What is the bandwidth and sampling rate of an oscilloscope?
What is bandwidth? Generally speaking: when the input signal amplitude is attenuated by 3dB, the bandwidth of the maximum input signal is defined as the bandwidth of the oscilloscope.
What is the sampling rate? How many points can be collected per second. The faster the speed, the smaller the error. Generally, the sampling rate is 4 times the bandwidth of the oscilloscope (the amplifier type is Gaussian response)
There are at least two parts to a digital oscilloscope: the Y channel of the signal under test and the sampling part.
The Y channel amplifies (or attenuates) the signal being measured, and the bandwidth is for the Y channel. If the Y channel can amplify all sinusoidal signals in the range of 0~10MHz uniformly without distortion, then its bandwidth is 10MHz. Since complex waveform signals are composed of sinusoidal signals with various harmonics, and the bandwidth composed of these harmonics may be very wide, so in order to ensure that complex signals are truly amplified, the larger the bandwidth of your Y channel, the better.
Just having a Y channel with sufficient bandwidth is not enough. In order to capture the waveform, you have to sample the signal amplified by the Y channel! The speed of this sampling is the sampling rate. The faster the sampling rate, the more points of the complex waveform are captured per unit time, and the final assembled and displayed waveform is closer to the real complex signal.
Therefore, although bandwidth and sampling rate are two different parameters, they are both very important for truly restoring the measured waveform.
Why does the larger the bandwidth, the less distorted the signal?
Complex signals can be decomposed into countless high-frequency sinusoidal harmonics, which make up the details of the original signal. If your bandwidth is not wide enough (mainly the high end is not high enough), higher harmonic signals cannot be effectively amplified and passed through (are blocked or attenuated). In this way, the signal obtained at the terminal of the Y channel will be distorted (the details of the complex signal are lost).
Therefore, it is very important to increase the Y channel bandwidth as much as possible to restore signal details (without distortion).
Bandwidth reflects the frequency passing ability of a signal. The larger the bandwidth, the more accurately and effectively the various frequency components (especially high-frequency components) in the signal can be amplified and displayed. If the bandwidth is not enough, a lot of high-frequency components will be lost. If there is no frequency component, the signal will naturally be displayed inaccurately and a large error will occur. The sampling rate is the frequency of signal conversion when converting analog quantities to digital quantities (that is, the number of acquisitions per second). The higher the frequency, the more signals are collected per unit time, and the more information in the signal is retained. The less information is lost, the converted digital quantity can accurately reflect the value of the signal, and then the LCD display can display the signal waveform more accurately and completely. The more sampling points, the more points will be displayed, and the clearer it will be.
Simply put, the bandwidth reflects the frequency range of the signal that can be displayed, while the sampling rate reflects the details of the signal waveform.
Why can the wider the bandwidth, accurately and effectively amplify and display various frequency components (especially high-frequency components) in the signal?
For example, if the bandwidth of an audio amplifier is relatively small, such as 50Hz~15KHz, then the signal above 15KHz cannot be effectively amplified, the output will be very small or even nonexistent, and the sound above 15KHz will not be heard. If the amplifier bandwidth is relatively wide, such as 10Hz~20KHz, then all audio can be amplified and output, and complete audio sound can be output. The same is true for oscilloscope displays.
