The root cause of signal distortion

Any rapidly changing signal (such as a digital pulse) is not a simple waveform, but rather a combination of many different frequency sine waves. The steep edges and fine details of the signal are mainly composed of high-frequency components. The bandwidth of the probe acts like a filter, determining the maximum frequency of the signal that can be effectively transmitted. If the bandwidth is insufficient, these critical highfrequency components will be blocked or attenuated, preventing you from seeing the true full picture of the signal.

Visible Measurement Disasters

The direct consequence of insufficient bandwidth is severe signal distortion. You will observe that the originally sharp and steep pulse edges become smooth and sluggish, with the measured rise time significantly slower than the actual value. Worse still, the critical features on the signal used for diagnosing issues—such as overshoot, ringing, and glitches (all high-frequency phenomena)—either diminish in amplitude or disappear entirely. This is like viewing the world through a pair of scratched glasses, where everything appears blurry and distorted, making accurate judgments impossible.

The Core Principle of Selection

Therefore, the bandwidth of the probe is the first threshold for ensuring measurement accuracy. A basic rule of thumb is that the probe's bandwidth should be at least 3 to 5 times the highest frequency component of the measured signal. For example, to measure a signal with a rise time of 1 nanosecond, you need a probe with a bandwidth of 1 GHz or higher. Only then can you trust the waveform displayed on the screen, ensuring that what you see is the true dynamic state of the electronic world, rather than a blurred snapshot caused by the probe's insufficient capabilities.