How to choose an oscilloscope? Which oscilloscope is better?

Since its introduction, the oscilloscope has been one of the most important and commonly used electronic test instruments. With the development of electronic technology, the capabilities of oscilloscopes are constantly improving, and their performance and prices are also varied, with uneven market conditions. Oscilloscopes may seem simple, but there are many problems in choosing one. Based on years of experience, this article will tell you from several aspects what you should pay attention to when choosing an oscilloscope.

Methods/Steps

1. Understand the signal you need to test

What do you want to observe with your oscilloscope? What is the typical performance of the signal you want to capture and observe? Does your signal have complex characteristics? Is your signal repetitive or a single-shot signal? What is the bandwidth or rise time of the signal transition process you want to measure? What signal characteristics do you plan to use to trigger on short pulses, pulse widths, narrow pulses, etc.? How many signals do you plan to display simultaneously? What processing do you do to the test signal?

2. The core technology differences in choosing an oscilloscope: analog (DRT), digital (DSO), or hybrid (DPO)

The traditional view is that analog oscilloscopes have familiar control panels and are inexpensive, so they are always considered "easy to use". However, with the increasing speed and decreasing price of A/D converters, as well as the increasing measurement capabilities and virtually unlimited measurement functions of digital oscilloscopes, digital oscilloscopes have become the leader. However, digital oscilloscopes have the disadvantages of three-dimensional display and slow processing of continuous data, and require oscilloscopes with digital-analog hybrid technology, such as DPO digital phosphor oscilloscopes.

3. Determine the test signal bandwidth

Bandwidth is generally defined as the frequency at which the amplitude of a sine wave input signal decays to -3dB, or 70.7% of the amplitude. Bandwidth determines the basic measurement capability of an oscilloscope for a signal. Without sufficient bandwidth, the oscilloscope will not be able to measure high-frequency signals, the amplitude will be distorted, the edges will disappear, and the detailed data will be lost; without sufficient bandwidth, all the characteristics of the obtained signal, including ringing and humming, are meaningless.

4. Sampling rate (or sampling speed) of the A/D converter

The unit is the number of samples per second (S/s), which refers to the frequency at which a digital oscilloscope samples a signal. The faster the sampling rate of the oscilloscope, the higher the resolution and clarity of the displayed waveform, and the lower the probability of losing important information and events.

5. Screen refresh rate is also called waveform update speed

All oscilloscopes flicker. An oscilloscope captures a signal a certain number of times per second. No measurements are taken between these measurement points. This is the waveform capture rate, also called the screen refresh rate, expressed as waveforms per second (wfms/s). It is important to distinguish between the waveform capture rate and the A/D sampling rate. The sampling rate indicates how often the oscilloscope A/D samples the input signal within a waveform or cycle; the waveform capture rate refers to how quickly the oscilloscope acquires waveforms. The waveform capture rate depends on the type and performance level of the oscilloscope and varies greatly. An oscilloscope with a high waveform capture rate will provide more important signal characteristics and greatly increase the probability that the oscilloscope will quickly capture transient anomalies such as jitter, runt pulses, low-frequency interference, and transient errors.

6. Choose the appropriate storage depth, also known as record length

Memory depth is a measure of how many sample points an oscilloscope can store. If you need to capture a pulse train without interruption, the oscilloscope must have enough memory to capture the entire event. The required memory depth can be calculated by dividing the length of time to be captured by the sampling rate required to accurately reproduce the signal.

7. Choose different trigger functions according to your needs

The trigger of the oscilloscope can synchronize the horizontal scanning of the signal at the correct position point, making the signal characteristics clear. The trigger control button can stabilize the repetitive waveform and capture the single waveform.

Most oscilloscope users only use edge triggering. Having other triggering capabilities is very useful in some applications, especially for troubleshooting of newly designed products. Advanced triggering methods can separate the events of interest and find the abnormal problems you are concerned about, thereby making the most effective use of sampling rate and storage depth.