What is an Oscilloscope?

What is an Oscilloscope?

Oscilloscopes are laboratory instruments commonly used to display and analyze waveforms of electronic signals. The instantaneous voltage signal waveform at a certain time can be displayed. An oscilloscope is an electronic measuring instrument with a wide range of uses. It can convert invisible electrical signals into visible images, which is convenient for people to study the changing process of various electrical phenomena. The oscilloscope uses a narrow electron beam composed of high-speed electrons to hit the screen coated with fluorescent material to produce tiny light spots. Under the action of the signal under test, the electron beam is like the tip of a pen, which can draw the change curve of the instantaneous value of the signal under test on the screen.

The oscilloscope can be used to observe the waveform curves of various signal amplitudes changing with time, and it can be used to test various electric quantities, such as voltage, current, frequency, phase difference, amplitude modulation, etc., in the form of images on the cathode ray tube fluorescent screen an electronic measuring instrument that displays the functional relationship between two or more parameters. There are three types of oscilloscopes: General-purpose oscilloscopes, storage oscilloscopes, and sampling oscilloscopes according to the requirements for different time-domain measurements.

A typical oscilloscope may display alternating current (AC) or pulsed direct current (DC) signal waveforms with frequencies below about 1 hertz (Hz) or above several megahertz (MHz). A high-end oscilloscope can display signals with frequencies ranging from a few hundred gigahertz (GHz). Displays are categorized into so-called horizontal divs and vertical divs. The time axis is displayed from the left on the x-axis and the horizontal line is on the right. Instantaneous voltage is shown on the vertical y-axis when positive voltage values are up and negative voltage values are down.

The traditional oscilloscope is the so-called cathode ray oscilloscope. It produces an image, or scan, by causing a focused electron beam to move, in a pattern across the front panel of a cathode ray tube (CRT). Modern oscilloscopes electronically replicate the CRT model using a liquid crystal display (LCD) similar to those screens on a notebook. The oldest oscilloscopes use microprocessors and display signal waveforms. These microprocessors can use any type of display, including CRT, LCD, and gas plasma. With the rapid development of electronic technology, the oscilloscope market is difficult to obtain or the cost is high due to the cathode ray tube (CRT). The traditional CRT display analog oscilloscope gradually turns to the digital storage oscilloscope. The function of the digital storage oscilloscope is to convert the analog signal into a digital signal after observation, it can observe the signal at the front edge of the trigger, and realize the process control of the oscilloscope and the return of waveform data through the connection between the USB cable and the computer. Although the digital storage oscilloscope has many advantages, it still cannot completely replace it. Compared with the best advantages of analog oscilloscopes in waveform update rate and display resolution. Virtually all oscilloscopes have system settings for an adjustable horizontal sweep and vertical amplitude.

• The time and the voltage value of the signal.
• The frequency of the oscillating signal.
• The movement of a circuit is represented by a signal.
• How often a particular part of a signal occurs relative to other parts?
• Whether the fault component distorts the signal?
• How many signals are direct current (DC) or alternating current (AC)?
• How much of the signal is noise, and whether the noise changes over time?

What is the Basic Principle of an Oscilloscope?

The function of an oscilloscope is to look at the voltage waveform because the operation of electronic circuits relies on changes in voltage for communication. If you can observe the changes in voltage on the time axis, that is, the waveform, you can know the health of the circuit.

The electron gun is responsible for emitting the electron beam. When the electron beam hits the fluorescent screen coated with phosphor, it will emit light, but this is not enough. To see the change in the signal, two metal plates will be placed in the vertical direction of the electron beam, as long as the signal voltage is applied to it. It will affect the degree of bending of the electron beam in the vertical direction. In this way, when the voltage of the signal changes, the degree of bending of the electron beam will faithfully reflect the size of the signal, and the up and down will appear on the screen. An oscillating light spot, but you can only see a vertical line in this way. If you want to see the waveform, you must let the light spot move from left to right. This action is sweep, so you need a set of horizontal lines the deflection plate can display the waveform on the screen.

When the electron beam hits the phosphor of the screen, the brightness of the light will last for a short period, maybe about 1 ms. This period helps to temporarily fix the waveform on the screen. If it is combined with the vision of the human eye with the persistence feature, the waveform will look more stable. The waveform will still flicker, but you may not feel it unless the scanning frequency is low, you can clearly feel it, but you can see the flickering effect of the waveform directly through the camera.

The panel of the oscilloscope has two groups, one is the vertical menu, and the other is the horizontal menu. These two groups of menus were originally used to control the vertical deflection board and the horizontal deflection board. Although these deflection boards are no longer there, it is still used to control the horizontal and vertical display waveform changes.

The general term for a pattern that repeats over time is a wave. Sound waves, brain waves, ocean waves, and voltage waves are all repeating patterns. An oscilloscope measures a voltage wave. A waveform is a graphical representation of a wave. Physical phenomena such as vibration and temperature or electrical phenomena such as current or power can be converted into voltage through sensors. A cycle of a wave is the repeated portion of the wave. A voltage waveform displays time on the horizontal axis and voltage on the vertical axis.

Waveforms reveal a great deal of information about a signal. Whenever you see a change in the height of the waveform, you know the voltage has changed. If a flat horizontal line is shown, it means there has been no change during that time. Straight lines and diagonal lines represent linear changes. The voltage rises or falls at a steady rate. Sharp angles on a waveform indicate a sudden change in voltage.

There are usually grid lines on the screen of the oscilloscope, and there are usually 10 divisions horizontally, and the time represented by each division will be displayed in a certain corner of the oscilloscope. The frequency is the reciprocal of the period, and the calculated frequency is 1kHz.

The amplitude is calculated from the center point of the swing to the peak value. In practice, it is more common to observe the peak-to-peak peak value because it is the most direct and convenient to observe. There is no need to divide by 2 to calculate, and some signals are not symmetrical up and down. Waveform, in this case, is impractical to find the center point and calculate the amplitude, vpp is mostly observed.

What Types of Waves are There?

• Sine Wave: A sine wave is a fundamental waveform for several reasons. Sine waves have harmonious mathematical properties. The test signal generated by the oscillator circuit of the signal generator is usually a sine wave.
• Square and Rectangular Waves: A square wave is another common waveform. A square wave is a voltage that turns on and off periodically. A square wave is the standard wave for testing amplifiers. A good amplifier will increase the amplitude of the square wave with minimal distortion.
• Sawtooth and Triangle Waves: Sawtooth and triangle waves are produced by circuits designed to control voltage linearly. The transitions between the voltage levels of these waves change at a constant rate and these transitions are ramps.
• Step and pulse shapes: Signals such as steps and pulses that occur rarely or a periodically are called one-shot or transient signals. A step represents a sudden change in voltage, similar to the voltage change you see when you turn on a power switch. A pulse indicates a sudden change in voltage, similar to what you see when you turn a power switch on and off again. A pulse may represent a bit of information transmitted through a computer circuit or a malfunction or defect in a circuit. A collection of pulses propagating together builds up a pulse train. Digital components in a computer communicate with each other using pulses. These pulses can be in the form of a serial data stream, or multiple signal lines can be used to represent values on a parallel data bus.
• Periodic and Aperiodic Signals: Repetitive signals are periodic signals while constantly changing signals are aperiodic signals. Images are similar to periodic signals, and movies are similar to non-periodic signals.
• Synchronous and non-synchronous signals: When there is a timing relationship between two signals, these signals are synchronous signals. Clock, data, and address signals inside a computer are synchronous signals. An asynchronous signal is a signal that does not have a timing relationship. Since there is no time correlation between touching the keys on a computer keyboard and the clock inside the computer, these are considered asynchronous signals.
• Complex waves: Some waveforms combine the properties of sine, square, step, and pulse to produce complex waveforms. Signal information can be embedded in the form of amplitude, phase, and/or frequency changes.