The difference between the working principles of analog oscilloscopes and digital oscilloscopes
The oscilloscope is a classic and universal instrument for testing time domain waveforms. Sometimes it can also be used to measure current or optical signals, but it needs to be converted into a voltage signal through a corresponding probe or converter for measurement.
An oscilloscope can literally be understood as an instrument that displays waveforms, so what exactly is a waveform? It is mainly divided into two types: time domain and frequency domain waveforms. For an oscilloscope, the waveform displayed is the change of voltage with time. On the product screen, the horizontal axis represents time, and the vertical axis represents the measured signal voltage. The waveform on the oscilloscope reflects the trajectory of the measured signal voltage changing with time.
Time domain waveform displayed on oscilloscope
Oscilloscopes can display the changes in the voltage signal of the measured point, and analyzing and understanding the changes in the voltage of each node of the device under test is a basic need in the electronics industry. Therefore, oscilloscopes are widely used in various industries such as electronics, communications, computers, medical, automobiles, and aerospace. . It is for this reason that oscilloscopes are universal and the most popular measuring instrument in terms of global sales. The annual sales of oscilloscopes exceed 1 billion US dollars.
Oscilloscopes are mainly divided into analog oscilloscopes and digital oscilloscopes according to their implementation principles. They are classified into real-time oscilloscopes and sampling oscilloscopes according to their sampling methods. Some oscilloscope manufacturers have given their oscilloscopes great names for the purpose of highlighting certain features in marketing promotions, or added There are some additional measurement modules, but in terms of the large basic structure, they do not deviate from the above basic classification.
1. Analog oscilloscope
Appeared in the 1940s, it was the earliest oscilloscope to appear. This oscilloscope used a cathode ray tube display screen, and its bandwidth was only a few MHz. The following figure is a structural block diagram:
The triggering of analog oscilloscopes is generally relatively simple, usually edge triggering. After setting the corresponding edge trigger conditions, once the valid edge of the signal under test comes, the oscilloscope will start to generate a sawtooth wave to control the horizontal scan, so that every waveform seen on the oscilloscope screen is the trigger point of the signal under test. future waveforms. If the signal being measured is periodic, such as a clock signal, a stable signal waveform can be seen on the oscilloscope.
2. Digital oscilloscope
This oscilloscope appeared a little later, in the 1980s, surpassing analog oscilloscopes in terms of bandwidth, triggering and analysis capabilities.
The difference between a digital oscilloscope and an analog oscilloscope is the input signal. The digital oscilloscope samples and digitizes the input signal through a high-speed chip, saves the digitized sample points into the cache, and then reads out the data in the cache through the signal processing circuit. The DAC chip converts the corresponding numbers into analog quantities and displays them on the CRT display.
