Introduction to Oscilloscopes-Part I

Introduction：

Oscilloscopes Introduction is mainly for zero basic engineering personnel to read, in the following introduction to oscilloscopes, you can understand the use of oscilloscopes, applications, functions, system components, operating principles and types of content starting from an all-round zero-based understanding of oscilloscopes such as a common electronic measuring instruments, to ensure that the later for the oscilloscopes to be selected and used with a certain knowledge base.

What is an oscilloscope?

oscillographIt is a conventional measuring instrument that can graphically display the waveform of time domain signals, and a comprehensive signal characteristic tester, which is a basic type of common electronic measuring instruments.

Types of different oscilloscopes:

Oscilloscopes have generated the following different types of measurements based on customer demand:

• analog oscilloscope
• Analog-Digital Hybrid Oscilloscopes
• digital oscilloscope
• Digital Fluorescence Oscilloscope
• sampling oscilloscope

Functions and uses of oscilloscopes:

Oscilloscopes are used:

Voltmeter, Ammeter, Power Meter, Frequency Meter, Phase Meter, Pulse Characterization, Damped Oscillation

Oscilloscope applications:

Electronics, Electricity, Electricians

Pressure, vibration, sound, light, heat, magnetism.

Oscilloscope-based instruments:

Logic Analyzer, Time Domain Reflectometer, Transistor Characterization Tester, ECG, etc.

Oscilloscope functions:

The main function of an oscilloscope is to accurately reproduce waveforms as a function of time and voltage amplitude. With it, the change of voltage amplitude with respect to time can be observed instantaneously, thus obtaining qualitative information about the waveforms, such as amplitude and frequency, waveforms, and the relationship between time and phase of different waveforms, using both vertical and horizontal scales.

Oscilloscopes show information about the quality of waveforms with vertical and horizontal scales

Conceptually, analog and digital oscilloscopes have the same goal of measurement, but in terms of actual structure they use different technologies internally, so they do not have the same presentation.

The booming development of digital oscilloscopes and the gradual demise of analog oscilloscopes will become an inevitable trend in history.

The development of digital technology gives the oscilloscope more waveform capture capabilities, more mathematical operations, it can be a power meter with waveform display, waveform parameter analysis, it can also store a variety of waveforms as well as related information.

Components of an oscilloscope:

The oscilloscope consists of five different systems, as shown below:

• Horizontal system
• vertical system
• scanning system
• trigger system
• Display System

The five components of an oscilloscope

Typical structure of an oscilloscope:

Different types of oscilloscopes are composed of different structures, as shown in the figure below, analog oscilloscopes do not have an A/D converter, while digital oscilloscopes are equipped with a frontal A/D converter.

Analog oscilloscopes and digital oscilloscopes are composed of different structures

The waveform shown below is captured differently when we measure it with an analog oscilloscope, a digital storage oscilloscope, and a digital fluorescence oscilloscope, respectively.

Three different types of oscilloscopes capture waveforms differently

Also, the parameter of waveform capture rate needs to be considered.

The waveform capture rate, also known as the waveform refresh rate, has become one of the most important parameters of an oscilloscope;

For oscilloscopes, a high waveform capture rate enables the organization of a larger data volume of waveform quality information, which is particularly useful in the capture of dynamic and complex signals and abnormal waveforms hidden under normal signals.

Disadvantages of ordinary digital oscilloscopes:

Low waveform capture rate

Mixed falls due to insufficient data

The 2-dimensional waveforms displayed do not indicate the frequency of events

Disadvantages of ordinary digital oscilloscopes

Disadvantages of analog oscilloscopes:

• Only purely visual information
• Flickering, lost
• Not enough bandwidth.
• Only edge triggering, no pre-triggering
• Unable to measure digital signals

Features of digital fluorescence oscilloscopes:

Digital fluorescence oscilloscopes provide three-dimensional waveform signal information, which can be used to interpret the dynamic characteristics of the signal, including signal transient changes and the frequency of the event, and can accurately display complex signals, such as video signals or high-speed anomalies in the digital waveform. Digital confusion can be prevented and incidental signal events can be easily captured.

Why measure waveforms with an oscilloscope?

What's a waveform?

Various waveforms common in life

There are many waveforms in life; patterns that change over time are called waves; sound waves, brain waves, ocean waves, and voltage waveforms are all waves, and waveforms can reveal many properties of transmitted signals:

• When a change in the height of the waveform is seen, it means that the voltage value is changing
• When a flat horizontal line is seen, it indicates that there has been no change in the signal over a period of time.
• A flat sloping line indicates a linear change, where the voltage rises or falls at a constant slope.
• The sharp corners in the waveform indicate sudden changes.

Type of wave:

Types of waves

There are several types of waves:

• simple harmonic vibration
• Square and rectangular waves
• Triangle and Ramp Wave
• Step and Pulse Waves
• noise wave
• complex wave
• There are also many waves that are combinations of the above waveforms

What are the parameters of the wave?

When we determine that we want to use an oscilloscope to measure waveforms, we need to determine exactly which of the following parameters we want to measure, and then shop for the right oscilloscope for the test.

Common oscilloscopes contain the following different measurable parameters:

• cyclicality
• frequency
• Positive pulse width
• Negative pulse width
• rising time
• descent time
• amplitude
• Duty cycle +
• Duty cycle-
• procrastinate
• phase (waves)
• burst width
• peak-to-peak
• average value
• cyclical mean
• High Low
• minimum value
• maximum values
• Overshoot +
• Overshoot-
• mean square value
• Periodic mean square value

Harmonics:

All frequency components contained in a periodic wave other than an absolute sine wave are called harmonics. Harmonic frequencies are integer multiples of the fundamental frequency;

All periodic waves have harmonics;

The frequency given for the periodic wave is the fundamental frequency.

Periodic waves - square waves also have harmonics

A square wave is composed of a fundamental wave superimposed on countless odd harmonics, and the more odd harmonics it contains, the more closely the waveform resembles a square wave.

A sine wave becomes a square wave when harmonics are added.

The quality of a square wave varies in its approximation depending on the number of harmonics included.

The amplitude of each harmonic must be of the proper value needed to make the waveform a square wave.

In addition, the phase relationship between harmonics must be correct:

Harmonics are delayed by unequal amounts, and square waves are distorted even if the harmonic amplitude is correct.

A sine wave has only one fundamental, and the bandwidth of the meter must be at least the frequency of the waveform.

However, in most cases, this is only the bare minimum, and if that's all it is, it's not precise enough, or even wrong.

To make accurate measurements of waveforms, harmonics must be considered for non-sinusoidal waveforms. If the major harmonic components that make up the waveform are outside the bandwidth of the instrument, then we cannot accurately measure the parameters of the waveform.

Learn more:

• Introduction to Oscilloscopes-Part I
• Principles and Use of Oscilloscopes-Part II
• Oscilloscope Triggering and Signal Storage-Part 3
• Oscilloscope Selection Methods-Part IV