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What is a CRO (Cathode Ray Oscilloscope) & Its Working

The CRO stands for a cathode ray oscilloscope . 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. The applications of CRO are mainly involved in the radio, TV receivers, also in laboratory work involving research and design. 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.

Block Diagram of CRO

The following block diagram shows the general-purpose CRO contraction . The CRO recruits 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.

To complete this task we need various electrical signals and voltages. 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. A 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 that 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 synchronizing these two types of detections. Hence the horizontal deflection starts at the same point as the input signal.

Working Principle

The CRO working principle depends on the electron ray movement because of the electrostatic force. Once an electron ray hits a phosphor face, then it makes a bright spot on it. A Cathode Ray Oscilloscope applies the electrostatic energy on the electron ray from two vertical ways. The spot on the phosphor monitor turns due to the effect of these two electrostatic forces which are mutually perpendicular. It moves to make the necessary waveform of the input signal.

Construction of Cathode Ray Oscilloscope

The construction of CRO includes the following.

Cathode Ray Tube

Electronic gun assembly, deflecting plate.

• Fluorescent Screen For CRT
• Glass Envelop

The CRO is the vacuum tube and the main function of this device is to change the signal from electrical to visual. This tube includes the electron gun as well as the electrostatic deflection plates. The main function of this electron gun is used to generate a focused electronic ray that speeds up to high frequency.

The vertical deflection plate will turn the ray up & down whereas the horizontal ray moved the electrons beams from the left side to the right side. These actions are autonomous from each other and thus the ray may be located anyplace on the monitor.

The main function of the electron gun is to emit the electrons to form them into a ray. This gun mainly includes a heater, a grid, cathode, and anodes like accelerating, pre-accelerating & focusing. At the cathode end, the strontium & barium layers are deposited to obtain the high electrons emission of electrons at the moderate temperature, the layers of barium, and are deposited at the end of the cathode.

Once the electrons are generated from the cathode grid, then it flows throughout the control grid that is generally a nickel cylinder through a centrally situated co-axial by the axis of CRT. So, it controls the strength of the generated electrons from the cathode.

When electrons flow throughout the control grid then it accelerates with the help of a high positive potential which is applied to the pre-accelerating or accelerating nodes. The electron ray is concentrated on electrodes to flow throughout the deflection plates like horizontal and vertical & supplies on to the fluorescent lamp.

The anodes like accelerating & pre-accelerating are connected to 1500v & the focusing electrode can be connected to 500v. The electron ray can be focused on using two techniques like Electrostatic & Electromagnetic focusing. Here, a cathode ray oscilloscope utilizes an electrostatic focusing tube.

Once the electron ray leaves the electron gun then this ray will pass throughout the two sets of the deflecting plate. This set will generate the vertical deflection that is known as Y plate’s otherwise vertical deflecting plate. The set of the plate is used for a horizontal deflection which is known as X plate’s otherwise horizontal deflection.

Fluorescent Screen of CRT

In the CRT, the front face is known as the faceplate, For the CRT screen, it is flat and its size is about 100mm×100mm. The CRT screen is somewhat bent for bigger displays and the formation of faceplate can be done by pressing the molten glass into a form & after that heating it.

The inner face of the faceplate is covered by using phosphor crystal to change the energy from electrical to light. Once an electronics ray hits phosphor crystal, the energy level can be enhanced & thus light is generated throughout phosphorous crystallization, so this occurrence is known as fluorescence.

Glass Envelope

It is an extremely evacuated conical form of construction. The inside faces of the CRT among the neck as well as the display are covered through the aquadag. This is a conducting material that acts like a high-voltage electrode. The surface of the coating is connected electrically toward the accelerating anode to help the electron to be the center.

Working of CRO

The following circuit diagram shows the basic circuit of a cathode ray oscilloscope . In this, we will discuss important parts of the oscilloscope.

Vertical Deflection System

The main function of this amplifier is to amplify the weak signal so that the amplified signal can produce the desired signal. To examine the input signals are penetrated to the vertical deflection plates through the input attenuator and the number of amplifier stages.

Horizontal Deflection System

The vertical and horizontal system consists of horizontal amplifiers to amplify the weak input signals, but it is different from the vertical deflection system. The horizontal deflection plates are penetrated by a sweep voltage that gives a time base. By seeing the circuit diagram the sawtooth sweep generator is triggered by the synchronizing amplifier while the sweep selector switches in the internal position. So the trigger saw tooth generator gives the input to the horizontal amplifier by following the mechanism. Here we will discuss the four types of sweeps.

Recurrent Sweep

As the name, itself says that the sawtooth is respective that is a new sweep is started immodestly at the end of the previous sweep.

Triggered Sweep

Sometimes the waveform should be observed that it may not be predicted thus, the desired that the sweep circuit remains inoperative and the sweep should be initiated by the waveform under the examination. In these cases, we will use the triggered sweep.

Driven Sweep

In general, the drive sweep is used when the sweep is free-running but it is triggered by the signal under the test.

Non-Saw Tooth Sweep

This sweep is used to find the difference between the two voltages. By using the non-sawtooth sweep we can compare the frequency of the input voltages.

Synchronization

The synchronization is done to produce a stationary pattern. The synchronization is between the sweep and the signal should measure. There are some sources of synchronization that can be selected by the synchronization selector. Which are discussed below.

In this, the signal is measured by the vertical amplifier and the trigger is abstained by the signal.

In the external trigger, the external trigger should be present.

The line trigger is produced by the power supply.

Intensity Modulation

This modulation is produced by inserting the signal between the ground and cathode. This modulation causes by brightening the display.

Positioning Control

By applying the small independent internal direct voltage source to the detecting plates through the potentiometer the position can be controlled and also we can control the position of the signal.

Intensity Control

The intensity has a difference by changing the grid potential with respect to the cathode.

Electrical Quantities Measurements

Electrical quantities measurements by using CRO can be done like amplitude, time period and frequency.

Measurement of Amplitude

Measurement of Time Period

Measurement of frequency.

The displays like CRO is used to exhibit the voltage signal like a time function on its display. The amplitude of this signal is stable; however, we can change the number of partitions that cover up the voltage signal within vertical way by changing volt/division button on top of the CRO board. So, we will acquire the signal’s amplitude, which is there on the CRO screen with the help of the below formula.

‘A’ is the amplitude

‘j’ is the volt/division value

‘nv’ is the no. of partitions that cover up the signal within a vertical way.

CRO displays the voltage signal as a function of time on its screen. The Time period of that periodic voltage signal is constant, but we can vary the number of divisions that cover one complete cycle of the voltage signal in the horizontal direction by varying the time/division knob on the CRO panel.

Therefore, we will get the Time period of the signal, which is present on the screen of CRO by using the following formula.

‘T’ is the Time period

‘j’ is the time/division value

‘nv’ is the number of partitions that cover up one whole cycle of the periodic signal within the horizontal way.

On the CRO screen, the measurement of tile & frequency can be done very simply through the horizontal scale. If you want to make sure accuracy while measuring a frequency, then it assists to enhance the area of the signal on your CRO display so that we can more simply convert the waveform.

Initially, the time can be measured with the help of the horizontal scale on the CRO & counting the number of flat partitions from one finish of the signal to the other wherever it crosses the flat line. After that, we can develop the number of flat partitions through the time or division to discover the time period of the signal. Mathematically the measurement of the frequency can be signified as frequency = 1/period.

Basic Controls of CRO

The basic controls of CRO mainly include position, brightness, focus, astigmatism, blanking & calibration.

In the oscilloscope, the position control knob is mainly used for position control of the intense spot from the left side to the right side. By regulating the knob, one can simply control the spot from left side to the right side.

The ray’s brightness mainly depends on the intensity of the electron. The control grids are accountable for the electron intensity within the electron ray. So, the grid voltage can be controlled by adjusting the electron ray brightness.

The focus control can be achieved by regulating the applied voltage toward the center anode of the CRO. The middle & other anodes in the region of it can form the electrostatic lens. Therefore, the main length of the lens can be changed by controlling the voltage across the center anode.

Astigmatism

In CRO, this is an extra focusing control & it is analogous toward astigmatism within optical lenses. A ray is focused in the middle of the monitor would be defocused on the screen edges as the electron paths lengths are dissimilar for the center & the edges.

Blanking Circuit

The time base generator present in the oscilloscope generated the blanking voltage.

Calibration Circuit

An oscillator is necessary for the purpose of calibration within an oscilloscope. However, the oscillator which is used should generate a square waveform for preset voltage.

Applications

• The CRO’s are used in huge applications like radio stations for observing the transmitting & receiving the properties of the signal.
• The CRO is used to measure the voltage, current, frequency, inductance, admittance, resistance, and power factor.
• This device is also used to check the AM and FM circuits characteristics
• This device is used to monitor the signal properties as well as characteristics and also controls the analog signals.
• The CRO is used through the resonance circuit to view the shape of the signal, bandwidth, etc.
• The shape of voltage and current waveform can be observed by CRO which helps to take the necessary decision in a radio station or communication station.
• It is used in laboratories for the purpose of research. Once researchers design a new circuit, then they use CRO to verify the waveforms of voltage and current of every element of the circuit.
• Used for comparing phase & frequency
• It is used in TV, Radar, and analysis of engine pressure
• To check the reactions of nervous and heartbeat.
• In the hysteresis loop, it is used to find BH curves
• Transistor curves can be traced.

The advantages of CRO include the following.

• Cost and Timeline
• Training requirements
• Consistency & quality
• Time efficiency
• Expertise & experience
• Capacity for problem-solving
• Hassle-free
• Assurance for regulatory compliance
• Voltage measurement
• Current measurement
• Examination of waveform
• Measurement of phase and frequency

Disadvantages

The disadvantages of CRO include the following.

• These oscilloscopes are expensive as compared with other measuring devices like multimeters.
• They are complicated to repair once it gets damaged.
• These devices need complete isolation
• These are huge, heavy and uses more power
• A lot of control terminals which is not so easy to understand at one instance But for easy of use,  multiple channel capture and screen and waveform clarity one could go for Digital Storage Oscilloscope. To know more on DSO click on this link

Uses of CRO

In the laboratory, the CRO can be used as

• It can display different types of waveforms
• It can measure the short time interval
• In voltmeter, it can measure the potential difference.

In this article, we have discussed the working of CRO and its application. By reading this article you have known some basic knowledge about the working & applications of the CRO. If you have any queries regarding this article or to implement the ECE & EEE projects , please comment in the below section. Here is the question for you, what are the functions of the CRO?

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• What is a CRO metroq
• Block Diagram of CRO electronicspost
• Working of CRO www.electrical4u

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CRO Working and Application

 cro working and application..

Application of CRO:

• For measure waveform.
• For measure voltage and current.
• For measure frequency and phase angle.
• For measure power , resistance Etc.                                  these are provide help to know about cro working and application.

1. Examination of wave forms  2. Voltage measurement

3. frequency measurement, 1. examination of waveform:, 2. voltage measurement.

As discussed before, if the signal is applied to the vertical deflection plates only, a vertical line appears s on the screen. The height of the line is proportional to peak to peak voltage of the applied signal. The following procedure is adopted for measuring voltages type application of cro. By this application of cro these can do…

3.  Frequency measurement

Working of cro ( cathode ray oscilloscope)..

What is CRO ?.

CRO full form is cathode ray oscilloscope. It is use to measure electrical parameters in time and amplitude form. it is used to obtain waveform when the different input signals are given. In the early days, it is called as an Oscilloscope. 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.

Block Diagram of CRO (CRO working and application)

It has mainly 5 part in it’s construction . By these points we can understand about working of CRO:

• Cathode ray tube
• Power supply
• Sweep generator
• Triggering circuit
• Cathode ray tube : it is the main part of CRO which is known as heart of CRO. It is further divide into four part
• Electron gun assembly: electron gun assembly is source of electrons.from where electron is generated and then by acceleration a direction is given. Electron is generated by cathode. On the edge of cathode, barium and strontium oxide layer is available. When it is heated electrons is generated. These electrons are passed from a control grid which give a required direction. Acceleration of electron is done by the help of anodes. These anodes are working on 1.5 kV supply. By focusing anodes electrons is focus towards screen. This is working on 500 volts.
• Deflection plates : electrons coming from electron gun is passed through horizontal and vertical deflection plates. Vertical plates give direction in vertical (Y-axis) and horizontal plates give direction in horizontal (X-axis).
• Florescent screen : a flat screen is in the front of CRO. Its normal size is 100mm×100mm. Screen is made of glass. It has a layer of phosphor . When electron hit the phosphor heat and light is generated, by this waveform is generated.
• Glass envelope: complete CRT is packed into a close envelope. This envelope is stop disturbance of measurement. By which electron can flow smoothly.
• Power supply : use of power supply is to powering up different different sections of CRO. For this a power transformer is use . This power transformer has many tapping of various voltage range in its secondary side. By using rectifier DC power is generated and use where required.
• Amplifier : deflection system of CRO require a high voltage DC supply. For this amplifier is used.
• Sweep generator: on screen of CRO, electron beam comes a very high speed. So that it is impossible to see by eyes. So a sweep generator is use to see. Sweep generator control the speed of electron beam.  So that waveform can be measured.
• Triggering circuit : work of triggering circuit is to switching of power supply and amplifier. By help of this require output get.

1. Attenuator

it is applied to the amplifier. The attenuators are employed at the input of both vertical and horizontal amplifiers.

2. Amplifier

The amplifiers of an oscilloscope consist of a vertical amplifier and a horizontal amplifier. The vertical amplifiers amplify the vertical input signal before it is applied to the Y-plates. The horizontal amplifier amplifies the signal, before it is connected to the X-plates.

3. Saw-tooth Generator 

4. gate amplifier or z-amplifier, 5. trigger (gate amplifier output), 1. internal triggering, 2. external triggering, 3. line triggering, application of cro.

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Cathode Ray Oscilloscope (CRO)

In this chapter, we are going to learn about the cathode ray oscilloscope (CRO), the Block diagram of CRO, the construction and working of CRO, and the applications of CRO. So let’s discuss from the beginning the basic concept of CRO.

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Table of Contents

• the cathode ray oscilloscope (CRO) is generally referred to as an oscilloscope or simply scope. It is a basic electronic test instrument that allows observations of constantly varying signal voltages usually as a two-dimensional graph of one or more electrical potential differences as shown in Fig.1. It allows an electronic engineer to ‘observe’ the signal in various parts of the electronic circuit.
• By ‘ observing ’ the signal waveforms, the engineers or technicians can correct errors, understand mistakes in the circuit design and thus make suitable adjustments. The circuit symbol of an oscilloscope is shown in Fig.2.
• A cathode ray oscilloscope or simply CRO or oscilloscope is one of the extremely useful and the most versatile tool used in the sciences, medicine, engineering, and telecommunication industry. These are commonly used to observe the exact wave shape of an electrical signal.
• In addition to the amplitude of the signal, an oscilloscope can show distortion, the time between two events (such as pulse width, period, or rise time), and the relative timing of two related signals.
• Originally all oscilloscopes used cathode ray tubes(CRTs) as their display element and linear amplifiers for signal processing. However, modern oscilloscopes have LCD or LED screens, fast analog-to-digital converters, and digital signal processors. Some oscilloscopes use storage CRTs to display single events for a limited time.
• These days oscilloscope peripheral modules are available for general-purpose laptop or desktop personal computers which allows the laptop or desktop computers to be used as test instruments.
• An oscilloscope allows us to observe the constantly varying signal, usually, as a two-dimensional graph of one or more electrical potential differences using the vertical or ‘Y’ axis, plotted as a function of time, (horizontal or ‘X-axis). Although an oscilloscope displays voltage on its vertical axis, any other quantity that can be converted to a voltage can be displayed as well.
• In most instances, oscilloscopes show events that repeat with either no change or change slowly. Whatever the type of oscilloscope, whether CRT or LCD, or LED screen, its front panel normally has control sections divided into Vertical, Horizontal, and Trigger sections. There are also display controls and input connectors.

• An oscilloscope can display and measure many electrical quantities like ac/dc voltage, time, phase relationships, frequency, and a wide range of waveform characteristics like rise-time, fall- time and overshoot, etc. Non-electrical quantities like pressure, strain, temperature, acceleration, etc. can also be measured by using different transducers to first convert them into an equivalent voltage.

Also Read : Measuring Instruments | Classification of Measuring Instruments

Block Diagram of CRO

Fig.3 shows the block diagram of a CRO. As seen in the diagram, it consists of the following major sub-systems:

Also Read : Errors in Measurement: Gross Errors, Systematic Errors, and Random Errors

Operation Control of Oscilloscope

The operating controls of a basic oscilloscope are shown in Fig.4. The different terminals provide.

• Horizontal Amplifier Input
• Vertical Amplifier Input
• Synchronous Input
• External Sweep Input.

Also Read : PMMC Instrument: Construction, Working & Its Applications

Working of CRO

• In the past, CRO consists mainly of a  vacuum tube that contains a  cathode, anode, grid,    X & Y -plates, and a fluorescent screen. When the cathode is heated (by applying a small potential difference across its terminals), it emits electrons. Having a potential difference between the cathode and the anode (electrodes), accelerate the emitted electrons towards the anode, forming an electron beam, which passes to fall on the screen.
• When the fast electron beam strikes the fluorescent screen, a bright visible spot is produced. The grid, which is situated between the electrodes, controls the number of electrons passing through it thereby controlling the intensity of the electron beam. The X & Y plates are responsible for deflecting the electron beam horizontally and vertically.
• A sweep generator is connected to the X -plates, which moves the bright spot horizontally across the screen and repeats that at a certain frequency as the source of the signal. The voltage to be studied is applied to the Y -plates. The combined sweep and Y voltages produce a graph showing the variation of voltage with time.

Applications of a CRO

As stated earlier, no other instrument in the electronic industry is as versatile as a CRO. In fact, a modern oscilloscope is the most useful single piece of electronic equipment that not only removes the guesswork from technical troubleshooting but makes it possible to determine the trouble quickly. Some of its uses are as under:

In Radio Work:

• to trace and measure a signal throughout the RF, IF, and AF channels of radio and television receivers .
• it provides the only effective way of adjusting FM receivers, broadband high-frequency
• RF amplifiers and automatic frequency control circuits;
• to test AF circuits for different types of distortions and other spurious oscillations;
• to give a visual display of wave shapes such as sine waves, square waves, and their many different combinations;
• to trace transistor curves
• to visually show the composite synchronized TV signal
• to display the response of tuned circuits etc.

Scientific and Engineering Applications:

• finding B/H curves for the hysteresis loop,
• for engine pressure analysis,
• for the study of stress, strain, torque, acceleration, etc.,
• frequency and phase determination by using Lissajous Figures,
• radiation patterns of antenna,
• amplifier gain,
• modulation percentage,
• complex waveform as a short-cut for Fourier analysis,
• Standing waves in transmission lines etc.

Frequently Asked Questions on CRO

What is the cathode ray oscilloscope.

A cathode ray oscilloscope is an instrument based upon the cathode ray tube, that provides a visible image of one or more rapidly varying electrical quantities. A cathode ray oscilloscope may be used to display the variations in voltage signals.

How does the cathode ray oscilloscope work?

The CRO recruits the cathode ray tube and acts as the heat of the oscilloscope. In an oscilloscope, the CRT produces the electron beam which is accelerated to a high velocity and brought to the focal point on a fluorescent screen. Thus, the screen produces a visible spot where the electron beam strikes with it

What is the application of CRO?

CRO applications are mainly involved in radio, and TV receivers, also in laboratory work involving research and design. In modern electronics, the CRO plays an important role in electronic circuits.

What are the three types of oscilloscopes ?

Digital storage oscilloscopes (DSO), Digital phosphor oscilloscopes (DPO), Mixed signal oscilloscopes (MSO)

What is the main function of an oscilloscope?

Oscilloscopes (or scopes) test and display voltage signals as waveforms, visual representations of the variation of voltage over time. The signals are plotted on a graph, which shows how the signal changes.

Hello friends, my name is Trupal Bhavsar, I am the Writer and Founder of this blog. I am Electronics Engineer(2014 pass out), Currently working as Junior Telecom Officer(B.S.N.L.) also I do Project Development, PCB designing and Teaching of Electronics Subjects.

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Cathode-Ray Oscilloscope

WARNING:    Never advance the Intensity Control so far that an excessively bright spot appears. Bright spots imply burning of the screen. A sharp focused spot of high intensity (great brightness) should never be allowed to remain fixed in one position on the screen for any length of time as damage to the screen may occur.

Cathode Ray Oscilloscope (CRO)

The cathode ray oscilloscope (CRO) is a type of electrical instrument that is used for showing the measurement and analysis of waveforms and other electronic and electrical phenomena. It is an extremely quick X-Y plotter that shows the input signal versus another signal or versus time. The CROs are used to analyze the waveforms, transient, phenomena, and other time-varying quantities from an extremely low-frequency variety to the radio frequencies.

• 1) Construction of CRO
• 2) Cathode Ray Tube
• 3.1) Deflecting Plate
• 3.2) Fluorescent Screen of CRT
• 3.3) Glass Envelope
• 4) Working of CRO
• 5) Applications of CRO
• 6) MCQs about Cathode Ray Oscilloscope (CRO)
• 7) Wrap up!
• 8) You may also like to learn:

Construction of CRO

The building of CRO consists of the following:

Cathode Ray Tube

Electronic gun assembly, deflecting plate.

• Fluorescent Screen For CRT
• Glass Envelop

The CRO is the vacuum tube and the primary function of this gadget is to change the signal from electrical to visual. This tube consists of the electron weapon along with the electrostatic deflection plates. The primary function of this electron gun is used to generate a concentrated electronic ray that accelerates to high frequency.

The vertical deflection plate will turn the ray up and down whereas the horizontal ray moved the electron beams from the left side to the right side. These actions are autonomous from each other and therefore the ray might lie anyplace on the display.

The primary function of the electron gun is to produce the electrons to form them into a ray. This gun generally includes a heating unit, a grid, cathode, and anodes like speeding up, pre-accelerating, and focusing.

At the cathode end, the strontium and barium layers are deposited to acquire the high electrons emission of electrons at the moderate temperature level, the layers of barium, and are transferred at the end of the cathode. There are two techniques of focusing on the electron beam. These techniques are.

• Electrostatic focusing.
• Electro-magnetic focusing.

The CRO uses an electrostatic focusing tube.

The electron beam after leaving the electron gun passes through the two sets of the deflecting plate. The pair of plate producing the vertical deflection is called a vertical deflecting plate or Y plates, and the pair of the plate which is utilized for horizontal deflection is called horizontal deflection plate or X plates.

Fluorescent Screen of CRT

In the CRT, the front face is called the faceplate, For the CRT screen, it is flat and its size is about 100mm × 100mm. The CRT screen is rather bent for bigger displays and the formation of faceplate can be done by pressing the molten glass into a form and after that heating it.

The inner face of the faceplate is covered by using phosphor crystal to alter the energy from electrical to light. Once an electronic device’s ray hits phosphor crystal, the energy level can be boosted, and thus light is produced throughout the phosphorous formation, so this occurrence is referred to as fluorescence.

Glass Envelope

It is an incredibly left cone-shaped form of construction. The inside faces of the CRT among the neck along with the display are covered through the aquadag. This is a conducting material that acts like a high-voltage electrode. The surface of the coating is connected electrically towards the accelerating anode to help the electron to be at the center.

Working of CRO

When the electron is injected through the electron gun, it passes through the control grid. The control grid controls the intensity of electrons in the vacuum tube. If the control grid has high negative potential, then it permits only a few electrons to travel through it. Hence, the dim spot is produced on the lightning screen. If the negative potential on the control grid is low, then the bright spot is produced. Thus, the intensity of light depends on the negative potential of the control grid.

After moving the control grid, the electron beam passing through the focusing and accelerating anodes. The accelerating anodes are at a high positive potential and thus they assemble the beam at a point on the screen.

After moving from the accelerating anode, the beam comes under the impact of the deflecting plates. When the deflecting plate is at zero potential, the beam produces an area at the Centre. If the voltage is applied to the vertical deflecting plate, the electron beam focuses upward and when the voltage is used horizontally the spot of light will be deflected horizontally.

Applications of CRO

While various, a CRO can be used for the following purposes:

• To identify the amplitude of a waveform.
• Comparison between the phases and frequencies of electrical signals.
• Assist procedure capacitance and inductance values.
• In the medical field and medical practice, it can be utilized for keeping an eye on different body specifications like heartbeat rates and nervous responses.
• It is likewise used for understanding the waveforms, short-term phenomenon, and other time-varying quantity from a really low-frequency range to the radio frequencies.

MCQs about Cathode Ray Oscilloscope (CRO)

• A) Cathode Ray Organization
• B) Central Ray Oscilloscope
• C) Cathode Ray Oscilloscope
• D) Conductor Resistance Observation
• Answer: C) Cathode Ray Oscilloscope
• A) To produce electrons
• B) To convert electrical signals to visual displays
• C) To regulate the intensity of electrons
• D) To accelerate electrons to high frequency
• Answer: B) To convert electrical signals to visual displays
• A) To control the intensity of electrons
• C) To generate electrons and form them into a ray
• D) To deflect the electron beam
• Answer: C) To generate electrons and form them into a ray
• A) Electromagnetic focusing
• B) Magnetic focusing
• C) Electrostatic focusing
• D) Ionizing focusing
• Answer: C) Electrostatic focusing
• A) To generate electrons
• B) To focus the electron beam
• D) To control the horizontal and vertical deflection of the electron beam
• Answer: D) To control the horizontal and vertical deflection of the electron beam
• A) To regulate the intensity of electrons
• C) To generate electrons
• A) Glass envelope
• B) Deflecting plates
• C) Cathode Ray Tube
• D) Fluorescent screen
• Answer: D) Fluorescent screen
• B) To generate electrons
• C) To accelerate electrons
• D) To act as a high-voltage electrode
• Answer: D) To act as a high-voltage electrode
• B) Accelerating anodes
• C) Deflecting plates
• D) Control grid
• Answer: D) Control grid
• A) A dim spot is produced on the screen
• B) A bright spot is produced on the screen
• C) No spot is produced on the screen
• D) The electron beam is deflected horizontally
• Answer: A) A dim spot is produced on the screen
• A) Regulate the intensity of electrons
• B) Deflect the electron beam
• C) Accelerate the electron beam
• D) Convert electrical signals to visual displays
• Answer: C) Accelerate the electron beam
• A) The electron beam moves upward
• B) The electron beam moves downward
• C) The spot of light is deflected horizontally
• D) The spot of light is deflected vertically
• Answer: D) The spot of light is deflected vertically
• A) To identify the color of a waveform
• B) To measure the weight of electrical signals
• C) To compare the phases and frequencies of electrical signals
• D) To analyze chemical reactions
• Answer: C) To compare the phases and frequencies of electrical signals
• A) By measuring blood pressure
• B) By monitoring heartbeat rates and nervous responses
• C) By analyzing DNA structures
• D) By detecting viruses
• Answer: B) By monitoring heartbeat rates and nervous responses
• A) Extremely low-frequency range only
• B) Radio frequencies only
• C) Both extremely low-frequency range and radio frequencies
• D) Microwave frequencies only
• Answer: C) Both extremely low-frequency range and radio frequencies

In conclusion, the Cathode Ray Oscilloscope (CRO) serves as a fundamental tool in electrical instrumentation, enabling the measurement and analysis of waveforms and various electronic phenomena.

Constructed with key components like the Cathode Ray Tube (CRT), Electronic Gun Assembly, Deflecting Plates, Fluorescent Screen, and Glass Envelope, the CRO efficiently converts electrical signals into visual displays for analysis.

Its working principle involves the manipulation of electron beams through control grids, focusing and accelerating anodes, and deflecting plates, resulting in the visualization of waveforms on the screen.

The applications of CRO span across multiple domains, including waveform analysis, frequency comparison, capacitance and inductance measurement, and even medical diagnostics. From low-frequency signals to radio frequencies, the CRO proves to be a versatile instrument in understanding time-varying quantities and phenomena.

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CRO – Cathode Ray Oscilloscope – Ultimate Guide

A CRO (Cathode Ray Oscilloscope) is an electronic instrument used for studying various electrical & electronic parameters and behaviors. CRO is basically an XY (2 dimensional) plotter which can plot an input signal vs another signal or an input signal vs time. A cathode ray oscilloscope is used to study waveforms, transients, time based or frequency based analysis.

Introduction to CRO – Cathode Ray Oscilloscope

The cathode ray oscilloscope is an extremely useful and versatile laboratory instrument used for studying wave shapes of alternating currents and voltages as well as for meas­urement of voltage, current, power and frequency, in fact, almost any quantity that involves amplitude and waveform. It allows the user to see the amplitude of electrical signals as a function of time on the screen. It is widely used for trouble shooting radio and TV receivers as well as laboratory work involving research and” design. It can also be employed for studying the wave shape of a signal with respect to amplitude distortion and deviation from the normal. In true sense the cathode ray oscilloscope has been one of the most important tools in the design and development of modern electronic circuits.

Buyers Guide – We have developed an excellent buyers guide for people who are looking to buy a CRO. So here is our first guide to  Buy an Analog Oscilloscope – which explains which all features to look for, compares the top selling products and much more.

Block Diagram of a CRO

The instrument employs a cathode ray tube (CRT), which is the heart of the oscilloscope. It generates the electron beam, accel­erates the beam to a high velocity, deflects the beam to create the image, and contains a phosphor screen where the electron beam eventually becomes visible. For accomplishing these tasks various electrical           signals and voltages are required, which are provided by the power supply circuit of the oscilloscope. Low voltage supply is required for the heater of the electron gun for gen­eration of electron beam and high voltage, of the order of few thousand volts, is required for cathode ray tube to accelerate the beam. Normal voltage supply, say a few hundred volts, is required for other control circuits of the oscilloscope.

Horizontal and vertical deflection plates are fitted between electron gun and screen to deflect the beam according to input signal. Electron beam strikes the screen and creates a visible spot. This spot is deflected on the screen in horizontal direction (X-axis) with constant time dependent rate. This is accomplished by a time base circuit provided in the oscilloscope. The signal to be viewed is supplied to the vertical deflection plates through the vertical amplifier, which raises the potential of the input signal to a level that will provide usable deflection of the electron beam. Now electron beam deflects in two directions, horizontal on X-axis and vertical on Y-axis. A triggering circuit is provided for synchronizing two types of deflections so that horizontal deflection starts at the same point of the input vertical signal each time it sweeps. A basic block diagram of a general purpose oscilloscope is shown in figure. Cathode ray tube and its various components will be discussed in the following Arts.

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How induction cooktops work, basic controls of a cro, crt-cathode ray tube, 36 comments.

NICE & THANKS

it is very good and is better than others.

IT VERY USEFUL

:-OIt is so large for practical theory.B-)But it is good for knowledge study. :-)THANK YOU;-)

most thanks

i think…delay line is responsible synchronising…

it is very useful to information to me

Thanque so much ..cro information is useful*

delay line basically used for delaying the input signal nearly around 80 to 200ns. you have not mentioned in it

nothing given regarding function of delay line

Thank you very much it was usefull for me in understanding cro better…..

information is very usefulto us thank you…………

a very useful study on CRO, thanks for this info

me too need the complete working of cro…

dear sir i need complete using procedure on cro . analog and digital circuits signal testing procedure via cro please help to me

It is very useful information to me.

thanx was very useful information

Hi Ankit go through the wiki site full of details. http://en.wikipedia.org/wiki/Oscilloscope

i need complete information in cro & function of cro.

love the pic of stevy wonder ……(wtf)

i need CRO FUNCTION… and how i can to calibrate to one step…

Each component of the oscilloscope has very important function. If one of them fails, it will give faulty readings.

u r material is so nice i want more information about cro and about picture tube and some pics of that so plz u send me quick

you could have explained the function of each block

Type above and press Enter to search. Press Esc to cancel.

Electronics Post

Cathode ray oscilloscope ( cro ), cathode ray oscilloscope.

The cathode Ray Oscilloscope or mostly called as CRO is an electronic device used for giving the visual indication of a signal waveform.

It is an extremely useful and the most versatile instrument in the electronic industry.

CRO is widely used for trouble shooting radio and television receivers as well as for laboratory research and design.

Using a CRO , the wave shapes of alternating currents and voltages can be studied.  It can also be used for measuring voltage, current, power, frequency and phase shift. Different types of oscilloscopes are available in the market for various purposes.

Block Diagram of CRO (Cathode Ray Oscilloscope)

The figure below shows the block diagram of a general purpose CRO .

As we can see from the above figure above, a CRO employs a cathode ray tube ( CRT) ,which acts as the heart of the oscilloscope.

In an oscilloscope, the CRT generates the electron beam which are accelerated to a high velocity and brought to focus on a fluorescent screen. This screen produces a visible spot where the electron beam strikes it. By deflecting the beam over the screen in response to the electrical signal, the electrons can be made to act as an electrical pencil of light which produces a spot of light wherever it strikes.

For accomplishing these tasks various electrical signals and voltages are needed, which are provided by the power supply circuit of the oscilloscope.

Low voltage supply is required for the heater of the electron gun to generate the electron beam and high voltage is required for the cathode ray tube to accelerate the beam. Normal voltage supply is required for other control units of the oscilloscope.

Horizontal and vertical deflection plates are fitted between the electron gun and the screen so that these can deflect the  beam according to the input signal.

To deflect the electron beam on the screen in horizontal direction i.e. X-axis with constant time dependent rate, a time base generator is provided in the oscilloscope.

The signal to be viewed is supplied to the vertical deflection plate through the vertical amplifier , so that it can amplify the signal to a level that will provide usable deflection of the electron beam.

As the electron beam is deflected in X-axis as well as Y-axis, a triggering circuit is provided for synchronizing these two types of deflections so that horizontal deflection starts at the same point of the input vertical signal each time it sweeps.

Since CRT is the heart of the oscilloscope, we are going to discuss its various components in detail.

Cathode Ray Tube

The cathode ray tube or CRT is a vacuum tube of special geometrical shape which converts an electrical signal into a visual one.

A CRT makes available a large number of electrons which are accelerated to high velocity and are brought to focus on a fluorescent screen where it produces a spot when strikes it. The electron beam is deflected during its journey in response to the applied electrical signal.  As a result, the electrical signal waveform is displayed  visually.

The figure below shows various parts of a cathode ray tube (CRT) .

Now we will discuss each part of the CRT in detail.

(i) Glass Envelope

It is a conical highly evacuated glass housing which maintains vacuum inside it  and supports various electrodes.

The inner wall of CRT between the neck and screen are usually coated with a conducting material known as aquadag. This coating is electrically connected to the accelerating anode so that the electrons which accidentally strike the walls are returned to the anode.  This prevents the walls from charging to a high negative potential.

(ii) Electron Gun Assembly

The electron gun assembly consists of an indirectly heated cathode, a control grid, a focussing anode and an accelerating anode and it is used to produce a focused beam of electrons.

The control grid is held at negative potential w.r.t. cathode. However, the two anodes are held at high positive potential w.r.t. cathode.

The cathode consists of a nickel cylinder coated with oxide coating and provides a large number of electrons.

The control grid encloses the cathode and consists of a metal cylinder with a tiny circular opening to keep the electron beam small.

By controlling the positive potential on it,the focusing anode focuses the electron beam into a sharp pin point.

Due to the positive potential of about 10,000 V on the accelerating anode which is much larger than on the focusing diode,  the electron beam is accelerated to a high velocity.

In this way, the electron gun assembly forms a narrow, accelerated electron beam which produces a spot of light when it strikes the screen.

(iii) Deflection Plate Assembly

It consists of two sets of deflecting plates within the tube beyond the accelerating anode and is used for the deflection of the beam.

One set is called as vertical deflection plates and the other set is called horizontal deflection plates.

The vertical deflection plates are mounted horizontally in the tube. On application of proper potential to these plates, the electron beam can be made to move up and down vertically on the screen.

The horizontal deflection plates  are mounted vertically in the tube. On application of proper potential to these plates, the electron beam can be made to move right and left horizontally on the screen.

(iv) Screen

The screen is coated with some fluorescent materials such as zinc orthosilicate, zinc oxide etc and is the inside face of the tube.

When high velocity electron beam strikes the screen, a spot of light appears at the point of impact. The colour of the spot depends upon the nature of fluorescent material.

Working of Cathode Ray Tube

As the cathode is heated, it produces a large number of electrons.

These electrons pass through the control grid on their way to the screen.

The control grid controls the amount of current flow as in standard vacuum tubes. If negative potential on the control grid is high, fewer electrons will pass through it. Hence the electron beam will produce a dim spot of light on striking the screen. Reverse will happen when the negative potential on the control grid is reduced.

Therefore, the intensity of the light spot on the screen can be controlled by changing the negative potential on the control grid.

After leaving the control grid, the electron beam comes under the influence of focusing and accelerating anodes.

Since, the two anodes are at high positive potential, therefore, they produce a field which acts as electrostatic lens to converge the electron beam at a point on the screen.

After leaving the accelerating anode, the electron beam comes under the influence of vertical and horizontal deflection plates.

When no voltage is applied to these deflection plates, the electron beam produces a spot of light at the centre as shown by  point O in fig below on the screen.

If the voltage is applied to the vertical deflection plates only, the electron beam and so as the spot of light  will be deflected upwards i.e. point O1. Ans if the potential on the plates is reversed, the spot of light will be deflected downwards i.e. point O2.

Similarly, the spot of light can be deflected horizontally by applying voltage across the horizontal deflection plates.

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Cathode Ray Oscilloscope Working Principle & Construction

What is Cathode Ray Oscilloscope(CRO):

              Cathode Ray Oscilloscope is a very useful and versatile laboratory instrument used for display, measurement and analysis of waveforms and other phenomena in electrical and electronic circuits.CRO’s are in fact very fast X-Y plotters, displaying an input signal versus another signal versus time. Cathode Ray Oscilloscopes operate on voltages. However, it is possible to convert current, strain, acceleration, pressure and other physical quantities into voltages with the help of transducers and thus to present visual representations of a wide variety of dynamic phenomena on CRO’s.In this, I will explain  Cathode Ray Oscilloscope Working Principle & Construction.

          Cathode Ray Oscilloscopes are used to investigate waveforms , transient phenomena and other time varying quantities from a very low frequency range to the radio frequencies. They are now available which can measure frequencies upto 1GHz and observer events as small as 20Hz in duration. Although , most oscilloscope are monochromatic, colour oscilloscope are finding increasing applications in computers and in television. Most present day oscilloscopes are capable of accepting two or more inputs displaying them simultaneously.

Construction of Cathode Ray Oscilloscope :

            A cathode ray oscilloscope consists of a cathode ray tube which is the heart of the tube and some additional circuitry to operate the CRT.The main parts of a CRT 

1) Electron gun assembly

2) Deflection plate assembly 

3) Fluorescent screen

4) Glass envelope

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The below figure shows construction of Cathode Ray Oscilloscope . 

1)Electron gun assembly :

               In cathode ray oscilloscope  , this is the part from where electrons are born initially. It produces a sharply focused beam of electrons which are accelerated to high velocity. This focused beam of electrons strikes the fluorescent screen with sufficient energy to cause a luminous spot on the screen. After leaving the electron gun the electron beam passes through two pairs of electrostatic deflection plates.

              Voltages applied to these plates deflects the beam. Voltage applied to one pair plates move the beam vertically up and down and the voltages applied to other pair of plates move the beam horizontally from one side to another. This two movements i.e horizontal and vertical are independent of each other and thus the beam may be positioned anywhere on the screen.

          The working parts of a CRT are enclosed in an evacuated glass envelope so that the emitted electrons are able to move about freely from one end of the tube to other. The source of focused and accelerated beam is the electron gun, which emits electrons and forms them into a beam consists of a heater, cathode, a grid, a pre-accelerating anode, a focusing anode and accelerating anode.

           In smaller CRT’ s connections to the various electrodes are brought out through pins in the base or the tube as shown in the figure. Large and medium-sized high-performance tubes operate at very high voltages and these leads are usually bought out through the sides of the glass envelope. 

          Electrons are emitted from the indirectly heated cathode. A layer of barium and Strontium oxide is deposited on the end of the cathode which is a cylinder to obtain high emission of electrons at moderate temperatures. The typical values of current and voltage required by an indirectly heated cathode are 600 mA at 6. 3 V. 

           These electrons past through a small hole in the control grid. This control grid is usually a Nickel cylinder with a centrally located hole coaxial with the CRT axis. This is usually a metal cup of low permeability Steel about 15 mm in diameter 15 mm long. And an aperture of about 0.25 mm is drilled in the cap of the grid for the electrons to flow through. The intensity of the electron beam depends upon the number of electrons emitted from the cathode.

           The grid with its negative bias controls the number of electrons emitted from the cathode and hence the intensity is controlled by the grid. The electrons emitted from the cathode and passing through the hole in the control grid are accelerated by the high positive potential which is applied to the pre-accelerating and accelerating anodes.

              The electron beam is focused by the focusing anode. The accelerating and focusing anodes are cylindrical in form with small openings located in the centre of each electrode coaxial with the tube axis. After leaving the focusing anodes, the electron beam passes through the vertical and horizontal deflection plates and then goes on to the fluorescent screen. The pre-accelerating and the accelerating anode  are connected to a common positive high voltage of about 1500v. The focusing anode is connected to a lower adjustable voltage of 500v.

Circuit diagram of Cathode Ray Oscilloscope:

Cathode Ray Oscilloscope Working Principle:

There are two methods of focusing an electron beam :

1) Electrostatic  focusing

2) Electromagnetic focusing

            The CRO uses electrostatic method of focusing as compared to a TV picture tube which employes electromagnetic focusing . Here we will discuss  Electrostatic focusing only.

1)Electrostatic  focusing:

The figure shows an electron at rest placed in an electric field produced parallel plates. Force on the electron is,

                                             F = – e.E  newtons

where E = electric field intensity ; V/m

          e = charge of electron = 1.602 * 10^(-19)

             The minus sign indicates that the force acts in the opposite direction to that of the field. The above discussion is valid only if the electron is situated in a field of uniform intensity. In practice, however, the field is not uniform. The lateral repulsion of the electric field lines causes a spreading of space between the lines, resulting in curved field lines at the ends. Thus the field intensity will be less at the ends. The figure also shows equipotential surfaces, indicated by solid Lines.

          Since the force is in a direction opposite the field and the equipotential surfaces are perpendicular to the field, the force on an electron is in a direction normal to the equipotential surfaces. The figure shows two concentric cylinders with a potential applied between them. Lateral repulsion again causes the spreading of the flux lines producing a field as shown. The equipotential surfaces are shown as solid lines. It is clear from the below diagram that the equipotential surfaces are curved.

                Let us consider the region on the two sides of an equipotential surface S as shown in the figure. The potential on the left side of the surface is – V and on the right side is +V. Let an electron moving in a direction AB enter the area to the left of S.This electron experiences of force which is normal to the surface S and is thus accelerated.

            Since the force acts in a direction normal to the surface, it is the normal component of velocity that is increased after refraction while the tangential component remains the same.

  The tangential components are

                    Vt1 = V1  sinθi        and           Vt2 = V2  sinθ

       Now           Vt1 = Vt2            or             V1  sinθi =    V2  sinθr

                       sinθi/ sinθr = V2/V1

where V1 =   Initial velocity of electrons

          V2 =  Velocity of electrons after leaving surface S

            θi =  angle of incidence

            θr =  angle of refraction

2)Deflection plate assembly :

        This explains Cathode Ray Oscilloscope Working Principle . Electron beam after leaving the electron gun passes through two pairs of deflection plates. One pair of plates is mounted horizontally and produces an electric field in the vertical plane. This place produces a vertical deflection and is called vertical deflection plates or Y plates. The other pair of plates is mounted vertically and produces a horizontal deflection. This pair of plates is called horizontal deflection plates or X plates. Plates are flared so as to allow the beam to pass through them without striking the plates.

i)Vertical deflection system :

            The signals to be examined are usually applied to the vertical or Y deflection plates through an input attenuator and a  number of amplifier stages. The vertical amplifier is required because the signals are not strong enough to produce measurable deflection on the CRT screen. When High Voltage signals are to be examined, they must be attenuated to bring them within the range of vertical amplifiers. The vertical amplifier output is also applied to the synchronizing amplifier through the synchronizer selector switch in the internal position.

ii)Horizontal deflection system :

          The horizontal deflection plates are fed by a  sweep voltage that provides time base. The horizontal plates are supplied through an amplifier but they can be fed directly when voltage is of sufficient magnitude. When external signals are to be applied to the horizontal deflection system they can also be fed through the horizontal amplifier via the sweep selector switch in the external position.When the sweep selector switch is in the internal position the horizontal amplifier receives an input from the sawtooth sweep generator which is triggered by the synchronising amplifier.

3)Fluorescent screen:

              The front of the CRT is called the faceplate. It is flat for screen sizes up to about 100mm * 100mm and is slightly curved for larger displays. Faceplate is formed by pressing molten glass in a mould and then annealing it. Some CRTs have a faceplate which is made from fibre optics. The inside surface of the faceplate is coated with phosphor. This consists of very pure inorganic crystalline phosphor crystals about 2 – 3 microns in diameter to which traces of other elements called activators are added. 

           Activator in current use are metals such as silver, manganese, Copper and chromium. When an electron beam strikes phosphor crystals it raises their energy level. This is called as cathodoluminescence . Light is emitted during phosphor excitation and this is called fluorescence . When the electron beam is switched off the phosphor crystals return to their initial states and release a quantum of light energy. This is called phosphorescence or persistence . 

           The writing speed of a phosphor is measured by its fluorescence rise time w hich is the time from the beginning of excitation to reach 90% of the maximum emission state and by the decay time which is time to fall from the maximum state to the 10% level. Writing speed is determined by the phosphor type, crystal size, impurity content and manufacturing process.

                 The bombarding electrons when strikes the screen release secondary electrons. The secondary electrons are collected by an aqueous solution of Graphite called Aquadag , which is connected to the second anode, the collection of secondary electrons is necessary to keep the CRT screen in a state of electrical equilibrium.

4)Glass envelope:

           The working parts of a CRT  are enclosed in an evacuated glass envelope so that the emitted electrons are able to move freely from one end of the tube to the other.

             Through this base, connections are made to various parts from cathode ray oscilloscope . Pins come out of this base and external connections are made.

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Specifications of CRO and their Significance

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Basics of Oscilloscopes

• Special Purpose Oscilloscopes
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Oscilloscope is an electronic equipment, which displays a voltage waveform. Among the oscilloscopes, Cathode Ray Oscilloscope (CRO) is the basic one and it displays a time varying signal or waveform.

In this chapter, let us discuss about the block diagram of CRO and measurements of some parameters by using CRO.

Block Diagram of CRO

Cathode Ray Oscilloscope (CRO) consists a set of blocks. Those are vertical amplifier, delay line, trigger circuit, time base generator, horizontal amplifier, Cathode Ray Tube (CRT) & power supply. The block diagram of CRO is shown in below figure.

The function of each block of CRO is mentioned below.

Vertical Amplifier − It amplifies the input signal, which is to be displayed on the screen of CRT.

Delay Line − It provides some amount of delay to the signal, which is obtained at the output of vertical amplifier. This delayed signal is then applied to vertical deflection plates of CRT.

Trigger Circuit − It produces a triggering signal in order to synchronize both horizontal and vertical deflections of electron beam.

Time base Generator − It produces a sawtooth signal, which is useful for horizontal deflection of electron beam.

Horizontal Amplifier − It amplifies the sawtooth signal and then connects it to the horizontal deflection plates of CRT.

Power supply − It produces both high and low voltages. The negative high voltage and positive low voltage are applied to CRT and other circuits respectively.

Cathode Ray Tube (CRT) − It is the major important block of CRO and mainly consists of four parts. Those are electron gun, vertical deflection plates, horizontal deflection plates and fluorescent screen.

The electron beam, which is produced by an electron gun gets deflected in both vertical and horizontal directions by a pair of vertical deflection plates and a pair of horizontal deflection plates respectively. Finally, the deflected beam will appear as a spot on the fluorescent screen.

In this way, CRO will display the applied input signal on the screen of CRT. So, we can analyse the signals in time domain by using CRO

Measurements by using CRO

We can do the following measurements by using CRO.

Measurement of Amplitude

Measurement of time period, measurement of frequency.

Now, let us discuss about these measurements one by one.

CRO displays the voltage signal as a function of time on its screen. The amplitude of that voltage signal is constant, but we can vary the number of divisions that cover the voltage signal in vertical direction by varying volt/division knob on the CRO panel. Therefore, we will get the amplitude of the signal, which is present on the screen of CRO by using following formula.

$$A=j\times n_{v}$$

$A$ is the amplitude

$j$ is the value of volt/division

$n_{v}$ is the number of divisions that cover the signal in vertical direction.

CRO displays the voltage signal as a function of time on its screen. The Time period of that periodic voltage signal is constant, but we can vary the number of divisions that cover one complete cycle of voltage signal in horizontal direction by varying time/division knob on the CRO panel.

Therefore, we will get the Time period of the signal, which is present on the screen of CRO by using following formula.

$$T=k\times n_{h}$$

$T$ is the Time period

$j$ is the value of time/division

$n_{v}$ is the number of divisions that cover one complete cycle of the periodic signal in horizontal direction.

The frequency, f of a periodic signal is the reciprocal of time period, T. Mathematically , it can be represented as

$$f=\frac{1}{T}$$

So, we can find the frequency, f of a periodic signal by following these two steps.

Step1 − Find the Time period of periodic signal

Step2 − Take reciprocal of Time period of periodic signal, which is obtained in Step1

We will discuss about special purpose oscilloscopes in next chapter.

Guest Column | June 14, 2018

Cro selection 101 — how to get started.

By Joelle Herman , president, NeoTrials, LLC

This three-part article series will look at how best to procure, manage, and implement best practices in this complicated market.

As companies continue to look for smarter ways to develop drugs, biologics, and devices, outsourcing clinical trials to contract research organizations (CROs) and niche providers continues to grow. A recent report from Statistica projects that global CRO revenues will reach $52.3 billion by 2021 just in locations outside of the Asia-Pacific (APAC) region. While that is impressive, APAC, which is one of the fastest growing markets in the world, is projected to grow at a 20 percent compound annual growth rate (CAGR), compared to 11.4 percent “rest of world” revenue. 1 This growth is substantial and plays into the critical nature of how product developers procure and utilize CROs. This is a complex process whether you are a large biopharma or a small one poised to initiate clinical trials. The complexity of a successful procurement can be managed with good early planning and a strategic approach. 

Champion/Selection Committee

Before you can go out and get bids, the needs of the project/program must be defined by an internal champion or selection committee. A person or team closest to the science or the person responsible for leading the program team or, in a small company, the person managing the clinical trial(s) often are best positioned to lead this effort. A champion will coordinate the entire process across multiple functions (project management, medical, finance, clinical operations, etc.) for the sole purpose of planning the best outsourcing strategy. The champion will ensure a process workflow, define roles/responsibilities, identify challenges (i.e., to eliminate silos or divisions because of competing priorities or lack of vested interest), and ensure goals are defined and agreed to by the selection committee.

A committee that is composed of multidisciplinary leaders often can determine the CRO that is the best fit for the organization. Not all CROs are aligned with your organizational culture, practices, or expertise, so it is a best practice to define these parameters. The selection committee must also have a vested and committed interest in this process. Depending on the size of the organization, the committee may want to define and agree on a communication strategy. This ensures the workflow is moving ahead as per plan and that all members are accountable for their roles and tasks. Additionally, good planning establishes how to maximize core assets and utilize internal resources, supplemented with external resources. A champion and selection committee will define exactly what tasks the CRO will perform and which procedures/processes will govern various tasks. For example, the sponsoring company will establish how the investigator site contracts will be negotiated and who will legally be bound by the agreement(s). CROs bidding on the work need to know exactly what tasks they will perform in order to provide their best approach. With that, the champion/committee will create a specifications document to communicate standard processes, tasks, and tools it is looking to procure. By further defining the scope of the services being procured, whether full service or partial service, companies create a strategic sourcing approach for the clinical trial. 

Procurement/Strategic Sourcing

In order to establish and assess the best fit, the committee may want to utilize its vendor network, current CROs, and/or conduct a competition through public announcement of the procurement.  A competition is not a new concept, but how you conduct the competition is key, especially if the project is partnered with another commercial entity or federal agency (i.e., federally funded). Also, as the committee considers long-term planning or portfolio management, it seems logical to maximize efficiencies with relationship management. How can teams reduce cost and time in this repetitive process? Commercial procurement models generally take one of three forms. The preferred provider model, which creates a more collaborative relationship with a CRO, ensures repeat business and allows for streamlined buying power. The performance-based model or managed services model drives accountability through incentives/penalties using milestones/target achievements. Another model is used when sponsors want to harness innovation to select the best value-added solution. Some CROs have new technology or innovative approaches aligned with the company’s goals to augment internal resources. Making these requirements clear to CROs that range from generalists to specialists with partial- to full-service clinical research functions allows the CRO procurement filter process to be maximized for best fit. What does this mean for the selection committee? What level of detail and criteria are needed?

The request for proposal (RFP) documentation is a vital piece in communicating the sponsor/client’s needs. The RFP will be addressed in Part 2 of this series, but before you can create an RFP, the committee must define criteria for selection. Matching chemistry like perception or perceived value is important on the surface, but the real measures of potential performance are the following criteria.

Risk management practices are now expected to be incorporated into the selection and oversight of CROs and other vendors. Find out more in SAM Sather's webinar:

CRO Oversight Post ICH GCP E6 (R2) Addendum

Selection Criteria For CRO Selection

• Specific therapeutic area and indication experience
• Team member experience in the indication
• Approach to current challenges (demonstrated understanding of enrollment, feasibility, access to KOLs, and investigative sites with the right population and experience)
• Responsiveness and ability to be limber with internal and external processes/systems (don’t forget to conduct a qualification audit as a contingency to an agreement)
• Quality/consistency of performance/financial stability/inspection history 2
• Value (determine the best service for best price)
• Transparency (confirm the scope of service delineates the client will have access to systems)
• Collaboration and communication planning (ask if they have escalation strategies)
• How do they plan (ask for examples of schedules, what plans will be part of the service, i.e., project plans, risk management plan, subcontractor management plan, monitoring plan, statistical analysis plan, data and pharmacovigilance plans)

According to Comprehend, 3 a clinical intelligence software provider, the three most common overlooked selection criteria are transparency, collaborative partnership, and real-time responsiveness. These intangible factors should be part of any strategic selection process. Sponsors struggle to quantify these factors, but to win the business, CROs can proactively demonstrate these intangibles with solid evidence. This isn’t one-sided. CROs can only provide their best services when all parties model transparent and collaborative relationships.

Future articles in this series will cover: developing a CRO selection workflow and checklist, addressing documentation and regulation concerns, and applying best practices to overcome the major challenges in outsourcing.

References:

• https://www.statista.com/statistics/817599/revenue-forecast-for-pharma-cros-by-location/
• https://www.pharmoutsourcing.com/Featured-Articles/172751-What-to-Look-for-in-Selecting-a-CRO-CMO-and-How-to-Ensure-the-Right-Choice-A-Quality-Assurance-Perspective/
• https://www.comprehend.com/overlooked-criteria-in-cro-selection/

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