What is oscilloscope bandwidth - how to choose oscilloscope bandwidth
Introduction to oscilloscopes
An oscilloscope is a very versatile electronic measuring instrument. It can transform invisible electrical signals into visible images, making it easier for people to study the changing processes of various electrical phenomena. The oscilloscope uses a narrow electron beam composed of high-speed electrons to hit a screen coated with fluorescent material to produce small light spots (this is the working principle of a traditional analog oscilloscope). Under the action of the measured signal, the electron beam is like the tip of a pen, which can depict the change curve of the instantaneous value of the measured signal on the screen. The oscilloscope can be used to observe the waveform curves of various signal amplitudes changing with time. It can also be used to test various electrical quantities, such as voltage, current, frequency, phase difference, amplitude modulation, etc.
Oscilloscope classification
Analog oscilloscopes use analog circuits (oscilloscope tubes, the basis of which is an electron gun). The electron gun emits electrons toward the screen. The emitted electrons are focused to form an electron beam and hit the screen. The inner surface of the screen is coated with a phosphor so that the point where the electron beam hits emits light.
Digital oscilloscopes are high-performance oscilloscopes manufactured by a series of technologies such as data acquisition, A/D conversion, and software programming. The way a digital oscilloscope works is to convert the measured voltage into digital information through an analog converter (ADC). The digital oscilloscope captures a series of samples of the waveform and stores the samples until the storage limit is determined to determine whether the accumulated samples can depict the waveform. Then, the digital oscilloscope reconstructs the waveform. Digital oscilloscopes can be divided into digital storage oscilloscopes (DSO), digital phosphor oscilloscopes (DPO) and sampling oscilloscopes.
To increase the bandwidth of analog oscilloscopes, oscilloscope tubes, vertical amplification and horizontal scanning need to be fully promoted. To improve the bandwidth of a digital oscilloscope, you only need to improve the performance of the front-end A/D converter, and there are no special requirements for the oscilloscope tube and scanning circuit. Plus digital oscilloscopes can make full use of memory, storage and processing, as well as multiple triggering and advance triggering capabilities. In the 1980s, digital oscilloscopes suddenly emerged and achieved numerous results. They have the potential to completely replace analog oscilloscopes. Analog oscilloscopes have indeed retreated from the front desk to the background.
2. Classification according to structure and performance
①Ordinary oscilloscope. The circuit structure is simple, the frequency band is narrow, and the scanning linearity is poor. It is only used to observe the waveform.
②Multi-purpose oscilloscope. It has a wide frequency band and good scanning linearity, and can conduct quantitative tests on DC, low frequency, high frequency, ultra-high frequency signals and pulse signals. With the help of amplitude calibrators and time calibrators, measurements can be made with an accuracy of ±5%.
③Multi-line oscilloscope. Using multi-beam oscilloscope tubes, the waveforms of more than two signals of the same frequency can be displayed on the fluorescent screen at the same time, with no time difference and accurate timing relationship.
④Multi-trace oscilloscope. It has the structure of electronic switch and gate control circuit, and can display the waveforms of more than two signals with the same frequency on the fluorescent screen of a single-beam oscilloscope tube at the same time. However, there is a time difference and the timing relationship is not accurate.
⑤Sampling oscilloscope. Sampling technology is used to convert high-frequency signals into analog low-frequency signals for display, and the effective frequency band can reach the GHz level.
⑥Memory oscilloscope. Using storage oscilloscope or digital storage technology, single electrical signal transient processes, non-periodic phenomena and ultra-low frequency signals are retained on the fluorescent screen of the oscilloscope or stored in the circuit for a long time for repeated testing.
⑦Digital oscilloscope. It has a microprocessor inside and a digital display outside. Some products can display both waveforms and characters on the oscilloscope tube fluorescent screen. The measured signal is sent to the data memory through the analog-to-digital converter (A/D converter). Through keyboard operation, the captured waveform parameter data can be added, subtracted, multiplied, divided, averaged, and squared. , calculate the root mean square value, etc., and display the answer number.
