The vertical deflection plate moves the beams up and down and the horizontal beam moved the electrons beams left to right. These movements are independent to each other and hence the beam may be positioned anywhere on the screen. Electronic Gun Assembly The electron gun emits the electrons and forms them into a beam.
It consists of six parts namely heater, a cathode, a grid, a pre-accelerating anode, a focusing anode and an accelerating anode. In order to obtain the high emission of electrons the layer of barium oxide which is deposited on the end of cathode is indirectly heated at moderate temperature.
The electrons after this passes through a small hole called control grid which is made up of nickel. As the name suggests the control grid with its negative bias, controls the number of electrons or indirectly we can say the intensity of emitted electrons from cathode.
After passing through the control grid these electrons are accelerated with the help of pre-accelerating and accelerating anodes. The pre-accelerating and accelerating anodes are connected to a common positive potential of volts.
Now after this the function of the focusing anode is to focus the beam of the electrons so produced. The focusing anode is connected to adjustable voltage volts. Now there are two methods of focusing the electron beam and are written below: Electrostatic focusing.
Here we will discuss electrostatic focusing method in detail. Now we will this force to defect the beam of electrons coming out of electron gun. Let us consider two cases: Case One In this case we are having two plates A and B as shown in the figure. The direction of electric field is from A plate to plate B at right angle to the surfaces of the plate.
The equipotential surfaces are also shown in the diagram which is perpendicular to the direction of electric field. As the beam of electron passes through this plate system, it deflects in the opposite direction of electric field. The deflection angle can be easily varied by changing the potential of the plates. Case Second Here we have two concentric cylinders with a potential difference applied between them as shown in the figure.
The resultant direction of electric field and the equipotential surfaces are also shown in the figure. The equipotential surfaces are marked by the dotted lines which are curved in shape.
Now here we are interested in calculating the deflection angle of electron beam when it passes through this curved equipotential surface. Let us consider the curved equipotential surface S as shown below. When a beam of electron is incident at angle A to the normal then it deflects by angle B after passing through the surface S as shown in the figure given below.
The normal component of velocity of the beam will increase as force is acting in s direction normal to the surface. We can from the above equation see that there is bending of the electron beam after passing through the equipotential surface. Therefore this system is also called focusing system.
These plates are also called deflection plates. The field produced by these plates is in the direction of positive y axis and there is no force along the x-axis. After deflection plates we have screen through which we can measure net deflection of the electron beam. Now let us consider a beam of electron coming along the x-axis as shown in the figure.
The beam deflects by angle A, due presence of electric field and deflection is in the positive direction of y axis as shown in the figure.
Now let us derive an expression for deflection of this beam. By the conservation of energy, we have loss in potential energy when the electron moves from cathode to accelerating anode should be equal to gain in kinetic energy of electron.
Mathematically we can write, Where, e is the charge on electron, E is the potential difference between the two plates, m is the mass of electron, and v is the velocity of the electron. It is typically divided into four sections which are display, vertical controllers, horizontal controllers, and Triggers. Most of the oscilloscopes are used the probes and they are used for the input of any instrument.
We can analyze the waveform by plotting amplitude along with the x-axis and y-axis. In modern electronics, the CRO plays an important role in the electronic circuits. What is a CRO? The cathode ray oscilloscope is an electronic test instrument, it is used to obtain waveforms when the different input signals are given.
In the early days, it is called as an Oscillograph. The oscilloscope observes the changes in the electrical signals over time, thus the voltage and time describe a shape and it is continuously graphed beside a scale.
By seeing the waveform, we can analyze some properties like amplitude, frequency, rise time, distortion, time interval and etc.
The CRO recruit the cathode ray tube and acts as a heat of the oscilloscope. In an oscilloscope, the CRT produces the electron beam which is accelerated to a high velocity and brings to the focal point on a fluorescent screen. Thus, the screen produces a visible spot where the electron beam strikes with it. By detecting the beam above the screen in reply to the electrical signal, the electrons can act as an electrical pencil of light which produces a light where it strikes.
This provides the power supply circuit of the oscilloscope. Here we will use high voltage and low voltage. The low voltage is used for the heater of the electron gun to generate the electron beam. The high voltage is required for the cathode ray tube to speed up the beam.
The normal voltage supply is necessary for other control units of the oscilloscope. The horizontal and vertical plates are placed between the electron gun and the screen, thus it can detect the beam according to the input signal. Just before detecting the electron beam on the screen in the horizontal direction which is in X-axis a constant time-dependent rate, a time base generator is given by the oscillator.
The signals are passed from the vertical deflection plate through the vertical amplifier. Thus, it can amplify the signal to a level will be provided the deflection of the electron beam.
If the electron beam is detected in the X-axis and the Y- axis a trigger circuit is given for the synchronizing these two types detections. Hence the horizontal deflection starts at the same point of the input signal. Working of CRO The following circuit diagram shows the basic circuit of a cathode ray oscilloscope.