The oscilloscope is one of the most widely used instruments. In this article, we will show you how oscilloscopes work and how they are used to interpret and measure signals.
The classic, naturally occurring waveform is the sine wave. Whether sea waves, earthquakes, supersonic shock waves, explosions, airborne sound or the natural vibration of a moving body – everything spreads out in a sinusoidal form. Energy, vibrating particles, and other invisible forces permeate our physical universe. Even the light, half particle, half wave, has a fundamental frequency that we can perceive as color.
With sensors, these forces can be converted into electrical signals that we can observe and examine with an oscilloscope. Oscilloscopes enable scientists, engineers, technicians or educators to visualize temporally variable events for the human eye.
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The measuring device oscilloscope
An oscilloscope is nothing more than a device for rendering graphs. It is most commonly used to indicate the change in electrical signals, with the vertical y-axis representing voltage and the horizontal x-axis representing time. The intensity or brightness of the display is called the z-axis. For digital phosphor oscilloscopes, the z-axis is represented by color gradations on display.
This simple graph can convey much information about a signal, for example:
- Time and voltage values
- The frequency of a vibration signal
- “Dynamic components” of a circuit represented by the signal
- The frequency with which a certain area of the signal occurs in other areas
- whether a faulty component disturbs the signal
- DC and AC components of the signal (usually DC and AC abbreviated)
- the amount of signal noise, and whether the noise changes over time
Understand signals and signal measurements of oscilloscopes
A pattern that repeats at regular intervals is called a wave – an oscilloscope, for example, measures ripple voltage waves. The cycle (or vibration) of a wave is its repetitive section. A signal is the graphical representation of a wave. For a voltage signal, the time is displayed on the horizontal axis and the voltage on the vertical axis.
The shape of a signal reveals much about its content. Any change in the level of the signal level indicates a change in the voltage. A flat horizontal line means that there has been no change over that period. Straight diagonal lines indicate linear changes, i.e., a constant increase or decrease in voltage, and a jagged signal of sudden changes. Figure 1 shows some typical waveforms.
Synchronous and asynchronous signals
When two signals are temporally related, they are called synchronous. Clock, data and address signals in a computer are examples of synchronous signals. Accordingly, signals between which there is no temporal relationship are called asynchronous. For example, since there is no temporal relationship between pressing a key on the computer keyboard and the clock signal in the computer, they are considered asynchronous signals.
Some signals combine the characteristics of sine, square, step and pulse signals, resulting in complex waveforms. The signal information may be embedded in amplitude, phase and frequency variations. Digital Phosphor Oscilloscopes are best suited for displaying complex signals, as their displays can provide the required information on the frequency of occurrences needed to interpret the behavior of the signal correctly. This is also called brightness modulation.
Which signals measure oscilloscopes
|Figure 2: Amplitude and degrees of a typical sinusoidal shape|
Different measurements can be made with oscilloscopes. Some of the most common measurements are presented below:
- Frequency and period: A signal that repeats has a frequency. The frequency is measured in hertz (Hz) and corresponds to the number of repetitions of the signal in one second, called cycles (or oscillations) per second. Each repetitive signal also has a period (or period of oscillation). This is the time it takes for the signal to complete a cycle. Period and frequency are reciprocal. One divided by the period gives the frequency and one divided by the frequency of the period.
- Voltage: Voltage is the electrical potential, or signal strength, between two points in a circuit. Usually one of these points is the mass or zero voltage, but not always. One possible measurement is, for example, the voltage between the highest and lowest vertex of a signal, the so-called peak-to-peak voltage.
- Amplitude: The amplitude refers to the magnitude of the voltage between two points in a circuit, usually the maximum voltage of a signal based on the ground or zero voltage. The signal in Figure 2 has an amplitude of 1 V and a peak-to-peak voltage of 2 V.
- Phase: The sine wave best explains the phase. The voltage level of a sine wave is based on a circular movement. Starting from a 360 ° full circle, a complete cycle of the signal is 360 °, as shown in Figure 2. By degrees, each phase angle of a sine wave can be accurately specified to describe how far the period has already advanced.
The phase shift refers to the time shift or “timing difference” between two equal period signals. The signal labeled “Current” in Figure 3 is offset by 90 ° concerning the voltage signal and the phase shift angle is 90 °, since the signals reach the same points in their cycles by precisely one-quarter cycle (360 ° / 4 = 90 °). , Phase shifts are a common phenomenon in electronics.
In the second part of the series, we introduce you to the different types of oscilloscopes currently available on the market and highlight the key factors to consider when choosing a measurement solution. If you want to buy an oscilloscope then read the Best Handheld Oscilloscope review guide.